SREL Reprint #3383

Phenotypic plasticity of nest timing in a post-glacial landscape: how do reptiles adapt to seasonal time constraints?

Christopher B. Edge1, Njal Rollinson1,7, Ronald J. Brooks2, Justin D. Congdon3, John B. Iverson4,
Fredric J. Janzen5, and Jacqueline D. Litzgus6

1Ecology and Evolutionary Biology, University of Toronto, Toronto, Ontario M5S 3G5 Canada
2Department of Integrative Biology, University of Guelph, Guelph, Ontario N1G 2W1 Canada
3Savannah River Ecology Laboratory, Aiken, South Carolina 29802 USA
4Department of Biology, Earlham College, Richmond, Indiana 47374 USA
5Department of Ecology, Evolution and Organismal Biology, Iowa State University,
Ames, Iowa 50011 USA
6Department of Biology, Laurentian University, Sudbury, Ontario P3E 2C6 Canada

Abstract: Life histories evolve in response to constraints on the time available for growth and development. Nesting date and its plasticity in response to spring temperature may therefore be important components of fitness in oviparous ectotherms near their northern range limit, as reproducing early provides more time for embryos to complete development before winter. We used data collected over several decades to compare air temperature and nest date plasticity in populations of painted turtles and snapping turtles from a relatively warm environment (southeastern Michigan) near the southern extent of the last glacial maximum to a relatively cool environment (central Ontario) near the northern extent of post-glacial recolonization. For painted turtles, population-level differences in reaction norm elevation for two phenological traits were consistent with adaptation to time constraints, but no differences in reaction norm slopes were observed. For snapping turtle populations, the difference in reaction norm elevation for a single phenological trait was in the opposite direction of what was expected under adaptation to time constraints, and no difference in reaction norm slope was observed. Finally, among-individual variation in individual plasticity for nesting date was detected only in the northern population of snapping turtles, suggesting that reaction norms are less canalized in this northern population. Overall, we observed evidence of phenological adaptation, and possibly maladaptation, to time constraints in long-lived reptiles. Where present, (mal) adaptation occurred by virtue of differences in reaction norm elevation, not reaction norm slope. Glacial history, generation time, and genetic constraint may all play an important role in the evolution of phenological timing and its plasticity in long-lived reptiles.

Keywords: glaciation; individual variation; Jinks-Connolly rule; random regression; range limit; reaction norm; turtle

SREL Reprint #3383

Edge, C. B., N. Rollinson, R. J. Brooks, J. D. Congdon, J. B. Iverson, F. J. Janzen, and J. D. Litzgus. 2017. Phenotypic plasticity of nest timing in a post-glacial landscape: how do reptiles adapt to seasonal time constraints? Ecology 98(2): 512-524.

This information was provided by the University of Georgia's Savannah River Ecology Laboratory (srel.uga.edu).