Proximate constraints on reproductive output in a northern population of painted turtles: an empirical test of the bet-hedging paradigm

Abstract

For long-lived, iteroparous organisms whose annual reproductive success is low and unpredictable, the “bet-hedging” life-history paradigm predicts that an increase in resource acquisition should result in an increase in stored lipids and not an increase in reproductive output. We tested whether reproductive patterns in a population of midland painted turtles ( Chrysemys picta marginata Agassiz, 1857) are consistent with this prediction. Assuming that annual temperature variation is a proxy for variation in resource acquisition, we hypothesized that if harvested resources are generally sequestered for future reproduction, then there should be no relationship between clutch frequency (the number of clutches laid per season) and the temperature experienced when no follicular growth occurred. We hypothesized further that if temperature constrains clutch frequency by limiting the amount of energy that can be allocated to reproduction, then clutch frequency would be related only to the temperature experienced during the period in which follicular growth occurred (fall temperature). We found that clutch frequency was primarily related to fall temperature, which suggests that the amount of thermal energy experienced during periods of follicular development limits the amount of stored energy that can be allocated to developing follicles. This pattern of reproductive allocation is consistent with the bet-hedging paradigm.