Habitat-mediated shifts and plasticity in the v 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
ABSTRACT
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.
SREL Reprint #2863
Moen, D. S., C. T. Winne and R. N. Reed. 2005. Habitat-mediated shifts and plasticity in the evaporative water loss rates of two congeneric pit vipers (Squamata, Viperidae, Agkistrodon). Evolutionary Ecology Research 7:759-766.
