20th International Congress of Arachnology

DENVER MUSEUM OF NATURE & SCIENCE

REPORTS

No. 3, July 2, 2016

Student - oral presentation

Species delimitation of the orchard-spider

Leucauge venusta

(Araneae, Tetragnathi-

dae) in North America

*Jesus A. Ballesteros, Gustavo Hormiga

The George Washington University, Department of Bio-

logical Sciences, 2029 G ST, NW, Bell 302 Washington

D. C. 20052

jabc@gwu.edu

The North American orchard-spider,

Leucauge venusta

is one of the most abundant and widespread species of

orb-weavers in the Americas. Records of this species

range from Southern Canada to Brazil. Of the 172 cur-

rently described species in the genus

Leucauge

, only

two are known to occur in the US, where

L. venusta

broadly distributed and

L. argyra

is restricted to the

subtropical parts in Florida. Preliminary analyses based

on the barcoding region of the mitochondrial Cyto-

chrome Oxidase subunit I (COI) gene, reveal a deep gap

between “northern” and “southern” populations of

venusta

in the US. Specimens from southern populations

(Florida) group with specimens collected in Brazil. This

biogeographic pattern is particularly surprising given the

absence of obvious barriers to dispersal. Morphologically,

individuals from these southern and northern popula-

tions are indistinguishable, and the possibility of a

cryptic species has important implications for nomencla-

ture because

L. venusta

is the type species of the genus

Leucauge

. We examine the phylogeographic structure

and test the species boundaries of

L. venusta

using mito-

chondrial and nuclear genes from specimens collected

in Central and South America and a dense sampling

of North-American populations across known biogeo-

graphic barriers such as the Appalachian Mountains and

the Mississippi River.

Leucauge

includes more than 170

described species but its taxonomy is very poorly under-

stood. Untangling the identity of its type species of the

genus is an important step toward understanding the

diversity and evolution of orchard-spiders.

Keywords: phylogeography, spiders, population genetics,

coalescence, taxonomy

Student - poster presentation

Submersion tolerance among riparian and

non-riparian spiders

*Tara Barbarich, Hailey Shannon, Derek Wilson,

Matthew Persons

Susquehanna University, 514 University Avenue,

Selinsgrove, PA, 17870

Barbarich@susqu.edu

Terrestrial arthropods that inhabit dynamic boundaries

between terrestrial and lotic systems are under constant

risk of flooding. Many spiders may have evolved behav-

ioral, physiological, or morphological adaptations to cope

with flooding either through avoidance or submersion tol-

erance. Mechanisms for coping with periodic flooding have

important implications for predicting species composition,

recolonization, and resilience against flood-related distur-

bance for riparian arthropod communities. We examined

submersion tolerance of spiders by taxon and microhabi-

tat. We compared web-building and cursorial, riparian and

non-riparian, and ground-dwelling versus more arboreal

species. We submerged individual spiders for three hours

in distilled water and recorded survival, activity level

immediately after removal, and activity level eight hours

after removal (N=1,154). During trials we noted spiders

that were in hypoxic comas versus those that formed puta-

tive plastrons (breathing bubbles) during submersion. We

found large differences in submergence tolerance by taxon

and habitat. Web-building spiders and vegetation dwelling

cursorial spiders showed poor survival post-submersion,

even those that live on overhanging vegetation along

rivers and streams. Most ground-dwelling cursorial spiders

including wolf spiders and fishing spiders showed no

negative effects of submersion and most were active the

entire time of submergence. We also found significant dif-

ferences in submersion tolerance between populations of

wolf spiders of the same species within the riparian zone

compared to populations from other habitats, suggesting

population-level local adaptation to flooding. Population-

level differences in submersion tolerance indicate that

riparian ground spiders likely persist during flood events

rather than being recolonized by new spider populations.

Keywords: flooding submergence, riparian, cursorial

International Congress of Arachnology