Mycol. Res. 9S (6): 641--655 (1991) Printed in Great Britain 641

Presidential address 1990

The fungal dimension of biodiversity: magnitude, significance,and conservation

D. L. HAWKSWORTH

International Mycological Institute, Kew, Surrey TW9 3AF, UK

Fungi, members of the kingdoms Chromista, Fungi S.str. and Protozoa studied by mycologists, have received scant consideration indiscussions on biodiversity. The number of known species is about 69000, but that in the world is conservatively estimated at1'5 million; six-times higher than hitherto suggested. The new world estimate is primarily based on vascular plant:fungus ratios indifferent regions. It is considered conservative as: (1) it is based on the lower estimates of world vascular plants; (2) no separateprovision is made for the vast numbers of insects now suggested to exist; (3) ratios are based on areas still not fully knownmycologically; and (4) no allowance is made for higher ratios in tropical and polar regions. Evidence that numerous new speciesremain to be found is presented. This realization has major implications for systematic manpower, resources, and classification. Fungihave and continue to playa vital role in the evolution of terrestrial life (especially through mutualisms), ecosystem function and themaintenance of biodiversity, human progress, and the operation of Gaia. Conservation in situ and ex situ are complementary, and thesignificance of culture collections is stressed. International collaboration is required to develop a world inventory, quantify functionalroles, and for effective conservation.

'Biodiversity', the extent of biological variation on Earth, hascome to the fore as a key issue in science and politics for the1990s. First used as 'BioDiversity' in the title of a scientificmeeting in Washington, D.C. in 1986 (Wilson, 1988: p. v), ithas been rapidly adopted as a contraction of 'biotic diversity'and 'biological diversity'. Interest has been inflamed byconcern over the conservation of genetic resources, destrudionof forests, extinction of species, and the effects of globalwarming. A plethora of texts and reports has resulted; someof the more significant since 1985 are Norton (1986a), Soule(1986), U.S. Congress Office of Technology Assessment(1987), Wolf (1987), Cronk (1988), Lugo (1988), Wilson(1988), Knutson & Stoner (1989), U.s. National Science Board(1989), di Castri & Younes (1990), Keystone Center (1990),

McNeely et al. (1990), and u.s. Board on Agriculture(1991).

While many of the principles and discussions of broaderissues raised in these works are relevant to mycology, mostlack any substantive content on fungi, or indeed in many caseson any micro-organisms. Exceptions with sections on at leastsome micro-organism aspects are: U.s. Congress Office ofTechnology Assessment (1987), Knutson & Stoner (1989),U.S. National Science Board (1989), di Castri & Younes (1990),and U.S. Board on Agriculture (1991).

The aim of this address is to broaden the biodiversitydebate by focusing on its fungal dimension; the magnitude ofthe task and its implications for systematics; the significanceof fungi in evolution, ecosystem function, human progress,and to Gaia; and the conservation of fungi. Biodiversity canbe explored at a variety of levels: in terms of ecosystems,

41

species, or populations. Knowledge of all of these is pertinentto a thorough appreciation of the fungal dimension, but hereI will centre on species biodiversity; that is basal to discussionsat other levels.

DAVID L. HAWKSWORTHPresident, British Mycological Society, 1990

MYC 95

Presidential address 642

MAGNITUDE

Circumscription

What are fungi? An answer is fundamental to a considerationof their magnitude. In the first half of this century, 'Fungi'were generally treated as a part of the kingdom 'Plantae' inthe subdivision 'Thallophyta' and placed alongside Bacteria,Lichenes, and Algae (e.g. Fitzpatrick 1930: p. 2). The five­kingdom system of Whittaker (1969) was rapidly adoptedwhich accepted a kingdom 'Fungi' (including myxomycetesand oomycetes) as distinct from Animalia, Monera (bacteriaand cyanobacteria), Plantae (including bryophytes and non­flagellate algae), and Prostista [i.e. 'Protoctista 'J (includingplasmodiophoromycetes and hyphochytridiomycetes). It isnow clear that this break from tradition did not go far enoughin representing the diversity of life. Greater numbers ofkingdoms and arrangements within those have been proposedby a variety of workers in the 1980s (e.g. Cavalier-Smith,1981, 1987; Corliss, 1984; Tehler, 1988; von Arx, 1987).

At present, the prevailing view, based on a combination ofthe limited ultrastructural and molecular data now available,is to distribute the phyla (i.e. 'divisions ') generally studiedby mycologists between the kingdoms Protozoa (incl.Myxomycota), Chromista (incl. Oomycota), and Fungi 5.5tr.

An attempt to reflect the current view of the overallrelationships and phylogeny of the phyla concerned isincorporated into Fig. 1. However. knowledge in this area isadvancing rapidly, and it has even been suggested that thewhole 'kingdom' concept in eukaryotes needs rethinking(Sogin et aI., 1989).

In the remainder of this address, 'fungi' is used in theadmittedly arbitrary but traditional sense of 'organismsstudied by mycologists', i.e. to encompass those now alsoplaced in other kingdoms. The inclusion of lichen-formingfungi in the sixth edition of the Dictionary of the Fungi(Ainsworth et al., 1971), and in the Index of Fungi from 1970,at first shocked some. However, a thorough integration wasthe only logical possibility, especially in view of the diversityof biologies involved (Hawksworth, 1988a); this is nowaccepted as the norm and does not merit further commenthere. Unless otherwise restricted, 'fungi' as used in thisaddress encompasses those forming lichens.

Described species

The best estimates for the number of known species of fungicome from the additions of totals of accepted species givenfor each genus in the first and seventh editions of theDictionary. These were the only two where counting wasundertaken from individual entries and gave about 38000(Ainsworth & Bisby, 1943: p. 204; Bisby & Ainsworth, 1943)and 64200 species (Hawksworth et al., 1983: p.266)respectively.

On average 700 species were described as new to scienceeach year from 1920 to 1950 (Ainsworth, 1954). The annualtotal catalogued in the Index of Fungi reached around 1400 in1961 (Ainsworth, 1963), 1500 by 1968 (Ainsworth, 1968),and has averaged 1700 each year for 1986-90 (p. M. Kirk, pers.comm.); that the pre-1970 issues did not cover Iichenizedspecies only partly accounts for this ' rise' (see below).

Taking the 1700 annual rate, it follows that approximately

BASIDIOMYCOTA

_________ Fruil body retained

The PHYLA of "FUNGI"

- - - - - - - - - Meiotic exospores fonned (basidiosporcs)

--------- Fruit body formed

USTOMYCOTAUREDINIOMYCOTA

_________ Dikaryon formedMeiotic endospores fanned (ascnspores)Zygospore lost

_________ Mitospores producedCilia lostZygospore developed

- - - - - - - - - Chi.i" cell wall

Loss of amoeboid trophic phase- - - - - - - - - Cilia developed

_________ Chromosomc!i formedMitochondria originate symhiotically

­"

,,,,,,,,,,,, ­, -, --..... ~,, ,

Fig. 1. Schematic representation of selected characteristics and probable relationships of the phyla of 'fungi', and the kingdoms towhich they are now assigned. The Eubacteria are included only for reference.

D. L. Hawksworth 643

Revised estimates. Four decades after Martin's (195 I) estimate,and to improve the mycological input to the biodiversity

1 Hawksworth et aI. (1983).2 Vol. 5 (6-20); twice-yearly, International Mycological Institute.3 2'5: 1 synonymy assumed.

II 900 'new' species have been described since 1983.Assuming that as in the past 'more than half' (Ainsworth &Ciferri, 1955) or 'one out of three' (Bisby & Ainsworth, 1943)can be expected to be unnecessary synonyms, it seems notunreasonable to accept a synonymy level of 2'5: 1. On thatbasis, the number of described species accepted in the latestDictionary should be increased by 4800 to up-date it to theend of 1990. Making no allowance for double counting due toseparately named anamorphs of known teleomorphs (seebelow), this provides a revised figure of 69000 for the numberof species of fungi currently known (Table I).

Undescribed species

Previous estimates. Fries (1825: p. 47) considered that thefungi would prove to be the largest group in the 'orbisvegetabilia', analogous to the insects in the' animalia'; that itwould be easy to make mycology larger than the rest ofbotany (Fries, 1828: p. 107); and that describing themindividually would frustrate the memory of man (Fries, 1829:p. vii). While, as far as I have been able to discover, hepublished no overall numerical estimate, he did indicate thatthe number of agaric species could well be as much as 40000(Fries, 1849: pp. 267-268), the pyrenomycetes alone 100000(lac. cit. p. 378), and that science could collapse if all foliicolousspecies were described (/oc. cit. p. 509). On the basis of thesestatements, I suspect he would have considered an estimate of250000 low. According to Cooke (1895: p.319), in 1872A. de Bary went for a more modest ISO 000 species.

Bisby & Ainsworth (1943: p. 18) made a 'guess' that aboutone third of the species were then known, Le. 'that there areabout 100000 species'. Based on an analysis of fungal data inIowa in relation to the numbers of vascular plants, Martin(1951: p. 177) regarded the figure of 100000 'excessivelyconservative and that the total number may be of substantiallythe same order of magnitude as the number of species ofvascular plants', then estimated at about 260000 Gones,1951). Ainsworth (1968: p.513) considered this 'probablystill on the conservative side', noting that the regularity in thepattern of description of new species found was as to beexpected if those 'proposed each year are a random samplefrom a large undescribed population '.

This issue has not attracted much subsequent attention,although Korf (1991) considered that at least half andprobably more than two thirds of the world's discomycetesremained undescribed.

A:BVascular Plants1 Fungi 2

(A) (B)Region

debate, it is opportune to calculate an updated figure.Intensive 'knock-down' studies of the insects associated withindividual trees in the tropics have provided the basis forrecalculations of the extent of insect diversity. Extrapolationshave led to estimates of the world's insect species as in therange 10-80000000 (Stork, 1988). While each step in sucharguments can be challenged, especially the extent ofinsect-host specificity in the tropics (May, 1988), the numberof insects is likely to be at least 6000000 (R. M. May,unpub!.; Thomas, 1990).

In order to provide new estimates in which we can haveconfidence, it is vital to base these on the best informationavailable. In the case of the fungi, the most intensively studiedregion in the world is the British Isles. Bisby & Ainsworth(1943) considered that there were perhaps then 6000 'good'fungus species recognized; however, they did not allow forlichen-forming species which at that time would have added1400 further species (Watson, 1953). The total figure in1943/53 would then have been 7400. Today that sum standsat around 12 000 (Sims et al., 1988), an increase of 62 % in47 years, and a rate of 13 % per decade. The total of acceptedBritish ascomycdes alone is currently 5100 species (Cannonet al., 1985), and a staggering 4931 fungi are known fromy orkshire (Table 2).

The ratio between the number of vascular plants and fungifrom all substrata (not only plants and plant products) in theBritish Isles as a whole is now about I: 6; i.e. about twice thatin 1943/53. In the better-studied counties, islands, or sites itis around I: 3 or I: 4 (Table 2). This difference is to beexpected as no site in Britain can yet claim to be fully recordedfor fungi. Indeed the high Yorkshire figure is certainly due to

Table 2. Comparison of the numbers of vascular plants and fungioccurring in well-studied sites in the British Isles

British Isles 20893 12000' 1: 6Warwickshire 1231' 2795 6 1:2

Yorkshire 1314' 4931 6 1:4Hebrides 860· 3769'0 1: 4

Isle of Mull 783" 276012 1: 4Slapton 49013 161914 1:3Wheatfen Broad 23815 99615 1: 4

1 Pteridophytes, gymnosperms and spermatophytes, not garden speciesunless common escapes; excluding 'microspecies' and hybrids.

2 In all habitats, including lichen-forming species, and not double-countinganamorphs with known teleomorphs (except for 'British Isles).

3 Clapham et al. (1987); S. L. Jury (pers. comm.); excluding ca. 25000species in gardens U. C. Alexander & S. L. Jury, pers. comm.).

• Sims et aI. (1968)., Cadbury el aI. (1971).6 Clark (1980, 1986).

, M. R. D. Seaward (pers. comm.).8 Bramley (1985); Seaward (1989, in lill.).9 M.RD. Seaward (pers. comm.).

10 Dennis (1986); M. R. D. Seaward (pers. comm.).11 Bangerter & Cannon (1978); Bangerter el aI. (1978); Clark & Jermy

(1990).

12 James (1976); Watling (1978); Henderson & Watling (1985).13 Brookes & Burns (1969).

" Hawksworth (1986, unpub!.).15 M. B. Ellis (in lill.).

Species

6420046003

69000

Dictionary of the Fungi 1983'Index of Fungi 1983-902

Total

Source

Table 1. The number of known species of fungi

41-2

Presidential address 644

Table 3. Estimates of the total number of species of fungi in the worldderived by different methods (see text for further explanation)

alone on 34 vascular plant species in an alpine sedgecommunity; a ratio of 1: 3'8. That ratio could not unreasonablybe expected to be as much as 1: 6 had all fungi (including rusts,other ascomycetes and conidial fungi) been taken into account.Extrapolated to the world that would give 1620000 [Estimate0] on vascular plants alone.

Based on less detailed enquiries, I previously and hesitantlysuggested that there might be 800000 species of fungi in theworld (in di Castri & Younes, 1990). The data now presenteddemonstrate that figure to be an underestimate. A mean ofEstimates A-O (admittedly not comparable) yields a figure of1262250 [Estimate E; Table 3]; as Estimates C and 0 are notbased on all substrata, B is certainly based on inadequatestudy, and hosts and additional fungi continue to be found inall these areas, it may seem not unreasonable to suggest1650000 [Estimate F] as a conservative figure for the actualnumber of species of fungi in the world.

However, all the preceding calculations do not allow foranamorphs where the corresponding teleomorphs are named,and so are also included. Bisby & Ainsworth (1943) made areduction of one third in the anamorph species totals to allowfor this factor. If the proportions between the different groupsrevealed by the seventh edition of the Dictionary are assumedstill to hold when all fungi are known, conidial fungi wouldrepresent about 26'5 % of the total. Applied to Estimate F, thatproVides a figure of 437750 species of conidial fungi; a onethird reduction therefore necessitates a cut of 145750 species.In the case of Estimate F, that proVides a corrected figure of1504800 species [Estimate G]. This is the number which Isuggest, rounded to 1'5 million, is used as the best estimate ofthe number of species of fungi in the world.

I consider that 1'5 million, although six times greater thanany previously proposed by other authors, will neverthelessprove to be conservative for four reasons:

(i) A world total of 270000 species of vascular plants hasbeen assumed, even though estimates up to 400000 havebeen published (Wolf, 1987). If the higher estimate werecorrect, that would provide a figure of 2400000 fungi.

(ii) No separate allowance has been made for fungi thatmight occur on the vast numbers of insects now postulated;that ecological niche has scarcely been studied in the BritishIsles and is therefore not adequately represented in the dataset. Of museum specimens of 1100 insect species from easternFennoscandia, 166 (15 %) supported 88 members of the

that county having been studied by more mycologists thanany other over the years, 65 as opposed to 35 in the nexthighest, Surrey (G. C. Ainsworth, in lift.). This interpretation isalso consistent with Dennis (1986: p. 9) who after 35 yearsexamining Hebridean fungi considered' ... it would be unwiseto imagine the list represents more than perhaps half of thespecies actually present '. For example, many species in a siteon mosses, lichens, in soil, on insects, in water, etc, which areknown elsewhere in the British Isles will be present but remainundetected unless the appropriate techniques and specialistsare employed.

Although the ratio presented for the British Isles does nottake into account 'garden species', most of the cultivatedspecies and casual aliens, of vascular plants, but doesincorporate fungi from them, I believe the 1: 6 ratio can besustained as: (a) the British fungus flora is still underworked,as evidenced by the continuing flow of new records (seeabove); and (b) cultivated' garden species' generally have fewof the specific fungi which occur on them in regions wherethey are native, indeed quarantine procedures aim to eliminatethem. If a ratio of 1: 6 is accepted and extrapolated to theworld, assuming a conservative 270000 vascular plants yieldsan estimate of 1620000 species of fungi [Estimate A].

Finland, which has received considerable but much lessmycological attention, has 1350 vascular plants and about5900 fungi (Rassi & Viisiiinen, 1987; T. Ahti. pers. comm.),giving a ratio of 1: 4. Similarly in Switzerland there are about2500 vascular plants and 10000 fungi recorded (E. Miiller, in

lift.) yielding a ratio of 1: 4. These data add weight to the viewthat the British data are not atypical, at least for Europe.

In the u.s.A. (including Alaska, Hawaii, Puerto Rico, andthe Virgin Islands), 8792 vascular plants have 12666 fungi onthem and their products (Farr et al., 1989). While this gives aratio of 1: 1'4, as 21500 plants are actually known in theregion 0. Kartesz, in lift.) that should be revised down to1: 0'6. However, the fungi on native vascular plants, especiallymicrofungi on species in the tropical U.s.A., have scarcelybeen investigated. How many fungi have been found on othersubstrata and hosts in the country has not been catalogued,but can be expected to include about 4000 lichens (3409 occurin the continental u.s.A. and Canada alone; Egan, 1987), and4000 from the remainder. That gives an approximate recordedtotal of about 20700 species and a ratio of only about 1: 1. Aworld extrapolation based on 270000 vascular plants thengives only 270000 [Estimate B].

No comparable total for fungi on plants and plant productsis available for the British Isles. However, the authors of 134of the accounts of individual plants in the series 'BiologicalFlora of the British Isles' Uournal of Ecology 29-77, 1948-89)have, to varying extents, attempted to catalogue associatedfungi; these data were mainly taken from literature sourcesand not based on critical mycological studies. The number perhost listed varied from 0 to 81, with a mean of 8'5. Not allwere restricted to a single host and if one third are taken notto be host specific, a mean of 5'7 results. Extrapolated to theworld that would give 1539000 fungi on vascular plants alone[Estimate C]. Some indication that this data set is notexceptional comes from the study of Nograsek (1990) whofound 128 ascomycetes (excluding inoperculate discomycetes)

Estimate Basis

A British IslesB US 'Plants and Plant Products'C 'Biological Flora of the British Isles'D Alpine sedge communityE Mean A-DF Plus allowance for unstudied substrataG Minus allowance for anamorphs having

known teleomorphsH Assuming 30 million insects

Ratio

1:61:1

1:5'71:6

Totalspeciesnwnber

1620000270000

15390001620000126225016500001504800

3004800

D. L. Hawksworth

Laboulbeniales (Hulden, 1983); that figure must be anunderestimate of those in nature because of the samplingmethod. As there are about 9850 species of Coleoptera andDiptera in the British Isles (Sims et aI., 1988), it might not beunreasonable to expect 750 species in that order alone ratherthan the 45 recorded (Cannon et al., 1985). If only 5 % of insectspecies had obligate mutualistic symbionts, parasites, orcommensals, that would give estimates of: 250000 fungi on5 million insects, 500000 fungi on 10 million insects, and1500000 on 30 million. Were the last figure correct, thefungal total could be as high as 3004800 species [Estimate H].If a 15 % rate were assumed on the highest insect estimate, ahighly speculative 13'5 million fungi emerges.

(iii) The ratios of vascular plants: fungi used in deriving theestimates can be expected to be too low when all possiblefungal habitats have been exhaustively studied. In the case ofthe British Isles, the total number of fungi recorded is rising atthe rate of about 13 % each decade (see above), and there is nosign of it diminishing, while that for vascular plants remains·almost constant; on that basis by the year 2000 the ratiowould be almost 1: 7 (13 600 fungi), by 2010 1: 7'5 (15100fungi), etc. Any critical study of an area in the British Islesyields new records; about 60 fungi have been added to thenational list during the Slapton survey alone.

(iv) Ratios derived almost entirely from North Temperateregions have been assumed to apply world-wide, but could behigher both in the tropics and polar regions. Although nocountry from either of these areas has been studied sufficientlyintensively to proVide information comparable to that for theBritish Isles, there are indications why higher ratios might beexpected in both.

In India, there are 15000 vascular plants (Nayar, 1989) andeither 15500 (Singh, 1980; Sarbhoy et al., 1986) or 23000(Nayar, 1989) fungi yielding ratios of 1: 1 or 1: 1'5. However,Subramanian (1986) provided evidence of the substantialnumbers of new species still to be found in India; for example10 (43 %) of 23 coronophoraceous fungi from the WesternGhats alone proved to be undescribed. In Sierra Leone, datasupplied by F. C. Deighton (in litt.) provide a ratio of 1:0'5 ifall vascular plants are totalled (about 4100 species), but 1:2 ifonly those collected from are considered. In Papua NewGuinea, there are 2390 species of fungi treated in Shaw (1984)and about 13000 vascular plants (Womersley, 1978; G.Guymer, in litt.), giving an even lower ratio of 1 :0'2. None ofthese areas has been sufficiently well-studied to enable anyfirm conclusions to be drawn.

It has been estimated that two thirds of the world'sflowering plants occur in the tropics (Raven, 1988), and theproportion for insects could be much more in that region if theresults of studies such as that of Stork (1988) are upheld. In theabsence of non-speculative data it would be unsound to raisethe vascular plant: fungus ratio on that basis. While it mightreasonably be expected that fungi on perennial leaves (withassociated fungicolous species) and the numbers of endophyticand entomogenous fungi could significantly affect that ratio,at present it cannot be confidently asserted that vascular planthost specificity occurs to the same extent in tropical as intemperate forests. It is also pOSSible that the lichen-formingspecies, at least on rocks and the ground, are proportionately

645

fewer in the tropics. In order to obtain sounder data,mycologists (and other microbiologists) should fonn anintegral part of tropical survey teams, as recommendedby the U.S. Strategy Conference on Biological Diversity(1982: p. 91). In-depth site studies are crucial to placingestimates on a finner base (U.S. National Science Board, 1989:

p.9).In boreal to arctic and antarctic habitats where vascular

plant numbers are low, the ratio will also be much higher. InAntarctica and the subantarctic islands where lichen-fonningfungi are especially important components of the vegetation,72 vascular plants compares with at least 529 fungi (Dodge,1974; Pegler et al., 1980; Pugh & Allsopp, 1982) giving 1: 7;excluding the antarctic islands, with only two vascular plantsthat ratio on current data appears to be about 1: 100, eventhough the non-lichenized fungi have scarcely been in­vestigated. 'Hot' deserts may follow a similar pattern to coldones, especially where lichen crusts are a major component ofthe ground cover, and if soil fungi are selectively isolated.

However, some fungi, for example lichen-fonning andruderal species, appear to have rather wide geographicaldistributions as compared to vascular plants. If these were amajority, this would be expected to reduce all calculated ratiosbased on described species with increases in the size of thegeographic region considered. In view of the scant data onfungal biogeography and endemism, a meaningful quantitativeallowance cannot be made for this tendency at present. Inview of discussions of the first three factors above, itnevertheless seems not unreasonable to assume that they willmore than compensate for any variances in the 1'5 million dueto any overall 'geographical' factor.

Additional evidence. If Estimate G of 1'5 million speciesapproximates to the real situation, only 4'6% of the world'sfungi have so far been recognized. If that hypothesis is correct,vast numbers of fungi must remain to be discovered. Evidencethat this is the case is provided by a variety of observationsand data sets, examples of which are presented here.

Tropical regions would be expected to be the richestsources of new species. In Brazil, A. C. Batista (1916-67) andhis co-workers described approximately 3500 species between1954 and 1972, mostly in the series Publicafoes Instituto deMicologia Universidade do Recife. These new fungi came mainlyfrom easily accessible parts of the Amazon, and several speciesnew to science were regularly discovered from single perennialleaves. Singer (1989) published 276 new species of agarics ofwhich 241 were from Central and South America. Particularlytellingly, Rogerson et al. (1990) found 10 of 242 species offungi collected by a non-specialist in the Guyana Highlands tobe new.

This pattern is reflected in other continents. In Sierra Leone,of 1848 species mostly collected by F. C. Deighton in1926-55, 554 (30%) have been described as new and manymore in IMI await fonnal description (F. C. Deighton, in lift.).In East Africa, of 628 macrolichens recognized by Swinscow& Krog (1988), 79 species (13 %) had been described as newfrom their material collected in 1969-77; and of 389 agaricsaccepted by Pegler (1977) 63 species (16%) were new. In theLesser Antilles, 70 (15 %) of the 457 species of agarics were

Presidential address 646

Table 4. Decadal rate of increase in numbers of described species inselected habitats

new species of ascomycetes were found on 52 specimens ofthe Australasian and south-east Asian moss genus Dawsoniathat chanced to be in the herbarium at Munchen (Dobbeler,1981); and the symbionts of hepatics are scarcely studied(Boullard, 1988). Fungi growing on fungi (fungicolous fungi),especially in the tropics, receive equally poor attention: 774conidial fungi alone occur on other fungi (Hawksworth, 1981);19 (32 %) of 60 fungicolous (including lichenicolous) nec­triaceous species, mainly from the tropics, studied by Samuels(1988) were new; and 120 new species have been describedfrom other fungi in Sierra Leone (F. C. Deighton, in litt.). Thesame pattern is to be expected for fungi on algae (algicolousfungi), especially in non-marine habitats, and this appears tobe true at least for chytridiaceous species on tropical heshwateralgae (G. A. Beakes, pers. comm.).

Fungi on and in insects and other arthropods are remarkablylittle studied, and it is difficult to be certain how host specificmany are. The Laboulbeniales are perhaps the largest group,occurring mainly on flies and beetles; Hulden (1983) foundthat 24 (27%) of 88 species in eastern Fennoscandia were new.Each species of thrips appears to have a unique Hirsutella (H. C.Evans, pers. camm.), and Cordyceps species also evidentlyhave narrow host ranges to judge hom the 224 species nowknown (Kobayasi & Shimizu, 1983). An indication of therichness of entomogenous fungi in the tropics is Petch's (1921)discovery of 60 Hypocrella species on scale insects just in SriLanka. Yeast-like mutualistic fungi in the guts of wood-boringbeetles and also Trichomycetes in the digestive tracts ofinsects are hardly known; when adequately studied numerousnew entomogenous species can be expected. Lichtwardt(1986: p. 42) noted that while trichomycete species appearedto often be able to infest more than one insect species orgenus, they could be restricted at the family level.

Nematophagous fungi, both endoparasitic and trapping,also remain scarcely studied outside temperate regions (Kerry,1984) and can be expected to be another rich source of novelfungi.

The fungi on vascular plants, especially native rather thancrop species, are inadequately known even in Europe.Nograsek (1990) found 28 (22 %) of 128 ascomycete speciesin a sedge community in the Alps to be new to science (seealso above). It is still far from clear how many fungi can beexpected to be restricted to particular host vascular plants.The numbers certainly vary widely between hosts, and in thecase of crop plants while large numbers may be known (e.g.about 200 known only on sugarcane; Sivanesan & Waller,1986), how many also may occur on native plants is uncertain.Hosts with no recorded fungi Widespread as weeds or ingardens when studied in their native habitats repeatedly yieldnovel species; for example, Evans et al. (l991) discovered four

undescribed (Pegler, 1983). In Papua New Guinea, Shaw(1984) reported that 30 genera and 604 (25 %) of 2390 speciesof fungi had been based on material from the country, manycollected in 1963-77. Growth in our knowledge of NorthernHemisphere fungi also remains grossly inadequate; forexample, 25 (15 %) of 168 hyphomycetes collected in Manitobaand Saskatchewan in 1965-69 were found to be new (Sutton,1973), and 61 new fungi to science were found during theSlapton and Warwickshire studies in the British Isles (Clark,1980; Hawksworth, 1986).

Critical world or even regional monographic studies canyield remarkably high numbers of new species; 95 (85 %) of112 veiled species of Hebeloma in the western u.s.A. (Smithet aI., 1983); 30 (86%) of 35 species of Oropogon mainly fromthe New World (Esslinger, 1989); 100 (71 %) of 140 boletespecies in Malaysia (Comer, 1972); 24 (29%) of 84 species ofMeliola in the State of Kerala in India (Hosagoudar & Goos,1990); 29 (57%) of 51 hygrophoraceous fungi in NewZealand (Horak, 1990); etc. Even traditionally well-studiedgenera are not exempt hom this trend; 123 new species namesin Penicillium have been introduced since the monographof Pitt (1980), approaching a doubling of the 150 thenaccepted.

Little-explored habitats are a major source of novel fungiworld-wide. The number of aquatic hyphomycetes, 'Ingoldianfungi', now stands at 261 species O. Webster, in litt.), all but38 of which (i.e. 85 %) have been described since 1960. Thatof marine fungi has risen hom 209 species in 1979 to 321 in1990 (Kohlmeyer & Volkmann-Kohlmeyer, 1991). That offoliicolous lichens from 236 in 1952 to 345 in 1985, all buttwo of the additional 109 species being recognized since 1970(Farkas, 1986).

The fungi obligately growing on lichens (lichenicolousfungi) have proved to be remarkably rich in novel taxa.The number known increased from 457 species in 1976 to 682in 1989 (Clauzade et al., 1989); that number continues toescallate. Of 124 species reported from Greenland, 24 (19%)were new to science (Alstrup & Hawksworth, 1990); 14 (24%)of 58 species on epiphytic lichens in Luxembourg wereundescribed (Diederich, 1989); 10 (22 %) of 45 species onlecideioid lichens were also new (Triebel, 1989). Some lichen

. hosts are remarkably rich in these special fungi; 82 speciesoccur on Peltigera, of which 52 are known only on that genus(Hawksworth, 1980; Alstrup, in litt.). I now consider myearlier estimate of 1000 lichenicolous species (Hawksworth,1982 a) to be too low, and the number of obligatelylichenicolous fungi to be at least 2000 (compared with around13 500 lichenized species); that total substantially exceedsthose of the known Oomycota, Zygomycota, gastroid fungi,Ustomycota, or Myxomycota.

There are indications that the above pattern of explosiveincreases in the number of species known in such niches, at arate of 20-49% per decade (Table 4), would be seen in otherswere sufficient numbers of workers to tum their attention tothem. For example, fungi on bryophytes (mosses andliverworts): Dobbeler (1978) described 9 (27%) new generaout of 33 accepted, and 62 (50%) new species amongst 123pyrenomycetes recognized on their gametophytes, mostmaterial coming from Central Europe; two new genera and 21

Habitat

Aquatic hyphomycetesFoliicolous lichensLichenicolous fungiMarine fungi

Decadal increase(%)

2820

3849

D. L. Hawksworth

new species (two also new genera) on the 2-3 m tall Mimosapigra in Mexico. That many hosts with reported speciesremain most inadequately studied can be illustrated bynumerous examples: Holm & Holm (1981) found six newascomycetes amongst 24 on five Lycopodium species in theNordic countries; B. C. Sutton and his co-workers havedescribed 18 new genera and 55 new species of conidial fungialone on Eucalyptus litter since 1973, and have at least 16 moreto publish (B. C. Sutton, pers. comm.); this pattern is repeatedin studies on Castanea fallen cupules, Juniperus, fallen Laurusleaves, etc.

Dung is also most inadequately studied. Lundqvist (1972)found that of 100 species of the primarily coprophilousSordariaceae s. lat. in the Nordic countries 28 (28%) were newto science. While soil isolations have been a focus of attentionfor screening by commercial concerns, the fungi obtained arerarely critically identified. Soils also, however, are a furthersource of undescribed species and even in genera such asPenicillium apparently local species are still being discovered;25 described since 1980 from soil are currently accepted(Z. Kozakiewicz, pers. comm.).

Further, previously unsuspected habitats with novel fungicontinue to come to light. For example, the' cryptoendolithic'communities immersed in rock in Antarctica (Friedmann,1982), and the anaerobic flagellate fungi in the guts ofruminant mammals (Orpin, 1988). Potentially the largestuntapped pool is almost certainly endophytic fungi formingmutualistic associations with the aerial parts of vascularplants; 'mycophyllas' (Lewis, 1987). It has been suggestedthat mycophyllas may be as frequent as mycorrhizas (Carroll,1988), and even that each tropical tree species has 3-4characteristic endophytic fungi (M. M. Dreyfuss, pers. comm.).How many of such fungi are new rather than morphs of onesfruiting on the surfaces, or after the hosts die on their debris,remains uncertain.

Perhaps most instructive overall is that the numbers of newspecies catalogued in the Index of Fungi are far from decliningand that the rate has increased (see above). The volume(excluding cumulative indexes) covering the years 1981-90 is1103 pages in length, compared with 649 pages for 1971-80;lichen-forming fungi were covered in both these decades. Thekey factor limiting the number of new species described is thenumber of systematic mycologists available to undertakesuch work. At the International Mycological Institute, forexample, I believe that we have material of about 1000 speciesawaiting description; a pattern reflected in mycologicallaboratories and herbaria throughout the world.

Implications for systematics

Manpower. The appreciation that only 4'6% of the world'sfungi are currently known has major implications forsystematic mycology. It has taken the 261 years since Micheli(1729) made his attempt at a critical compilation of the knownfungi to reach this point. At the current rate of 1700 speciesper year and even assuming all were 'good' (see above),the remaining 1435 800 species would take 844 years. Thescale of the research effort to significantly reduce that timescale would be enormous. To complete the inventory in 100

647

years would involve increasing the existing systematicmanpower by over eight times, and to achieve this by the year2000 a staggering 80 times.

The demand for the products of systematics is currentlygreater than it has ever been (Hawksworth & Bisby, 1988).This arises from a renewed interest in conservation, bio­diversity, the environment. and biotechnology at theprofeSSional scientist, amateur, and public levels. The growthin membership of charities and public organizations in theconservation arena since 1970 has been remarkable (Hodge,1990). This situation has arisen at a time when the number oftaxonomic positions in developed countries is in decline.Burdsall (1990) notes that in the U.S.A. the number ofsystematic mycological positions in three key institutions hasdeclined from 13 to 6 in recent years. In the UK, while thissituation has not been mirrored in the prinCiple mycologicalinstitutions, there is now no university department in thecountry with a head or personal chair in systematic mycology.This has grave implications for mycological training, sys­tematic aspects of which are increasingly falling to otherinstitutions, including IML

Such institutions have, however, progressively come underfinancial pressure to focus on revenue-generating activities.While these are not necessarily incompatible with soundsystematic work and indeed can enable resources to bechanelled to areas of greatest need, the time many professionaltaxonomists can devote to the description and illustration ofspecies which are not yet known to be of importance iscurtailed.

It is imperative that the time those with taxonomic skillscan employ in this field is utilized to maximum effect.Particularly disturbing is the time it often takes to unravellegalistic nomenclatural problems, or to obtain original materialof inadequately described long-forgotten species names thatjust might be the one in hand. To describe a species as new ismuch less time consuming than finding if it has already beennamed, but perhaps in an incorrect genus, family, or group.There is a need for more taxonomy and less nomenclature;indeed this complements improved nomenclatural stability asone of the two main driving forces behind the currentinternational move to establish Lists of Names in Current Useaccorded a specially protected status (Hawksworth & Greuter,1989; Hawksworth, 1991).

Resources. Ainsworth (1963) foresaw that computers wouldplay a major role in handling the data on fungi. The vastnumbers of species will necessitate the computerization ofcomparative descriptive data (including illustrations), and notmerely names and specimen details. Some of the largestmycological herbaria, notably that of IMI and the u.s.National Fungus Collection, have now installed computersystems, but find the task of keying in all past acquisitionsdaunting. Rapid progress is taking place in the handling andexchange of biosystematic information across biology as awhole (Allkin & Bisby, 1984). Mycologists can learn fromwhat has already been achieved, and also contribute to thefuture development of such systems (for example through theIUBS Taxonomic Databases Working Group) to enable themto be as widely compatible as possible.

Presidential address

The rapidly expanding CD-ROM technology, already inuse as a medium for the CAB ABSTRACTS bibliographicdatabase, and CD-STRAINS (Hitachi Ltd) for culture collectioninformation, can be expected to emerge as an appropriatemedium for the storage and dissemination of systematicinformation. In time, particularly when graphic and picture­storage capabilities improve and costs fall, CD-ROM discscould become a more effective outlet than hard copy fordescriptive information.

Storage space for collections will also increasingly becomean issue. Dried preserved specimens provide the referencepoints for the application of names and are the scientific basisof verifiable information on distributions, substrata and hosts(Hawksworth & Mound, 1991). Now that DNA can bereplicated from such material (Bruns et 141., 1989), and even asingle ascospore (Lee & Taylor, 1990), by means of thepolymerase chain reaction (PCR; Innis ef 141., 1990), driedspecimens are a genetic and not only a reference resource ableto complement that in culture collections (see below). At IMLfor example, about 3 1500 species are represented by 330000dried reference specimens; these currently occupy 1456 m ofshelving in compactors. At an equivalent level of rep­resentation, shelf runs of 70 km would be required for acomparable reference collection of the world's fungi. -

Scientific. If current classification systems are based on thecharacteristics of just under 5 % of the world's fungi, the levelof confidence we can have that any proposed classification willbe able to accommodate the remaining 95 % of variation mustinevitably be extremely low. Even in those fungi which aredescribed, it has also to be recognized that key data relevantto the development of taxonomic hierarchies and phylogeneticreconstruction are often lacking. For this reason, and toincrease the stability of names in higher categories, it isprudent and scientifically more honest to endeavour tocircumscribe families and orders for clearly closely allied fungi,but not to arrange them in additional formal groupings withinthe phyla (Hawksworth, 1985).

AHempts at phylogenetic reconstruction within the fungiare similarly inhibited by this same data lack, but further bythe inadequately known fossil record, problems of convergenceand paedomorphosis (Eriksson, 198I; Hawksworth, 1987;Thiers, 1984), and so the difficulty of being certain whichcharacters are plesiomorphic. Major strides can be expectedthrough the application of molecular techniques, especiallyRNAs (Blanz & GoHschalk, 1986) and DNAs (by PCR~mplification; see above), and these are already starting to beImportant. However, in interpreting such results the completelack of data on so many fungi must not be forgotten.

SIGNIFICANCE

Why is fungal biodiversity significant 7 The scant aHentionfungi have received in the biodiversity debate is due in mostcases to a lack of awareness amongst biologists of theirsignificance in evolution, ecosystem function, human progress,and Gaia.

648

In evolution

The origin of land plants may not have been pOSSible withoutfungi. Fungi have been found in the creeping organs and stemsof the earliest rhynioids of the late Silurian and LowerDevonian, for example Palaeomyces asteroxyli inside Asteroxylonrhizomes. This led to the hypothesis that such plants were theproduct of an association between a green alga and a fungus(Pirozynski & Malloch, 1975); Palaeomyces, although lacking'arbuscules', has been considered as possibly congeneric withthe modern endomycorrhizal (VAM) genus Glomus in theEndogonales (pirozynski & Dalpe, 1989). The possibility thatthese fungi were saprobes cannot be discounted, but even ifthey were they would have been crucial as biodegradersproviding material on which the earliest land plants couldgrow (Taylor, 1990).

The earliest filamentous fungal hyphae occurred endo­lithically in the much earlier Cambrian shelly faunas (Taylor,1990), interestingly, a habitat in which some ascomyceteslichenized with cyanobacteria occur today. As noted by vonArx (1987) there are claims of Precambrian fungi, but the truenature of those is less clear. There continues to be a disputeas to whether the ascomycetes had a common ancestor withearly 'phycomycetous' fungi or arose separately from redalgae; evidence for the laHer route is substantial (Demoulin,1985). By whatever course, asci adapted to aerial dischargemust have arisen by about 500 million years ago, before orcontemporaneous with the earliest rhinioids, as in the Silurianthe ascomycetes were evidently already diverse (Sherwood­Pike & Gray, 1985). It has been suggested that the first maywell have been lichen-like, associated initially with cyano­bacteria and later with green algae (Cain, 1972; Eriksson,1981; Hawksworth, 1982b, 1988 b). Indeed Church (1921)considered that lichens were transmigrants, developing fromthe sea onto the land; this view has continued to receive somesupport (Corner, 1967: p. 260). Lichens could also have had akey role in accelerating rock breakdown as they do today(Lawrey, 1984; Jones & Wilson, 1985; Wessels & Schoeman,1988), and so have been instrumental in the production ofmaterial in which the first land plants were' rooted '.

Fossil trunks of the progymnosperm Callixylon newberryiexhibit patterns of wood-decay characteristic of hymeno­mycetes in the Upper Devonian, and could be the firstevidence of a basidiomycete, but clamp connections were notseen (Stubblefield ef 141., 1985). The earliest documented clampconnections are from the Carboniferous (Dennis, 1970), butbasidiomycetes were perhaps not then common or suchextensive coal measures would never have formed. As wood­and liHer-rotting fungi evolved, they must have made anincreasing contribution to biodegradation and the develop­ment of soils.

If rock breakdown involving fungi and the establishment ofmycorrhizas were crucial to the evolution of the land florawithout fungi there would have been no lichens or bryo~phytes, no vascular plants, no dinosaurs to feed on them, andconsequently no man. There might even have been no insectsas mycophagy may be primitive in the group (Crowson,1984; Pirozynski & Hawksworth, 1988: p. 11), and the

D. L. Hawksworth

enigmatic Blochmann bodies and other organelles in insecttissues could also be of fungal origin (Smith & Douglas, 1987).

In addition to the colonization of land, fungi have had amajor role in the subsequent radiation of other groups,especially vascular plants, through the development ofmutualisms. VAM mycorrhizas with arbuscules were definitelypresent in the Triassic (Stubblefield et aI., 1987). Ecto­mycorrhizas developed later and enabled forests to spreadfrom the tropics into temperate regions with fluctuatingclimates and on poor soils from the Middle Cretaceous(Malloch et al., 1980). Mycorrhizas occur in 75-80% of ourpresent vascular plants (Malloch et aI., 1980; Harley & Harley,1987). Mycophyllas (see above) also place plants withendophytic fungi at a competitive advantage, for exampleagainst herbivores and insect pests (Carroll, 1988), and mustsimilarly have influenced the course of evolution.

Lamboy (1984) and Pirozynski (1988) suggested thathorizontal gene transfer by incorporation of DNA from fungiinto vascular plant genomes may have contributed to thedevelopment, and especially diversification of, leaves, flowers,and fruits. Gut endosymbionts in gall-fanning (often pol­linating) insects could have played a crucial role in this process(Pirozynski, 1991). Atsatt (1988) even proposed that vascularplants were a mosaic of tissues of algal and fungal origins;, inside-out' lichens.

Intimate associations continue to be important in evolutiontoday, and the range of coevolutionary situations identifiedwhich involve fungi is impressive (Pirozynski & Hawksworth,1988). Mutualisms are especially important in this connection.Indeed it is becoming clear that in an evolutionary context aplant (or insect) should not be viewed as a single organism,but rather a mutualistic association including endophytic andmycorrhizal fungi (or gut endosymbionts). The unit subject tonatural selection, and so to the evolution of biodiversity, istherefore the mutualism and not members of one species. Aseloquently argued by Price (1988), mutualism facilitatesadaptive radiation; fungi have had this crucial role for bothplants and animals.

In ecosystem function

Scant attention has been accorded to the role of fungi inecosystem function, and so in the maintenance of biodiversityitself. Apinis (1972) drew attention to many aspects of thistopic, and Wicklow & Carroll (1981) bring together somepertinent papers. However, broadly based integrated inter­disciplinary studies are required to place fungi in an ecosystemcontext. While the biomass involved may be considerable,especially when below-ground and litter-inhabiting fungi areconsidered, it is their functions which are crucial to ecosystemmaintenance. In addition to 75-80% of vascular plants havingmutualistic mycorrhizal fungi (see above), they have significantroles as parasites in the natural biocontrol of other organisms,as sources of food for a great variety of organisms (insects,small mammals, nematodes, molluscs, etc.), mutualists inwood-boring insects, saprobes in the breakdown and nutrientcycling of dead plant and animal remains, carbon entrapment,and nitrogen-fixation. The latter is often overlooked in a

649

mycological context, but is achieved through cyanobacteriawithin lichen thalli; this phenomenon merits particularattention in south-temperate and subtropical forests (Guzmanet al., 1990). Major gaps remain even in our understanding ofthe interactions of phylloplane, rhizoplane and rhizospherefungi with crop plants, as highlighted in Grossblatt (1989).

Food webs are ultimately based on micro-organisms,including fungi, reflecting the course of evolution (Price,1988). Species diversity tends to be greatest amongst smallerorganisms (May, 1988), but it has been argued that much ofthis variation can be functionally redundant (Norton, 1986b:p. 122). In fungi it might be thought reasonable to assume thatall wood-decay or litter-rotting species in a site are notnecessary for that ecological function to occur effectively.However, such 'redundancy' can also endow an ecosystemwith resilience against the loss of some species with similarfunctions; such 'bootstrapping' involving fungi may beespecially important in the maintenance of soils (Perry et al.,1989). The ability of many deciduous temperate trees toassociate with a variety of ectomycorrhizal fungi also placesthem at a competitive advantage by 'bootstrapping' ascompared with unimycorrhizal species. In the British Islesthere are indications that at least 55 hymenomycetes can fonnmycorrhizas with Quercus (Watling, 1974); 103 with Betula, 90with Pinus sylvestris, etc. (Alexander & Watling, 1987). Thecapacity to utilize a selection of species contributes to thesuccess of such ecosystems by providing a 'bootstrapping'buffer to the loss of individual associates.

Conversely, in some cases fungi may be 'keystone species'which if lost would lead to a major change in the ecosystem;for example if the species was the only one fonning amycorrhiza with the dominant plant, limiting an insect thatwould otherwise become a major pest, a pathogen keepinganother plant 'down', etc. While it is opportune that theeffects of ecological disturbance or change on fungi are nowbeing considered (Boddy et aI., 1988), in-depth ecologicalstudies in different ecotones remain necessary in order toquantify the role of fungi and other microorganisms inecosystem function (di Castri & Younes, 1990).

Finally, fungi have a major role as indicators of ecosystemhealth as monitors of disturbance of the soil, and throughlichens of above-soil ecological continuity (Harding & Rose,1986; Thomson, 1990), and further environmental pollution(see below). Further work can be expected to reveal newmonitoring applications.

In human progress

The just under 5 % of known fungi include some put to a greatvariety and extending range of applications to further man'sprogress. Their economic value world-wide has not beenquantified, but must be counted in billions of US $. Currentcommercial uses include: amino acid production; antibiotics;beers, wines, brandies and distilled alcohols; breads; biocontrolagents; cheeses; enzymes; fennented foods; food (mushroomsetc); flavours; food colorants; fuel (ethanol, biogas); herbi­cides; organic acids; pesticides; preservatives; Single-celledprotein (' Quom '); soy sauce; vitamins; and waste bio-

Presidential address

degradation. Exciting new applications and products continueto be developed from both known and new species. This isreflected in a three-fold increase in the number of patentstrains being deposited annually at IMI since 1986.

Of particular importance at a time of public concern overchemical pesticides is their use as biocontrol agents of fungicausing plant diseases, of weeds, or of insect pests. Theypersist in populations at low levels avoiding the needfor repeated applications. A multinational US$4'5 millionexamination of their potential for locust control. launched in1989 and co-ordinated by the International Institute ofBiological Control. is indicative of the possibilities.

Secondary metabolites have only been documented inabout 5000 of the species of known fungi (i.e. 7%). Thesecontinue to yield new commercially important products, suchas cyclosporin used in preventing the body from rejectingorgan transplants. That many pharmaceutical companies areactively screening tropical fungi for desired activities was tobe expected, and numerous biologically active productsclearly remain to be detected and characterized.

The range of genes in fungi far exceeds that in othermicroorganisms; bacteria have much smaller genomes. Thesearch for useful genes has received new impetus from geneticengineering, protoplast fusion, and now gene gun technology;fungal genes can now be transferred into and expressedthrough more rapidly growing bacterial and particularly yeastproduction systems. The insertion of fungal genes for featuressuch as natural insecticide production directly into crop plantscan now be foreseen; most of the required technology alreadyexists.

The world's undescribed fungi can be viewed as a massivepotential resource which awaits realization. And a time whenthe need to find new and improve sources of food inparticular is greater than at any period in its history.

In Gaia

The concept of Gaia (Lovelock, 1988; Margulis & Lovelock1989), has focused attention on the need to consider the earthin the total context of atmosphere, oceans, biota, andlithosphere; it has further highlighted the major contributionof microorganisms to the breakdown of rocks and compositionof the atmosphere. It seems impossible to quantify theimportance of fungi in major earth processes at this time, butthey must be considerable.

(i) The biomass of fungi in soils, plant parts, and rocks mustbe substantial. especially in temperate forests and lichen­dominated regions, and therefore traps significant amounts ofcarbon. They may be major components of soil biomass,substantially exceeding that of bacteria, nematodes, orarthropods (Lynch, 1988). Lichens fix atmospheric carbondioxide photosynthetically (see above), while saprobic,parasitic, mycorrhizal and other mutualistic fungi keep thatderived from decay materials in their tissues rather than in theatmosphere.

(ii) Fungi involved in decay form parts of the nutrientcycles of nitrogen, phosphorous, and sulphur as well ascarbon.

(iii) Gaseous methylated compounds relevant to atmos-

650

pheric composition can be produced by fungi, notablymethyl chloride (chloromethane) during wood decay (White,1982), but also others such as trimethyl arsine (Cullen &Reimer, 1989). High-efficiency methylation of halide ions byfungi has been considered to probably make a substantialcontribution to the atmospheric methyl chloride burden(Harper, 1985).

(iv) Accelerated rock weathering by microorganisms,including fungi (especially those in lichens), removes carbondioxide from the atmosphere, for example through conversionof silicates to oxalates (see above). The role of fungi in suchprocesses has as yet received scant attention compared withbacteria (Krumbein, 1983).

While the role and so the effect of losses of fungi on Gaiacannot be quantified, it is prudent to be concerned. Aseloquently portrayed by Durrell (1972: p. 210): 'The world isas delicate and as complicated as a spider's web, if you touchone thread, you send shudders running through all the otherthreads that make up the web. But we're not just touching theweb, we're tearing great holes in it.'

This is especially true as Gaia may now be becomingstressed to the extent that compensating mechanisms and'bootstrapping' may not enable life as we know it to continueindefinitely. By changing the climate through global warming'we make every spot on earth man-made and artificial'(McKibben, 1990: p. 54). The effects of the probable I-2°Crise in mean world temperatures by 2030 (Holdgate, 1989:p. 29) on fungi are uncertain. However, they would ineVitablyinvolve: crops being challenged by fungi which they do notnow encounter (both as vegetation changes and potentialranges of disease fungi are modified), leading to increased croplosses; increased incidences of dermatophytic infections andmycotoxicoses in regions where they are now rare, forexample in North America and Europe; changing seasonalpatterns of macromycete fruiting; and differential rates ofspread of vascular plants (including trees) and their mycorrhiza­forming fungi hindering the migration of such associations(and so their associated biotas). Such factors merit seriousconsideration in endeavouring to forecast and model theimpact of climatic change on man, his crops, forests, and soGaia.

CONSERVAnON

The conservation of fungi has received scant attention in mostcountries. This is regrettable in view of their role in ecosystemfunction, and so the maintenance of biodiversity (see above),but further because of the unexploited genetic resource theyrepresent. There are also ethical arguments (Norton, 1986a;McNeely et aI., 1990). The conservation of fungi can beeffected by two complementary approaches, in situ and ex situ,both of which deserve increased attention.

In situ

The in situ conservation of fungi is hampered by the lack ofinformation as to the species present in particular sites, thelength of time and labour-intensiveness of producing lists,knowledge of the rareity of individual species, and in most

D. L. Hawksworth 651

CONCLUSIONS

Table S. Fungi in the world's culture collections

1 long (1989)., Staines el al. (I986), allowing for synonymy and anamorphy.

Further, it is uncertain how many strains should bepreserved to adequately represent the infraspecific geneticvariability of a fungus. Indeed this can be expected to varymarkedly between groups. As poignantly emphasized byMason (1940: p. 116) 'it is not pOSSible to collect a species'.

Protocols for the preservation of fungi which it has hithertobeen difficult to maintain by cryopreservation are now rapidlybeing improved (Smith, 1988). The potential for securing thefungal genetic resource for future generations in the face ofhabitat destruction consequently exists if isolates of thespecies are obtained. In view of the scale of the problem,however, this objective can only be realized throughinternational collaboration and massive additional resources.

2540001

11500'170'8

Strains maintainedSpecies representedPercentage known speciesPercentage total species

This consideration of the fungal dimension of biodiversitypresents numerous scientifically exciting new research oppor­tunities, but also major organizational and structuralchallenges.

(i) The fungi are the second largest group of organisms inthe world after the insects; the prediction of Fries (1825:p. 47) is thus upheld. The task of completing a world inventoryis consequently of a greater magnitude than in any group ofmicroorganisms or plants, possibly apart from the viruses(Table 6). In order to progress towards this, and to ensure thatfungi are adequately represented in herbaria and culturecollections, it will be necessary to substantially increaseinternational collaboration. Such collaboration of necessitymust encompass and build up national and regional centres inthe less-developed countries. It is in these that so many of theunknown fungi live. An increased knowledge of tropicalmycology is a vital component of development (Subramanian,1982).

(ii) The quantification of the importance of fungal bio­diversity in both ecosystem function and to the maintenanceof Gaia poses many challenging questions. Fungi merit seriousattention in future debates on biodiversity, and global ecology;both need to extend their horizons to encompass them.

(iii) The destruction of tropical and temperate habitats yetnot or inadequately explored for fungi, makes conservation akey issue for mycologists. Knowledge of the functionalcharacteristics of the majority of fungi already described iscurrently lacking, and it is not yet possible to forecast in whichhabitats or ecosystems those with the greatest potential forexploitation will be discovered. In situ and ex situ conservationare therefore complementary priorities. Unlike many aspectsof science, the study of biodiversity, ecosystem function, andthe securing of the resource is time-limited. There can be littledoubt that 'future generations will find it blankly incom-

cases a lack of understanding of the precise ecologicalrequirements of species. Even in the relatively intensivelystudied British Isles, only in the case of lichenized species is itpossible to have confidence that the database on which tomake judgements on rarity is reasonably adequate.

In situ conservation of fungi is therefore best effected byensuring the preservation of the widest range of least­disturbed habitat types, and both lichens (see above) andmacromycetes can be of value in determining such sites(Arnolds, 1991). The safeguarding of centres of plant diversitythroughout the world, which the International Union for theConservation of Nature and Natural Resources (1987) plans toidentify, would be a major step in securing the associatedfungi. However, many of the world's undescribed fungi are intropical forests undergoing massive reductions at this time.Losses are estimated at over 100000 km2 each year, morethan the area of The Netherlands and Switzerland combined(Wilson, 1989). As a result, one quarter of the world'sbiological diversity present in the mid-1980s is expected todisappear during the next 25 years (Raven, 1988: p. 225); byextrapolation, 376000 species of fungi will become extinct inthis period - over five times the number currently described.In view of the uses to which many such fungi might have beenput to the benefits of man (see above) this destruction iscomparable to the throwing away of a food basket withoutour even looking inside.

Conservation in situ will, however, only be effective if thelocal populace reaps some short-term benefit from it (Bessinger,1990). This necessitates the revision of world intellectualproperty rights (Keystone Center, 1990; McNeely et al.. 1990)so that, for example, they apply to fungal strains explOitedoutside the country of origin.

Preserving a site may not ensure that the fungi present willbe conserved in perpetuity. For example, acid rain may havebeen the major reason for the decline of many macromycetesthat has taken place in Austria, The Netherlands and Germanyduring this century (Arnolds, 1991); this has major implic­ations for the vegetation as a whole due to the potential lossof mycorrhizal species. The effects of air pollutants on lichensare well-documented, and the depletion this causes can bedramatic (Nash & Wirth, 1987; Hawksworth, 1990); this ispotentially of major concern in the lichen-dominated tundra(Hutchinson et al., 1987) with implications for soil erosion anddependent organisms (including caribou and reindeer).

Ex situ

Culture collections are the botanical gardens and seed banksof microbiologists. These hold about 254000 strains of fungiOong, 1989: p.262), but allowing for synonymy andanamorphy, the listed names (Staines et al., 1986) onlyrepresent about 11500 species; i.e. 17% of the known and justunder 1% of the world's estimated fungi (Table 5).Nevertheless, such collections have a particular importance asthey provide a source of strains that it may be extremelydifficult or not cost-effective to endeavour to reisolate fromnature. A surprisingly large number of fungi are representedby less than five strains, indicating the infrequency of theirisolation from nature.

Presidential address 652

Table 6. Comparison of the numbers of known and estimated totalspecies in the world of selected groups of organisms

, Hawksworth & Greuter (1989).

• Wolf (1987).3 M. R. Crosby (pers. comm.).

• di Castri & Younes (1990).

Group

Vascular PlantsBryophytesAlgaeFungiBacteriaViruses

Knownspecies

220000'17000'40000'690003000'5000'

Totalspecies

270000'250003

60000'1500000

30000'130000'

Percentageknown (%)

816867

5

104

on Antarctica; to Professor E. Muller (Zollikon, Switzerland)for information on the numbers of vascular plants and fungi inSwitzerland; to Drs D. E. Shaw and G. Guymer Ondooroopilly,Queensland) for Papua New Guinea data; to Professor J.Webster (University of Exeter) for updated numbers of aquatichyphomycetes; and to many of my colleagues at IMI forassistance in diverse ways, including Mrs V. Barkham, Mrs V.]. Dring, Dr H. C. Evans, Ms G. Godwin, Dr P. M. Kirk, Dr Z.Kozakiewicz, Dr C. Prior, Ms M. S. Rainbow, Dr B. C. Sutton,Mrs P. A. Taylor, and Mrs C. Thatcher (who extracted thedata from the Biological Flora of the British Isles).

REFERENCES

prehensible that we are devoting so little money and effort ofthe study of these questions' (May, 1988: p. 1448).

(iv) The increasing realization of the widespread nature ofmutualisms involving fungi, and evidence for their co­evolution, raises questions in regard to both the origin of landplants and to the subsequent evolution of them and theirdependent organisms. In particular it emphasizes the need toexamine the nature of the evolutionary unit on which naturalselection operates.

In summary, the study of the vast array and multifariousaspects of fungal biodiversity is not for the faint-hearted, buta pleasure-ground for those seeking intellectually rewardingand also relevant endeavour. Fungi should no longer beexcluded from the current world discussions on the con­servation of biodiversity, ecosystem function, and globalecology.

I am grateful to Dr G. C. Ainsworth (Derby), ProfessorW. G. Chaloner (Royal Holloway and Bedford New College),Professor J. E. Lovelock (Launceston), Professor R. M. May(University of Oxford), Dr K. A. Pirozynski (NationalMuseums of Canada), and Dr P. H. Raven (Missouri BotanicalGarden) for valuable discussions, reading sections, or com­ments; to Professor T. Ahti (University of Helsinki) forinformation on the fungi in Finland; to Mr V. Alstrup(University of Copenhagen) for recent data on Peltigera fungi;to Dr G. A. Beakes (University of Newcastle-upon-Tyne) forcomments on algicolous fungi; to Dr M. R. Crosby (MissouriBotanical Garden) for discussions on bryophyte numbers; toMr F. C. Deighton (Great Gransden) for making availableunpublished information on Sierra Leone; Dr M. M. Dreyfuss(Sandoz, Basel) for views on tropical endophyte frequency; toDr M. B. Ellis (Southwold) for data on Wheatfen Broad; DrD.F. Farr (USDA, Beltsville) for information on host plantswith fungi in the U.S.A.; to Dr J. Kartesz (University of NorthCarolina) for that on potential host plants in the U.S.A.; toProfessor M. R. D. Seaward (University of Bradford) forcalculating numbers of vascular plants and lichens (Table 2); toDr J. C. Alexander (Royal Botanic Garden, Edinburgh), DrS. L. Jury (University of Reading), and Professor D. M. Moore(University of Reading) for that on vascular plants in theBritish Isles; to Dr J. Kohlmeyer (University of North Carolina)for a proof copy of a paper in press; to Dr R. E. Longton(University of Reading) for assistance with references to data

Ainsworth, G. C. (1954). The pattem of mycological taxonomy. Taxon 3,

77-79.Ainsworth, G. C. (1963). The pattem of mycological information. Mycologia

55,65-72.Ainsworth, G C. (1968). The number of fungi. In The Fungi. An Advanced

Treatise, vol. 3, (ed. G. C. Ainsworth & A S. Sussman), pp. 505-514.Academic Press: New York, U.s.A

Ainsworth, G. C. & Bisby, G. R. (1943). A Dictionary of the Fungi. 359 pp.Imperial Mycological Institute: Kew, U.K.

Ainsworth, G. C. & Ciferri, R. (1955). Mycological taxonomic literature andpublication. Taxon 4. 3-6.

Ainsworth, G. c.. james, P. W. & Hawksworth, D. L. (1971). Ainsworlh &

Bisby's Dictionary of the Fungi. 6th edn. 663 pp. Commonwealth MycologicalInstitute: Kew, U.K.

Alexander, I. & Watling, R. (1987). Macrofungi of sitka spruce in Scotland.Proceedings of the Royal Society of Edinburgh 93 B, 107-II5.

Allicin, R. & Bisby, F. A, eds (1984). Databases in Syslematics. 331 pp.Academic Press: London, U.K.

Alstrup, V. & Hawksworth, D. L. (1990). The lichenicolous fungi of Greenland.Meddelelser om Gmnla>td. Bioscience 31, 1-90.

Apinis, A. E. (1972). Fads and problems. Mycopalhologia et Mycologia

Applicala 48, 93-109.Amolds, E. (1991). Mycologists and nature conservation. In Frontiers in

Mycology (ed. D. L. Hawksworth), in press. CAB International: Wallingford,U.K.

von Arx, j. A. (1987). Plant pathogenic fungi. Beihefle zur Nova Hedwigia 87,

1-288.Atsatt, P. R. (1988). Are vascular plants 'inside-out' lichens? Ecology 69,

17-23.Bangerter, E. B. & Cannon, j. F. M. (1978). Flowering plants and conifers. In

The Island of Mull: a Survey of its Flora and Environmenl (ed. A C. jermy &

j. A. Crabbe), pp. 1I.1-II.77. British Museum (Natural History): London,UK.

Bangerter, E. B., Cannon, ). F. M. & jermy, A. C. (1978). Ferns and fern allies.In The Island of Mull: a Survey of ils Flora and Environmenl (ed. A. C. jermy& j. A. Crabbe), pp. 12.1-12.7. British Museum (Natural History): London,UK.

Beissinger. S. R. (1990). On the limits and diredions of conservation biology.BioScience 40, 456-457.

Bisby, G. R. & Ainsworth, G. C. (1943). The numbers of fungi. Transactions of

the British Mycological Society 26, 16-19.Blanz, P. A. & Gottschalk, M. (1986). Systematic position of Septobasidium,

Graphiola and other basidiomycetes as deduced on the basis of their 5Sribosomal RNA nucleotide sequence. Systemalic and Applied Microbiology 8,

121-127.Boddy, L., Watling, R. & Lyon, A). E., eds (1988). Fungi and ecological

disturbance. Proceedings of the Royal Society of Edinburgh 94 B, i-xii, 1-188.Boullard, B. (1988). Observations on the coevolution of fungi with hepatics.

In Coevolution of Fungi with Plants and Animals (ed. K. A. Pirozynslci &

D. L. Hawksworth), pp. 107-124. Academic Press: London, U.K.Bramley, W. G. (1985). A Fungus Flora of Yorkshire 1985.277 pp. Leeds, UK.:

Yorkshire Naturalists' Union.Brookes, B. S. & Burns, S. (1969). The natural history of Slapton Ley Nature

Reserve. III. The flowering plants and fems. Field Studies 3, 125-157.

D. L. Hawksworth

Bruns, T. D., Fogel. R., White, T. j. 8< Palmer, j. D. (1989). Acceleratedevolution of a false-truffle from a mushroom ancestor. Nature, London 339,140-142.

Burdsall, H. H. (1990). Taxonomic mycology: concerns about the present;optimism for the future. Mycologia 82, 1-8.

Cadbury, D. A, Hawkes, j. G. 8< Readett, R. C. (1971). A Computer-rMppedFlora. A Study of the County of Warwickshire. 768 pp. Academic Press:London, U.K.

Cain, R. F. (1972). Evolution of the fungi. Mycologia 64, 1-14.Cannon, P. F., Hawksworth, D. L. 8< Sherwood-Pike, M. A (1985). The British

Ascomycotina. An Annotated Checklist. 302 pp. Commonwealth AgriculturalBureaux: Slough, U.K.

Carroll, G. (1988). Fungal endophytes in stems and leaves: from latentpathogen to mutualistic symbiont. Ecology 69, 2-9.

Cavalier-Smith, T. (1981). Eukaryote kingdoms: seven or nine? BioSystems 14,461-481.

Cavalier-Smith, T. (1987). The origin of fungi and pseudofungi. In EvolutionaryBiology of the Fungi (ed. A D. M. Rayner, C. M. Brasier 8< D. Moore), pp.339-353. Cambridge University Press: Cambridge, UK

Church, A H. (1921). The lichen as transmigrant. journal of Botany, London 59,

7-13, 40-46.Clapham, A R" Tutin, T. G. 8< Moore, D. M. (1987). Flora of the British Isles.

3rd edn. 688 pp. Cambridge University Press: Cambridge, UKClark j. W. 8< jermy, A C. (1990). Additions to the flora of Mull and adjacent

islands. Watsonia 18, 179-187.Clark, M. C. (1980). A Fungus Flora of Warwickshire. 272 pp. British

Mycological Society: London, U.K.Clark, M. C. (1986). The fungus flora of Warwickshire. Further records.

Bulletin of the British Mycological Society 20, 105-119.Clauzade, G., Diederich, P. 8< Roux, C. (1989). Nelikenigintaj fungos

likenlogai. Illustrita determinlibro. Bulletin de la Societe linneenne de Provence,numero special 1, 1-142.

Cooke, M. C. (1895). Introduction to the Study of Fungi. 360 pp. A 8< C. Black:London, U.K.

Corliss, J. O. (1984). The kingdom Protista and its 45 phyla. BioSystems 17,87-126.

Comer, E. j. H. (1967). The Life of Plants. 315 pp. Weidenfeld and Nicolson:London, UK

Corner, E. j. H. (1972). Boletus in Malaysia. 263 pp. Government PrintingOffice: Singapore, Malaysia.

Cronk Q. (1988). Biodiversity: the Key Role of Plants. 13 pp. InternationalUnion for the Conservation of Nature: Kew, U.K.

Crowson, R. A (1984). The association of Coleoptera with ascomycetes. InFungus-Insect Relationships (ed. Q. Wheeler 8< M. Blackwell), pp. 256-285.Columbia University Press: New York, U.s.A

Cullen, W. R. 8< Reimer, K. j. (1989). Arsenic speciation in the environment.Chemical Reviews 89, 713-764.

Demoulin, V. (1985). The red algal-higher fungi phylogenetic link: the last tenyears. BioSystems 18, 347-356.

Dennis, R. L. (1970). A middle Pennsylvanian basidiomycete mycelium withclamp connections. Mycologia 62, 578-584.

Dennis, R. W. G. (1986). Fungi of the Hebrides. 383 pp. Royal Botanic Gardens:Kew, U.K.

Di Castri, F. & Younes, T. (1990). Ecosystem function of biological diversity.Biology International, Special Issue 22, 1-20.

Diederich, P. (1989). Les lichens epiphytiques et leurs champignons lichenicoles(macrolichens exceptes) du Luxembourg. Travaux Scientifiques du MuseeNational d'Histoire Naturelle de Luxembourg 14, 1-268.

Diibbeler, P. (1978). Moosbewohnende Ascomyceten I. Die Pyrenocarpen,den Gametophyten besiedelnden Arlen. Mitteilungen der BotanischenStaatssammlung Miinchen 14, 1-360.

Diibbeler, P. (1981). Moosebewohnende Ascomyceten V. Die auf DaW50niavorkommenden Arten der Botanischen Staatssammlung Miinchen.Mitteilungen der Botanischen Staatssammlung Miinchen 17, 393-474.

Dodge, C. W. (1974) [' 1973'J. Lichen Flora of the Antarctic Continent andadjacent islands. 399 pp. Phoenix Publishing: Canaan, New Hampshire,U.s.A.

Durrell, G. (1972). Catch me a Colobus. 221 pp. Penguin Books: Harmonds­worth, U.K.

Egan, R. S. (1987). A fifth checklist of the lichen-forming, lichenicolous and

653

allied fungi of the continental United States and Canada. Bryologist 90,

77-173.Eriksson, O. [E.] (1981). The families of bitunicate ascomycetes. Opera Botanica

60,1-220.Esslinger, T. L. (1989). Systematics of Oropogon (A1ectoriaceae) in the New

World. Systematic Botany Monographs 28, 1-111.Evans, H. c., Carrion, G. 8< Guzman, G. (1991). Fungal pathogens of Mimosa

pigra in Mexico. Mycological Research 95, in press.Farkas, E. (1986). Uj levellako zuzmo-taxonok es kombinaciok jegyzeke,

1952-1985. Botanikai Kiizlemenyek 73, 87-91.Farr, D. F.. Bills, G. F.. Chamuris, G. P. 8< Rossman, A Y. (1989). Fungi on

Plants and Plant Products in the United States. 1252 pp. AmericanPhytopathological Society: St Paul. Minnesota, U.S.A

Fitzpatrick, H. M. (1930). The Lower Fungi. Phycomycetes. 331 pp. McGraw-HillBook Company: New York USA

Friedmann, E. I. (1982). Endolithic microorganisms in the Antarctic colddesert. Science, New York 215, 1045-1053.

Fries, E. M. (1825). Systema Orbis Vegetabilis. Vol. 1. 374 pp. TypographiaAcademica: Lund, Sweden.

Fries, E. M. (1828). Elenchus Fungorum. Vol. 2. 154 pp. E. Mauritii: Greifswald,Germany.

Fries, E. M. (1829). Systema Mycologicum. Vol. 3(1). 259 pp. E. Mauritii:Greifswald, Germany.

Fries, E. M. (1849). Summa Vegetabilium Scandinaviae. Vol. 2. 572 pp. ABonnier: Stockholm, Sweden.

Grossblatt, N .. ed. (1989). The Ecology of Plant-Associated Microorganisms. 34pp. National Academy Press: Washington, D.C., U.s.A

Guzman, G., Quilhot. W. & Galloway, D. J. (1990). Decomposition of speciesof Pseudocyphellaria and Sticta in a southern Chilean forest. Lichenologist 22,325-331.

Harding, P. T. & Rose, F. (1986). Pasture-Woodlands in Lowland Britain. 89 pp.Institute of Terrestial Ecology: Huntington, U.K.

Harley, j. L. & Harley, E. L. (1987). A check-list of mycorrhiza in the BritishFlora. New Phytologist 105 (Supplement), 1-102.

Harper, D. B. (1985). Halomethane from halide ion - a highly efficient fungalconversion of environmental significance. Nature, London 315, 55-57.

Hawksworth, D. L. (1980). Notes on some fungi occurring on Peltigera, witha key to accepted species. Transactions of the British Mycological Society 74,363-386.

Hawksworth, D. L. (1981). A survey of the fungicolous conidial fungi. In TheBiology of Conidial Fungi, Vol. 1, (ed. G. T. Cole & B. Kendrick), pp.171-244. Academic Press: New York, U.s.A

Hawksworth, D. L. (I982a). Secondary fungi in lichen symbioses: parasites,saprophytes and parasymbionts. journal of the Hat/ori Botanical Laboratory52, 357-366.

Hawksworth, D. L. (1982 b). Co-evolution and the detection of ancestry inlichens. journal of the Hat/ori Botanical Laboratory 52, 323-329.

Hawksworth, D. L. (1985). Problems and prospects in the systematics of theAscomycotina. Proceedings of the Indian Academy of Sciences, Plant Sciences94, 319-339.

Hawksworth, D. L. (1986). The natural history of Slapton Ley Nature ReserveXVII. Additions to and changes in the fungi (including the lichens). FieldStudies 6, 365-382.

Hawksworth, D. L. (1987). The evolution and adaptation of sexualreproductive structures in the Ascomycotina. In Evolutionary Biology of theFungi (ed. A D. Rayner, C. M. Brasier 8< D. Moore), pp. 179-189.Cambridge University Press: Cambridge, U.K.

Hawksworth, D. L. (1988 a). The variety of fungal-algal symbioses, theirevolutionary significance, and the nature of lichens. Botanical journal of theLinnean Society 96, 3-20.

Hawksworth, D. L. (1988 b). Coevolution of fungi with algae and cyanobacteriain lichen symbioses. In Coevolution of Fungi with Plants and Animals (ed.K. A Pirozynski 8< D. L. Hawksworth), pp. 125-148. Academic Press:London, U.K.

Hawksworth, D. L. (1990). The long-term effects of air pollutants on lichencommunities in Europe and North America. In The Earth in Transition:Patterns and Processes of Biotic Impoverishment (ed. G. M. Woodwell), pp.45-64. Cambridge University Press: New York, USA

Hawksworth, D. L. (1991). Lists of names in current use: a new initiative toaddress a continuing problem. Mycotaxon 40, 445-458.

Presidential address

Hawksworth, D. L. & Bisby, F. A. (1988). Systematics: the keystone ofbiology. In Prospects in Systematics (ed. D. L. Hawksworth), pp. 3-30.

Clarendon Press: Oxford, U.K.Hawksworth, D. L. & Greuter, W. (1989). Report of the first meeting of

a working group on Lists of Names in Current Use. Taxon 38,

142-148.

Hawksworth, D. L. & Mound, L. A. (1991). Biodiversity databases: the crucialsignificance of collections. In Biodiversity of Microorganisms and

Invertebrates and its role in Sustainable Agriculture (ed. D. L. Hawksworth),in press. CAB International: Wallingford, U.K.

Hawksworth, D. L., Sutton, B. C. & Ainsworth, G. C. (1983). Ainsworth &

Bisby's Dictionary of the Fungi. 7th edn. 445 pp. Commonwealth MycologicalInstitute: Kew, U.K.

Henderson, D. M. & Watling, R. (1978). Fungi. In The Island of Mull: a Survey

of its Flora and Environment (ed. A. C. jermy & j. A. Crabbe), pp. 15.1-15.74.

British Museum (Natural History): London, U.K.Hodge, I. (1990). Conflict or consensus over agricultural countryside issues. In

Agriculture in Britain: Changing Pressures and Policies (ed. D. Britton), pp.94-104. CAB International: Wallingford, U.K.

Holdgate. M. W. (1989). Climate Change. Meeting the Challenge. 131 pp.Commonwealth Secretariat: London, u.K.

Holm, L. & Holm, K. (1981). Ascomycetes on Nordic lycopods. Karstenia 21,

57-72.

Horak, E. (1990). Monograph of the New Zealand Hygrophoraceae(Agaricales). New Zealand Journal of Botany 28, 255-309.

Hosagoudar, V. B. & Goos, R. D. (1990). Meliolaceous fungi from the Stateof Kerala, India II. The genus Meliola. Mycotaxon 37, 217-272.

Hulden, L. (1983). Laboulbeniales (ascomycetes) of Finland and adjacent partsof the USS.R. Karstenia 23, 31-136.

Hutchinson, T. c.. Scott, M., Sato, C. & Diran, M. (1987). The effect ofsimulated acid rain on boreal forest floor feather moss and lichen species.In Effect of Atmospheric Pollutants on Forests, Wetlands and Agricultural

Ecosystems (ed. T. C. Hutchinson & K. M. Meema), pp. 411-426. Springer­Verlag: Berlin, Germany.

Innis, M. A., Gelfand, D. H.. Sninsky, ).). & White, T. L eds (1990). PCR

Protocols. A Guide to Methods and Applications. 482 pp. Academic Press: SanDiego, U.s.A.

International Union for the Conservation of Nature and Natural Resources(1987). Centres of Plant Diversity. A Guide and Strategy for their Conservation.

40 pp. International Union for the Conservation of Nature and NaturalResources Threatened Plants Unit: Kew, U.K.

james, P. W. (1978). Lichens. In The Island of Mull: a Survey of its Flora and

Environment (ed. A. C. jermy & ). A. Crabbe), pp. 14.1-14.62. BritishMuseum (Natural History): London, U.K.

jones, D. & Wilson, M. j. (1985). Chemical activity of lichens on mineralsurfaces-a review. International Biodeterioration 21,99-104.

jones, G. N. (1951). On the number of species of plants. Scientific Monthly 72,

289-295.jong, S.-c. (1989). Microbial germ plasm. In Biotic Diversity and Germplasm

Preservation, Global Imperatives (ed. L. Knutson & A. K. Stoner), pp. 241-273.Kluwer Academic: Dordrecht. Netherlands.

Kerry, B. R. (1984). Nematophagous fungi and the regulation of nematodepopulations in soil. Helminthological Abstracts, series B, 53, 1-14.

Keystone Center (1990). Final Consensus Report of the Keystone International

Dialogue Series on Planl Genetic Resources. 39 pp. The Keystone Center:Keystone, Colorado, US.A.

Knutson, L. & Stoner, A. K., eds (1989). Biotic Diversity and Germplasm

Preservation, Global Imperatives. 530 pp. Kluwer Academic: Dordrecht, TheNetherlands.

Kobayasi, Y. & Shimizu, D. (1983). Iconography of Vegelable Wasps and Plant

Worms. 280 pp. Hoikusha Publishing: Osaka, japan.Kohlmeyer, ). & Volkmann-Kohlmeyer, B. (1991). Illustrated key to the

filamentous higher marine fungi. Botanica Manna 34, in press.Korf. R. P. (1991). Discomycete systematics today: a look at some unanswered

questions in a group of unitunicate ascomycetes. Mycosystema 3, in press.Krumbein, W. E., ed. (1983). Microbial Geochemistry. 330 pp. Blackwell

Scientific Publications: Oxford, UX.Lamboy, W. F. (1984). Evolution of flowering plants by fungus-to-host

horizontal gene transfer. Evolutionary Theory 7, 45-51.

Lawrey, j. D. (1984). Biology of Lichenized Fungi. 408 pp. Praeger Publishers:New York, US.A.

654

Lee, S. B. & Taylor, j. W. (1990). Isolation of DNA from fungal mycelia andsingle spores. [n PCR Protocols. A Guide to Methods and Applications (ed.M. A. Innis, D. H. Gelfand, j. j. Sninsky & T. j. White), pp. 282-287.Academic Press: San Diego, US.A.

Lewis, D. H (1987). Evolutionary aspects of mutualistic associations betweenfungi and photosynthetic organisms. In Evolutionary Biology of the Fungi (ed.A. D. M. Rayner, C. M. Brasier & D. Moore), pp. 161-178. CambridgeUniversity Press: Cambridge, U.K.

Lichtwardt. R. W. (1986). The Trichomycetes. Fungal Associates of Arthropods.

343 pp. Springer-Verlag: New York. US.A.Lovelock. j. E. (1988). The Ages of Gaia. 252 pp. Oxford University Press:

Oxford, U.K.Lugo, A. (1988). Diversity of tropical species: questions that elude answers.

Biology International, Special Issue 19, 1-37.

Lundqvist, N. (1972). Nordic Sordariaceae s.lat. Symbolae Botanicae Upsalienses20(1), 1-374.

Lynch, j. M. (1988). The terrestrial environment. In Micro-organisms in Action:

Concepts and Applications in Microbial Ecology (ed. j. M. Lynch & j. E.Hobbie), pp. 103-131. Blackwell Scientific Publications: Oxford, U.K.

McKibben, B. (1990). The End of Nature. 212 pp. Penguin Books:Harrnondsworth, U.K.

McNeely, j. A., Miller, K. R., Reid, W. V., Mittermeier, R. A. & Werner. T. B.(1990). Conserving the World's Biological Diversity. 193 pp. InternationalUnion for Conservation of Nature and Natural Resources: Gland,Switzerland.

Malloch, D. W.. Pirozynski, K. A. & Raven, P. H. (1980). Ecological andevolutionary significance of mycorrhizal symbioses in vascular plants (areview). Proceedings of the National Academy of Sciences, U.S.A. 77,

2113-2118.

Margulis, L. & Lovelock. j. E. (1989). Gaia and geognosy. In Global Ecology.

Towards a Science of the Biosphere (ed. M. B. Rambler, L. Margulis & R.Fester), pp. 1-30. Academic Press: San Diego, US.A.

Martin, G. W. (1951). The numbers of fungi. Proceedings of the Iowa Academy

of Science 58, 175-178.

Mason, E. W. (1940). On specimens, species and names. Transactions of the

British Mycological Society 24, 115-125.

May, R. M. (1988). How many species are there on earth? Science, New York

241, 1441-1449.

Micheli, P. A. (1729). Nova Plantarum Genera. 223 pp. Florence, Italy.Nash, T. H. J[] & Wirth, V., eds (1987). Lichens, bryophytes and air quality.

Bibliotheca Lichenologica 30, 1-297.Nayar, M. P. (1989) [' 1987']. In situ conservation of wild flora resources.

Bulletin of the Bolanical Survey of India 29, 319-333.Nograsek, A. (1990). Ascomyceten auf Gefaj3pflanzen der Polsterseggenrasen

in den Ostalpen. Bibliotheca Mycologica 133, 1-271.Norton, B. G., ed. (1986 a). The Preservation of Species: the Value of Biological

Diversify. 305 "p. Princetown University Press: Princetown, U.s.A.Norton, B. G. (1.986 b). On the inherent danger of undervaluing species. In

Preservalion of Species: the Value of Biological Diversity (ed. B. G. Norton), pp.110--137. Princetown University Press: Princetown, U.s.A.

Orpin, C. G. (1988). Nutrition and biochemistry of anaerobic Chytridio­mycetes. BioSystems 21, 365-370.

Pegler, D. N. (1977). A preliminary agaric flora of East Africa. Kew Bulletin,

additional series 6, 1-615.Pegler, D. N. (1983). Agaric flora of the Lesser Antilles. Kew Bulletin, additional

series 9, 1-668.Pegler, D. N., Spooner, B. M. & Smith, R. I. L. (1980). Higher fungi of

Antarctica, the subantarctic zone and Falkland Islands. Kew Bullelin 35,

499-562.Perry, D. A., Amaranthus, M. P., Borchers, j. G., Borchers, S. L. & Brainerd,

R. E. (1989). Bootstrapping in ecosystems. BioScience 39, 230-237.Petch, T. (1921). Studies in entomogenous fungi. II. The genera Hypocrella and

Aschersonia. Annals of the Royal Botanic Garden, Peradeniya 7, 167-278.Pirozynski, K. A. (1988). Coevolution by horizontal gene transfer: a

speculation on the role of fungi. In Coevolulion of Fungi with Plants and

Animals (ed. K. A. Pirozynski & D. L. Hawksworth), pp. 247-268. AcademicPress: London, U.K.

Pirozynski, K. A. (1991). Galls, flowers, fruits and fungi. In Symbiosis as a

Source of Evolutionary Innovation in Speciation and Morphogenesis (ed. L.Margulis & R. Fester), in press. Massachusetts Institute of TechnologyPress: Cambridge, Mass., U.s.A.

D. L. Hawksworth

Pirozynsh K. A. & Dalpe. Y. (1989). Geological history of the Glomaceaewith particular reference to mycorrhizal symbiosis. Symbiosis 7, 1-36.

Pirozynski, K. A. & Hawksworth, D. L., eds (1988). Coevolution of Fungi with

Plants and Animals. 285 pp. Academic Press: London, U.K.Pirozynski, K. A. & Malloch, D. W. (1975). The origin of land plants: a matter

of mycotrophism. BioSystems 6, 153-164.Pitt, ). I. (1980) [' 1979 'j. The Genus Penicillium and its Teleomorphic States

Eupenicillium and Talaromyces. 634 pp. Academic Press: London, U.K.Price, P. W. (1988). An overview of organismal interactions in ecosystems in

evolutionary and ecological time. Agriculture, Ecosystems and Environment

24, 369-377.Pugh, G. j. F. & Allsopp, D. (1982). Microfungi on Signy Island, South

Orkney Islands. British Antarctic Survey Bulletin 57, 55-67.Rassi, P. & Vaisanen, R., eds (1987). Threatened Animals and Plants in Finland.

82 pp. jalkaisija Ymparisti:iministerii:i: Helsinki, Finland.Raven, P. H. (1988). The cause and impact of deforestation. In Earth '88.

Changing Geographic Perspectives (ed. H. j. de Blij), pp. 212-227. NationalGeographic Society: Washington, D.c., U.s.A.

Rogerson, C. T, Harris, R. C. & Samuels, G. j. (1990). Fungi collected byBasset Maguire and Collaborators in the Guyana Highlands, 1944-1983.Memoirs of the New York Botanical Garden, in press.

Samuels, G. j. (1988). Fungicolous, lichenicolous, and myxomyceticolousspecies of Hypocreopsis, Nectriopsis, Nectria, Peristomialis, and Trichonedria.

Memoirs of the New York Botanical Garden 48, 1-78.Sarbhoy, A. K., Agarwal, D. K. & Varshney, ). L. (1986). Fungi of India

1977-81.274 pp. New Delhi, India: Associated Publishing.Seaward, M. R. D. (1989). Progress in the study of the Yorkshire lichen flora.

Naturalist, Hull 144,31-33.Shaw, D. E. (1984). Microorganisms in Papua New Guinea. Research Bulletin,

Department of Primary Industry, Port Moresby 33, 1-344.Sherwood-Pike, M. A. & Gray, j. (1985). Silurian fungal remains: probable

records of the class Ascomycetes. Lethaia 18, 1-20.

Sims, R. W., Freeman, P. & Hawksworth, D. L., eds (1988). Key Works to the

Fauna and Flora of the British Isles and North-western Europe. 5th edn. 312 pp.Clarendon Press: Oxford, U.K.

Singer, R. (1989). New taxa and new combinations of Agaricales (Diagnosesfungorum novorum agaricalium IV). Fieldiana, Botany, n.s. 21, 1-133.

Singh, A. (1980). Lichenology in Indian Subcontinent 1966-1977. 112 pp.National Botanical Research Institute: Lucknow, India.

Sivanesan, A. & Waller, j. M. (1986). Sugarcane diseases. Phytopathological

Papers 29, 1-88.Smith, A. H., Evenson, V. S. & Mitchell, D. H. (1983). The veiled species of

Hebeloma in the Western United States. 219 pp. University of MichiganPress: Ann Arbor, Michigan, USA.

Smith, D. (1988). Culture and preservation. In Living Resources for Biotechnology.

Filamentous Fungi (ed. D. L. Hawksworth & B. E. Kirsop), pp. 75-99.Cambridge University Press: Cambridge, U.K.

Smith, D. C. & Douglas, A. E. (1987). The Biology of Symbiosis. 302 pp. EdwardArnold: London, U.K.

Smith, R. I. L. (1984). Terrestrial plant biology of the sub-Antarctic andAntarctic. In Antarctic Ecology, vol. 1, (ed. R. M. Laws), pp.61-162.Academic Press: London, U.K.

Sogin, M. L.. Gunderson, j. H., Elwood, H. ]., Alonso, R. A. & Peattie, D. A.(1989). Phylogenetic meaning of the kingdom concept: an unusualribosomal RNA from Giardia lamblia. Science, New York 243, 75-77.

Soule, M. E., ed. (1986). Conservation Biology. The Science of Scarcity

and Diversity. 584 pp. Sinauer Associates: Sunderland, Massachusetts,U.s.A.

Staines, j. F.. McGowan, V. F. & Skerrnan, V. D. B. (1986). World Directory of

Collections of Cultures of Microorganisms. 3rd edition. 678 pp. World DataCenter: Brisbane, Australia.

(Received for publication 31 December 1990)

655

Stork, N. E. (1988). Insect diversity: facts. fiction and speculation. Biological

Journal of the Linnean Society 35, 321-337.Stubblefield. S. P., Taylor, T. N. & Beck, C. B. (1985). Studies in Paleozoic

fungi. IV. Wood-decaying fungi in Callixylon newberryi from the UpperDevonian. American Journal of Botany 72. 1765-1774.

Stubblefield. S. P., Taylor. T N. & Trappe.). M. (1987). Fossil mycorrhizae: acase for symbiosis. Science. New York 237. 59-60.

Subramanian, C. V. (1982). Tropical mycology: future needs and development.Current Science 51. 321-325.

Subramanian. C. V. (1986). The progress and status of mycology in India.Proceedings of the Indian Academy of Sciences, Plant Sciences 96, 379-392.

Sutton, B. C. (1973). Hyphomycetes from Manitoba and Saskatchewan,Canada. Mycological Papers 132, 1-143.

Swinscow, T. D. V. & Krog. H. (1988). Macrolichens of East Africa. 390 pp.British Museum (Natural History): London. U.K.

Taylor. T. N. (1990). Fungal associations in the terrestrial paleoecosystem.Trends in Ecology and Evolution 5. 21-25.

Tehler, A. (1988). A cladistic outline of the Eumycota. Cladistics 4, 227-277.Thiers. H. D. (1984). The secotioid syndrome. Mycologia 76, 1-8.Thomas, C. D. (1990). Fewer species. Nature, London 347. 237.Thomson, j. W. (1990). Lichens in old-growth woodlands. Bulletin of the

Botanical Club of Wisconsin 22, 7-10.

Triebel, D. (1989). Lecideicole Ascomyceten. Eine Revision der obligatlichenicolen Flechten. Bibliotheca Lichenologica 35. 1-278.

U.s. Board on Agriculture (1991). Global Genetic Resources: Agricultural

Imperatives. In Press. National Academy Press: Washington, D.C.. U.s.A.U.s. Congress Office of Technology Assessment (1987). Technologies to

Maintain Biological Diversity. 334 pp. U.S. Government Printing Office:Washington, D.c., U.s.A.

US National Science Board (1989). Loss of Biological Diversity: A Global Crisis

Requiring International Solutions. 19 pp. National Science Foundation:Washington. D.C, U.S.A.

U.s. Strategy Conference on Biological Diversity (1982). Proceedings of the

U.S. Strategy Conference on Biological Diversity November 16-18, 1981. 126pp. Department of State: Washington. D.c., U.s.A.

Watling, R. (1974). Macrofungi in the oak woods of Britain. In The British Oak

(ed. M. G. Morris & F. H. Perring), pp. 222-234. E. W. Classey: Faringdon.U.K.

Watling, R. (1985). The Fungal Flora of Mull- Additions. 31 pp. Royal BotanicGarden: Edinburgh, U.K.

Watson, W. (1953). Census Catalogue of British Lichens. 91 pp. BritishMycological Society: London. U.K.

Wessels, D. C. j. & Schoeman. P. (1988). Mechanisms of weathering ofClarens sandstone by an endolithic lichen. South African Journal of Botany

84. 274-277.White. R. H. (1982). Biosynthesis of methyl chloride in the fungus Phellinus

pomaceus. Archives of Microbiology 132, 100-102.Whittaker, R. H. (1969). New concepts of kingdoms of organisms. Science.

New York 163. 150-160.

Wicklow, D. T & Carroll, G. c., eds (1981). The Fungal Community. Its

Organization and Role in the Ecosystem. 855 pp. Marcel Dekker: New York,u.s.A.

Wilson. E.O., ed. (1988). Biodiversity. 521 pp. National Academy Press:Washington, D.c., U.S.A.

Wilson, E. O. (1989). Threats to biodiversity. Scientific American 261(3),

60-66.

Wolf. E. C. (1987). On the brink of extinction: conserving the diversity of life.Worldwatch Paper 78, 1-54.

Womersley, j. S. (1978). Introduction. In Handbooks of the Flora of Papua NewGuinea, vol. 1, (ed. ]. S. Womersley), pp. xiii-xvi. Melbourne UniversityPress: Melbourne, Australia.