Maternal Choice

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Science  22 Nov 2013:
Vol. 342, Issue 6161, pp. 910-911
DOI: 10.1126/science.342.6161.910-d

Temperature-dependent sex determination (TDSD), a phenomenon in which offspring sex is affected by the temperature experienced during embryonic development, occurs in many ectothermic species, such as reptiles and fishes. However, a purely environmental control of sex could lead to evolutionarily unstable sex ratios, suggesting that selection for a maternal behavior, such as the choice of nest sites, could be strong. Mitchell et al. used a set of controlled experiments in painted turtles to test whether nest sites selected by females affected sex ratios. That is, they cross-fostered eggs and hatchlings in nest sites that had been chosen by mother turtles, relative to sites selected at random, across both the incubation and hatchling hibernation stages. They found no difference in survival or success between maternally or randomly selected nest sites, but random sites yielded a significant male bias in offspring, with maternal sites—characterized by a more open canopy, more solar radiation, and warmer temperatures in the nest—being more balanced. These results show that maternal influence on sex ratio is probably an important component of reproduction in species with TDSD. Further, the habitats selected by female turtles in this study, specifically warmer sites with less vegetation, indicate the potential for conflict with viability selection in this and other ectothermic species as the climate warms.

Proc. R. Soc. London Ser. B. 280, 20132460 (2013).

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