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Evidence for Selection on Thermoregulation: Effects of Temperature on Embryo Mortality in the Garter Snake Thamnophis elegans
 

Summary: Evidence for Selection on Thermoregulation: Effects of Temperature on
Embryo Mortality in the Garter Snake Thamnophis elegans
RYAN P. O'DONNELL AND STEVAN J. ARNOLD
Despite widespread belief that selection molds thermoregulatory behaviors, direct
evidence for fitness effects is extremely rare. We studied the effect of developmental
temperature on embryo mortality in a viviparous snake. Seventy-four female
Thamnophis elegans were maintained at one of nine constant temperatures during
pregnancy (21­33 C). The duration of pregnancy was recorded for each female as well
as the sex, snout­vent length, mass, and survival of 504 newborns. Embryo survival was
highest at an intermediate temperature (26.6 C). The developmental temperature of
maximum survivorship in T. elegans corresponds to the temperature that induces
minimum developmental abnormality and the optimum temperature for whole
organism performance. These three thermal optima together correspond with the
average temperatures imposed on embryos by free-ranging pregnant females (26.6 C).
This correspondence implies that thermal optima are coadapted to thermoregulation
in T. elegans.
THERMOREGULATION is often considered
an adaptive activity, but few data directly
support this conventional wisdom (Cowles and
Bogert, 1944). Most studies that have examined

  

Source: Arnold, Stevan J. - Department of Zoology, Oregon State University

 

Collections: Biology and Medicine; Environmental Sciences and Ecology