Climate and predation dominate juvenile and adult recruitment in a turtle with temperature-dependent sex determination.
Conditions experienced early in life can influence phenotypes in ecologically important ways, as exemplified by organisms with environmental sex determination. For organisms with temperature-dependent sex determination (TSD), variation in nest temperatures induces phenotypic variation that could impact population growth rates. In environments that vary over space and time, how does this variation influence key demographic parameters (cohort sex ratio and hatchling recruitment) in early life stages of populations exhibiting TSD? We leverage a 17-year data set on a population of painted turtles, Chrysemys picta, to investigate how spatial variation in nest vegetation cover and temporal variation in climate influence early life-history demography. We found that spatial variation in nest cover strongly influenced nest temperature and sex ratio, but was not correlated with clutch size, nest predation, total nest failure, or hatching success. Temporal variation in climate influenced percentage of total nest failure and cohort sex ratio, but not depredation rate, mean clutch size, or mean hatching success. Total hatchling recruitment in a year was influenced primarily by temporal variation in climate-independent factors, number of nests constructed, and depredation rate. Recruitment of female hatchlings was determined by stochastic variation in nest depredation and annual climate and also by the total nest production. Overall population demography depends more strongly on annual variation in climate and predation than it does on the intricacies of nest-specific biology. Finally, we demonstrate that recruitment of female hatchlings translates into recruitment of breeding females into the population, thus linking climate (and other) effects on early life stages to adult demographics.
Department of Ecology, Evolution and Organismal Biology, Iowa State University, Ames, Iowa 50011, USA. lisa.schwanz@jcu.edu.au
Lisa E
LE
Schwanz
Ricky-John
RJ
Spencer
Rachel M
RM
Bowden
Fredric J
FJ
Janzen
D000818:Animals; D002980:Climate; D005260:Female; D011157:Population Dynamics; D011235:Predatory Behavior; D012733:Sex Differentiation / Q000502:physiology*; D013696:Temperature; D014426:Turtles / Q000502:physiology*