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QUATERNARY RESEARCH 13, 93- 110 (1980)
Paleoenvironmental Implications of a Late Glacial Insect Assemblage from Northwestern New York
DONALD P. SCHWERT’ AND ALAN V. MORGAN
Received November 17, 1978
The Winter Gulf site near North Collins, New York is a 0.8-m sequence of organic detritus dated
at approximately 12.700 yr B.P. A 260-kg sample produced over 500 identified individuals repre- senting five orders of insects. Three insect zones were recognized, the lowest representing an open
mire with sparse numbers of carices and other sedges: aquatic beetles were rare. and no trees were in the vicinity of the sample site. The middle zone indicated an extensive marsh or moist meadow environment with spruce nearby. The upper zone represented a mixed riparian and spruce forest
insect assemblage. The results of the Winter Gulf insect analyses support published hypotheses that the site was
probably a protected embayment of early Lake Warren. Although the flora at the site has been
previously interpreted as representing parkland tundra, temperature analyses of the fauna indicate
that the thermal conditions were much warmer than parkland tundra regions of North America today. These results have important significance for the region immediately south of the Laurentide
Ice Sheet during this period of the Late Wisconsinan.
INTRODUCTION
In 1972 one of the authors (A.V.M.) col- lected a small sample (ca. 5 kg) of peaty detritus from the bed of a small stream sec- tion described by Calkin and McAndrews (1969) as the Winter Gulf site. The sample produced a rich, well-preserved fauna of in- sects, primarily Coleoptera. In 1975 the site was resampled, and once again a well- preserved fauna was extracted which forms the basis of this paper. The insect as- semblage provides additional evidence about the paleoecology and climate of the eastern end of the Lake Erie basin in late- glacial times.
LOCATION AND STRATIGRAPHY OF THE SITE
The Winter Gulf site is located 3.8 km south of North Collins (Erie Co.) New York (Fig. 1) at the west edge of U.S. Route 62. The section is exposed along a streamcut in an old field area.
The stratigraphy of the section sampled is given in Figure 2. A borehole drilled nearby
’ Present address: Geology Department, North
Dakota State University. Fargo. N. D. 58105.
to a depth of 19.5 m has revealed a thick underlying sequence of tills, bedded silts, and gravels below stream level (P. E. Cal- kin, pers. comm., 1977). A preliminary re- port on the stratigraphy of this site has been published by Calkin (1970); however, be- cause of the regional implications of the discussion of this site, it should be placed in the context of Pleistocene events which were happening at the time of deposition.
LATE PLEISTOCENE GEOLOGICAL AND ENVIRONMENTAL HISTORY
The Late Wisconsinan history of the eastern Great Lakes region reflects the in- fluence of several ice lobes. The maximum advance occurred during the Nissouri Stade and extended south into Ohio, Pennsyl- vania, and New York (Calkin and Miller, 1977). Ice retreat began at about 17,000 yr B.P. and during the Erie Interstade, the Ontario and Erie lobes receded to at least the Niagara Escarpment. Subsequent gla- cial readvances during the Port Bruce Stade deposited a number of tills in southern On- tario and the Levery, Defiance, Lake Es- carpment (with its probable correlative Valley Heads), and Gowanda moraines in
93
0033-5894/80/010093-18$02.00/O Copyright a 1980 by the Universtty of Washington All rights of reproduction in any form reserved.
94 SCHWERT AND MORGAN
KITCHENER
Wilcox Rd.
FIG. I. Location of the Winter Gulf site (42”33’40” N. 78”56’0?” W, elev. 245 m).
western New York (Calkin and Miller, 1977; Muller, 1977).
Ice retreat early in the Mackinaw In- terstade resulted in the formation of glacial Lake Maumee and. at about 13.300 yr B.P., Lake Arkona in the Erie Basin. Geomor- phic evidence of either lake is absent from western New York, although beaches and sediments are present for both in southern Ontario (Terasmae <‘I al., 1972; Calkin and Miller, 1977).
During the Port Huron Stade ice ad- vanced to the limits of the present Wyo- ming and Port Huron moraines in Ontario and the Hamburg moraine in western New
York (Calkin and Miller, 1977; Terasmae rt cl/. , 1972). Higher water levels in the Erie Basin, resulting from Port Huron ice across the Niagara Peninsula, forced a northward change of drainage into the Saginaw Basin, and formed Lake Whittlesey at about 13,000 to 12,900 yr B.P. Subsequent ice re- treat to positions north of the Erie Basin (and most of the Huron basin) resulted in the formation of Lake Warren in the Erie-Huron basins, draining westward via the Grand River channel in Michigan. The deglaciation of southwestern Ontario was complete by 12,300 yr B.P. (Cowan rf uf., 1975).
LATE GLACIAL INSECTS FROM NEW YORK 95
Evidence for constructing the Late Wis- consinan environment of the region has been inhibited by insufficient paleoecologi- cal data and by the few or inconclusive radiocarbon dates. Pollen profiles recording vegetational change following deglaciation of the region have been described by Bell ( 1965), Sreenivasa (1968, 1973), Calkin and McAndrews (1969), Anderson (1971), Mil- ler (1973a), and Spear and Miller (1976). In addition to pollen, Miller (1973b) has com- piled a list of the known plant macrofossils from northwestern New York. Sreenivasa (1973) used Cladocera and other animal microfossils to record environmental fluc- tuations at a kettle pond near Kitchener in the Waterloo Interlobate Moraine of south- ern Ontario 170 km northwest of the Winter Gulf site.
Evidence compiled by Miller (1973a) and Spear and Miller (1976) indicates that a tundra environment existed in southwest- ern New York from about 16,400 (interpo- lated age) to 12,600 yr B.P. The first 2200 yr of this zone were treeless tundra, later being replaced gradually by a park tundra flora. Although the base of Sreenivasa’s (1973) core is interpreted as Port Bruce in age, the pollen is a mixture of Picea, Pinus. Quercus, and Ulmus.
Morgan’s (1972) interpretation from periglacial features in southern Ontario that the Mackinaw Interstade was a time of se- vere, tundra-like conditions generally coin- cides with the palynological evidence of Miller (1973a) and Spear and Miller (1976) in southwestern New York. These con- tradict Sreenivasa’s (1968, 1973) interpre- tations of the interstadial climate as “not severe” and a period of warmer, drier con- ditions relative to the Port Bruce Stade.
Evidence of a xeric transition in the flora during the Port Huron Stade, with a de- crease in wetland species such as Picea and Ulmus and an increase in Artemesia, was noted by Sreenivasa (1973) in southern Ontario. Similar peaks in Artemesia per- centages were observed in pollen profiles in bogs of southwestern New York by Miller (1973a) and Spear and Miller (1976), and
both zones were interpreted by these au- thors as indicative of a gradual amelioration of climate.
Palynological evidence and radiocarbon dates from the Winter Gulf site (Calkin and McAndrews, 1969) and the Belmont Bog (Spear and Miller, 1976) in southwestern New York indicate that the tundra zone ended about 12,600 yr ago. A postglacial phase with a moist, cool climate and Picea as the dominant tree type followed the final melting of the Erie and Ontario lobes (Bell, 1965; Sreenivasa, 1968, 1973; Anderson, 1971; Miller, 1973a; Spear and Miller, 1976).
Pinus-dominant forests replaced Picea at about 11,000 yr B.P. in southwestern New York and 10,600 yr B.P. in southwestern Ontario. Events following this lie outside of the scope of this paper, and will not be dis- cussed further.
RADIOCARBON DATING
No radiocarbon dates from the Winter Gulf section were determined for this study. However, two dates have been analyzed for the site in other studies. A date of 12,730 & 220 yr B.P. (I-3665) was deter- mined from woody peat in a study by Cal- kin and McAndrews (1969). A second date of 12,610 + 200 yr B.P. (I-8022) was deter- mined from spruce wood collected 17 cm above the woody peat used for the first date (P. E. Calkin. pers. comm., 1977). The ap- proximate position of these samples is indi- cated in Figures 2 and 3.
SAMPLING AND PREPARATION TECHNIQUES
Bulk samples were collected from a cleaned section of the site. Sampling com- menced at a depth of 0.84 m and continued to the base of the organic zone at a depth of 2.06 m. The respective weight of samples and sampling horizons are given in Table 1. All the samples were stored in sealed plas- tic bags at room temperature until they were processed.
The samples were treated by washing the sediment through a 52-mesh (300-pm) sieve. The detrital plant debris retained on
96 SCHWER’I AND MORGAN
TABLE 1
SAMPI.ING INTERVALS AND SAMPLE WEIGHI s FOR I HL WIN f ER GULF SI I L
Interval No. Depth (m)
Wet
weight (kg)
WOI
wo2 wo3
wo4 wo5
W06
wo7 W08
0.84-0.99 38.826 Clay
0.99- 1.14 13.565 Silty clay/shale
1.14-1.30 9.752 Silty clay/shale
1.30- 1.45 49.110 Silty sand/organic matter
1.45-1.60 43.639 Silty sand/organic matter
1.60-1.75 52.318 Silt/organic matter
1.75-1.90 40.872 Silt/organic matter
1.90-2.06 15.389 Silt/organic matter
Material
the sieve was placed in plastic bowls in sub- samples of about 1 kg and mixed with kerosene (coal oil) for several minutes. Ex- cess kerosene was decanted and cold water was slowly added to the mixture. After sev- eral hours the kerosene surface film, con- taining a concentrate of insect fragments, was slowly decanted through a 52-mesh sieve, washed with detergent, and then a 50% ethanol solution. This process was re- peated on each sample until most of the chitinous fragments had been removed. The insect concentrate was then stored in 95% ethanol until sorting, and the organic resi- dues were stored moist in plastic bags. All fragments were mounted on white cardboard micropaleontological slides with a water-soluble paste of gum tragacanth. All slides have been labeled with reference numbers indicating the site, interval number, and slide number and are depos- ited in the paleoentomological collection at the Department of Earth Sciences, Univer- sity of Waterloo.
The mounted and unmounted fragments were compared with identified museum specimens in the insect collections of the Canadian National Collection, Ottawa, and the Smithsonian Institution in Washington, D.C. A number of specimens were referred to qualified taxonomists for identification or confirmation. In cases of synonymy, nomenclatural assignment followed either the most recently published revisions or the opinions of qualified taxonomists. The family names applied to the fossil Coleop- tera are those currently recognized by the
Department of Entomology at the British Museum of Natural History.
THE PALEOENVIRONMENT OF THE WINTER GULF SITE
The paleoenvironmental interpretations made in this paper are based upon a number of ecological factors which are known to influence the presence or absence of a par- ticular species in a habitat today. The va- lidity of this approach is based upon the acceptance of two assumptions.
1. The ~~cologicul and distrihutionul clutu u\wilublp for each t~xuminrd tuxon ure uccurutc. The size and diversity of the North American insect fauna has tended to restrict detailed research in insect ecology only to those species of economic importance. Because such species are rare in both sites, the ecological information to be utilized has been obtained largely from speci- men labels in museum collections and from brief reports in the literature.
The distribution data on which the paleoclimatic interpretations are de- pendent is, likewise. derived from museum and literature sources. In our opinion, the accuracy of the range limits is questionable (and minimal) for most species. The distribution maps presented, however, should in- dicate a general range for the species today.
2. Euch tuxon bus undergoncJ HO physiological erdution since the time its ,fossil reprr~srntutir-r li\‘cJtl. Con-
LATE GLACIAL INSECTS FROM NEW YORK 97
ceivably, some insect species have adapted to different environmental conditions since the last glaciation. However, either the number of such species is very small or the degree of change negligible as analogous insect communities exist today for most of the late Quaternary fossil insect as- semblages described from North America. In addition, it is unlikely that an entire species assemblage has undergone unidirectional physiologi- cal evolution.
Undoubtedly, temperature is a major ecological factor in determining the range of an insect species, but its relative impor- tance in relation to other factors, such as habitat availability, food source, or mois- ture conditions, is not always clear. An ap- parent stenothermic species of southern distribution might, for example, rapidly extend its range northward given a similar extension of a niche prerequisite.
Because the life cycle of a temperate- zone beetle is usually completed in the summer months, temperatures of the late spring and of summer probably have the greatest effect on the ranges of the ther- mophilic species within this zone; Goulet (1974) has demonstrated the influences of such temperatures on the life cycles of two species of the carabid Pterostichus. How- ever, the temperatures of the other seasons, although more difficult to analyze, may likewise affect the survival of a species by, for example, inhibiting activity during crit- ical feeding or breeding times or by pre- venting successful winter diapause.
Hygric factors are usually of critical im- portance to an insect species and most of the species encountered at the Winter Gulf site were strongly hygrophilous. The depth of water can often be closely estimated by examining the aquatic insect assemblage. In addition, the energy of the aquatic envi- ronment can be ascertained, with some species preferring rapidly flowing water and some slow flowing or still.
The influences of other ecological fac- tors, such as soil conditions, chemical ef-
fects, photoperiod, and botanical factors, have been adequately summarized by Cooper (1967) and Morgan (1973).
DISCUSSION OF THE WINTER GULF FAUNA
The relative percentages of the major identified Coleoptera components for this site are illustrated in Figure 3. This stan- dardization removes any effects resulting from sample size or from differential sedimentation of insect fragments through time, and it permits examination of the major components of the Coleoptera. Be- cause only three individuals were recov- ered from Interval W03, percentages de- rived from this sample would be misleading and are omitted from Figure 3. Similarly, because the identified non-Coleoptera component totaled only 22 individuals, or less than 5% of the total fauna, it is not presented as a separate category on the diagram; however, the non-Coleoptera component is included in the calculation of the “percentage aquatic vs terrestrial in- sects” section on the diagram. Aquatic taxa for this category were defined using Usinger (1956) as a standard reference. In this sense, “aquatic” refers to any insect that spends a significant portion of its life on or within water: ’ ‘terrestrial’ ’ refers to any species that is not categorized as “aquatic,” including many hygrophilic species.
Correlations of radiocarbon dates (dis- cussed above) with the section sampled for insects have been approximated based upon lithology and inserted in Figure 3. Similarly, the limits of a single pollen zone described by Calkin and McAndrews (1969) have also been approximated on this dia- gram. The profile, which is reproduced in Figure 4 will be discussed later with respect to the insect results.
The numbers of individuals for each in- sect taxon identified from the Winter Gulf site are presented in Table 2. In the zonal interpretations the reader should refer to both this table and to the insect percentage diagram (Fig. 3) for the stratigraphic loca- tion of each fossil species.
/--
COLE
OPT
ERA?
101(
101)
66
(71)
237
(248
1
62
(66)
j 12
,6aJ
+m-
>I ~1
2.7o
ot20
0-
I
w-3
w-2
FIG.
3.
In
sect
pe
rcen
tage
di
agra
m
for
Win
ter
Gulf
si
te.
-zT’
Tr
-r--
’
0 60
80
PE
RCEN
T
LATE GLACIAL INSECTS FROM NEW YORK 99
FIG. 4. Pollen diagram for Winter Gulf site (adapted from Calkin and McAndrews, 1969)
The Winter Gulf sequence was separated into zones based on the fauna1 events indi- cated on the insect percentage diagram. Three zones, W-l, W-2, and W-3, were recognized, and each is described.
Zone W-l
Zone W-l (1.90-2.06 m, interval W08) represents only the basal sample interval and a total of 44 individuals. This zone is distinguished by peaks in the staphylinid genera Bledius and Stenus, plus moderate numbers of the weevil Hyperodes and the leiodid Agathidium. In comparison with the other two zones, however, the most marked characteristic of Zone W-l is the small percentage of fossils of the chry- somelid genus Plateumaris.
Stenus is a frequent inhabitant of silty streambanks, moist meadows, and sphag- num bogs. Bfedius is a numerically large genus which typically burrows into moist sand or mud and feeds on algae and diatoms (Herman, 1972). The majority of species of Bledius occur together today with species of the carabid genus Dyschirius (Lindroth, 1961), a fossil of which was also found in this zone. Hyperodes, like Bledius, occurs beneath sandy or muddy ground near water, where it feeds upon aquatic plants (Blatch- ley and Leng, 1916).
The moist, eutrophic environment indi- cated by these genera is further supported by the occurrence of the limnichid Lim- nichites. the leiodid Agathidium, and the limnebiid Ochthebius. Truly aquatic beetles
were limited in number either due to water temperature, or more probably, to a lack of open water. Those aquatic beetles which did occur, such as the dytiscid tribe Agabini and the hydrophilid genus Helophorus, are usually inhabitants of marshy areas or tem- porary pools.
The carabid beetle fauna is representa- tive of that which might occur on an open, drying mire. Agonum gratiosum (Fig. SA) and Pterostichus patruelis are both com- mon inhabitants of moist peat or mud, often with carices (Lindroth, 1966). Tachys an- caps (Fig. 5B) and T. incurvus both occur near water in areas of open, clayey sand (Lindroth, 1966).
Significantly, no arboreal or forest floor-inhabiting insects were present in Zone W- 1. Although the numbers of all fos- sils were small in this zone, the complete absence of this component together with the apparent absence of such plant mac- rofossils as needles and cones, might indi- cate that the forest edge was not adjacent to the sample site during the deposition of this zone.
The sediments of Zone W-l, therefore, probably represent an open, shoreline mire. The vegetation of the area was limited to some carices and other sedges, with possi- bly a complete absence of forest cover from the sample site area.
Zone W-2
Zone W-2 (1.60- 1.90 m, intervals WO6- W07) is defined by a decrease in
TABL
E 2
TAX~
NOM
IC
LISI
O
F TH
E ID
ENTI
FIED
FO
SSII
FAUN
A FR
OM
THE
WIN
TFR
GULF
SI
TE,
NORT
H CO
I.LIN
S.
N.Y.
”
Phylu
m:
Clas
s:
Orde
r: Subo
rder
: Or
der:
Arac
hnid
a Ac
arin
a O
ribat
ei
Aran
eae
Pisa
urid
ae
Sam
ple
inte
rval
To
tal
num
bers
of
in
divid
uals
wos
Cl
ass:
Su
bcla
ss:
Orde
r in
det
Clas
s:
Orde
r:
Orde
r:
Orde
r:
Dolw
wdes
sp
Cr
usta
cea
Mal
acos
traca
lnse
cta
Hem
ipter
a Pe
ntat
omid
ae
Neor
i&~s
.sn
cf.
rtrxlr
rrtr
(Say
) Ho
mop
tera
Ci
cade
llidae
ge
nera
in
det.
Coleo
pter
a
Cara
bidae
W05
. W
06
3
WO
S -
WO8
I5
WO
8 W
06
W06
wa
s
wo7
was
W03
, W
06,
W07
W
06
wo5
wo4,
wo
7 D
ysch
iriub
in
tege
r Le
Cont
e D
ywhi
rirts
J~
‘t~~.
~N.\
LeCo
nte
Dys
chiri
rrs
sp.
Nurio
plril
as
trqlrr
lricr
ts
(Lin
naeu
s)
Ptem
sric
hm
Irrc~
t~o.
\ct.~
De
jean
Ptfw
sric
l2rr.
t pr
rfrua
li.r
(Deje
an)
Tuch
ys c
r,rcc
~ps
LeCo
nte
Tuc~
h?.r i
nc~n
rl~us
Say
Tr
rLkr
ts trp
icnl
is
Mot
schu
lsky
W06
wo
7 W
O8
was
wo7
WO8
W08
W
O8
wo4,
wo
5
4 I 1 7 1 z I 3
“Dyt
isci
dae
~Lin
dess
us
a.fjn
i.s
(Say
) *R
hant
us
sp.
*Aga
bini
ge
nera
in
det.
*Hyd
raen
idae
*H
ydra
ena.
spp.
“H
ydro
philid
ae
*Eno
chru
s sp
p. a
nd/o
r Cy
mbio
dyta
sp
p.
*Hel
opho
rus
cf.
orie
ntql
is M
otsc
huls
ky
*Hel
opho
rrts
spp.
*Hvd
rohit
rs
and/
or
Heko
mha
s sp
p.
*Lim
nebi
idae
*O
chth
ebiu
s cf
. di
scre
tas
LeC
onte
*G
eory
ssid
ae
*Geo
ryss
us
sp.
Stap
hylin
idae
Ac
idof
a cr
enaf
u Fa
bric
ius
B/ed
icts
spp.
Brat
hinu
s ni
tidas
Le
Con
te
Olop
hrum
co
nsim
ile
(Gyl
lenh
al)
Olop
hrum
ro
tund
irolle
(C
. R
. Sa
hlbe
rg)
Philo
rzfh
us
cf. f
iuvu
s N
ordm
ann
Philo
nthu
s sp
p.
Sten
us
spp.
Al
eoch
arin
ae
gene
ra
inde
t. La
thro
biin
i ge
nera
in
det.
Leio
dida
e Ag
athi
diam
sp
p.
Scar
abae
idae
Ae
gial
ia
hum
eral
is Br
own
Aegi
alia
la
crts
tris
LeC
onte
Ap
hodi
us
spp.
*H
elod
idae
*C
ypho
n sp
. By
rrhid
ae
Cyrilu
s al
fern
afas
(S
ay)
*Het
eroc
erid
ae
“Lan
tern
arias
br
unne
rrs
Mel
sche
imer
or
par
rota
s Pa
chec
o *L
imni
chid
ae
*Lim
nich
ites
spp.
‘Dry
opid
ae
*Hel
ichus
st
riate
s Le
Con
te
WO
4-
W06
8
W06
1
WO
f- W
O8
3
wo4-
wo7
wo5-
WO
I
woti
WO
8 W
06
WO
f- W
O8
wos
wo6
, wo
7 W
OS-
WO
8 W
04
WO
&WO
S W
O5,
W06
W
06,
W08
WO
5-
WO
8 W
O8
WO
4-W
06.
WO
8
WO
6- W
O8
23
W06
W
O8
wo4
. wo
7
wo5.
wo
6
WO
4
9 15 2 2 4 21 1 2 14 1
33 5 2 6 10 2 5 3
TABL
E 2G
Cont
itlrtrd
Sam
ple
inte
rval
To
tal
num
bers
of
in
divid
uals
Orde
r:
Orde
r:
Elat
erid
ae
Hypo
lithus
Ie
conr
ei
(Len
& Cu
cujid
ae
Pedi
acrrs
fu
scus
Er
ichso
n Cr
ypto
phag
idae
Pter
yngiu
m
sp.
Cocc
inel
lidae
An
isos
ticto
hi
trian
g~tla
ris
(Say
) Co
lydiid
ae
Lasc
onot
rr~
sp.
Chry
som
elid
ae
Chae
loc~r
~ern
a sp
p.
Diah
roric
cr
otrip
enui
5 (S
ay)
“Dun
uc~i
cr
spp.
Hi
ppur
iphi
la
ccrt~
rrdet
z.si.
s Br
own
Oph
roell
a sp
. A
“PIu
terrr
i2ar
is sp
p.
Curu
lioni
dae
Hype
rode
.\ sp
. Sc
olyt
idae
Ca
rpho
horrr
5 cr
ndrr.
tr~ni
Swai
ne
Carp
hoho
rrrs
corri
Sw
aine
Ph
loeo
sinus
pi
ni
Swai
ne
Phlo
eotri
bus
pice
tre
Swai
ne
Polyg
raph
u.s
rrrjip
rrznis
(K
irby)
S~
~ol\.
tlrs sp
. Di
pter
a “Chir
onom
idae
gene
ra
inde
t. Hy
men
opte
ra
Form
icida
e ge
nera
in
det.
wo5
W06
wo5
W06
2
W06
W06
, W
O?
7 W
06
1
WO4
- W
08
26
wo5-
wo7
9
wo4,
wo
6 4
WO3
- W
08
211
W04
, W
06
- W
08
W04
wo4
wo4
WO4
W
06
wo4-
W
O?
wo5
W05
, W
O7-
W08
1 1 II 4
” Ar
rang
emen
t of
or
ders
of
ins
ects
ad
opte
d fro
m
Borro
r (‘t
u/.
1976
; wi
th
fam
ilies
in a
lpha
betic
al
orde
r. Aq
uatic
ta
xa
base
d on
th
e lis
ting
of
Usin
ger
t 195
6)
are
indi
cate
d by
an
ast
erisk
(.
). Th
e Co
leopt
era
are
clas
sifie
d ac
cord
ing
to
Arne
tt (1
973)
an
d Vi
edm
a an
d Ne
lson
(197
5).
LATE GLACIAL INSECTS FROM NEW YORK 103
FIG. 5. Selected fossils recovered from the Winter Gulf site. The scale bar represents 1 mm. (A)
Agonum grafiosum (thorax), (B) Tachys anceps (right elytron), (C) Hippuriphila canadensis (left elytron), (D) Dolomrks sp. (cephalothorax), (E) Hclichus srriurus (thorax and left elytron), (F) Cur-
phoborus carri (left elytron), (G) Carphoborus urdersorli (right elytron). (H) Phloeosinus pini (left elytron), (I) Po/.vgraphus rufipennis (left elytron), (J) Anisostictn bitriungularis (left elytron).
104 SCHWERT AND MORGAN
fossils of Bledius and Strnus and by a marked increase in the chrysomelid genus Plateumaris. The latter genus comprised 30% of the total identified fauna of Zone W-2. Aside from fragments of adults, sev- eral pupal cocoons containing nearly com- plete adults were found. Despite the abun- dance of fragments of Plateumaris, species identification was not possible as the taxonomy of the genus is based principally on the structure of genitalia and articulated legs.
Like other Donaciinae, adult Plateumaris are usually found in association with aquatic and semiaquatic plants, and most of their adult life is spent above the surface of the water. The larvae feed on the stems or plant roots and, at pupation, form a silken cocoon at these feeding points.
In addition to these genera, Zone W-2 is distinguished by fauna1 component peaks in the hydraenid Hydraena, the limnebiid Ochthebius, the hydrophilids Enochrus and/or Cymbiodyta, the staphylinid Oloph- rum consimile, and the dytiscid Liodessus affinis .
L. affinis today inhabits a wide variety of aquatic habitats. It has been recorded from rocky shorelines of alpine lakes, margins of quiet pools, warm prairie ponds, Carex marshes, and occasionally in sphagnum bogs. L. afJinis is strongly associated with mats of filamentous algae and ranges in distribution from Alaska to Argentina (Lar- son, 1975).
All of the dominant taxa of this zone and a large proportion of the remaining taxa, including those classified as “terrestrial,” are strongly hygrophilous. These include the weevil Hyperodes, the heterocerid Lanternarius, the limnichid Limnichites, the staphylinid Philonthus, and the Donaciinae.
A marsh environment could be a habitat common to all of the previously mentioned taxa, plus six of the identified carabid species. Bembidion nigripes. B. versicolor, Dyschirius integer, and D. setosus are all inhabitants of bare spots near water (Lind- roth, 1961, 1963). Pterostichus luctuosus
occurs in rich vegetation. often mosses. at the border of eutrophic and mesotrophic standing water (Lindroth, 1966). B. (‘on- cretum occurs in Cares swamps and is as- sociated with mosses, but never Splrrrgm4m
(Lindroth, 1963). At least three of the more xerophilic in-
sect species of this zone are inhabitants of open areas. The byrrhid beetle Cytilus al- ternatus is common among the roots of grasses; the chrysomelid Hippuriphila canadensis (Fig. 5C) inhabits Equisetum (Brown, 1942); the pentatomid Neotiglossrr undata. like the homopteran cicadellids. often occur in large numbers among grasses (Blatchley, 1926).
Although at least 40% of the identified insects of this zone are listed as “terres- trial.” the number of arboreal or forest floor-inhabitants is low. Those present in- clude the cucujid beetle Pediacus .fuscus and the scolytid bark beetles Phloeotribus piceae and Polygraphus rufipennis. The latter two species are inhabitants of coni- fers, P. piceae specifically inhabiting spruce (Bright, 1976).
The insect fauna, therefore, indicates that Zone W-2 represents a fairly open, moist meadow or marsh environment. Small pools were, at least temporarily, present among the mosses and carices. Both insect and plant fossils confirm that coniferous trees, probably dominated by spruce, were present near the site, although the forest environment was rather of park- land nature.
Zone W-3
This subzone (1.22- 1.60 m, intervals WO3- WO5) is defined by the following fauna1 events:
1. An increase in the scolytid beetle com- ponent.
2. Increasing numerical dominance of Plateumaris.
3. Marked decreases in several Zone W-2 fauna1 components, including Heydraena. Ochthebius, Olophrum. and Liodessus.
Although Piuteumaris greatly dominates
LATE GLACIAL INSECTS FROM NEW YORK 105
this zone (comprising up to 78% of the total identified Coleoptera), much of the marsh element indicated in Zone W-2 has di- minished. No leiodids or limnebiids are present, and the populations of Liodessus affinis, Olophrum consimile, and Hyperodes spp. are greatly reduced. The marsh beetle Cyphon sp. (Helodidae) and the minute mud-loving beetle Georyssus sp. (Georyssidae) were each represented by single elytra.
With the possible exception of Trechus apicalis, not one of the carabid fauna is today a regular inhabitant of marshy areas. T. apicalis often occurs in shaded areas and occasionally in the drier areas of Carex marshes (Lindroth, 1961). Bembidion scopulinum and B. \arsicolor are both ri- parian inhabitants of barren areas. B. mutatum occurs in areas of open moist sand with only sparse vegetation cover (Lindroth, 1963). Notiophilus aquaticus is also an inhabitant of open, often xeric places (Lindroth, 1961).
The shoreline element among this fauna is further affirmed by the fossil occurrence of a “fishing spider” of the genus Dolomedes (Fig. 5D). The large spiders of this genus frequent the margins of both still and flowing water, preying on arthropods trapped on the surface film or, occasion- ally, on live fish beneath the surface (Carico, 1973).
A thorax and elytron of the dryopid bee- tle Helichus striatus (Fig. 5E) were found in interval W04 (1.30-1.45 m). This species is a frequent inhabitant of shallow, rapidly flowing water, and its occurrence may mark the initial establishment of the Winter Gulf stream.
Aside from some of the carabid species, inhabitants of open ground are rare in this subzone. Unlike Zone W-2, the W-3 as- semblage includes few terrestrial chrys- omelids (e.g., Hippuriphila canadensis, Chaetocnema spp., and Ophraella sp.) and few homopteran cicadellids, probably indicating the onset of closed forest.
The abundance and diversity of the scolytid fauna confirms this conclusion.
Three species, Phloeotribus piceae. Car- phoborus carri (Fig. 5F), and C. andersoni (Fig. 5G) are restricted to spruce forests, the latter species apparently to white spruce (Picea glauca). Phloeosinus pini (Fig. 5H) and Polygraphus ru$pennis (Fig. 51), although not restricted to spruce, occur only on coniferous trees (Bright, 1976).
Zone W-3, therefore, represents a shoreline environment with little associated marsh habitat along the margin. A stream may have entered the lake near the sample site, resulting in deposition of fossils of Helichus striatus and possibly some of the terrestrial beetles and plant macrofossils found in this zone. The coniferous forest, dominated by spruce, approached the shoreline, advancing in the process over an area which was previously meadow or marshland.
CLIMATIC ANALYSIS OF THE WINTER GULF INSECT ASSEMBLAGE
The ranges of all of the species identified from the Winter Gulf sequence extend, at least, into the southern boreal forest today. Many, such as the cucujid Pediacus fiscus, the scolytid Phloeosinus pini, the carabid Bembidion mutatum, and the scarabaeid Aegialia larustris, are predominantly northern in distribution; however, the number of apparently stenothermic species is, unfortunately, low at this site, making a zone-by-zone analysis of climatic change impossible.
One of the most interesting aspects of the Winter Gulf fauna is the difficulty in locat- ing an area of North America where an exact analog of these assemblages might occur today. An example of this problem may be given by a comparison of the ranges of the elaterid Hypolithus lecontei, the chrysomelid Hippuriphila canadensis. and the scolytid Carphoborus andersoni, all fossils in Zone W-3. H. lecontei has been collected no further west than 80” W. Long. (Fig. 6) and H. canadensis no further west than 100” W. Long. (Fig. 6). However, C. andrrsoni has never been collected east of 110” W. Long. (Fig. 7), well beyond the
106 SCHWERT AND MORGAN
FIG. 6. Approximate modern distributions of Hypolithrrs /cc.cJnlri (black spots) and Hippuriphila
c~unudrnsis (open circles).
FIG. 7. Approximate modern distributions of C‘crrplrorhrwos rr~&r.st~ni (black spots) and Aegicrlitr
hurrrrrolis (open circles).
LATE GLACIAL INSECTS FROM NEW YORK 107
western limit of the previous two species; this fact indicates an apparently significant range disjunction.
If the previously stated assumption that the “distributional data available for each taxon are accurate” is strictly enforced, then the Winter Gulf site contains fossils of a mixed fauna with no known analog in North America today. However, it must be emphasized that most of the species in each zone do occur today together and that the degree of these disjunctions may well be reduced upon further collecting in north- central Canada.
For example, fossils of C. andersoni have been identified from other Quaternary de- posits in eastern North America. A. Mor- gan and A. V. Morgan (pers. comm., 1975) record it from the Don Formation (San- gamonian) and Scarborough Formation (early Wisconsinan) in Toronto as well as the 10.900-yr-old Lockport Gulf site only 75 km northeast of North Collins. Ashworth (1977) has also recorded it from the 10,600-yr-old Eighteen Mile River section in Huron County, Ontario. S. Wood and D. E. Bright, Jr. (pers. comm., 1972), both note that the occurrence of this species is rare and that its range may be extended with more intensive sampling of eastern Canada.
Three of the Winter Gulf species, Brathinus nitidus, Aegialia humeralis (Fig. 7), and Hypolithus lecontei occur no further north than 48” N. Lat. today. In eastern Canada, Carphoborus carri, Phloeosinus pini. Phloeotribus piceae, Ophraella sp. A (a color form listed as a “new species” in the CNC collection), and Liodessus affinis likewise are not present north of 48” N. Lat. Except in high elevation areas, Pediacus fuscus and Phloeosinus pini occur no further south than 46” N. Lat., and records of Aegialia lacustris south of this latitude are rare in the east. Anisosticta bitrian- gularis ranges widely throughout North America, but one color form of this species has been recorded only north of 52” N. Lat. in Labrador, Yukon, and Northwest Ter- ritories (Brown and de Ruette, 1962). This
color form is nearly identical to that of the Winter Gulf fossils (Fig. 5J). With the ex- ception of C. andersoni and the northern color form of A. bitriangularis, the ranges of all of the other identified Winter Gulf species extend into the 46”-48” N. Lat. zone, and thermal conditions there may be analogous to those at Winter Gulf 12,700 yr ago.
The mean temperature range for this zone in Ontario is about 16” to 18°C in July and - 18” to - 14°C in January, and the av- erage frost-free season is approximately 80 to 100 days.
The significance of these values is dis- cussed in the next section.
SUMMARY OF THE WINTER GULF FAUNA AND PALEOENVIRONMENT
A taxonomic list of the Winter Gulf fauna and a quantitative summary of the insect taxa identified from this site is given in Table 2.
The sequence at Winter Gulf represents a succession of shoreline communities at the edge of the Erie Basin at about 12,700 yr B.P. During Zone W-l, the sample site was likely an open mire, sparsely vegetated with carices and other sedges. Aquatic beetles were rare in this zone, possibly due to a lack of open water or to its cold tempera- ture. Arboreal vegetation was probably some distance from the sample site.
The sedges flourished in Zone W-2, forming an extensive marsh or moist meadow depositional environment along the shoreline. Occasional pools of open water supported a small population of aquatic beetles. The first occurrence of scolytid beetles in the sequence may have marked the first presence of spruce trees in the area, although the open element of the remaining terrestrial fauna indicated a parkland rather than forest environment.
In Zone W-3, the marsh element was considerably reduced, probably resulting in part from the encroachment of a dense spruce forest on the sample site. At least a portion of this zone may have represented sediments laid down in running water, as
108 SCHWERT AND MORGAN
fossils of a stream-dwelling beetle species plus numerous plant macrofossils were present.
The nature of these insect communities and their preservation indicates that the depositional area was protected from wave action and erosion, and it was, therefore, within an embayment of the lake. In the original description of the Winter Gulf site, Calkin and McAndrews (1969) hypothesize that a spit across this arm of the lake at North Collins could have provided such protection and allowed the deposition of peat.
However, the relationship of this deposit to the postglacial lake history of the Erie Basin is still uncertain. Calkin and McAndrews (1969) reject a Lake Arkona age for the peat on the basis of stratigraphy, and hypothesize that it was deposited during late Lake Whittlesey or the highest stage of Lake Warren (Warren I). Because the Whittlesey surface would have been 14 m above the peat sediments, a correlation with Warren I, whose levels about equaled the elevation of the peat, is more probable.
The parkland/marsh environment indicated by the insect fauna is further confirmed by palynological and plant macrofossil analyses by Calkin and McAndrews (1969). Spruce cones and wood, as well as seeds of two boreal sedges, Carex aquatilis Wahlenb. and C. rostrata Stokes, were abundant. The pollen diagram, reproduced in Figure 4, is dominated by spruce, sedge, and northern spikemoss (Selaginella rupestris L.) and is interpreted by Calkin and McAndrews (1969) and Calkin (1970) as representing a shoreline meadow within open forest, growing under periglacial conditions. Precise correlation of the insect zones with this diagram was not possible.
Lindroth (1965) observed beetle assemblages, including several thermophilous species, surviving periglacial conditions on Skaftafell, Iceland in isolated microhabitats within 2 km of glacial ice. Although the ice margin is estimated by Calkin (1970) to have been less than 50 km north of the
Winter Gulf site at the time of its deposition, we believe that the insect fauna described probably does not represent such a periglacial environment. Over a long period, the faunal assemblage at the site is too temperate and diverse for such physical conditions. The direction of the prevailing winds, at least during the summer, may have been from the west or south, rather than off the ice to the north to maintain these mild conditions. Regional summer temperature could have even been higher that those estimated in this paper as a cooler microclimate influenced by the cold, meltwater-fed water in the Erie Basin may have prevailed about the Winter Gulf site.
These environmental conditions may have no analog in North America today. The mild temperature values do, however, coincide with an interpretation of temperatures derived from insect remains in the base of a marl sequence at Kitchener, Ontario of slightly younger age (Schwert, 1978); the existence of such temperature values helps to explain the rapid mass wastage of ice which was occurring at that time. Significantly, on independent criteria Morgan and Morgan (1977) postulated that the widespread regional permafrost present in nearby areas of southwestern Ontario disappeared about 13,000 yr B.P. at a time corresponding to the early phase of the Port Huron advance and approximately contemporaneous with or just postdating Lake Whittlesey. The Winter Gulf fauna represents an assemblage not of tundra severity, but one indicating the thermophilous regime which created the demise of the periglacial conditions near the ice margin.
Finally, the insect, pollen, and radiocarbon data indicate that the peat deposition occurred over a relatively short period of time. The exact length of this period is indeterminable, but it must have been sufficient to allow the peat accumulation to occur, as well as to permit the significant changes just outlined in the fauna and flora. This deposit, therefore, certainly represents at least 100 yr but probably no more than 200 or 300 yr of climatic history.
LATE GLACIAL INSECTS FROM NEW YORK 109
ACKNOWLEDGMENTS For their aid in species determinations and for pro-
viding access to beetle collections. we are indebted to the coleopterists at the Biosystematics Research In-
stitute in Ottawa and the Smithsonian Institution in Washington, D.C. Parker Calkin of the State Univer-
sity of New York at Buffalo helped us sample the site and generously provided us with information on the stratigraphic history of the Winter Gulf site. We thank
Anne Morgan, Paul Karrow, and Richard Hebda of the University of Waterloo for their useful suggestions during this work. This paper is derived from disserta-
tion research undertaken in the Department of Earth Sciences at the University of Waterloo and was sup-
ported in part by National Research Council of Canada Grant A8294.
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