THE IMPACT OF INVASIVE FISH AND INVASIVE RIPARIAN PLANTS ON

THE INVERTEBRATE FAUNA OF THE RONDEGAT RIVER IN

THE CAPE FLORISTIC REGION, SOUTH AFRICA

Steven R. Lowe', Darragh J. Woodford', Dean N. Impsorr' and Jenny A. Dayl

IFreshwater Research Unit, Department of Zoology, University of Cape Town,

Rondebosch 7700, South Africa.

2Scientific Services, Cape Nature, Jonkershoek, Stellenbosch, South Africa.

Corresponding Author: S.Lowe. e-mail: slowe@botzoo.uct.ac.za

Keywords: invasive species; bass; biotope; trophic response; invertebrateassemblages.

The current paper is presented in partial fulfilment for the degree ofM.Sc.

Percy FitzPatrick InstituteUniversity of Cape Town

Rondebosch 7700South Africa

The copyright of this thesis rests with the University of Cape Town. No

quotation from it or information derived from it is to be published

without full acknowledgement of the source. The thesis is to be used

for private study or non-commercial research purposes only.

Univers

ity of

Cap

e Tow

n

ABSTRACT

1. The freshwater biota of the Cape Floristic Region of South Africa is characterised

by high levels of endemism. Invasive plants and fish are widespread in the region and

represent major threats to indigenous communities. We investigated the impact of

invasive smallmouth bass (Micropterus dolomieu) and black wattle (Acacia mearnsii)

on macroinvertebrate assemblages in a cobble-bed foothill river within the Region.

2. Eight sites were sampled corresponding to four invasion conditions: no invasion;

invasive trees only; invasive fish only; invasive trees and invasive fish. These sites

represented two predation regimes: Sites with many indigenous fish and no bass; sites

with bass and no indigenous fish. Invertebrates were collected from 7 sampling

occasions during spring/summer seasons from September 2003 to January 2005 and

identified to family or genus, assigned to functional feeding groups and biomass

measured. Results were analysed by multivariate analyses of similarity.

3. Invertebrate assemblages clustered into three distinct biotopes: sand, cobble and

marginal vegetation. The abundance or biomass of assemblages within sand were

insensitive to invasion whereas assemblages from marginal vegetation were altered by

the presence of bass alone. Invertebrate assemblages in cobble were affected by the

presence of bass or black wattle or both. The process by which invasive trees

influence invertebrate assemblages is unclear. Cironomidae larvae were greatly

increased in the presence of bass and Simuliidae, Baetidae and most large invertebrate

predators, such as the Odonata, were moderately increased in the presence of bass.

Most other grazing and algae-consuming invertebrates, such as the Heptageniidae and

Elmidae were reduced at bass-invaded sites.

4. Analysis of fish gut contents revealed a preponderance of Chironomidae and

Simuliidae larvae in the diet of the indigenous fish, whereas a wide variety of prey,

particularly the Ephemeroptera, featured in the diet of smallmouth bass. We propose

that established populations of bass in the Rondegat River do not exert a predatory

control over their invertebrate prey whereas indigenous fish do. Bass may alter

invertebrate assemblage structure by removing the key fish predators from the

indigenous freshwater community, causing predatory release on benthic dipteran

larvae and possibly the Baetidae, with subsequent trophic effects throughout the

invertebrate assemblage.

1

INTRODUCTION

Endemism and the freshwater fauna of The Cape Floristic Region

The Cape Floristic Region (CFR) is one of the world's most diverse and endangered

bioregions (CEPF/CI 2002). The exceptional biodiversity of the CFR is under

increasing threat from habitat destruction and fragmentation by agricultural and urban

development, invasion by introduced alien species and the potential effects of global

warming. The freshwater ichthyofauna of the CFR is relatively species poor but

represents a hotspot of endemism, with 16 of the 19 currently described indigenous

species being endemic (Impson et al., 2002). Fifteen of the indigenous species are

listed as threatened, nine of these being considered endangered or critically

endangered (Baillie and Groombridge 1996).

As is the case with the freshwater fish, the freshwater invertebrate biota of the CFR is

less species rich and less intensely studied than the terrestrial floral component but

contains equivalent high levels of endemism: approximately two-thirds of the

freshwater invertebrate species of the CFR are endemic to it and represent one-third

of South Africa's freshwater invertebrate species (Wishart and Day, 2002). Many of

the species are Gondwanan relicts that have persisted in a relatively unchanged

geological and climatic landscape for more than 200 million years (Stuckenberg,

1962).

Invasive species in the CFR

One of the greatest threats to the biodiversity of the CFR is the spread of invasive

species. Invasion by introduced plants currently affects 8% of the surface area of

South Africa and 29% of the Western Cape (the province that encompasses the

majority of the CFR) is invaded by invasive plant species (Versveld et al., 1998). The

riparian zones are susceptible to invasion by dense stands of alien plants and it is

estimated that the area of invaded riparian habitat will double in the next twenty years

(Versveld et al., 1998). Rivers are effective corridors for invasion by plants due to the

transport of seeds by water, frequent disturbance (flooding and changing seasonal

water level), constant moisture and frequently a lack of a light-competing riparian

canopy (Henderson & Wells, 1986; MacDonald and Richardson, 1986). In the

Western Cape, the primary riparian invasive plant is Acacia mearnsii, with other

2

species of Acacia, Prosopis and Sesbania also invading extensive areas of riparian

habitat (Versve1d et al., 1998).

Impacts of invasive riparian plants

In addition to the well documented reduction in stream flow due to greater water

consumption by alien plants than by many indigenous plants (e.g. Versve1d et al.,

1998; Davies and Day, 1998), other dramatic changes may result from the invasion of

riparian habitats. Overshading by taller, faster-growing and more rapidly-recruiting

invasive plants may result in the loss of the indigenous riparian community. Some

invasive trees, such as A. mearnsii, lack a dense root system and may be responsible

for the loss of marginal root mats associated with low-cover indigenous riparian

vegetation, thereby increasing erosion (Rowntree, 1991; Ractliffe et al., 2003).

Invasive vegetation may increase the incidence of debris dams, features typical of

rivers with large woody plants, which restrict instream flow and typically cause

upstream channel widening (Rowntree, 1991). The nature of change will depend on

the particular biological, geophysical and hydrological characteristics of the river

(Ractliffe et al., 2003), making the impacts of invasive vegetation on a river

ecosystem difficult to predict beyond the local level.

Invasive plants and freshwater invertebrates

The replacement of indigenous vegetation with invasive plants may have diverse

effects on the freshwater invertebrate community: the loss of species due to alteration

of the marginal habitat required for specialised life cycles; a change in the

invertebrate assemblage due to hydrological changes such as altered channel shape or

reduced flow (Ractliffe et al., 2003, King & Schael 2001). Increased siltation due to

increased bank and/or bed erosion may smother the natural benthic substratum and

alter rates of leaf litter decomposition and algal growth.(Martin & Neely, 2001;

Ractliffe et al., 2003; Pusey & Arthington, 2003). Increased shading and leaf-litter

input associated with invasive trees (Le Maitre et al., 1996) may shift the river from

an autochthotrophic to an allochthotrophic system and consequently alter the

invertebrate species composition (Feminella et al., 1989). In addition to quantity, the

timing of the allochthonous input and its chemical properties differ greatly between

invasive acacia species and fynbos (King 1987) and may affect the diversity and

abundance of invertebrate taxa (King 1987, Duggan et al., 2002).

3

Smallmouth bass, Micropterus Dolomieu, in the CFR

The impacts of alien invasive fish on South African rivers are poorly documented.

Impson et al., (2002) noted the presence of 16 species of introduced fish in the CFR

with smallmouth bass (Micropterus dolomieu) being one of the most successful

invaders. M dolomieu was first introduced into the Western Cape in 1937 and to the

Olifants River in 1943 (Harrison, 1953). Since then, M dolomieu has become

established in all the major river systems in the Western Cape (Bruton & de Moor,

1988) so that indigenous fishes are now largely confined to smaller tributaries and

headwaters, often above waterfalls that prevent the spread of invasive fishes (Gaiger

et al., 1980). M dolomieu has been implicated in the decline of six endemic species in

the Olifants River (Bruton and de Moor, 1988) and several observations and studies

have noted the lack of co-occurrence between bass and indigenous fishes (Harrison,

1953; Christie, 2002; Shelton, 2003; Woodford, 2005). To date, no studies have

investigated ecosystem-wide or multi-trophic-Ievel impacts of M dolomieu in South

Africa.

The potential for ecosystem-wide impacts of invasive fish

Experimental and field studies in New Zealand (on trout) and the USA (on bass

species) have shown that invasive fish can exert a top-down impact on river

ecosystems. These impacts are often mediated by changes in the abundance,

composition or behaviour of grazing invertebrates (McIntosh & Townsend, 1994;

Peacor & Werner, 2000) and fish (Power & Matthews, 1983; Power et aI., 1985). The

effects may translate to a change in primary production by algae in the river and

altered nutrient turnover (Power 1992a,b; Flecker & Townsend 1994. The community

or ecosystem-wide impact of invasive fishes is currently difficult to predict due to the

paucity of studies undertaken and the range of systems and of fish species studied.

The context of the study

The Table Mountain Fund (TMF) was created to implement projects identified by The

Cape Action for People and the Environment (CAPE). The Rondegat River, a

tributary of the Olifants River, was identified as a priority site for rehabilitation due to

the threat posed by M dolomieu, which had invaded lower reaches of the river. This

study provides data to inform the TMF of the impacts of alien fish (M dolomieu) and

vegetation (particularly A. mearnsii) on the invertebrate fauna of the Rondegat River

4

in conjunction with a complementary report (Woodford, 2005) on the impacts of M

dolomieu on indigenous fishes.

Purpose of the study

This study investigated whether invasive fish or invasive vegetation influence the

structure of the invertebrate community within the Rondegat River. The focus was on

characterising any patterns of impacts due to invasive species and thereafter to define

some of the processes by which these may be caused.

The impact of invasive fish on river biota, particularly on indigenous fish species,

provides the context of the study. By describing responses, if any, of the invertebrate

community to invasion, information will be provided that will contribute to the

understanding of ecosystem-wide impacts of riparian invasions in the Cape Floristic

Region.

METHODS

Site description

The Rondegat River (32°24'S; 19°05'E) has its source in the Cedarberg mountains at

an elevation of 1000 metres and flows in a north-westerly direction, over a

predominantly Table Mountain Sandstone substratum, for 25 km, until it joins the

Olifants River at Clanwilliam Dam (Figure 1). The catchment is approximately 111

km2 in area and receives 711 mm annual average rainfall, of which the majority falls

in winter (June-August), February being the driest month (Mannicon, 1998). The river

flows through pristine fynbos in its upper reaches, then through a catchment featuring

citrus plantations, two campsites, a forestry station, cattle pasture, areas of dense

infestation by alien trees (mainly A. mearnsii and, to a lesser extent, A. melanoxylon)

and several artificial weirs and water-abstraction points. A natural waterfall about 18

km from the source acts as a barrier to the upstream invasion of M dolomieu and

appears to be an important factor in defining the nature of the fish populations, with

large specimens of the Clanwilliam yellowfish (Labeobarbus capensis) the only

downstream representatives of the six species of indigenous fish found in the river

(Woodford, 2005).

5

Collection sites and dates

Eight sites were chosen along the river (Figure 1) as duplicates of four invasion

conditions (invasion status, IS1-4. IS1: no invasion; IS2: invasive plants only; IS3:

invasive fish only; IS4: invasive plants and fish). Some characteristics of each site are

summarised in Table 1. At sites 3-7 the small flood plain, approximately 150 m wide,

has been converted to cattle pasture. At sites 6 and 7 cattle frequently cross the river.

These sites (IS3), which were largely cleared of invasive trees by early 1990, are

characterised by a narrow margin of indigenous riparian vegetation with some small

recruits ofA. mearnsii.

Sampling was conducted over two spring/summer seasons. In total seven invertebrate

collections were made: September 2003 and October 2003 and February 2004 and

April 2004 represent year 1. October 2004 and November 2004 and January 2005

represent year 2. After the first year of sampling, site 8ii was chosen upstream of a

nearby extraction weir, which almost eliminated flow from site 8i that summer.

No flow measurements were made on the Rondegat River. However, data from a flow

meter (EIH006, DWAF hydrological services) on the Jan Dissels River, which runs

parallel to the Rondegat in an adjacent valley, and which usually receives rainfall at

the same time, was used to indicate relative flow rates on the Rondegat. Figure 2

shows the average daily flow rate for each month on the Jan Dissels River. The

average rainfall for August 2003 and 2004 was similar but the rainfall for September

in 2004 was much reduced compared to the previous year. Possibly of more

importance to the river ecosystem however, were two floods in late August and early

September 2003 which were much larger than any floods in the following year. Sitel

(lSI) and site 3 (IS2) were lacking in sand habitat during year 1, possibly as a result

of scouring by the floods. Therefore, data on sand for IS1 (pristine) and IS2 (invasive

vegetation) from year 1 are based on samples from only site 2 and site 4 respectively.

Collections from cobble, sand and marginal vegetation were made from site 6 (IS3)

starting in April 2004, therefore data for IS3 (invasive fish) for September and

October 2003 are from site 7 only.

Temperature, conductivity and pH were recorded at each site on each collection date

between 10:00 and 16:00 hours. These parameters were not measured in November

2004 or January 2005. The temperature recorded in riffles from sites 1-8 along the

river typically did not exceed a difference of 3°C during any sampling occasion with

the exception of two outstanding recordings in October 2003 and one much cooler

6

recording in September 2003. The variation in pH at different sample sites was less

than 1.0 during any sampling occasion. However, conductivity varied by an average

of 150% from site 1 to site 8 from the same sampling dates.

Shading was estimated at each site by assuming a virtual arc transversing the river

from one bank to the other. From the center of the river, the percentage of open sky

versus vegetation, river banks and rocks on the arc was estimated.

Invertebrate collection and identification

Invertebrates were collected separately from sand, marginal vegetation and cobble, if

present, at each site, using a kick-net. Each of the three habitats was sampled for two

minutes or until the entire available habitat had been sampled within a 20 m stretch of

river. All in-current cobble biotopes in at least 15 cm of water were sampled and

pooled. Habitats in pools were not sampled.

Invertebrates were preserved immediately in 5% formalin and transferred to 70%

ethanol within 48 h of collection for subsequent identification and counting using a

dissecting microscope. Organisms were identified to a taxonomic level suitable for

classification into functional feeding groups (FFG) as defined by Schael and King

(2005, in prep)(Table 2), with the exception of the Chironomidae (Diptera). Baetidae

(Ephemeroptera) from various samples were identified to genus and most of these

were classified as type 1 deposit feeders (DFl). Therefore, in the analysis of FFGs,

Baetidae are either included as DFl, or removed from the analysis as stipulated.

The following texts were used for identification: Day, Harrison and de Moor, 2002;

de Moor, Day and de Moor, 2003a,b.

Biomass

Mean biomass values were measured for all common taxa (those contributing to

>0.5% total abundance). For each taxon, between five and 300 individuals were

selected, depending on the numbers available and body size, from samples collected

in November 2003 and 2004. The samples were dried in an oven at 40°C for 48 hand

weighed to 0.1 mg accuracy.

7

Fish stomach analysis (by D. Woodford)

Fish were caught in seine or fyke nets or by electrofishing in season I (09/2003 ­

04/2004). Smaller fish «10 em) were preserved in 10% formalin. Stomachs from

larger fish were removed immediately and injected with 10% formalin. Stomach

contents were removed and separated into major food item groups: invertebrates, fish,

detritus, filamentous algae and other plant material. These were then placed into a

glass vial containing 70% ethanol and the volume estimated according to the

following formula:

v = (x.100·I )IIr h

where: v = volume, r = radius of the vial base, x = estimated gut content cover of vial

base, h = the height of food component in the vial.

The invertebrate component was then further identified to order or family depending

on the level of digestion of the prey items.

Data analysis

Data were entered into the software package PRIMER (Clarke and Gorley, 2001) and

analysed using Multi Dimensional Scaling ordination (MDS) and CLUSTER analyses

to detect patterns of relative (dis)similarity between samples. Bray-Curtis similarity

was used for all tests and data were standardised to account for variation in the

amount of substratum sampled at each site and between habitats (cobble, sand and

marginal vegetation). ANOSIM (analysis of similarity) was performed on the

similarity matrices generated in PRIMER and differences between specific pairs of

samples compared (e.g. invertebrates in sand from invaded status I compared to those

from sand at invaded status 4). A 95% confidence interval was chosen in order to

accept (p>0.05) or reject (p<0.05) the null hypothesis (Ro) that the mean and variance

of two samples are not different. Abundance data were fourth-root transformed, in

order to give weighting to rarer taxa, and all taxa included in the analysis unless stated

otherwise. Biomass data were fourth-root transformed (unless otherwise stated), and

only those organisms contributing to >0.5% of total biomass within each habitat were

included in the analyses.

Samples that were statistically dissimilar (as determined by ANOSIM) were then

subjected to SIMPER analysis in order to determine the degree of dissimilarity and to

identify which taxa contributed to the dissimilarity.

8

The potential influence of environmental variables was investigated using the

following procedure: conductivity (IlS em"), temperature (Qq, pH, shading (% cover)

and flow (nr's") were entered into a Draftsman's Plot (PRIMER) and transformed to

increase linearity and reduce skewness. These variables were then used, in

conjunction with the similarity matrix generated for the corresponding invertebrate

sample data, in the BIO-ENV analysis procedure (PRIMER). Dissimilarities,

calculated by Normalised Euclidean distance and Spearman's Ranking, were used to

provide a correlation between combinations of environmental variables and the

invertebrate data. The association between the grouping of samples and

environmental factors was then compared and overlaid on MDS plots.

RESULTS

Invertebrate diversity in the Rondegat River

Appendix 1 lists all taxa identified from the Rondegat River. For each year, the

average abundance and standard deviation of taxa in each sample from sand, marginal

vegetation and cobble is given. Appendix 2 displays the average abundances over all

sampling occasions for each taxon at each of the eight sites during year 2

(2004/2005).

Environmental influence

The five environmental factors (conductivity, temperature, pH, shading and flow)

were not closely linked to each other, but the most closely correlated were (in order of

correlation): temperature and flow; pH and shade; conductivity and flow (correlation

= -0.599,0.483, -0.437 respectively). The environmental factors that best explained

the distribution of the collected invertebrates were a combination of conductivity, pH

and flow. However, this combination of variables appeared to be poorly correlated to

the sample data (correlation = 0.166) as confirmed by MDS ordination overlay of the

individual factors.

Similarity and dissimilarity within invertebrate abundance data

Inter-year variation

Within all the three habitat types there was significant difference between the two

sample years (2003/4 and 2004/5, p<O.Ol) for taxon abundance (Table 4a) whether

data were untransformed or fourth-root transformed. Presence/absence transformation

9

of the data showed significant differences between the means of the two years for

sand only (P<0.05). This may be accounted for by the lack of sand substratum at some

sites due to scouring by floods in August/September 2003. Due to these differences,

data were analysed separately for each year.

Habitat differences

Analysis of inter-habitat differences by MDS and cluster dendrograms showed

distinct grouping of samples from cobble, sand and marginal vegetation for both

years. Figures 3 and 4 are two-dimensional representations of the similarity of

samples from habitats representing the four different invasion conditions during year

2 (see Table 1 for details of invasion status). The invertebrate assemblages of the

three habitats were significantly different within year 1 and year 2 in pairwise analysis

of similarity (sand/marginal vegetation; sand/cobble; marginal vegetation/cobble

within each year. p < 0.01 for all tests, ANOSIM, Table 4b). Table 5 shows the

average abundance of taxa per sample and the similarity scores of the taxa that

collectively contributed to >75% of the similarity within each habitat in year 2.

The Baetidae and Chironomidae were ubiquitous and numerous and consistently

contributed the most to the similarity for each habitat. Other taxa characteristic of the

three habitats for both years were the Gomphidae in sand, the Zygoptera, Caenidae,

Veliidae and Athripsodini in marginal vegetation, and Cheumatopsyche,

Leptophlebiidae and Heptageniidae in cobble. The life histories of these taxa are

consistent with the location from which they were sampled (Day et aI, 2002; de Moor

et at., 2003a,b).

Differences between invasion conditions

The MDS ordination of invertebrate samples grouped by habitat and invasion status

indicated that within the habitat clusters there was grouping of samples for different

conditions of invasion (lSl-4) (Figure 3). Table 6a summarises the results of

significant dissimilarities of pairwise ANOSIM analysis between these groups. There

was no significant difference between the sand sites in any of the four invasive

conditions in either year. The invertebrate assemblage in cobble substrata of the

pristine, uninvaded sites (IS1) differed significantly from those in the cobble of the

other three conditions (lS2, IS3 and IS4). In addition, cobble sites invaded by alien

vegetation only (lS2) were significantly different from those with only alien fish

10

(IS3). The invertebrate communities in marginal vegetation were significantly

dissimilar only between uninvaded areas and those invaded only with alien fish (IS1

compared to IS3). All other conditions within the same habitats were not significantly

different. Figure 5 a-e graphically represents pairwise comparisons of the taxa that

cumulatively contribute to >25% of the dissimilarity between samples from year 2

grouped by habitat and invasive status. On each graph, the taxa are ranked from left to

right, with those on the left contributing most to the dissimilarity between the invasion

conditions. Consideration of the biology of each of these taxa can provide an

indication of the processes which may be operating to produce differences between

the invasion conditions.

The same analysis procedure for year 1 revealed largely similar results to those from

year 2. The MDS produced a high stress factor (0.25, 50 iterations) and less distinct

groupings than those for year 2. Samples from sand showed no visible clustering for

different invasion conditions (as for year 2) and were not statistically dissimilar from

each other (ANOSIM). Invertebrate communities in cobble from pristine sites were

significantly dissimilar to those in cobble from sites invaded by alien fish alone

(cobble IS3) and from those sites invaded by both alien fish and alien vegetation

(cobble IS4). A summary of these results is provided in table 6b. In contrast to year 2,

however, invertebrate lSI cobble samples (uninvaded sites) were not dissimilar to IS2

samples (alien plant invaded sites). Also in contrast to year 2, marginal vegetation

samples from sites invaded by alien fish alone were dissimilar to sites with both alien

fish and vegetation in year I (IS3 compared to IS4). All other sample groups from the

same habitats were not significantly dissimilar when compared between invasion

conditions.

As implied by the discrete separation of samples from sand and cobble in year 2

(Figure 4), analysis of similarity between all sample groups from sand compared to

those from cobble for the four invasion conditions are significantly dissimilar

(p<0.05). For year I however, all sand samples (sand ISl-4) are significantly

dissimilar to cobble samples from IS1 and IS2 groups, but not from IS3 and IS4

groups (with the exception of sand lSI to cobble IS3). These data imply increased

sedimentation and a more embedded cobble substratum at downstream sites.

11

Functional Feeding Groups (FFGs)

Taxa were aggregated into FFGs (see Table 2 for FFG definitions and abbreviations

and appendix 1 for the FFG of individual taxa) and analysed by the same process as

described above for unaggregated taxa. This broader-scale analysis of taxonomic

grouping was used in order to characterise particular life-history traits of taxa that

may be affected by the changing conditions along the river. The number of

individuals in each FFG from each sample was square-root transformed and revealed

clustering into the three distinct habitat types, comparable with unaggregated data.

With the exception of Grazer 2 (mostly Heptageniidae), the abundance of all FFG

categories per collection was greater in year 2 than in year 1. Notably, the number of

individuals per sample from the predator 2 (P2) group was over three times greater in

year 2 than in year 1. Clustering by invasion status was also similar to that for

unaggregated taxa: in year 2, samples from cobble at pristine sites were significantly

dissimilar (31%) from sites invaded by alien fish alone (p<0.05; r = 0.444). FFGs

contributing most to the dissimilarity were the deposit feeder 1 group (DFl), followed

by the predator 2 group (P2), followed by the filter feeders (FF). These groups vary

from the functional feeding status of the individual taxa that contributed to the

dissimilarity between pristine (lSI) and alien fish only (lS3) groups with

unaggregated data as shown in figure 5b. (The FFG categories of the individual taxa

contributing to ISl/lS3 dissimilarity for unaggregated data are (not including

chironomids): DF2, followed by P2, followed by grazer 1, followed by scraper 2).

Pristine sites were not significantly dissimilar from sites invaded by alien vegetation

(lS2, p = 0.08) and totally invaded sites (lS4, p = 0.06) despite low p-values, and

therefore warrant further investigation. FFGs from cobble IS2 samples were

significantly dissimilar from cobble IS4 samples (p = 0.04; r = 0.465; 33.1%

dissimilarity) in contrast to unaggregated taxa IS2 samples which differed from

cobble IS3 samples. As with unaggregated data, samples from marginal vegetation

differed significantly only between pristine (lSI) and alien fish only (lS3) invaded

sites (p <0.01; r = 0.464; 35% dissimilarity).

The analysis of square-root-transformed data for FFGs from year 1 shows the same

grouping of sites when compared to the analysis for individual taxon abundances.

Cobble samples from pristine (IS1) sites were dissimilar from fish-only invaded sites

(lS3) (p <0.05, r = 0.425) and fully invaded sites (p <0.01; r = 0.5). Also, samples

12

from marginal vegetation differed significantly only between fish invaded (lS3) and

fully invaded sites (lS4) ..

Biomass

The relationship of biomass and diversity between samples was analysed by grouping

samples into each habitat type and then selecting only those taxa that contribute

>0.5% to the total biomass for that habitat. A list of the taxa weighed can be seen in

Table 3. Table 7 summarises the analysis of the biomass of samples from the four

different invasion statuses. The results show related trends of dissimilarity between

groups when compared to the similar analysis performed with taxa abundance (shown

in Figure Sa and e). Samples from sand showed no significant dissimilarity between

the four invasion conditions and showed the same similarity between all sand sites

and cobble IS3 and IS4 sites in year 1 as for abundance data. Samples from marginal

vegetation were significantly dissimilar only between pristine (IS1) and alien fish

(lS3) sites and samples from cobble were dissimilar when compared between lSI and

IS2, IS1 and IS3 and IS2 and IS3 sites (not between IS1 and IS4 as for abundance).

Despite these similar trends, the taxa contributing towards the differences in biomass

were considerably different from those contributing to the dissimilarity of taxa

abundance for the same groups. Notably, the taxa contributing most to the

dissimilarity in biomass were large-bodied predators such as the Megaloptera and

Odonata.

Biomass was compared between the three habitats and subsequently within the

habitats for the four invasion conditions in year 2 using ANOYA and Tukey's tests.

These analyses were undertaken to test whether univariate analysis of untransformed

data can detect similar patterns to those observed by the multivariate Bray-Curtis

similarity method employed by PRIMER. Pairwise analysis of cobble, marginal

vegetation and sand revealed that only cobble and sand differed significantly (f =

14.7, p = 0.018, ANOYA). Subsequent analysis revealed that the only significant

differences between sites within any of the habitats were samples from cobble IS1

sites and cobble IS3 sites (p <0.05, df = 46, Tukey HSD). Figure 7 shows the average

biomass per sample (and SD) for cobble, marginal vegetation and sand from year 2 at

each site along the river.

13

Biomass of FFGs

The biomass of FFGs was assessed in order to investigate whether the changes in the

invertebrate assemblages described above are characterised by groups of taxa with

particular feeding traits. The biomass of taxa from each sample was aggregated

according to their assigned FFG (see appendix I for FFG of individual taxa). FFGs

utilising a similar food resource were aggregated: the deposit feeder 2 group and

scraper 2 group were aggregated, also, the grazer 2 and scraper 1 groups were

aggregated. Figure 8 a-d represents the average biomass and standard deviation of

each FFG per sample from each habitat. The predator 2 group is displayed separately

due to the much larger biomass of this group. The results of these analyses are

summarised in Table 8. No differences were detected between samples from different

invasion conditions from sand or marginal vegetation. Significant differences were

detected between cobble samples from pristine sites (lSI) and sites invaded by alien

vegetation alone (lS2) and sites invaded by alien fish alone (lS3). Cobble samples

from IS2 sites were also significantly different from IS3 site cobble samples. These

differences are accounted for mostly by the predator 2 and predator 1 groups. The

grazer2/scraperl group was characteristic of the dissimilarity between pristine (IS1)

and invasive vegetation-only (lS2) groups and deposit feeder 1 (DFl, primarily

Baetidae) accounted for differences between alien vegetation-only (lS2) and alien

fish-only (lS3) groups.

The removal of either the predators (PI and P2) or the herbivores (all other groups)

from the analysis did not alter the significance of the dissimilarity between pristine

sites and the IS2 and IS3 sites. However, the sites invaded by alien vegetation alone

(lS2) showed no dissimilarity to alien fish-only invaded sites (lS3) upon removal of

predators from the analysis, but retained the dissimilarity upon removal of herbivores.

Removal of herbivores from the analysis of the FFG biomass revealed a significant

dissimilarity between samples from marginal vegetation where the river was

uninvaded (lSI) compared to areas invaded by alien fish alone (lS3).

Fish diet (collected and processed by D Woodford).

An understanding of the feeding preferences of the fish that characterise different

parts of the river is important in order to appreciate how an invasive fish may exert an

impact on the invertebrate assemblages. Gut contents were analysed from M

14

dolomieu (n == 32) and four indigenous fish species: Labeobarbus capensis, n == 30;

Pseudobarbus phlegethon, n == 30; Barbus calidus, n == 30 and Austroglanis gilli ee 32

(Figure 9 a-e). Invertebrates composed a minimum of 60% of the gut content volume

of all fish species (Woodford, 2005). Identification of the invertebrate taxa from gut

contents yielded results consistent with the feeding strategies of the fish species (see

Woodford 2005 for details): the most notable differences between the indigenous fish

species and the invasive M dolomieu, was the large number of dipteran larvae

(Chironomidae and Simuliidae) in the gut contents of indigenous fish, in contrast to

the guts of M dolomieu, which contained mostly Ephemeroptera, particularly the

Baetidae. Other notable differences between the indigenous and invasive fish were

trichopteran larvae in the gut contents ofP. phlegethon and A. gilli and Odonata in the

diet ofM dolomieu.

The dipteran larvae (Chironomidae and Simuliidae) and Baetidae are the most

abundant taxa in the diet of the indigenous fish and M dolomieu respectively. The

biomass and calorific content of each prey taxa are the most important factors

determining the contribution to the diet of the fish. The numerical contribution of

Odonata compared to Baetidae in the diet of M. dolomieu is only 7.5%. However, if

those Odonata are large Gomphidae, the total biomass of Gomphidae will be 450%

greater than that of the Baetidae.

DISCUSSION

Heterogeneity is a striking characteristic of freshwater biota (Palmer and Poff, 1997;

Li et al., 2001) but the type of heterogeneity observed will depend upon the scale of

the observation, and the spatial arrangement and quantity of resources and consumers

(McIntosh et a1., 2004). The scale of the sampling technique and the level of

taxonomic identification used in this study can detect patterns of invertebrate

assemblages characteristic of the three habitat types, or biotopes, within the river:

sand, marginal vegetation and cobble. The ability to detect these trends was consistent

for similarities in abundance and biomass and for different transformations of the

data. Patterns of invertebrate species composition that coincide with different invasion

conditions can also be detected along the Rondegat River. However, the taxa

contributing to these dissimilarities vary depending on the type of data used

(unaggregated abundance of taxa, FFGs or biomass). These data imply that the causes

15

of the dissimilarity at sites invaded by alien species may have impacts at multiple

levels within the invertebrate assemblages.

Inferring causality to observed patterns is difficult even with experimental

manipulation (such as fish or invertebrate exclusion zones) or closely comparable

rivers (if, indeed, such suitable 'control' reference sites can be applied), neither of

which were included in the present study. The spatial separation of sites with different

invasion conditions along the river is problematic for formulating conclusions based

on differences between samples from these sites. However, contrary to previous

notions of longitudinal river zoning, extensive work recently undertaken on macro­

invertebrate distributions within rivers in the Western Cape, has provided strong

evidence that the catchment (for the current study: the Olifants River) and the bedrock

substratum (Table Mountain sandstone) are stronger influences on invertebrate

assemblages than the longitudinal zone (King and Schae1, 2001). Upland rivers in the

Western Cape are known to exhibit high variability, but differentiation within upland

sites into mountain streams and foothill-cobble beds is not apparent (Dallas, 2002). In

the current study, comparison of temperature, pH, conductivity and coarse measures

of shade and flow with the invertebrate data set from the Rondegat River, implies that

there were factors that exerted a stronger influence in the grouping of the invertebrate

samples other than the type and method of environmental factors measured.

The potential influence of fish predation on invertebrate assemblages

By comparing the gut contents of fish with the distribution of the prey items found at

each site (see appendix 2) it seems likely that M dolomieu does not constrain the

population size of its invertebrate prey items: Baetidae and Odonata were generally

more numerous at lower sites, despite featuring proportionately higher in the diets of

Midolomieu than of the indigenous fish found upstream. In contrast, the main prey

items of the indigenous fish, the Chironomidae and Simulidae, are less numerous at

the upper sites and it is possible that the numerically superior indigenous fish exert a

top-down control of their prey items. In the absence experimental studies and of

biomass and energy assimilation measurements for fish at different sites, it is not

possible to conclude if river reaches populated by indigenous fish are subjected to

greater top-down control. It is the opinion of the author that the fish biomass in the

Rondegat River is greater in the absence of invasive fish. This is in contrast to studies

on invasive trout, which generally indicate an increased predation pressure in the

16

invaded as opposed to the native state (Flecker and Townsend, 1994; Simon and

Townsend, 2003). Trout are visual diurnal predators (as are bass) that typically

achieve a higher biomass than the indigenous fish they displace. The impacts of

increased predation pressure by trout on invertebrates have been shown to have a

number of potential mechanisms: direct control of prey by consumption, shifts from

daytime to nocturnal drift of mayflies in the water column (McIntosh et al., 2002) and

reduced total foraging time of invertebrate grazers (McIntosh and Townsend 1995).

Data on temporal changes of fish feeding preferences and experimental methods to

quantify the predatory control exerted by the fish species on invertebrate prey, will

greatly enhance our understanding of the community-level effects of introduced fish

species.

Patterns of invertebrate responses along different invasion conditions:

The cobble biotope

The invertebrate assemblage within the cobble biotope consistently possessed the

highest biomass and species diversity of the biotopes sampled, as has been shown for

other studies (Dallas 2002). Cobble samples also demonstrated the most frequent

differences between the four invasion conditions, implying that cobble is the most

sensitive of the biotopes to invasion. Cobble samples from pristine areas of the river

are significantly different from areas invaded by alien fish alone, whether analysed by

univariate statistics, or multivariate measures of similarity based on the abundance or

biomass of taxa. In the presence of M dolomieu, the total invertebrate biomass is

significantly higher. Notably, there is a greater number and biomass of predatory

invertebrates in the alien fish-only invaded areas and there are more algae-consuming

scrapers (Sl), grazers (G2) and deposit feeders (DF2) within the pristine sites (see

Figures 5b and 8d).

Significant dissimilarity between the biomass of samples from pristine sites and sites

invaded by alien vegetation or alien fish is retained whether analysed for predators or

herbivores only. This implies that the invertebrate assemblage structure of sites

invaded by alien fish or vegetation alone is altered at multiple trophic levels compared

to uninvaded sites. In contrast, invertebrate predator composition, rather than the

composition of invertebrate herbivores, is largely responsible for differences between

cobble samples from sites invaded by only alien vegetation compared to areas invaded

only by alien fish.

17

As discussed above, the indigenous fish are likely to exert a greater control of

Chironomidae larvae than M doiomieu. Most of the Chironomidae are classified

within the grazer 2 FFG, and an increase in their numbers in the invaded sites, due to

predatory release in the absence of indigenous fish, could result in competitive

exclusion of other algae-eaters. The presence of Ephemeroptera other than the

Baetidae in the diet of M doiomieu, but not in the diet of indigenous fish (Figure 8),

indicates that increased selective predation could also be responsible for the reduction

of the Heptageniidae at sites invaded by alien fish (Figure 5b and c).

The dramatic increase in both small and large invertebrate predators in the presence of

alien fish is coincidental with a large increase in the total number primary consumers.

It is possible that the increased food resource for the invertebrate predators outweighs

the increased risk of predation from M doiomieu. The greater number of Baetidae at

alien fish-invaded sites is difficult to explain considering the high propensity of

Baetidae in the diet ofMdoiomieu. It is possible that bass-invaded sites still represent

a decreased risk of predation to Baetidae, based on fish biomass at different sites.

Increased predation, however, can also result in an unchanged, or even increased

number of Baetidae, due to complex interactions between foraging behaviour and

algal abundance (Diehl et ai., 2000; McIntosh & Taylor, 2004).

The dissimilarity between cobble samples from pristine sites and those from sites

invaded by alien vegetation (IS2 and IS4 sites) is difficult to interpret. The Caenidae

contribute most to the difference between these invasion conditions and are more

numerous at both conditions invaded by alien vegetation. The Caenidae were more

numerous in marginal vegetation than in cobble samples (see appendix 1), however,

the Caenidae are known to feed in silty deposits (de Moor et al., 2003a) and their

increase in cobble samples from IS2 and IS4 conditions could represent increased

sedimentation at these sites due to the increased presence of debris dams and bank

erosion resulting from the presence of alien vegetation (with the exception of site 5,

IS4).

The sand biotope

Sand exhibited the lowest diversity and biomass of the biotopes, consistent with

SASS (South African Scoring System) scoring from other studies (Dallas, 2002). The

18

consistent lack of dissimilarity in samples from sand indicates that the organisms

inhabiting this substratum are resilient to change in the river food web. Sand may act

as a refuge from predation pressure for those organisms adapted to living in it, such as

the burrowing Gomphidae. It is also possible that sand is a lower nutrient, less

heterogenous environment, requiring specialised life histories that make the resident

organisms less vulnerable to competition. Sand was also the only biotope to show

significant differences between collection dates for year 2, for which there are many

possible explanations including emigration and reduced or increased sedimentation

from October 2004 to January 2005.

The marginal vegetation biotope

The invertebrate communities in marginal vegetation showed fewer differences

between invasion conditions than for cobble. There were significant differences only

between pristine sites and sites invaded by alien fish alone in year 2 and between

invasive fish only and both invasive fish and vegetation (lS3 and 4) in year 1. The

taxa contributing to dissimilarity between marginal vegetation samples from pristine

sites compared to those from sites invaded by alien fish alone are consistent with the

proposed predatory control of specific invertebrate taxa for cobble samples (see

Figure 5e): the Chironomidae were far more abundant in the absence of indigenous

fish (at IS3 sites). The Simulidae were also consistently more abundant in the absence

of indigenous fish with the exception of one collection date (average and standard

deviation for lSI and IS3 repectively; 23.5 ± 34.8; 23 ± 14.8). The greater number of

Athripsodes (Trichoptera) at alien fish-only invaded sites confirms the hypothesis that

indigenous fish are exerting a predatory control on their prey.

It was expected that the invertebrate assemblages most affected by the replacement of

indigenous riparian vegetation by invasive trees (as is the case for sites with invasion

status 2 and 4) would be the assemblages residing in the marginal vegetation because

of the direct loss and fragmentation of habitat. Due to the lack of instream marginal

vegetation at sites 8i and ii (lS4), samples could only be collected on two out of four

dates for year 1 (site 8i) and for two samples out of three in year 2 (site 8ii).

However, the other fully invaded site, site 5, still retained patches of indigenous in­

stream riparian vegetation, possible due to the rocky nature of the banks preventing

invasion at these points. It is from this site that most of the marginal vegetation data

for invasion status 4 is derived.

19

The kick-sampling technique (described in the methods) may result in sites with a

small amount of a particular habitat being overestimated in terms of overall diversity

and abundance. This is due to sampling a higher proportion of the total amount of the

habitat. The effect will be more pronounced if the species/area relationship is

logarithmic, particularly when taxa are relatively homogenously distributed. A

species/area plot for marginal vegetation samples in year 2 (PRIMER, data not

shown) revealed that, on average, two and five collections will capture >50% and

>75% of species richness respectively. Invertebrate assemblages from marginal

vegetation show little change compared to cobble assemblages, with marginal

vegetation acting as a refuge. Based on these data, a measure of the abundance of

marginal vegetation may be a reasonableindication of the state of the populations of

resident invertebrate taxa.

Addressing potential sampling bias

In order to address the problem of uneven representation when sampling, a survey

should be conducted to map the physical characteristics of the site and then a

proportion of each habitat sampled consistently between sites. Alternatively, all of a

particular habitat should be sampled in a short stretch of river and the species

abundance adjusted for the area of habitat sampled. Normalising data for sampling

effort is necessary in heterogenous systems if different sites or streams are to be

comparable (Li et al., 2001). Analysis in the PRIMER programme partially addresses

these issues by providing the option to 'standardise' between samples.

Changes in the invertebrate community can also be masked if the level of taxonomic

identification is too coarse to capture changes at a lower taxonomic grouping.

Examples from freshwater and marine benthic systems suggest that, depending on the

questions being investigated, information may not be lost by aggregating species to

higher taxonomic groupings (Clarke and Warwick, 1994; Dallas 2002). Finer

taxonomic identification will be required, however, if the conservation of rare species

is to be addressed.

The Rondegat River appears to be a predator-dominated system with respect to the

biomass of the invertebrate assemblage. Predatory invertebrates, such as the abundant

Odonata within the Rondegat River, could exert a strong influence on primary

consumers and play an important role in structuring the invertebrate community in

20

addition to providing food for higher trophic consumers. Consistent with the findings

of the current report, dragonfly larvae may reflect the physical environment of a river

and have been shown to increase in diversity due to the presence of invasive species

(Stewart and Samways, 1998). Studies have demonstrated trophic cascades mediated

by multiple invertebrate feeding strategies (Flecker and Townsend, 1994; Huryn,

1998; Carlisle & Hawkins, 1998) and have demonstrated the potential for size-related

alteration of predatory invertebrate taxa by introduced fish species, with subsequent

consequences for trophic interactions (Huryn, 1998).

Predatory invertebrates consistently contributed to the differences between sites with

and without invasive fish, as shown in Figure 8 and summarised in Table 7 and

Appendix 2. Further investigation could reveal an important component of the river

ecosystem described in the current report and for similar rivers of the region.

Collectively, our results demonstrate that invasive plants and invasive fish may alter

invertebrate community assemblages. In the absence of experimental controls, the

mechanisms by which the exotic species exert their effects are difficult to asses. It is

also difficult to account for the influence of catchment practices on the pattern of

invertebrate assemblages in the system studied the current report. We propose,

however, that invasive fish cause multiple trophic alterations of macroinvertebrate

assemblages by removing key predators from the indigenous river ecosystem. Further

studies are required to: confirm the findings presented here, to investigate the

possibility of ecosystem-wide consequences of smallmouth bass invasions and to

determine the extent to which the pattern of invertebrate assemblage response persists

throughout the range of invasive smallmouth bass in the CFR.

Acknowledgments

We thank Donni Malherbe, Rika du Plessi and field rangers of Cape Nature for their

help and use of facilities. Also, the Nieuwouldt families at Keurbos and Grootkloof

for use of their land and discussion. Thanks to Angus McNielage and Mark Burman

for laboratory assistance. Geordie Ractliffe, Candice Hill, Sean Marr and Bruce

Paxton of the Freshwater Research Unit, UCT provided helpful discussion and

Colleen Seymore and Tammy Roberts of Zoology department for help with PRIMER.

Dennise Schae1 and Jackie King of FRU provided the FFG classifications. Funding

was provided by the TMF alien fish programme 0NWF SA).

21

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25

I19'00'

lIfOO'

/

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Cedarberg

Wilderness

Area

4

3

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zkm \

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7• Keurbos

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Waterfall

Olifants River

Figure 1 Map of the Rondegat Riverand location of the study sites

9876

2004

543210 11 12 1_1 _

2003

9

3.5 ,----------------------~------­3+-----------------------.-::~-----

2.5 -\-----\-------------------+--\-----­

2-1-----\-----------------1----\-----­

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0.5 -l-------~------------I-------~==~~­O--l----~----,-----.--~~~;::±:~~~~~~~~~~

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Figure 2 Average daily discharge per month of the Jan Dissels River during the study period.(data from Department of Water Affairs and Forestry)

Key:A 0 A 0 .I. 181 • 182181 182 marginal 181 182

cobble vegetationsand

0 184 o 1830 183 e 184 • 184 • 183

Stress: 0.18

Figure 3 MD8 ordination of invertebrate samples grouped by habitat and invasion condition.Year2. 181: no invasion; 182: invasive plants only; 183: invasive fish only; 184: invasive plants and fish.

~-

~~rf

A~

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- -1

,--

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I40

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I80

mv4mv4mv4mv2mv2mv3mv3mv3mv3mv3mv4mv2mv1mv1mv3mv2mv3mv383mv2mv1mv1mv1mv1c2c3c4c2c3c3c3c3c1c1c1c1c1c1c4c2c4c4c4c2c2c4c2c3c184828483848282818281818484818383838182828184

I81

100

MarginalVegetationIS1-4

cobbleIS1-4

sandIS1-4

Figure 4 Dendrogram of year 2 group similarity

Hierarchical clustering of habitats across all invasion conditions Invasion condition1 (IS1) within the cobble habitat ishighlighted

a50

~ 45~ 40lii 35a.~ 30

~ 25E 20~ 15e 10"iV 5

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d5045403530252015105Ot-""UL....J---.-'"""--'--r-..lWWo~,----L.-L--.-"UUL--'---r----'---'--r---'lllll'--'--,

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Figure 5 a - e The average number of individuals for each taxon whichcontribute to >25% cumulative dissimilarity between sample groups (rankedfrom left to right). Comparisons are between significantly dissimilar samplegroups of the same habitat with a different invasion status (181-4): 181: noinvasion; 182: invasive plants only; 183: invasive fish only; 184: invasive plantsand fish.a: cobble 181/182; b: cobble 181/183; c: cobble 181/184; d: cobble 182/183e: marginal vegetation 181/183

200

600

400

~Cobble

o Marginal \eg

lDISand

800

1400

1200

1600

~

'""C<:o'tl~

"8....~ 1000<I>OJ~

~~

..!!l

'":::l"C:;;:"C<:

~....<I>.0E:::l<:

~~~~~~~~~~~~~~~~~#~~~~~~~~~~~~~~~~~~~~~~~~~~ 'O~'O~

Figure 6 Taxa abundances of Functional Feeding Groups within each habitat for each year(see table 2 for FFG definitions)

fA.cobble

lDIm. veg

<>sand

6 7 8

181182 ~I

Invasion status (181-4) 184

Figure 7 Biomass (mean and standard deviation) at each site for cobble, marginal vegetationand sand (year 2)

a b

Cobble Marginal vegetation

0.1 0.1

0.08 0.08

" "~ 0.06 ~0.06

'" '"'"'" ~ 0.04<00.04E .S!a .c

.c 0.020.02

cobble 181 cobble 182 cobble 183 cobble IS4mveg181 mveg 182 mveg IS3 mveg IS4

hvasion Status invasion status

c

0.01

0.0081:';; 0.006

'"<0

~ 0.004:c

0.002

o

SandKey to Figure 8a-c

o Deposit Feeder 1

~ Deposit Feeder 2/scraper 2

~ Filter Feeder

II Grazer 1

• Grazer 2/scraper 1

~ Predator 1

sand 181 sand 132 sand 133 sand 134

d

invasion status

Predator 2 FFGIn each habitat

0.7

0.6

~0.5

<II 0.4<II11l

0.3E.Q.0

0.2

0.1

0

III cobble

om. veg

Dsand

151 152 153

Invasion status

154

Figure 8 a-dAverage biomass of functional feeding groups within each habitat for year 2.Note: different y-axis scales to account for large variation in biomass between FFGs.

A) Labeobarbuscapensls B)Pseudobarb/#l phlegethon

All otherInvertebrates

7.3%

Corixldae26.4%

AU otherinvertebrates

5.5% Trlchoptera6.8%

O1lrononidae80.9%

0) Barbus calidus 0) Austroglants gill/

Terrestrtalinvertebrates

20.9%

Other aquaticinvertebrates

14.2%

SinlIlidae6.7%

Baetldae9.7%

Coleoptere11.2%

Chironorridae37.3%

E)M/cropterus dolom/eu

Otheraquetlcinvertebrates

9.4%

SllllJlldae11.8%

Terrestrialinvertebrates

1.0%

O1irononidee48.1%

Trlchoptera6.7%

TerrestrialInvertebrates

8.4%

Other aquaticInvertebrates

14.4%

Odonata4.4%

OtherEphemeroptera

11.7%

Fish0.3%

Crab2.2%

Baetidae58.6%

Figure 9 a-e The proportional abundances of animal taxa from fish gutsA: Labeobarbus capensis, n =30; B: Pseudobarbus phlegethon, n =30;C:Barbus calidus, n =30; D: Austroglanis gilli =32; D: M. dolomieu n =32

Table 1. Characteristics of each sample site in the Rondegat River. Invasion statusdefinitions (lSl-4)are refered to throughout the text. Minimum and maximum figuresare derived from all sampling occasions.

Site #Invasion status (IS) pH

Average daytime Conductivity Shadeand IS temperature (0C) (IlS em") (%cover)

1 (lSI) - alien fish min: 5.2 min: 14.0 min: 20.520%

- alien vegetation max: 5.8 max: 16.3 max: 51.0

2 (lSI)- alien fish min: 5.3 min: 12.6 min: 21.4

40%- alien vegetation max: 5.9 max: 17.7 max: 52.7

3 (lS2)- alien fish min: 5.5 min: 14.5 min: 31.5

60%+ alien vegetation max: 5.8 max:J8.4 max: 102.0

4 (lS2)- alien fish min: 5.5 min: 14.6 min: 33.2

70%+ alien vegetation max: 6.0 max: 18.5 max: 103.0

5 (lS4)+ alien fish min: 5.9 min: 15.2 min: 35.5

70%+ alien vegetation max: 6.2 max: 20.6 max: 111.0

6 (lS3)+ alien fish min: 5.8 min: 15.5 min: 37.3 20%- alien vegetation max: 6.1 max: 19.0 max: 118.8

7 (lS3)+ alien fish min: 5.8 min: 16.0 min: 38.9

30%- alien vegetation max: 6.1 max: 22.0 max: 118.8

8i, ii + alien fish min: 6.1 min: 17.5 min: 34.790%

(lS4) + alien vegetation max: 6.3 max: 18.0 max: 147.7

Table 2 Functional feeding group definitions, derived from Schae1 and King (2005).

FFG (code) Feeding Mode Dominant Food TypePredator I (PI) Predator - feeds on organisms by active Micro-organisms - bacteria to

predation zooplankton, zoobenthos, etc.Predator 2 (P2) Insects to small vertebratesFilter feeder Filter by collecting small particles of Micro-organisms: bacteria - algae -(FF) food suspended in the water column zooplankton and particulate organic

matterDeposit feeder I Collecting/gathering deposited organic Detritus (VFPOM and FPOM) only(DFI) material from the substratumDeposit feeder 2 Algae and detritus in similar amounts(DF2) dependent on availabilityShredder Shredder - feeds by fragmenting leaves Vegetation. Usually allochthonous(shred) and large pieces of plant material terrestrial materialScraper I (S I) Scraper - scrapes thin film of micro- Algae (and other micro-organisms)

organisms off substrataScraper 2 (S2) Algae and detritusGrazer I (GI) Grazer - feeds on whole living plants, Living aquatic plants

leaves and stems. Algal mats can beincluded where scraping is not employedas mechanism for collection.

Grazer 2 (G2) AlgaeOmnivore (Om) Feeds on anything and everything Everything

available; mainly reserved forscavengers such as crabs.

Table 3 Taxa weighed for biomass measurements

Taxa Number·of Individuals Masslindivldual (g)weighed

Elmidae adult 150 0.00021

Elmidae larvae 150 0.00019

Gyrinldae adult 6 0.00403

Gyrinidae larvae 22 0.00052

Limnichnidae 50 0.00031

Helodldae 40 0.00018

Chlronomid 300 0.00007

Simulldae 200 0.00033

Baetidae (small) 150 0.00010

Baetldae (lame) 100 0~00052

Caenidae 100 0.00030

Heptaqenldae 50 0.00174

l.eptophlebldae 50 0.00128

Teloqonadldae 50 0.00082

Corixidae 10 0.00328

Naucoridae 20 0.00735

Meualootera 5 0.04964

Aeshnid (small) 16 0.00061

Aeshnld (large) 8 0.06156

Gomphidae (small) 50 0.00029

Gomphidae (large) 10 0.03226

Libellulldae (small) 25 0.00081

IIbeliulidae (larqe) 10 0.05179

Zygoptera (small) 50 0.00030

Zygoptera (large) 20 0.00390

Athripsodes 40 0.00064

C. afra 50 0.00190

Table 4a Inter-year variation of taxon abundance for each habitat type as indicated byANOSIM analysis. (m. veg =marginal vegetation)

Comparison r pSand yearl/year2 0.177 <0.01

m. veg yearl/year2 0.161 <0.01Cobble yearl/year2 0.171 <0.01

Table 4b Inter-habitat variation of taxon abundance for each year as indicated byANOSIM analysis.

comparison r pYear 1 sand/m. veg 0.613 <0.01Year 1 sand/cobble 0.602 <0.01Year 1 m.veg/cobb1e 0.367 <0.01Year 2 sand/m. veg 0.660 <0.01Year 2 sand/cobble 0.746 <0.01Year 2 m.veg/cobb1e 0.367 <0.01

Tab

le5.

Tax

aco

ntri

buti

ngto

>75

%cu

mul

ativ

esi

mil

arit

yfo

rth

ree

habi

tats

.Y

ear

Ian

d2.

Ha

bita

t(%

sim

ilari

tyb

etw

ee

nY

ear1

Ha

bit

at(

%si

mila

rity

Yea

r2sa

mp

les)

be

twe

en

sam

ple

s)

San

d(3

5.71

%)

Ab

un

da

nce

Sim

ilari

ty%

Sim

/SO

Co

ntr

ibu

tio

n%

San

d(4

6.56

%)

Ab

un

da

nce

Sim

ilari

ty%

Sim

/SO

Co

ntr

ibu

tio

n%

(av.

nu

mb

er/

sam

ple

)(a

vera

ge

)(a

v.n

um

be

r/sa

mp

le)(

aver

age)

Bae

tidae

(larg

e)6.

838.

591.

1424

.07

Bae

tidae

(larg

e)8.

639.

182.

4719

.72

Gom

phid

ae(s

mal

l)8.

616.

810.

9819

.07

Chi

rono

mid

ae55

.29

9.08

1.62

19.5

Chi

rono

mid

ae28

.78

6.66

1.08

18.6

6G

omph

idae

(larg

e)4.

797.

21.

9115

.46

Gom

phid

ae(la

rge)

2.17

4.63

0.8

12.9

7E

lmid

ae(la

rvae

)6.

134.

621.

199.

92E

lmid

ae(la

rvae

)2

1.72

0.54

4.83

Gom

phid

ae(s

mal

l)20

.71

4.16

0.92

8.93

Cae

nida

e7.

043.

530.

837.

59M

arg

ina

lveg

(46.

54%

)M

arg

ina

lveg

(56.

56%

)B

aetid

ae(la

rge)

50.1

10.2

15.

2321

.94

Chi

rono

mid

ae14

4.96

7.65

2.62

13.5

3C

hiro

nom

idae

28.5

57.

862.

7116

.9B

aetid

ae(la

rge)

88.8

37.

315.

4812

.92

Cae

nida

e9.

454.

011.

288.

62C

aeni

dae

23.2

24.

11.

877.

24Z

ygop

tera

(larg

e)6.

383.

61.

217.

74Z

ygop

tera

(larg

e)9.

783.

932.

716.

95B

aetid

ae(s

mal

l)4

2.79

0.92

5.99

Zyg

opte

ra(s

mal

l)24

.78

3.86

1.94

6.82

Sim

uliid

ae24

.93

2.74

0.78

5.88

Elm

idae

(larv

ae)

6.7

2.99

1.56

5.29

Ath

ripso

dini

4.03

1.9

0.68

4.08

Libe

llulid

ae(s

mal

l)8.

392.

861.

365.

05V

eliid

ae1.

411.

680.

693.

62B

aetid

ae(s

mal

l)15

.87

2.79

1.06

4.93

Zyg

opte

ra(s

mal

l)4.

831.

380.

582.

97S

imul

iidae

15.6

12.

611.

154.

62Li

bellu

lidae

(larg

e)3

2.41

1.39

4.25

Vel

iidae

4.09

1.8

0.9

3.17

Ath

ripso

dini

10.3

51.

50.

732.

65C

ob

ble

(47.

33%

)C

ob

ble

(57.

8%)

Bae

tidae

(larg

e)46

.94

10.5

13.

9822

.2B

aetid

ae(la

rge)

60.8

47.

286.

3212

.6C

hiro

nom

idae

32.8

46.

541.

8513

.82

Chi

rono

mid

ae60

.04

6.36

4.23

11.0

1S

imul

iidae

20.1

65.

651.

5711

.94

Elm

idae

(larv

ae)

29.6

5.8

4.28

10.0

3C

.afr

a7.

714

1.41

8.46

C.a

fra

35.6

5.24

2.67

9.07

Bae

tidae

(sm

all)

5.68

3.04

0.95

6.42

Sim

uliid

ae39

.44.

682.

018.

09E

lmid

ae(la

rvae

)4.

742.

650.

965.

59Le

ptop

hleb

idae

13.0

43.

811.

956.

59Le

ptop

hleb

idae

4.48

2.57

0.95

5.43

Bae

tidae

(sm

all)

12.4

43.

351.

465.

8H

epta

geni

dae

3.87

2.11

0.81

4.45

Elm

idae

(adu

lt)19

.64

3.12

1.32

5.39

Lim

nich

idae

11.8

42.

81.

414.

84H

epta

geni

dae

8.64

2.44

1.05

4.23

Table 6a Summary of the pairwise analysis of significantly dissimilar sample groupsfrom different invasion conditions within the same habitat (year 2). IS1: no invasion;IS2: invasive plants only;"IS3: invasive fish only; IS4: invasive plants and fish

Taxa, ranked in order of contribution toInvaded Status p r Dissimilarity dissimilarity between the sites (only the

ton four are listed)

Cobble ISlIIS2 0.04 0.583 59.3%Caenidae, E1midaeadult, Ecnomidae,simuliidae.

Cobble IS1/IS3 0.01 0.573 58.9%Heptageniidae, Aeshnidae small,Chironomidae, Gyrinidae larvae.

Cobble IS 1/IS4 0.02 0.417 56.0%Caenidae, Heptageniidae, Aeshnidae small,Elmidae adult.

Cobble IS211S3 0.02 0.419 55.25%Simuliidae, Baetidae small, Ecnomidae,Tipulidae.

Marginal vegatation0.03 0.386 54.0%

Simuliidae, Chironomidae, Athripsodes,IS1IlS3 Baetidae small.

Table 6b Summary of the pairwise analysis of significantly dissimilar sample groupsfrom different invasion conditions within the same habitat (year 1).

Invaded status p r DissimilarityCobble IS1IIS3 0.01 0.641 53.5%Cobble ISlIIS4 0.02 0.504 60.8%

Marginal vegetation0.02 0.736 51.6%

IS3/IS4

Table 7 Similarity analysis of taxa biomass from samples within habitats anddifferent invasion conditions (year 2).

Invaded status p r dissimilarityTaxa, ranked in order of contribution todissimilarity

Cobble IS1/IS2 0.05 0.444 30.52%Megaloptera, Elmidae adult, Simuliiidae,Aeshnidae large.

Cobble IS111S3 0.01 0.64 38.04%Libellulidae large, Megaloptera, Aeshnidae large,Heptageniidae.

Cobble IS2/IS3 0.02 0.567 36.72%Libellulidae large, Aeshnidae large, Megaloptera,Simuliidae.

M.veg IS1IIS3 0.01 0.437 41.19%Libellulidae large, Gomphidae large, Athripsodes,C. afra, Naucoridae.

Table 8 Similarity analysis of the biomass ofFFGs from samples within habitats anddifferent invasion conditions (year 2).

Invaded status p r FFG, ranked in order ofcontribution to dissimilarity

AllFFGsCobble IS1IIS2 0.05 0.437 P2, Grazer2/scraper 1, PI, DF2Cobble IS111S3 0.02 0.656 P2, PI, DF1, Grazer2/scraperlCobble IS211S3 0.02 0.622 P2,P1Herbivores onlyCobble IS1/IS2 0.01 0.561Cobble IS111S3 0.02 0.726Predators onlyCobble IS1IIS2 0.01 0.82Cobble IS111S2 0.04 0.544M. vegetation IS111S3 0.01 0.519

Appendix 1 Taxa of the Rondegat River. September 2003 - January 2005.Key: Tabanidae/Tany = Tabanidae/Tanypodidae (Diptera); C. afra = Cheumatopsyche afra, M.capense =Macrostemum capense (Trichoptera); Noto/Nepidae =notonectidae/Nepidae (Hemiptera)For key to FFGs, see Table 2.

YEAR 1 YEAR 2Taxa sand sand m.veg m.veg cobble cobble FFG sand

~~~~ ~..v~~m.veg cobble cobble

(av.) ISm lav.)- (SD) (av.) ISDl lav.l avo ISDi' (av.) ISDlChlronomldae 28.78 63.47 28.55 31.24 32.84 56.80 FF 55.29 83.33 144.96 102.50 60.04 86.54Simulildae 0.67 5.68 24.93 69.74 20.16 25.70 P1 2.04 3.47 15.61 21.40 39.40 43.35Athericldae 0.06 0.71 0.45 1.33 0.68 1.62 FF 0.08 0.41 0.26 0.62 0.20 0.65Culicidae 0.00 0.00 0.72 1.96 0.39 1.65 S1 0.58 2.86 3.22 9.83 0.16 0.80Blephariceridae 0.00 0.00 0.21 0.82 0.77 2.16 FF 0.00 0.00 0.00 0.00 0.36 1.08Dixldae 0.06 0.23 0.93 2.42 0.00 0.00 G2 0.00 0.00 0.61 1.03 0.04 0.20Ceratopogonidae 0.22 0.63 0.24 0.91 0.23 0.80 P2 0.50 0.88 0.70 1.18 0.52 1.19Empldldae 0.11 0.32 0.03 0.19 0.16 0.52 P2 0.00 0.00 0.48 1.12 0.68 1.35TabanldaelTany 0.00 0.00 0.03 0.19 0.19 0.54 P2 0.08 0.41 0.09 0.42 0.68 1.11Tlpulidae 0.00 0.00 0.07 0.37 0.16 0.45 P2 0.33 0.76 0.30 0.82 1.00 1.71Muscidae 0.06 0.23 0.03 0.19 0.06 0.36 0.08 0.41 0.13 0.46 0.16 0.47Syrphldae 0.00 0.23 0.03 0.19 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

Baetidae (large) 6.83 8.66 50.10 42.24 46.94 32.53 DF1 8.63 5.66 88.83 72.27 60.84 34.66Caenldae 1.39 2.22 9.45 13.36 6.16 14.26 DF2 7.04 9.35 23.22 26.33 5.52 9.21

Telogonadidae 0.33 1.38 0.24 0.83 9.39 23.57 DF2 0.00 0.00 0.26 0.75 0.96 3.26

Baetidae (small) 0.33 1.02 4.00 4.86 5.68 7.38 DF1 3.96 6.02 15.87 18.11 12.44 12.58

Leptophlebidae 0.06 0.23 0.55 1.57 4.48 7.93 DF1 0.46 1.14 1.65 2.04 13.04 13.65

Hentauenldae 0.06 0.23 0.69 2.98 3.87 8.44 G2 0.04 0.20 0.00 0.00 8.64 12.64

Gomphldae (small) 8.61 13.53 0.10 0.56 2.35 9.33 P2 20.71 41.04 1.48 2.57 3.44 8.50

Gomphidae (large) 2.17 2.01 0.31 1.14 0.77 1.50 P2 4.79 3.24 0.57 1.08 0.20 0.50Zygoptera (large) 0.06 0.23 6.38 8.81 0.10 0.54 P2 0.00 0.00 9.78 8.03 0.04 0.20

Zygoptera (small) 0.11 0.46 4.83 10.29 0.16 0.73 P2 0.33 0.76 24.78 52.41 0.36 0.76

Libellulldae(small) 2.17 3.17 2.21 4.51 0.74 1.32 P2 2.42 5.11 8.39 8.41 0.84 1.95

Libellulldae(large) 0.78 2.10 1.10 1.63 0.32 0.94 P2 0.38 0.77 3.00 2.34 0.84 1.60Aeshnldae (large) 0.00 0.00 0.97 2.65 0.74 1.67 P2 0.00 0.00 0.09 0.42 0.72 1.67Aeshnldae Ismalll 0.17 0.50 0.72 1.56 0.45 1.55 P2 0.58 1.38 2.87 4.08 9.16 14.40

C. afra 0.11 1.00 1.97 3.78 7.71 8.17 P1 1.08 1.67 4.00 8.33 35.60 34.20Athripsodlni 0.89 1.63 4.03 10.46 0.48 1.00 DF2 0.75 1.19 10.35 17.59 0.44 1.26Hydroptilldae 0.94 2.85 1.69 5.66 1.32 5.39 S1 0.75 1.51 5.65 8.65 4.40 19.13Leptecho/cerus 0.50 1.17 1.48 2.08 0.29 0.53 Shr 0.50 1.06 1.91 3.42 0.32 0.69Ecnomidae 2.00 5.20 0.07 0.26 0.45 1.09 DF1 0.58 2.17 0.04 0.21 1.36 2.61Oecetis 0.06 0.23 0.55 1.57 0.45 1.09 P2 0.17 0.82 1.30 1.84 0.92 1.91Philopotamidae 0.00 0.00 0.14 0.74 0.32 1.14 FF 0.00 0.00 0.09 0.42 1.12 2.32

Parecnomlna 0.00 0.00 0.14 0.58 0.10 0.40 0.00 0.00 0.04 0.21 0.08 0.40

Sericostomatldae 0.06 0.50 0.07 0.37 0.13 0.34 Sh 0.42 1.06 0.22 0.60 0.32 0.75

Macrostemum 0.00 0.00 0.00 0.00 0.03 0.18 P2 0.00 0.00 0.17 0.83 1.00 1.91

Barbarochthonldae 0.00 0.00 0.00 0.00 0.03 0.18 0.00 0.00 0.00 0.00 0.00 0.00

Leptocerldae sp. 0.00 0.00 0.00 0.00 0.03 0.18 0.00 0.00 0.13 0.63 0.16 0.55

Glossosomatidae 0.00 0.00 0.00 0.00 0.00 0.00 0.08 0.41 0.52 1.24 2.64 7.65

Petrothrincidae 0.00 0.00 0.00 0.00 0.00 0.00 0.21 0.59 0.57 0.99 1.60 1.98

Polvcentropodldae 0.00 0.00 0.00 0.00 0.00 0.00 0.50 1.06 1.91 3.42 0.32 0.69

Elmidae (larvae) 2.00 3.16 1.03 1.59 4.74 5.55 S1 6.13 9.01 6.70 6.85 29.60 19.03

Elmidae (adult) 0.06 0.23 1.86 5.57 3.03 4.96 S2 0.58 1.06 4.30 12.14 19.64 27.53

Helodidae 0.44 1.07 1.07 1.89 0.97 2.02 G1 2.83 8.32 1.52 3.87 2.56 3.27

Hydrophllldae 0.00 0.00 0.21 0.56 0.45 0.93 S1 0.17 0.82 0.30 0.93 3.28 4.90

Limnlchldae 0.11 0.46 0.34 0.90 1.06 1.48 G1 0.88 2.27 3.04 4.55 11.84 18.14

Gyrlnldae (larvae) 0.22 0.54 0.34 1.01 0.71 2.10 P2 0.04 0.20 2.39 5.10 2.32 3.08

Dytlscldae (adult) 0.06 0.23 0.97 2.77 0.00 0.00 P2 0.00 0.00 0.74 1.39 0.00 0.00

Dytiscidae (larvae) 0.17 0.69 0.34 1.34 0.00 0.00 P2 0.42 1.67 2.78 4.49 0.36 0.95

Hydraenldae 0.00 0.00 0.07 0.37 0.26 0.73 S2 0.00 0.00 0.13 0.46 0.32 0.80

Gvrlnldae (adult) 0.06 0.23 0.07 0.37 0.00 0.00 P2 0.08 0.41 0.52 1.24 2.64 7.65

Corlxldae 3.22 7.58 1.00 1.87 0.48 1.15 P1 0.50 1.69 0.48 1.04 0.16 0.55

Naucorldae 1.06 2.83 1.86 5.22 0.26 0.82 P2 0.25 1.22 3.30 7.21 0.16 0.47

Vellldae 0.06 0.32 1.41 1.78 0.32 0.87 P1 0.17 0.56 4.09 4.94 0.16 0.55

Mesovellldae 0.00 0.00 0.14 0.74 0.03 0.18 P2 0.00 0.00 0.09 0.42 0.04 0.20

Gerridae/Saldidae 0.00 0.00 0.07 0.26 0.00 0.00 P2 0.00 0.00 0.04 0.21 0.00 0.00

Noto/NeDidae 0.00 0.00 0.03 0.19 0.00 0.00 P2 0.00 0.00 0.30 0.70 0.00 0.00

Oligochaeta 0.89 2.79 0.83 1.85 1.68 5.58 G2 0.17 0.48 1.57 4.41 1.08 2.56

Lepidoptera 0.00 0.00 0.48 1.02 0.03 0.18 G1 0.08 0.41 0.87 2.22 0.32 0.95

Hydrachnellae 0.00 0.00 0.14 0.52 0.29 0.64 0.21 0.59 0.57 0.99 1.60 1.98Megaloptera 0.00 0.00 0.07 0.37 0.26 0.63 P2 0.00 0.00 0.00 0.00 1.44 1.94Plecootera 0.00 0.00 0.17 0.54 0.10 2.72 Shr 0.17 0.82 0.04 0.21 0.40 0.91

Appendix 2The average number of taxa per sampling occasion at each site (year 2).lSI: no invasion; IS2: invasive plants only; IS3: invasive fish only; IS4: invasiveplants and fish.

Key: Tabanidae/Tany =Tabanidae/Tanypodidae (Diptera); C. afra =Cheumatopsyche afra,M. capense = Macrostemum capense (Trichoptera); Noto/Nepidae = notonectidae/Nepidae(Hemiptera)

Site number and invasion status (IS)Taxa 1 (181) 2 (181) 3 (182) 4 (182) 5 (184) 6 (183) 7 (183) 8 (184)Chironomidae 50.44 44.89 94.11 77.00 122.44 155.56 128.50 28.88Simuliidae 16.44 22.44 18.67 2.67 22.33 41.22 12.88 20.50Culicidae 0.33 0.33 0.00 0.00 2.22 6.89 0.50 0.00Ceratopogonidae 0.89 0.33 1.33 0.89 0.00 0.44 0.25 0.50Tipulidae 0.89 0.22 0.22 0.56 0.22 1.33 1.13 0.00Empldidae 0.67 0.00 0.89 0.00 0.56 0.67 0.00 0.38TabanidaelTany 0.22 0.22 0.11 0.67 0.00 0.22 0.50 0.50Dixldae 0.11 0.33 0.22 0.00 0.33 0.22 0.13 0.38Athericidae 0.22 0.11 0.33 0.00 0.44 0.22 0.13 0.00Blephariceridae 0.00 0.00 0.56 0.00 0.22 0.00 0.00 0.25Muscidae 0.00 0.00 0.22 0.00 0.33 0.00 0.25 0.25Baetidae (large) 44.44 30.11 51.11 39.78 51.22 51.67 119.63 47.88Caenidae 4.56 7.11 25.89 8.33 29.78 6.00 7.00 6.25Baetidae (small) 17.56 3.11 2.22 5.56 8.44 25.56 14.50 11.25Leptophlebidae 1.56 2.89 3.67 7.89 4.22 9.78 9.50 2.13Heptagenidae 4.11 11.89 1.67 1.33 3.89 0.22 1.00 0.00Teloqonadldae 1.33 0.33 0.00 0.00 0.00 0.00 0.00 0.00Gomphidae (small) 4.44 0.44 7.11 1.89 5.44 1.78 18.75 34.63Zygoptera (small) 1.33 1.11 6.89 4.00 32.00 7.78 7.25 6.38Aeshnidae (small) 0.44 0.67 1.78 3.00 3.33 8.44 6.25 12.50Libellulidae (small) 1.33 0.67 5.11 3.56 5.56 7.56 6.25 1.00Zygoptera (large) 2.56 1.78 2.11 2.22 3.44 1.56 7.88 5.00Gomphidae (large) 1.33 1.78 2.78 2.00 1.78 1.11 1.38 3.00L1bellulidae(large) 0.78 0.89 1.44 0.56 2.44 3.00 1.75 0.38Aeshnidae (iargef 0.00 0.00 0.00 0.22 0.22 0.11 1.50 0.25C. afra 11.44 15.00 7.33 6.22 6.00 30.89 11.75 27.25Athrip/Setodes 0.44 0.67 6.33 2.11 9.22 1.11 9.75 1.25Hydrophilidae 3.22 2.11 1.00 0.67 0.33 2.22 0.38 0.25leptecho/cerus 0.33 0.44 0.89 2.44 1.44 0.67 0.50 0.50Oecetis 0.67 1.22 0.00 1.22 2.22 0.00 0.50 0.50Ecnomidae 0.00 1.11 2.11 1.44 0.56 0.22 0.00 0.00Philopotamidae 0.22 0.22 0.67 0.11 1.33 0.78 0.00 0.00Macrostemum 0.00 0.11 0.22 0.67 0.00 1.78 0.50 0.00Sericostomatidae 0.33 0.56 0.00 0.22 1.00 0.00 0.50 0.00Polycentropodidae 0.00 0.00 0.00 0.44 1.22 0.00 0.00 0.00Lepta, unplaced 0.33 0.44 0.00 0.00 0.00 0.00 0.00 0.00Glossosomalidae 0.00 0.00 0.00 0.00 0.56 0.00 0.00 0.00Parecnomia 0.11 0.00 0.00 0.00 0.22 0.00 0.00 0.00Petrothrincidae 0.00 0.22 0.00 0.00 0.00 0.00 0.00 0.00Elmidae larvae 21.56 15.78 21.67 7.11 9.00 19.89 12.13 10.75Elmidae adult 33.11 10.22 1.89 0.56 1.89 10.44 3.00 7.00Limnichidae 3.11 2.44 15.89 4.89 0.44 12.00 3.50 1.25Hydroptilidae 0.78 0.00 2.89 2.89 2.44 14.22 5.00 1.13Helodidae 7.33 2.00 5.00 1.89 0.22 1.67 0.25 0.00Gyrinidae larvae 0.89 1.33 0.33 0.67 0.44 2.44 6.25 1.13Dytiscidae larvae 0.11 0.22 0.11 0.22 1.78 3.11 3.13 1.00Gyrinidae adult 0.22 0.00 0.00 0.67 0.00 0.22 3.63 5.13Dytiscidae adult 0.00 0.00 0.11 0.00 0.33 0.67 0.00 0.88Hvdraenidae 0.56 0.00 0.00 0.00 0.00 0.00 0.13 0.50Veliidae 1.33 0.22 3.22 3.56 0.11 0.00 1.25 2.00Naucoridae 1.00 1.89 4.67 0.89 0.44 0.22 0.50 0.00Corixidae 0.00 0.44 0.00 0.22 0.56 1.78 0.00 0.00Noto/Nepidae 0.00 0.22 0.00 0.22 0.11 0.00 0.00 0.25Mesoveliidae 0.00 0.11 0.00 0.00 0.22 0.00 0.00 0.00Gerrid/Saldidae 0.00 0.00 0.00 0.00 0.00 0.00 0.13 0.00Oligochaeta 0.44 0.11 0.78 0.44 0.22 1.11 4.50 0.38Hydrachnellae 0.44 0.56 1.00 0.56 0.78 1.00 0.50 1.88Megaloptera 0.44 0.78 0.22 0.00 1.11 1.22 0.00 0.00Lepidoptera 0.89 0.33 2.00 0.00 0.00 0.00 0.13 0.00Plecoptera 0.67 0.11 0.00 0.00 0.56 0.00 0.25 0.00Total 246.00 190.56 306.78 202.44 345.67 439.00 415.00 245.25