DIVERSITY AMONG GROUND-DWELLING SPIDER ASSEMBLAGES: HABITAT GENERALISTS AND SPECIALISTS

2005·10.1 MB·English

by  Rachael E Mallis

2005. The Journal of Arachnology 33:101-109
DIVERSITY AMONG GROUND^DWELLING SPIDER
ASSEMBLAGES: HABITAT GENERALISTS AND SPECIALISTS
Rachael E, Mallis and Lawrence E. Hurd^: Department of Biology, Washington &
Lee University, Lexington, Virginia 24450 USA, E-mail: [email protected]
ABSTRACT, We sampled assemblages of ground-dwelling spiders with pitfall traps in six terrestrial
habitats representing a successional gradient in southwestern Virginia, during the summer of 2002. Ap-
proximately halfofthe 50 species trapped were habitat specialists with low abundance, found at only one
of the sites, which is qualitatively consistent with the literature. Only four species, Schizocosa ocreata
(Hentz 1844), Pirata insularis (Emeiton 1885) Pirata aspiram (Chamberlain 1904) andNeoantisteamag-
na (Keyserling 1887) were found at as many as four sites. A few species that were found in more than
one study from disparate geographical communities, such as Trochosa terricola (Thorell 1856) tended
also to berelatively abundanthabitat generalists. In general, themajority ofspiderspecies foundin studies
such as ours that examined multiple sites were habitat specialists and had low abundance. For our sample
sites, there was no relationship between any measure of spider diversity (V H\ /’) and successional age.
Our results, and those of most other published studies, are consistent with the hypothesis that spider
assemblages do not undergo succession and except for a few very common generalist species the com-
position of these communities is unpredictable, and may depend more on stochastic colonization and
specific resource requirements of specialists following immigration than on any predictable association
with successional parameters,
Keywords: Cursorial spiders, habitat specialization, spider diversity, succession
The importance ofpredators in the structure old field, and forest litter communities (Hurd
and function of natural ecosystems is becom- & Eisenberg 1990; Riechert & Bishop 1990;
ing increasingly well documented (Terborgh Moran et aL 1996; Lawrence & Wise 2000).
et aL 2001). Spiders are widespread and di- Given their demonstrated importance to the
verse predators that are part of terrestrial ar- structure and function of many communities,
thropod assemblages (Wise 1993) and arthro- it is important to gather information on the
pods comprise more than half of known distribution and abundance of cursorial spider
species (Wilson 1992). Cursorial spiders in species. Often it has been difficult to deter-
particular are the dominant arthropod preda- mine what features of an environment deter-
tors in many terrestrial communities, e.g., mine which, orhow many, species ofcursorial
&
grasslands (Weeks Holtzer 2000) and forest spiders will be present. For example, spider
floor litter (Uetz 1979). Their position in tro- diversity may not follow a treed toward in-
phic structure of communities often is com- creasing diversity with increasing succession-
plex: spiders in forest litter belong to both the al age (Hurd & Fagan 1992; Aitchison &
decomposition and the grazing food webs be- Sutherland 2000; Buddie et al, 2000) that has
cause they consume detritivores/fuegivores been a traditional expectation for species of
and herbivores (Uetz 1975; Wise et aL 1999). plants and animals during terrestrial succes-
As larger species ofwolf spiders mature, they sion (Odum 1969).
prey more on herbivores that are part of the Spiders have legendary powers ofdispersal
grazing food web (Uetz 1975; McNabb et aL and often are among the firstcolonizers ofdis-
2001). Spiders have been experimentally dem-
turbed sites (Hodkinsoe et al. 2001); the first
onstrated to exert important effects on the known colonist of Krakatoa was a spider
populations ofother arthropods in a variety of (Spiller et al. 1998). Many spiders have the
experimental systems, including agricultural,
ability to disperse by “ballooning” with silk
at some point in their life cycles (Hodkinson
’ Corresponding author. et al. 2001). Lycosids and geaphosids balloon
101
102 THE JOURNAL OF ARACHNOLOGY
—
Figure 1. Map ofthe Science Park on the campus ofWashington & Lee University. The habitats used
for sampling sites are described in the text: CG = cedargrove; OF = old field; DR = disturbancerecovery;
LH = lowland hardwoods; UH = upland hardwoods; PW = Pine woods.
as juveniles, while many linyphiids retain the der guilds is farfrom being answered, and will
capability throughout adulthood (Mrzljak & require the accumulation of much more data
Wiegleb 2000). However adept they are at ini- (Uetz et ak 1999).
tially getting to new sites, cursorial spiders We report here on a field study in which six
should have specific habitat preferences that field sites, representing different successional
dictate which species will become established seres, are compared with respect to ground-
and how abundant they will be. Some species dwelling spider species captured by pitfall
are more particular than others: along a suc- trap sampling. We compared diversity among
cessional gradient in Delaware, the lycosid sites, and the extent of habitat specialization
Pirata insularis (Emerton 1885) was found (relative number of habitats in which species
abundantly in all four communities examined, were found in this, and in previous studies) in
whereas the gnaphosid Zelotes hentzi (Bar- these spiders.
rows 1945) was rare and confined to the youn- METHODS
&
gest successional site (Hurd Fagan 1992). —
The structure ofvegetation and some physico- Study Sites. The study sites we used for
chemical habitat parameters may determine a this study are located in the 35ha Science Park
& &
spider's habitat choice (Mrzljak Wiegleb of Washington Lee University in Rock-
2000). Along forest litter gradients and in bridge Co, Virginia, USA (Fig. 1). The sites
agroecosystems, lycosids manifest microhab- were chosen to represent different habitat
itat preferences possibly based upon leaflitter, types and stages of secondary terrestrial suc-
herbaceous vegetation and available moisture cession typical ofthis region, as described be-
(Weeks & Holtzer 2000). The question of low in order of successional age.
what determines the structure ofcursorial spi- /. Disturbance recovery (DR): This site is
MALLIS & HURD-~CURSORIAL SPIDER DIVERSITY 103
a 0.5ha patch of level ground, surrounded by placed by hardwoods. The ground is mostly
woods, that is being used in a long-term study in shade, with small patches of sunlight most
of community succession. The ground had ofthe day. The soil is sandy and well-drained.
been stripped of all native top soil prior to The litter layer consists of a < 1.0cm layer of
2001, leaving a bare, hard clay surface. Dur- dead cedar needles. We considered this site to
ing fall and winter 2001 ground leaf mulch be the earliest forest community, between OF
PW
was applied to the bare clay and tilled into the and in age.
upper 2-3cm, after which seeds of 19 native 4. Pine woods (PW): This site is in deep
forb species and five native grasses were shade, provided by an overstory of tall
planted. The plant assemblage that sprouted (>10m) white pines (Pinus strobus) and
during spring and summer 2002 constituted a mixed species of smaller hardwoods, espe-
dense mixture of these intentionally planted cially red maple {Acer rubrum) and white ash
species and incidental species that were pres- (Fraxinus americana), with an uederstory of
ent as seed in the mulch (an especially con- saplings and shrubs. This species mix repre-
spicuous member of the second category dur- sents an alternative intermediate stage of suc-
ing late summer was ragweed, Ambrosia cession to the assemblage in CG; the relative
artemisiifoUa). The vegetation, which reached height ofthe hardwoods in this standindicated
a height of approximately 0.5m, was dense that PW may be the older of the two, at least
enough to provide shade at the soil surface. 40 years old. The site is located on a flood
There was no organic litter layer on the soil, plain, with relatively most soil. The litterlayer
owing to the absence ofplants on the site dur- is mainly dead needles, but somewhat thicker
ing the previous year. This site is surrounded (>lcm).
by a wire fence to keep out deer, and is sur- 5. Upland hardwoods (UH): This site is
rounded by woods. within the woodlot boundary of the DR site.
2. Old-field (OF): This site is a third year The overstory is ofmixed hardwoods 10-15m
successioeal sere, which was previously sub- high, especially white ash and tulip poplar
jected to mowing once or twice annually. It is {Liriodendron tulipifera), with several species
fully open to the sun, and consists of grasses of oaks (Quercus spp.), and red maple in the
and forbs growing up to approximately 0.5m uederstory. This species mix is typical of the
high typical ofearly successional old-fields in community that replaces coniferous species,
PW
this region, including patches of emergent (ca i.e., perhaps 10-15 years older than site
1.5m high) late-seasoe goldenrod {Solidago (i.e., 50-55 years old). The soil here is well-
spp.), teasel {Dipsacus sylvestris), and rag- drained and rich in organic matter, with a rel-
weed {Ambrosia artemisiifoUa). Plant height atively deep (3-4cm) leaf litter layer.
and soil shading at this site were similar to 6. Lowland hardwoods (LH): This is a ma-
those at site DR (see above), but here there ture hardwood forest that has been subjected
was a sparse and shallow (<0.5cm depth) lit- to little disturbance for at least the past 70
ter layer consisting of dead plant stalks and years, with canopy trees (tulip, maple, white
leaves from the previous year's growth. An ash, and mixed oak) > 30m. This site is deep-
abundant and diverse arthropod assemblage ly shaded and is on a floodplain at the bottom
inhabits this site, the most conspicuous of of a slope, downward from site UH. The leaf
which are several species of grasshoppers litter is more compacted than and not as thick
(Acrididae). The cedar grove site {CG, see be- as at site UH, probably because of the in-
low) forms the western border ofthe old-field creased soil m—oisture and humidity.
site. Sampling* We sampled ground-dwelling
3. Cedar grove (CG): This site consists of spiders at each site with six pitfall traps set
a near monoculture of 6“-8m high eastern red out in a 2 X 3 array, such that no trap was
cedar (Juniperus communis) from 30=-40 closer than approximately 1.5m from its near-
years old, with a sparse understory of hard- est neighbor. Trap arrays were at least 10m
wood saplings and very little herbaceous from the edge of the habitats they sampled.
ground cover. In our geographical area, cedars Each trap consisted ofa 10cm diameter, 11cm
grow in old-fields until they shade out her- deep polypropylene cup fitted into a perma-
baceous vegetation, and thee may dominate nent sleeve that was sunk into the ground
the community until they senesce and are re- flush with the soil surface. A cover for each
"
104 THE JOURNAL OF ARACHNOLOGY
—
Table 1. Total numbers ofcursorial spidersbyhabitattype (sampling site): DR = disturbancerecovery;
OF = old field; CG = cedar grove; PW = pine woods; UH = upland hardwoods; LH = lowland hard-
woods. Superscripts denote other studies in which species were found: 1 = Hurd & Fagan (1992); 2 =
Buddie et al. (2000); 3 = Aitcheson & Sutherland (2000); 4 = Bonte et al. (2002); 5 = Gajdos & Toft
(2000); 6 = Uetz (1975); 7 = Uetz (1976); 8 = Uetz (1977); 9 = Uetz (1979); 10 = Buddie and Rypstra
(2003); and 11 = Draney (1997). Nomenclature follows Platnick (2003).
DR OF CG PW UH LH Species
Family Genus;species Total Total Total Total Total Total Total
Agelenidae Koch 1837 Agelenopsispennsylvanica^ Koch
1843
Antrodiaetidae Gertsch 1940Antrodiaetus unicolor Hentz 2
1842
Corinnidae Karsch 1880 Castianeira cingulata^-^’^'^’ 1
Koch 1841
Castianeira longipalpus^’ “ 1 3 4
Hentz 1847
Phrurotimpus alarms'' Hentz 2 4 16 22
1847
Phrurotimpus borealis^’ ^ Emer- 3 2 5
ton 1911
Phrurotimpus minutus'-^ Banks 1 1 2
1892
Phrurotimpus sp. Chamberlin & 2
Ivie 1935
Scotinella britcheri Petrunke- 1
vitch 1910
Scotinellaformica' Banks 1911 8 9
Scotinella sp. Banks 1911
Cybaeidae Banks 1892 Cybaeus sp. Koch 1868 3 1 5
Dysderidae Koch 1837 Dysdera crocata"' Koch 1838 1 1
Gnaphosidae Pocock 1898 Drassyllus depressus Emerton 1 1
1890
Hahniidae Bertkau 1878 Hahnia cinerea^’^ Emerton 1890 1 5 6
Antistea brunnea Emerton 1909 1 1 2
Hahnidae sp. 1 1 3 4
Neoantistea agilis^' Keyserling 11 11 11 2
1887
Neoantistea magna Keyserling 4
1887
Linyphiidae Blackwall 1859 Drapetisca alteranda Chamber- 1 1
lin 1909
Subfamily: Linyphiinae Stemonyphantes lineatus Linnae- 1 1
us 1758
Tenuiphantes zebra Emerton 1
1882
Lycosidae Sundevall 1833 Allocosafunerea'- Hentz 1844 2 1 3
Allopecosa aculeata Clerck 1757 1 1
Arctosa virgo Chamberlin 1925 1
Hogna helluo'' Walckenaer 1 2
1837
Pardosa distincta' Blackwall 2 1 3
1846
Pardosa milvina'' " Hentz 11 11
1844
Pardosa saxatilis''^ Hentz 1844 16 16
Pardosa sp. I Koch 1847 1
Pardosa sp. 2 Koch 1847 7 7
Pirata aspirans''^ ChambQvXm 1 2 1
1904
MALLIS & HURD—CURSORIAL SPIDER DIVERSITY 105
—
Table 1. Continued.
DR OF CG PW UH LH Species
Family Genus;species Total Total Total Total Total Total Total
Pirata imularis^'^'^ Emerton 25 37 1 141 204
1885
Rabidosa rabida^- Walckanaer 5 5
1837
Schizocosa avida^ Walckanaer 3 4 7
1837
Lycosidae Sundevall 1833 Schizocosa bilineata^'“ Emerton 2 2
1885
Schizocosa ocreata^' 7,8, ii 6 1 5 3 15
Hentz 1844
Trochosa terricola^' ^ Tho- 2 1 3
reli 1856
Trochosa sp Kock 1847 1 1
Oonopidae Simon 1890 Orchestina saltitam Banks 1894 1 1
Oxyopidae Thorell 1870 Oxyopes salticus^'^^ Hentz 1845 2 2
PMlodromidae Thorell 1870 Thanatusforrnicinus^^ Clerck 1 1
1757
Pisauridae Simon 1890 Dolomedes tenebrosus Hentz 1 1 2
1844
Salticidae Blackwall 1841 Habronattus borealis Banks 1 1
1895
Neon neliP PecMiam & Peckham 1 1 2
1888
Theridiidae Sundevall 1833 Euryopsis argentea Emerton 1 1
1882
Thomisidae Sundevall 1833 Ozyptila sp. Simon 1864 1 1
Xysticusferox^’'^’^’ Hentz 1847 1 1 2
Xysticuspunctatus Keyserling 0
1880
Xysticus sp. Koch 1835 1 1
Habitat Total Abundance = 50 35 41 47 31 178 382
trap was constructed using a Petri dish lid Linyphiidae), which were infrequently cap-
with nails to elevate it 3cm above the lip of tured, and most of which were represented by
the trap. These covers kept out rainwater and a single individual. At least one individual of
falling debris. Sampling occurred at weekly each species collected (a male and female of
intervals from early June to mid-August, and each, when available) was preserved in Kah-
then once at the end of September 2002 (total le’s fluid as part of a reference collection.
= 354 trap-days). Each time we sampled, we As with any field study in a diverse species
put approximately 2cm of 70% ethanol into assemhlage, sampling efficacy is not likely to
each trap during the afternoon (ca 1600h), and be equal among taxa. In the case of pitfall
collected the samples 16-18h later. traps, for instance, the most active spiders
All adult spiders collected from the traps (e.g., many lycosids) may have a tendency to
were counted and identified using taxonomic be disproportionately sampledrelative to more
keys (Kaston 1978, 1981; online taxonomic sedentary species (e.g., clubionids). There-
updates http://kastoii.traesy.edu/spiderlist/ fore, species richness and relative abundance
Kaston78.htm and http://kastoe.traesy.edu/ of captured spiders may not accurately reflect
spiderlist/kast.htm; Roth 1993). Our nomen- the entire resident assemblage, but can be
clature follows Plateick (2003). We did not used for comparisons among sites of those
attempt to enumerate or identify to species taxa that are susceptible to pitfall trapping.
spiders in the subfamily Erigonieae (family Data analysis.—We compared sampling
106 THE JOURNAL OF ARACHNOLOGY
—
Table 2. The number of shared cursorial species between habitats, and species diversity (richness =
S; J' = evenness; Shannon’s diversity = H') for each habitat based on pit trap samples. Sites arranged in
order of increasing successional age from left to right and top to bottom. Site descriptions given in
Methods.
DR OF CG PW UH LH
Sites:
— — — — —
DR 14 — — — —
OF 6 18 — — —
CG 0 3 12 — —
PW 1 2 4 9 —
UH 1 1 6 5 18
LH 2 1 3 4 9 13
H' = 2.06 2.57 1.45 0.94 2.63 0.96
5 = 14 18 12 9 18 13
f = 0.78 0.89 0.58 0.43 0.91 0.37
sites with regard to diversity, measured as (1) 2). The pine stand (PW), representing the in-
the number of species found, or species rich- termediate stage of succession, had the lowest
ness, S, (2) Evenness of distribution of indi- spider diversity (Table 2). This site also had
viduals among species, J\ and (3) Shannon’s the lowest apparent vegetational diversity
diversity, H\ which is a measure of the inter- among the six sites: there was almost no
action between evenness and richness (Pielou ground cover vegetation, and the tree diversity
1969; Hill 1973). was limited to white pine and a few small de-
RESULTS ciduous saplings. However, there were no oth-
er apparent correlative trends between spider
We collected a total of 50 species of diversity and site structure. The highest H' di-
ground-dwelling spiders from our six sam- versity and 7’ evenness values we found were
pling sites (Table 1). Twenty-six ofthese were in the nearly mature forest (UH), and the old
habitat specialists, found at only one site; no field (OF), our second to youngest site, yield-
species was found at all six sites. The spiders ing virtually identical rank abundance patterns
with the broadest distribution, found at fourof (Fig. 2). Although species richness was the
the six sites, were the lycosids Schizocosa same (18) for both of these sites, they only
otchreeahtaah,nPiiirdataNeionasunltairisst,eaPirmaatagnaare.niBcooltahanSd. Tshhaerecdliamasxinfgolreesstp(ecLiHe)s,haTVd. tmhaeglnoawes(tTaHb'leva2l)-.
ocreata and P. insularis were found at all four
ue even though species richness was about av-
wooded sites and none was collected at either
erage among the sites. This was because of
of the open held sites. However, P. arenicola
the high dominance ofa single species {Pirata
and TV. magna were found at combinations of
wooded and open held sites. insularis), which wa&s reflected by the low val-
Some of the spiders we found appear to ue of 7’ (Tables 1 2),
have wide geographical distributions. Five Our most abundant species trapped was P.
species in Table 1 were also reported in four insularis, accounting for more than half of all
or more other studies from Denmark, Belgium spiders trapped (Table 1). The abundance of
and Manitoba, as well as sites in the U. S. P. insularis in our traps was highest in mid-
(Delaware, Ohio, Georgia and Virginia). June, decreasing tojusttwo individuals caught
However, there appears to be no reliable re- in August and September. From the beginning
lationship between how broadly cursorial spi- ofthe sample season, the sex ratio ofthis spe-
der species are distributed among geographic cies was highly male-biased. As the season
sites, how many sites they occupy within a progressed it shifted to a female-biased ratio.
study, or what kind of habitat (e.g., wooded July appeared to be the month of reproduc-
or open) they prefer in those studies that sam- tion: females were caught with egg sacs on 2
pled more than one habitat type. July, and withjuveniles riding on the dorsa of
We found no relationship between succes- their abdomens on 10 and 19 July.
sional age and any measure ofdiversity (Table We also were able to record some repro-
MALLIS & HURD—CURSORIAL SPIDER DIVERSITY 107
ductive data for S. ocreata and P. saxatilis. most abundant lycosids (Pardosa milvina and
On 1 July we found a female S. ocreata with P. saxatilis) were confined to the most open
a new (white) egg case. On 10 July a female site (DR). Buddie & Rypstra (2003) also not-
with a gray (older) egg case was captured. The ed that Pardosa species achieve dense popu-
case was dissected and almost fully developed lations in barren exposed habitats. Schizocosa
eggs were found inside, with fangs evident. ocreata was found in all four wooded sites.
On 19 July a female was caught withjuveniles This species is commonly found in leaf litter
on her back. On 20 June we found a female ofdeciduous forests in eastern North America
P. saxatilis, with an egg case. On two other (Wagner & Wise 1996). Uetz (1977) noted
occasions (2 and 17 July) we found females that S. ocreata occurs in simple litter where
with egg cases. On 26 July we found one with the leaves are compressed and the ground is
spiderlings on herdorsum, and brought itback relatively moist.
to the lab for observation. On 29 July spider- The diversity of sampled spiders in our
lings were seen leaving the mother’s dorsum study did not follow a successional gradient,
and by 30 July they had all dispersed. a finding ofother studies as well: a forest suc-
&
cessional gradient in Delaware (Hurd Fagan
DISCUSSION 1992), and forests in Manitoba (Aitchison &
As with previously reported studies, we Sutherland 2000; Buddie et al. 2000). Part of
found that most ground-dwelling spider spe- the difficulty may lie in the relative scarcity
cies were habitat specialists, found at one or of studies that examine a wide range of suc-
two sites, and very few were generalists. Be- cessional seres at a given locale. In any event,
cause rare species may be present in such low attempting to find predictable environmental
numbers that they may be missed by sam- correlates to spiderdiversity have proved frus-
pling, we cannot conclude that a species that trating for many researchers. In their 20 year
did not show up in our samples was complete- study of coastal dunes Gajdos & Toft (2000)
ly absent from a given site, but we can at least found that temporal changes in community
score a species as present if we captured it in composition were greater than differences oc-
a sample. This is a problem common among curring between habitats. It was impossible
studies that report the presence ofrare species, for them to determine what ways ecological
many of which are represented by a single characteristics changed for those spider spe-
trapped individual (e.g., 31 of 105 species re- cies in which abundance changed over time.
ported by Buddie et al. 2000). Differences in the physical structure of leaf
&
Both Aitchison Sutherland (2000) and litter and its complexity can influence species
Hurd & Fagan (1992) found only three species composition, spider abundance and diversity
that occupied four or more sites; we found generally increasing with increased litter
only four species in that category. However, depth in some studies (Uetz 1975, 1977, 1979;
very few ofthese are the same species. Six of Buddie & Rypstra 2003). Uetz (1975) found
the species we found were also reported from that weather patterns, which could be tied to
these two studies in Manitoba, one of which prey productivity for spiders, did not correlate
{Trochosa terricola) was found in both Man- significantly to any diversity measure. Instead,
itoba studies and in our present study (Table he found that richness and evenness were re-
1) and has been reported to occur from as far lated to litter depth, and moderately well re-
away as Finland (Aitchison & Sutherland lated to successional age and plant cover.
2000) and Belgium (Bonte et al. 2002). Not However, in our study we found as many spi-
surprisingly, there were more spider species der species in the two open habitats with al-
(20) in common between our present study most no litter (DR and OF) as we did in the
and the geographically closer Delaware sites two hardwood forest habitats (UH and LH).
of Hurd & Fagan (1992). The most abundant Mrzljak & Wiegleb (2000) presented evidence
species in both the present Virginia study and that species richness and abundance are lim-
the Delaware study was the lycosid, Pirata in- ited by vegetative stratification and height,
sularis. e.g., tall grass stands had more species than
The majority of spiders we encountered be- short grass stands. Hurd & Fagan’s (1992)
longed to the family Lycosidae. While P. in- study of spider assemblages in Delaware
sularis preferred wooded sites, the next two found the main difference to be between
108 THE JOURNAL OF ARACHNOLOGY
woodland and open habitats and not age of ating emigration oftwo wolf spider species (Ar-
the habitats: diversity ofcursorial spiders gen- anae:Lycosidae) in an agroecosystem. Environ-
erally was greater in open field habitats than mental Entomology 32:88-95.
in woodlands. However, in our present study Buddie, C.M., J.R. Spence & D.W. Langor. 2000.
we found no clear difference among sites Succession of boreal forest spider assemblages
following wildfire andharvesting. Ecography23:
based on presence, absence, or extent of tree
424-436.
cover. Diamond, J.M. 1975. Assembly of species com-
It is apparently not difficult to predict the munities. Pp. 342-444. In Ecology and Evolu-
presence in spider assemblages of some very tion of Communities (M.L. Cody and J.M. Dia-
broad generalists such as Trochosa terricola, mond, eds.). Belknap Press, Massachusetts.
but for most habitat speeialists, such predic- Draney, M.L. 1997. Ground-layer species (Aranae)
tion is problematic. Given the data so far, it is of a Georgia piedmont flood plain agroecosys-
hard to refute the null hypothesis that spider tem: species list, phenology andhabitatselection.
diversity within a site may be more a function GajJdoousr,naPl o&f SA.raTcofhtn.ol2o00g0y.2A5:3t3we3n-t3y5-1y.ear compar-
of stochastic colonization opportunities ofdif-
ison of epigeic spider communities (Aranae) of
ferent species rather than a set of intra-com-
Danish coastal heath habitats. Journal of Arach-
munity assembly rules (sensu Diamond 1975). nology 28:90-96.
Other factors that can influence species mem- Hanski, LA. 1999. MetapopulationEcology. Oxford
bership in arthropod assemblages, including University Press, Oxford, U.K.
spiders, are habitat features such as area, de- Hill, M.O. 1973. Diversity andevenness: aunifying
gree of isolation, and movement patterns of notion and its consequences. Ecology 54:427-
animals relative to their resouree requirements 432.
(Matter 1996, 2000; Hanski 1999; Marshall et Hodkinson, I.D., S.J. Coulson, J. Harrison & N R.
al. 2000; Samu et al. 2003). Thus, changing Webb. 2001. What a wonderful web they weave:
spider community composition over time is spiders, nutrient capture and e—arly ecosystem de-
velopment in the high Arctic some counter-in-
not really true succession at all, but rather re- tuitive ideas on community assembly. Oikos 95:
peated colonization by opportunistic species.
349-352.
The success of such colonists, once they in- Hurd, L.E. & R.M. Eisenberg. 1990. Arthropod
vade a habitat, may well depend on competi- community responses to manipulation of a bi-
tive abilities (Marshall et al. 2000) and the trophic predator guild. Ecology 71:2107-2114.
changing environmental conditions that ac- Hurd, L.E. & W.E Fagan. 1992. Cursorial spiders
company plant succession (Mrzljak & Wie- and succession: age or habitat structure? OecoL
gleb 2000; Hodkinson et al. 2001), but as yet ogia 92:215-221.
we are far from being able to predict cursorial Kaston, B.J. 1978. How to Know the Spiders. Wm.
spider composition among seres with any de- C. Brown Company Publishers, Dubuque, Iowa.
gree of precision. Kaston, B.J. 1981. Spiders of Connecticut. State
Geological and Natural History Survey of Con-
ACKNOWLEDGMENTS necticut, Hartford, Connecticut.
&
Lawrence, K.L. D.H. Wise. 2000. Spider preda-
This study is part of ongoing long-term re- tion on forest-floor Collembola and evidence for
search on succession and disturbance recovery indirect effects on decomposition. Pedobiologia
in the Science Park ofWashington & Lee Uni- 44:33-39.
versity. Our research was supported by grants Marshall, S.D., S.E. Walker & A.L. Rypstra. 2000.
from the R. E. Lee (REM) and John M. Glenn A test for a differential colonization and com-
(LEH) research programs of the university. petitive ability in two generalist predators. Ecol-
ogy 81:3341-3349.
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