LIGON, D.B.*; LOVERN, M.B.; Oklahoma State University; Oklahoma State University: Maternal, Sex and Incubation Temperature Effects on an Endangered Tortoise, Geochelone sulcata

Embryonic and neonatal phenotypes are affected by a number of factors such as genotype, maternal investment and environmental conditions during development. Because of its role in determining sex in many turtle species, effects of incubation temperature (T_inc) on hatchling turtles have received a great deal of attention from evolutionary ecologists. Additionally, population declines experienced by many turtle species around the world have resulted in several conservation programs aimed at producing turtles in captivity for subsequent release. Thus, our goals for this study were two-fold: (1) to investigate ways in which effects of T_inc might be evolutionarily adaptive; and (2) to determine whether T_inc could be manipulated in captivity to maximize hatchling quality. To this end, we investigated the effects of T_inc on a wide variety of traits in an endangered tortoise, Geochelone sulcata. Eggs were collected from six nests produced in captivity and incubated at five constant temperatures spaced at 1° C intervals (range = 28.5°-32.5° C). Our results indicate that, independent of sex, T_inc affected hatchling size and body condition, both of which are predicted to affect hatchling quality. Additionally, males had higher levels of circulating testosterone than females, and females exhibited a higher incidence of scute abnormalities than males. There was no indication of metabolic compensation to T_inc. After statistically correcting for differences in egg mass, clutch differences were observed in hatchling size, body condition, and testosterone. Our results remain inconclusive regarding the adaptiveness of TSD, but suggest that, in addition to sex, T_inc effects on hatchling quality should be considered in conservation-oriented propagation programs.