Table Of Content2000. The Journal of Arachnology 28:97-106
HABITAT DISTRIBUTION, LIFE HISTORY AND BEHAVIOR
OF TETRAGNATHA SPIDER SPECIES IN THE
GREAT SMOKY MOUNTAINS NATIONAL PARK
Marie Aiken and Frederick A. Coyle; Department of Biology, Western Carolina
University, Cullowhee, North Carolina 28723 USA
ABSTRACT. Habitat distribution patterns of five species of Tetragnatha Latreille 1804 were studied
by analyzing 1163 one-hour samples collected at 17 focal sites representing 16 major biotic communities
(habitats) in the Great Smoky Mountains National Park. Tetragnatha versicolor Walckenaer 1841 is a
habitat generalist, being common over a wide range of elevations (520-1755 m) and in 10 of the 16
habitats, including seven forest habitats as well as wetland, high grass bald, and grassland habitats. Te-
tragnatha laboriosa Hentz 1850 is virtually restricted to non-wetland grassy habitats, T elongata Wal-
ckenaer 1805 to streams, T. viridis Walckenaer 1841 to hemlock trees, and T. straminea Emerton 1884
to non-forested wetlands (marshes). Microhabitat segregation exists in the high grass bald community
between T. versicolor(prefers trees and shrubs)and T laboriosa (prefers herbs). Sizefrequencyhistograms
ofseasonal samples ofT. straminea specimens indicate that this species has a one-yearlife cycle with six
post-emergent instars, and that most individuals overwinter in the antepenultimate instar and mature and
mate in May and June. Tetragnatha straminea is able to capture prey with or without using a web and
adopts stick-like cryptic postures in three different contexts.
Keywords; Tetragnatha, spider, habitat preference, life cycle, cryptic behavior
Being highly diverse and abundant preda- & Croom 1995). Fifteen Tetragnatha species
tors, spiders are important regulators of ter- are known from North America north ofMex-
restrial arthropod populations (Riechert & ico (Levi 1981), and some of these are nu-
Bishop 1990; Coddington & Levi 1991; Mor- merically dominant spiders in particular hab-
an et al. 1996) and may prove to be useful itats and over whole regions (Lowrie 1953;
indicators of the overall species richness and LeSar & Unzicker 1978). Despite the promi-
health of terrestrial communities (Noss 1990; nence of this genus, the life histories of only
Kremen et al. 1993; Colwell & Coddington one North American species (7. laboriosa
1994; Hanggi et al. 1995). But progress to- Hentz 1850) and a few species in other parts
ward understanding the ecological roles of of the world have been rigorously analyzed
spiders is limited by a lack of knowledge of and described (Juberthie 1954; Toft 1976;
the habitat preferences and life histories of LeSar & Unzicker 1978), and knowledge of
many species (Duffy 1978; Hanggi et al. the habitat preferences ofNorth American Te-
1995). Ecologists must know the autecology tragnatha species consists of collecting re-
and life histories ofimportant constituent spe- cords and comments scattered widely in the
cies before they can gain key insights into literature.
food web dynamics and other aspects of a In this study, we describe the habitat distri-
community’s dynamics (Olive 1980; Strong et bution patterns of five Tetragnatha species
al. 1984; Wilson 1992; Polls et al. 1996). found in the Great Smoky Mountains National
Tetragnatha Latreille 1804 may bethemost Park Biosphere Reserve (GSMNP) by using
widespread and abundant orb-weaving spider large sets of spider samples collected from 16
genus in the world (Levi 1981). Tetragnatha major habitats with a standardized protocol
species live in tropical, temperate, and arctic used to inventory the spiders of the GSMNP.
climates and on all continents (except Antarc- Located in the southern Appalachian Moun-
tica) and many islands. On the Hawaiian Is- tains, the GSMNP, due partly to its wide ele-
lands a major adaptive radiation of Tetrag- vation range (275-2013 m), large size
natha species has been discovered (Gillespie (207,000 ha), and low temperate latitude
97
98 THE JOURNAL OF ARACHNOLOGY
(35°35'N), comprises a rich mosaic of biotic study. For a given focal site, the number of
communities appropriate for investigating samples collected in the spring and summer
habitat preferences on a landscape scale. We were equal or very nearly so, as were the
also provide the first analysis and description number of samples collected in 1996 and
of the life history, phenology, and behavior of 1997. At each site (with the exception of the
Tetragnatha straminea Emerton 1884. Our high grass bald and both montane wetland
main goal is to make this important assem- sites) nearly equal numbers of samples were
blage of spiders more accessible to ecologists. collected with each ofthe methods employed.
Descriptions of most of the sampled commu-
METHODS
nity types can be found in Whittaker (1956).
Habitat distribution.—-Teams of3-5 (usu- Vegetation is being analyzed at each focal site
ally 4) collectors used a modified Coddington by GSMNP botanists, and the results ofthese
sampling protocol (Coddington et al. 1996) to analyses will be posted in one or two years
obtain the 1163 one-hour ground (408), aerial on the World Wide Web.
(310), beat (360), and sweep (85) samples of Adult and juvenile Tetragnatha specimens
spiders used in this project. Ground sampling were sorted from each sample and identified
involved searching below knee level mostly to species. By using eye arrangement, pigment
on hands and knees, exploring leaflitter, logs, pattern, and abdominal shape, we were able
rocks, and plant surfaces. Aerial sampling in- to identify all but about 1% of the juveniles.
volved searching foliage, branches, tree Tetragnatha versicolor Walckenaer 1841 and
trunks, and spaces in between, from knee T. laboriosa juveniles cannot be separated by
height up to maximum overhead arm’s reach. eye and body shape characters, but can be dis-
Beating consisted of striking vegetation with tinguished by the following: in versicolor the
aim
long stick and dislodging spiders onto black pigment area surrounding each lateral
a 0.5 m^ canvas sheet held horizontally below eye touches that of its neighboring lateral eye
the vegetation. Hands and aspirators were (clearly separate in laboriosa except in some
used to collect the spiders into vials contain- of the youngest individuals), the abdominal
ing 80% ethanol. One sample unit equaled one venter is light (dark in laboriosa), and the sil-
hour ofuninterrupted effort using one ofthese ver pigment dorsally on the abdomen of the
three methods during which the collector at- smallest specimens is often interrupted by a
tempted to collect every spider encountered. median dorsal line of no pigment (not inter-
During each hour the team as a whole typi- rupted in laboriosa). All specimens will be
cally used all three methods in the same area. deposited in the Smithsonian Institution.
In non-forest communities (grass bald, wet- The relative abundance (mean number of
land, and native grassland sites) one-hour individuals per one-hour sample) ofeach spe-
sweep sampling was substituted foraerial and/ cies in each year was computed for each of
or beating methods; sturdy sweep nets with 38 the 17 sites. It is important to note that this
cm diameterhoops were used, and thenumber index of abundance does not reveal the often
of sweeps per hour (175-400, mean and SD wide variation in number of individuals
— 268 ± 48) depended primarily on vegeta- among one-hour samples at each site, varia-
tion structure and spider abundance. tion due largely to method bias to particular
Two sets of samples (one in the spring and microhabitats, spatial environmental variation
one in late summer) were collected in each of within each site, and seasonal changes in spi-
two years (1996 and 1997) from 15 sites and der abundance correlated with species’ phe-
in 1995 from two other sites, the low grass nologies. An ANOVA (StatView 4.5 from
bald and heath bald sites. These 17 focal sites Abacus Concepts) was used to examine the
were selected by GSMNP ecologists to rep- effect of year and method on spider abun-
resent the 16 major habitat (community) types dance; P < 0.05 was our significance criteri-
found in the GSMNP. Habitat type, locality on.
data, collecting dates, and sampling effort for Life history.—We measured the length of
each focal site are given in the Appendix. Two the left tibia I (ITL) (along the dorsal surface)
montane wetland focal sites were chosen be- ofall 220 T. straminea specimens collected at
cause each one was too small to support the the two montane wetland sites, Meadow
sampling effort judged necessary for this Branch marsh (15 May and 17 July 1996; 23
AIKEN & COTLE—TETRAGNATHA SPECIES IN THE GREAT SMOKY MOUNTAINS 99
May, 1 August, and 7 October 1997) and In- No Tetragnatha species were common at
dian Creek marsh (27 May and 16 August the spruce-fir, spruce, northern hardwood, low
1996; 12 May and 29 July 1997). Toft (1976) grass bald, or heath bald sites, and none were
demonstrated that ITL often distinguishes spi- collected at the pine-oak (395 m) site (Table
der instars more clearly than does either the 1, Fig. 1). Sites with two or more common
length or width of the carapace. Measure- species of Tetragnatha were the high grass
ments were performed with a Wild M-5 ste- bald {versicolorand laboriosa), both wetlands
reomicroscope at 24X and 12X magnification {versicolor and straminea), and the native
and are accurate to ± 0.077 mm. We used the grassland {versicolor, laboriosa, and strami-
StatView 4.5 computer program to generate nea) (Fig. 1).
ITL frequency distribution histograms. By ex- There were significant relative abundance
amining these histograms of seasonal subsets differences between 1996 and 1997 for T. ver-
(spring, summer, and fall) ofdata pooled from sicolor at the mixed oak. Table Mountain
both sites, it was possible to reveal phenology pine, hemlock/hardwood cove, hardwood
(seasonal timing of development) and gener- cove, and Meadow Branch wetland sites, and
ation time (life cycle length). The histogram for T. laboriosa at the native grassland (Fig.
for all data pooled revealed the total number 1). In each case, the relative abundance was
of instars. higher in 1997.
Behavior.-—We observed and photo- Microhabitat distribution.—At the high
graphed live specimens in the field. Several T. grass bald, T. laboriosa was more abundant in
straminea juveniles (antepenultimate instar) sweep samples (collected from herbaceous
were placed in separate terraria and main- vegetation) than in beat samples (collected
tained for several weeks on Drosophila flies from shrubs and trees) {F = 5.64, df = I, P
while we observed prey capture and cryptic = 0.025), whereas T. versicolor was more
postures, sometimes using a hand-held mag- abundant in beat than in sweep samples {F =
nifier. 5.64, df^ 1, P = 0.025) (Fig. 2). At the In-
dian Creek wetland site, T straminea was
RESULTS
more abundant in sweep samples than in beat
Habitat distribution.-”Five species of Te- samples (F = 5.17, # = 1, P - 0.041), but
tragnatha were collected in the GSMNP: T. r. versicolor was equally common in both
elongata Walckenaer 1805, T. laboriosa, T. sweep and beat samples (F = 0.24, df— P
straminea, T. versicolor, and T. viridis Wal- = 0.632) (Fig. 3). Although we were unable
ckenaer 1841. Table 1 and Fig. 1 show the to make this kind ofmicrohabitat comparison
relative abundance ofthese species ateach fo- at the Meadow Branch wetland or native
cal site. Tetragnatha versicolor was found at grassland sites (because the beat method was
16 ofthe 17 focal sites and was common (rel- not used at these sites), we observed that T.
ative abundance = 0.5-2.0) or abundant (rel- straminea was more common in the low
ative abundance > 2.0) in 10 of the 16 habi- grassy vegetation of the wetter parts of these
tats, including seven forest habitats as well as habitats than was T. versicolor. The few spec-
montane wetland, high grass bald, and native imens of T. viridis that were found were col-
grassland habitats. It was especially abundant lected only by beating the foliage of hemlock
in mixed oak forest, Tetragnatha laboriosa trees. Tetragnatha elongata was collected
was found at nine sites, but was rare at all but only over the small streams flowing through
two of these sites, native grassland and high the hemlock and native grassland —sites.
grass bald. Tetragnatha versicolor and T. la- Life history of T, straminea. The size
boriosa were found over a wide elevational frequency histogram of all T. straminea indi-
range (520-1830 m). Tetragnatha straminea viduals collected at the wetland sites during
was collected at only three sites, the montane both years indicates a total of six size/age
wetland and native grassland sites, and was classes and, therefore, six post-emergent in-
common or abundant at all three. Tetragnatha stars (instars living outside the egg sac) (Fig.
elongata was found only at the two sites 4). As is typical for spiders (Toft 1976; Coyle
through which streams flow. Tetragnatha vir- 1985) the older the instar, the greater the var-
idis was found only at the two sites where iation in size. Fortwo reasons, we suspectthat
hemlock trees are abundant. the ITL frequency peak between 4.5 and 5.0
—
100 THE JOURNAL OF ARACHNOLOGY
Table 1. -Relative abundance of Tetragnatha species at 17 focal sites representing 16 biotic commu-
nities in the Great Smoky Mountains National Park in both 1996 and 1997 (1996 and 1997 values are
separated by a comma). Low grass and heath balds were sampled in 1995 only. Elevation (m) of each
site is given in parentheses. Relative abundance value is underlined if at least one adult was collected.
Relative abundance
(mean number of individuals per sample)
Habitat/focal site elongata laboriosa straminea versicolor viridis
Spruce-fir (1830) 0, 0.04 0,0.08
High grass bald (1755) 0.88, 1.67 1.46, 2.25
Spruce (1715) 0, 0.08 0,13,0.04
Beech gap (1645) 0.50, 0,21
Northern hardwood (1615) 0.16,0.30
Red oak (1555) 0.40, 1.08
Low grass bald (1505) 0.17 0.40
Heath bald (1390) 0.10
Mixed oak (1115) 5.82, 18.0
Table Mtn. pine (1005) 0.02, 0 0.06, 0.58
Hemlock-hardwood cove (945) 1.15,2.75 0.04,0.06
Hemlock (885) 0.17,0.19 1.73,3.36 0.02,0.03
Hardwood cove (740) 0, 0.02 0.43, 1.25
Wetland (Indian Cr.) (685) 0.06, 0 2.00,3.31 0.24, 1.38
Wetland (Meadow Br.) (535) 0, 0.19 2.00, 3.94 0.24,3.31
Native grassland (520) 0,0.13 0.13,2.17 0.08, 0.80 0.04, 0.54
Pine-oak (395)
mm
does not represent the modal value ofone samples. These seasonal patterns strongly sup-
instar with a very broad size range, but is in- port a life history pattern of one generation
stead the result of size overlap between post- per year with most individuals overwintering
emergent instars IV and V: 1) The size range in the antepenultimate instar. Males and fe-
of adult females should be greater than that of males appear to mature and mate in May and
any younger instar. 2) The ITL range of the June. Many adult females persist well into the
penultimate male cohort (recognized by swol- summer months, but males are absent then,
len palpal tarsi) should approximate thatofthe suggesting that they die soon after mating.
penultimate females. Adult females were dis- BehaviorofT s^aminea~ln the field, the
tinguished by their protuberant genital area orientation of T. straminea orbs varied from
(and by fully developed spermathecae when- horizontal to diagonal. Some spiders were in
ever dissections were performed). Penultimate the center of their web adopting a roughly
females (instar V) were distinguished on the stick-like posture (legs I and II extended for-
basis of size and the absence of a protuberant ward fairly close to one another and legs III
genital area. Size frequency histograms ofsea- and IV extended backward near the sides of
sonal subsets of T. straminea specimens col- the abdomen). Others were stretched out on a
lected at both wetland sites show in late spring twig or grass blade with legs I and II held
(12-27 May) adult and penultimate males, together, the much shorterlegs III surrounding
adult and penultimate females, and relatively and gripping the substrate, and legs IV ex-
largejuveniles, most ofwhich are presumably tended backward along the sides of the ab-
antepenultimate (Fig. 5). The summer (17 domen. This second posture, in concert with
July-16 August) sample setcontained a small- the slender abdomen and pale yellow-brown
er number of adult females and younger ju- color, made the spider exceedingly difficult
veniles (instars I-III) than were present in the for us to locate. Sometimes we could not find-
spring. The fall (7 October) sample set (from the captive spiders that had adopted this very
Meadow Branch wetland) was composed only cryptic posture withoutjarring the dead grass
of ajuvenile class (instars III-IV) with a mean stems in their containers. When disturbed in
ITL between that of the spring and summer this way, the spider would sometimes drop
AIKEN & COTLE^-TETRAGNATHA SPECIES IN THE GREAT SMOKY MOUNTAINS 101
1996 1997
spruce-fir(1830)
high grassbald (1755) 22ZZZ zzzzzzzzz:^
spruce (1715)
laboriosa
beechgap (1645)
H straminea ZI
northernhardwood (1615)
versicolor IZl
red oak (1555)
ZZl
m
lowgri^sbald (1505) Z3
heathbald (1390)
mixed oak (1115)
TableMtn.pine (1005) 5.8 18.0
hemlock-hardwoodcove (945) ’ZZZZ21 /77/A'/Z777ZZZ3*
hemlock (885)
hardwoodcove (740)
ZZl
wetland (Indian Cr.) (685)
sss
wetland (MeadowBr.) (535)
nativegrassland (520)
0123401234
pine-oak (395)
relative abundance
(mean no,spidersper1 hrsample)
Figure L-—Relative abundance of the three most common Tetragnatha species in 1996 and 1997 at 17
focal sites representing 16 biotic communities in the Great Smoky Mountains National Park. Low grass
and heath bald sites were sampled in 1995 only. Focal sites are listed in order from lowest to highest
elevation (in meters within parentheses). An asterisk marks any bar representing a relative abundance
value significantly higher than one for the same species and site in the other year (ANOVA, P < 0.05).
laboriosa versicoior Straminea versicoior
BEAT SWEEP BEAT SWEEP BEAT SWEEP BEAT SWEEP
(shrubs/trees) (herbs) (shrubs/trees) (herbs) (shrubs/trees) (herbs) (shrubs/trees) (herbs)
Figure 2.~Microhabitat distribution of Tetrag- Figure 3.—Microhabitat distribution of Tetrag-
natha species at the high grass bald site, n ” 12 natha species at the Indian Creek wetland, n = 8
beatand 18 sweep samples. Standarderroris shown beat and 7 sweep samples. Standard error is shown
on top of each bar. The P-value is generated by on top of each bar. The P-value is generated by
ANOVA; see text for test statistics. ANOVA; see text for test statistics.
1
102 THE JOURNAL OF ARACHNOLOGY
I TT TTl
-
I
Tibia iength (mm)
i
—
Figure 4, Size (ITL) frequency distribution histograms of all 220 Tetragnatha straminea individuals
collected at the two montane wetland sites during 1996 and 1997. Females and individuals too young to
be sexed are graphed separately from penultimate and adult males. Labeled horizontal bars indicate ITL
ranges of putative and known (adults and penultimate males) posLemergent instars.
Spring (12-27 May)
wvr nenult.female.*! adultfemale*!
Fall (7 October)
in
IV
4 5 6 7 10 1
Tibia length (mm)
I
—
Figure 5. Size (ITL) frequency distribution histograms of seasonal subsets of all 220 Tetragnatha |i
straminea individuals collected at the two montane wetland sites during 1996 and 1997, Females and. 1
individuals too young to be sexed are graphed separately from penultimate and adult males. Labeled
||
horizontal bars indicate ITL ranges of putative and known (adults and penultimate males) postemergent
,|j
instars. ^
AIKEN & COYl^E^TETRAGNATHA SPECIES IN THE GREAT SMOKY MOUNTAINS 103
and assume this cryptic stick-Mke posture and elevations (Levi 1981) and is the most
while hanging suspended in mid-air from its abundant spider in New York alfalfa fields
dragline. (Wheeler 1973) and central Illinois soybean
Twice we were able to directly observe fields (LeSar & Unzicker 1978). We suspect
these spiders capture Drosophila flies without that the very few individuals of T, laboriosa
GSMNP
using a web. In the first observation, the fly collected at forest sites within the
was walking on the twig under which the spi- were immigrants thathad ballooned from non-
der was positioned cryptically. The fly ap- forest habitats and would not have matured
peared to hit one of the spider’s third legs and reproduced where we found them; this
(which were wrapped around the twig) and it view is supported by LeSar & Unzicker’s
was seized instantly. In the second observa- (1978) observations that early instars ofT. la-
tion, the spider was ascending the side of its boriosa are good ballooners and colonizers
glass cage when a fly walked into it. The spi- and by the fact that every forest-dwelling in-
der’s first two pairs oflegs instantly surround- dividual we collected was an early instar ju-
ed the fly for a brief moment until the spider venile.
could grasp it with its chelicerae. Silk was not Our data indicate that T, siraminea, T. vir-
used to immobilize either of these flies. Fol- idis, and T. elongata are all habitat specialists.
lowing these and other less closely observed The restriction ofT. straminea to non-forested
GSMNP
capture attempts not involving webs, the spi- wetlands in the is consistent with
der crushed and manipulated the prey with its collection records cited by Levi (1981), Levi’s
chelicerae and pedipalps. We often observed (1981) observation that T. viridis is restricted
individuals holding in their chelicerae 1-5 to conifers matches our findings. We suspect
flies which had been captured without a web. that our data underestimates the abundance of
Occasionally, such spiders with two or more T. viridis at the two sites where we found it
flies in their mouthparts would capture addi- because 1) it may frequent the large volume
tional live flies (that we held in contact with of hemlock canopy foliage above our sam-
the web) by grabbing them with the first legs pling zone, 2) its green color and abandon-
and immediately wrapping them in silk with ment of web-building make it difficult to lo-
the hind legs. These immobilized flies were cate visually, and 3) it may be especially
left attached to the web, and since we could difficult to dislodge (Levi 1981). Our obser-
not find them on the following day, we pre- vation that r. elongata is strictly riparian and
sume they were eaten. nearly always builds its webs over open water
match those of Lowrie (1953), Levi (1981),
DISCUSSION
Kaston (1981), and Gillespie (1987). Accord-
Habitat and microhabitat distribution,— ing to the distribution records in Levi (1981),
Clearly, T, versicolor is a habitat generalist. there are only two other species of Tetrag-
Out finding that it is common or abundant natha that we think might eventually be found
over a wide elevation range in a wide variety in the GSMNP, T, guatemalensis O.P.-Cam-
of forest communities as well as wetland, bridge 1889 and T. pallescens F.P, Cambridge
grass bald, and grassland habitats, is consis- 1903. If these two are living in the GSMNP,
tent with collection records cited by Levi they are not common.
(1981), Although it appears to prefer woody The finding that T. versicolor is distributed
vegetation and can thrive in dryer situations among more habitats in the GSMNP and else-
than many of its congeners, it can also be where than are T. straminea, T. viridis, and T.
found on herbaceous vegetation in marshy ar- elongata, and the observation that this species
eas. Our observations, which are consistent has ahigher (67®N) and larger (54') latitudinal
with those of Comstock (1912), Lowrie and geographic (ca. 20.7 billion km^) range
(1953), Levi (1981), and Kaston (1981), show than the other three species (46-57°N; 16-34';
that T. laboriosa, like T, versicolor, often lives 1.6-7.8 billion krn^) (Levi 1981), appear to fit
far from aquatic habitats, but, unlike T. ver- a taxonomically widespread biodiversity pat-
sicolor, rarely occurs in forests andis virtually tern where habitat generalists in many taxa
restricted to non-wetland grassy habitats. In tend to occupy broader latitudinal and geo-
spite of this restriction, it thrives over a wide graphical ranges than do habitat specialists
range of natural and agricultural communities (Stevens 1989; Wilson 1992). However, T. la-
104 THE JOURNAL OF ARACHNOLOGY
boriosa, which appears from our data to be may be the rale in this genus; Finnish popu-
less of a habitat generalist than T. versicolor, lations of T. extensa (Linnaeus 1758), T. ob-
has much the same geographic range as ver- tusa C.L. Koch 1837, and T, montana Simon
sicolor. Apparently, the ability of T. laboriosa 1874, and Illinois populations of T. laboriosa
to colonize and reproduce in open habitats all have annual cycles (Toft 1976; LeSar & •
suits it well to utilizing a wide array ofedaph- Unzicker 1978), Much like T, straminea, these '
ic and early successional non-forest habitats species overwinter in mid-to-late juvenile in-
which have proliferated because of increased stars and mature and mate in late spring or j;
;
human impact on landscapes and which are early summer. However, Juberthie (1954)
simply not well represented in the GSMNP. In showed that in southern France Tetragnatha |
other words, its status as a habitat generalist species may have two generations per year. j.
cannotbe fully expressedin the GSMNPland- LeSar & Unzicker (1978) found that lab- ;
i
scape. reared T. laboriosa has eight posternergent in-
I
Our results indicate that the coexistence of stars, rather than the six our field data indicate
1
r. versicolor and T. laboriosa at the high for T. straminea, but the natural phenologies
grass bald site involves microhabitat segre- of these two species are very similar. ;
gation in a patchy community; versicolorlives Behavior.—The cryptic, stretched~out
I
primarily in the shrubs and small trees that are stick-like postures ofT. straminea (on its web,
I'
scattered within and surround the open areas on vegetation, or hanging in mid-air), like
:
of grass and other herbs where laboriosa similar postures adopted by other species of
lives. It is puzzling why no adults of T. ver- Tetragnatha and unrelated spiders like Dei-
sicolor were collected here despite the abun- nopis MacLeay 1839 (Comstock 1912; Bris-
dance ofjuveniles (Table 1). Perhaps this pop- towe 1958; McKeown 1963; Forster& Forster
ulation is largely or wholly maintained by 1973; Levi 1981; Kaston 1981; Gillespie &
aerial immigration from .high density forest- Groom 1995; Getty & Coyle 1996), surely t
I
dwelling populations at lower elevations; this must serve to reduce an individual’s chances ‘
hypothesis remains to be tested. The beat vs, of being detected or recognized as prey by
f
sweep data from the Indian Creek wetland site visual predators. The remarkably flexible prey
suggest that the T. versicolor population there capture behavior we have observed in T. stra-
is not as distinctly segregated from the stra- minea—-the ability to catch prey both with and |;
minea population. However, observations dur- without the use of a web—has also been ob-
ing an autumn sampling effort in the Meadow served by Luezak & Dabrowska-Prot (1966)
Branch wetland, as well as T. versicolors in a Eurasian species, T. montana. This ver-
ability to prosper away from aquatic habitats, satile capture program, which may be more
[I
suggest to us that an appropriate sampling de- widespread in the genus than is currently ap- '
sign would reveal that the straminea popula- predated, may help explain the origin ofnon-
tion is concentrated in grasses and other herbs web-building cursorial spiny-legged lineages
in the wetter part of these wetlands while the represented by T. viridis (Levi 1981) and sev-
versicolorpopulation is chiefly found on taller eral Hawaiian species (Gillespie & Croom
and more sturdy vegetation in the dryer areas. 1995).
i
The significantly higher relative abundance
ACKNOWLEDGMENTS
values in 1997 as compared to 1996 for T. ;
versicolor at several sites and for T. laboriosa Robert Edwards, Jeff Stiles, Ricky Wright,
:
at one site may be the result of population Doug Toti, Jeremy Miller, Melinda Davis, and
i;
increases. However, we suspect that the 1997 Ian Stocks all helped sample and process
sampling team devoted more effort to collect- specimens, Richard Brace, Jonathan Codding- ;
ing small juveniles (particularly from beating ton, Michael Lewder, Denise McNabb, Trevor
sheets and sweep nets) than did the 1996 Bundle, and an anonymous reviewer provided ;
team, thus creating a bias which might have helpful comments on drafts ofthis paper. This
[
caused these relative abundance differences. research was supported by a Western Carolina
Life history.—Ours is the first life history MUnAiversity Undergraduate Research Grant to :
analysis of T. straminea. This and other life and National Science Foundation (DEB-
history analyses of north temperate Tetrag- 9626734) and National Park Service Chal-
natha species show that one-year life cycles lenge Cost Share grants to FAC.
AIKEN & COYLE—-TETRAGNATHA SPECIES IN THE GREAT SMOKY MOUNTAINS 105
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APPENDIX
cut, Bulletin No. 70.
Kremen, C., R.K. Colwell, TL. Erwin, D.D. Mur-
phy, R.F. Noss & M.A. Sanjayan. 1993, Terres-
Habitat type, locality data, collecting dates,
trial arthropod assemblages: their use in conser-
vation planning. Conserv. Biol., 7(4):796-808. and sampling effort for each of the 17 focal
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habits, and prey preferences of Tetragnatha ia- elevation). Number of ground, aerial, beat,
boriosa (Araneae: Tetragnathidae). Environ. En- and sweep samples given in parentheses after
tomoL, 7:879-884. total number of one-hour samples.
106 THE JOURNAL OF ARACHNOLOGY
Spruce-fir forest: NORTH CAROLINA: Table Mountainpineforest: TENNESSEE:
Swain County, 0.5 km SW Mt. Collins, N & Sevier County, about 200 m N of route 441
NW
5 sides ofAppalachian Trail, E2755, N39403, loop of Chimneys picnic area, E2738,
1815-1845 m elev., 26 June 1996, 14 Septem- N39471, 976-1037 m elev., 6 June 1996, 6
ber 1996, 11 June 1997, 23 August 1997. 48 August 1996, 27 May 1997, 6 August 1997.
samples (16-16-16-0). 64 samples (23-18-23-0).
High grass bald: NORTH CAROLINA: Hemlock-hardwood coveforest: TENNES-
Swain County, Andrews Bald, E2738, SEE: Sevier County, N & E Grotto Falls Trail-
N39354, 1755 m elev., 27 June 1996, 22 Sep- head at Roaring Fork Motor Traiml, P. White I
tember 1996, 12 June 1997, 6 September veg. plot, E2772, N39512, 945 elev., 22
1997. 48 samples (18-0-12-18). May 1996, 30 July and 1 August 1996, 19
Spruceforest: NORTH CAROLINA: Swain May 1997, 4 August 1997. 96 samples (32-
County, just SW junction of Noland Divide 32-32-0).
NTr3a9i3l82a,nd17r1o5admtoelepvu.,mp2i0nJgunsetat1i9o9n6,,E727S5e5p,- HaHyewmoloodckCofuonrteys,t:CNatOalRoTocHheeC,AR1O50LImNA:S '
tember 1996, 10 June 1997, 23 August 1997. mouth of Palmer Branch atmCaldwell Fork,
48 samples (16-16-16-0). E3107, N39436, 854-915 elev,, 4 June
Beech gap forest: NORTH CAROLINA: 1996, 5 August 1996, 18 May 1997, 1 June
Swain County, in hog exclosure below Ap- 1997, 10 and 24 August 1997. 84 samples '
palachian Trail at 350 m E Road Prong Trail- (29-26-29-0).
head, E2786, N39433, 1645 m elev., 14 June Hardwood cove forest: TENNESSEE: Se-
1996, 15 August 1996, 10 June 1997, 13 Au- vier County, along Porter’s Creek Trail at 200
paces above bridge over Porter’s Creek,
gust 1997. 48 samples (16-16-16-0). m !
Northern hardwoodforest: NORTH CAR- E2830, N39508, 740 elev., 18-19 June '
OLINA: Haywood County, Cataloochee Di- 1996, 24-25 August 1996, 21-22 May 1997,
m 31 July 1997. 116 samples (39-37-40-0).
EvidGeajrursettta’sbovGeapH,emEp3h0i5l5l,BaNl3d93T5ra9i,l a1t621050 m Wetland (Indian Creek): NORTH CARO-
LINA: Swain County, marsh between Indian
elev., 12 and 15 June 1996, 14 August 1996, Creek Trail and Indian Creek at 2 mi, NE of
6 June 1997, 12 August 1997. 84 samples
junction with Deep Creek Trail, E2817,
(29R-e2d7-2o8a-k0)f.orest: NORTH CAROLINA: Ngu3s9t29169,966,8512mMaelyev.,192977,M2a9yJ1u9l9y6,191967.Au3-3
Swain County, Roundtop Knob, E of Noland
samples (14-4-8-7).
Divide Trail about 2 mi SE Clingman’s Dome Wetland (Meadow Branch): TENNESSEE:
m '
Road, E2770, N39364, 1555 elev., 24 June Blount County, marsh along Meadow Branch
1996, 31 August 1996, 4 June 1997, 11 Au- at 0.5 km ENE of Dosey Gap, E2527,
gusLtow1997g.ra8s8s sbaamlpdl:esN(O3R0-T2H8-30C-A0R)O.LINA: N1399964,701,5 5M3a5ym19e9l7ev,.,1723JuMlyay1919979.63,31sAaumgpulsets
Swain County, Gregory Bald, E2401, N39343, (13-8-0-12).
1505 m elev., 3-5 June 1995, 29-30 Septem- Native grassland: TENNESSEE: Blount
ber 1995. 72 samples (24-0-24-24). County, Cades Cove, S side Abrams Creek
Heath bald: TENNESSEE: Sevier County, about 0.3 mi. upstream from Cades Cove
Inspiration Point on Alum Cave Trail, E2789, Loop Road bridge, E2426, N39423, 520 m
N39461, 1390 m elev., 25-25 May 1995, 23- elev., 5 June 1996, 8 August 1996, 15 May
24 September 1995. 72 samples (24-24-24- 1997, 17 July 1997. 48 samples (24-0-0-24). ,'
0). Pine-oak forest: TENNESSEE: Blount
Mixed oak foresWt: TENNESSEE: Sevier County, 300 m N ofjunction ofTabcat Creek
County, E, S, & slopes of Chinquapin and Maynard Creek, E2301, N39347, 395 m
Knob, E2639, N39512, 1083-1144 m elev., elev., 28-29 May 1996, 2 August 1996, 14
13 June 1996, 13 August 1996, 2 June 1997, May 1997, 15 July 1997. 96 samples (32-32-
7 August 1997. 85 samples (29-26-30-0). 32-0).
