Evol Ecol Res 7: 759-766 (2005)     Full PDF if your library subscribes.

Habitat-mediated shifts and plasticity in the evaporative water loss rates of two congeneric pit vipers (Squamata, Viperidae, Agkistrodon)

Daniel S. Moen,* Christopher T. Winne and Robert N. Reed‡

Savannah River Ecology Laboratory, University of Georgia, Drawer E, Aiken, SC 29802, USA

Address all correspondence to Daniel S. Moen, Department of Ecology and Evolution, State University of New York, Stony Brook, NY 11794, USA.
e-mail: dmoen@life.bio.sunysb.edu


Question: Are increased rates of total evaporative water loss (TEWL) associated with evolutionary transitions from terrestrial to aquatic habitats? Do individuals acclimated to wet conditions demonstrate higher TEWL rates than those acclimated to dry conditions?

Organisms: Individuals of the snake species Agkistrodon piscivorus (Viperidae; semi-aquatic) and Agkistrodon contortrix (terrestrial) collected from the Savannah River Site, Aiken, SC, USA.

Methods: We held individuals in either wet or dry acclimation conditions for 10 days. We then measured TEWL of individuals in an environmental chamber and tested the effects of humidity acclimation and species on TEWL rate. The TEWL rate was evaluated in the context of hypothesized habitat transitions within Agkistrodon.

Results: The semi-aquatic A. piscivorus exhibited higher TEWL rates than A. contortrix, the species which represents the putatively ancestral condition (terrestriality). The higher TEWL rate in A. piscivorus is concordant with the evolutionary shift to aquatic habitats in this species. Additionally, snakes in wet acclimation treatments had higher TEWL rates than those in dry treatments, as predicted.

Keywords: habitat aridity, habitat transition, phylogeny, semi-aquatic, snakes.

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