20th International Congress of Arachnology

patterns of retinal movement of jumping spiders in three

treatments: during fly display, fly walking and a still fly.

This study has implications for the study on signalling and

visual ecology of jumping spiders.

Keywords: display, signalling, salticidae, retina

Poster presentation

Islands in the trees: A biogeographic

exploration of epiphyte-dwelling spiders

Dinesh Rao

, Francisco Emmanuel Méndez-Castro

Maaike Y. Bader

, Glenda Mendieta-Leiva

Instituto de Biotecnología y Ecología Aplicada (INBIO-

TECA), Universidad Veracruzana, Av. de las Culturas

Veracruzanas No. 101, Col. Emiliano Zapata, CP 91090

Xalapa, Veracruz, México.;

Ecological Plant Geography,

Faculty of Geography, Univ. of Marburg, Germany.

dinrao@gmail.com

Epiphytic plants can be considered as tree-top islands.

In this sense, a single tree represents a landscape where

an archipelago of epiphytes influences ecological rela-

tionships dependent on geographic-spatial position,

species-habitat size dynamics and species-isolation

gradients. We studied these island-biogeographic rela-

tionships in spider communities that inhabit epiphyte

archipelagos in a shade coffee plantation of Veracruz,

Mexico. Spider diversity increased with epiphyte-island

size. In contrast to other studies, our results showed

no evidence of spatial position within the tree affecting

diversity, but position relative to other epiphytes did

affect diversity patterns. Thereby, direct distance (Euclid-

ean) was more important than walking distance (along

branches). This is the first study presenting evidence

of species-isolation processes driving the diversity of

epiphyte-dwelling spider communities. Tree architecture

influenced the distribution of epiphytes and thereby

also affected spider diversity. The three-dimensional

archipelago structure and high biodiversity of epiphyte

communities presents an excellent opportunity for

further developing advanced island-biogeographic

theory and testing the generality of existing predictions.

Keywords: topology, structure, distance, 3d position,

epiphytes

Oral presentation

How habitat and retreat limitation influ-

ence sociality in prolonged subsocial

huntsman spiders

Linda S. Rayor

Department of Entomology, Cornell University,

Ithaca, NY 14853, USA

LSR1@cornell.edu

Many aspects of group-living in spiders are influenced

by parameters of the habitat: biotic factors, such as prey

availability and predation risk, as well as abiotic factors,

such as rain and wind, and sites for web or retreats. All

these factors influence the costs and benefits of living in

groups, which in turn provide selective pressure on the

relative social complexity of a species. Diurnal retreats

are critical for all three prolonged subsocial huntsman

spiders (Sparassidae: Deleninae:

Delena cancerides,

D. lapidicola, D. melanochelis

), which live in interac-

tive matrilineal family groups with a single adult female

and multiple cohorts of siblings who remain together for

many months prior to individual dispersal. The retreats

provide the adults and developing offspring protection

from predators, and moderate climatic factors. As rela-

tively permanent structures in the environment, retreats

are a resource “inherited” by lineages, but fought over if

limited. All three social huntsman species live exclusively

in retreats with specific features, under exfoliating bark

of certain trees, flat rocks on granite headlands, or rolls

of sloughed bark of

Eucalyptus regnans

, respectively. The

three social species differ from each other in their age of

dispersal, tolerance of immigrants, prey sharing, and

number of sibling cohorts together. Ecological forces, par-

ticularly saturated habitats with limited retreat options for

larger social groups and retreat size, have influenced the

social ecology of these species. In

D. cancerides

habitats

85 to 100% of all possible retreats are occupied resulting

in intense competition among maturing females. Off-

spring remain in the natal colony until sexual maturity

to increase their resource holding power. Conflicts with

potential reproductive competitors and immigrants are

intense. In contrast, the other two species are less con-

strained by retreat limitation, so the payoffs for offspring

158

DENVER MUSEUM OF NATURE & SCIENCE

REPORTS

No. 3, July 2, 2016

Cushing