Taxa with large geographic distributions generally encompass diverse macroclimatic conditions, potentially requiring local adaptation and/or phenotypic plasticity to match their phenotypes to differing environments. These eco-evolutionary processes are of particular interest in organisms with traits that are directly affected by temperature, such as embryonic development in oviparous ectotherms. Here we examine the spatial distribution of fitness-related early life phenotypes across the range of a widespread vertebrate, the painted turtle (Chrysemys picta). We quantified embryonic and hatchling traits from seven locations (in Idaho, Minnesota, Oregon, Illinois, Nebraska, Kansas, and New Mexico) after incubating eggs under constant conditions across a series of environmentally relevant temperatures. Thermal reaction norms for incubation duration and hatchling mass varied among locations under this common-garden experiment, indicating genetic differentiation or pre-ovulatory maternal effects. However, latitude, a commonly used proxy for geographic variation, was not a strong predictor of these geographic differences. Our findings suggest that this macroclimatic proxy may be an unreliable surrogate for microclimatic conditions experienced locally in nests. Instead, complex interactions between abiotic and biotic factors likely drive among-population phenotypic variation in this system. Understanding spatial variation in key life-history traits provides an important perspective on adaptation to contemporary and future climatic conditions.
Bibliographical noteFunding Information:
This research was supported by NSF IOS-1257857 and DEB-1242510. All research was done in accordance with IACUC approved protocols and with permission from all necessary federal, state, and local agencies. We thank Eric Gangloff for statistical advice, Nathan Kutok for the photograph, and Anna Carter, Vincent Farallo, Martha Muñoz, members of the Janzen lab group, and anonymous reviewers for constructive comments.
© 2019 The Authors. Ecology and Evolution published by John Wiley & Sons Ltd.
- Chrysemys picta
- geographic variation
- local adaptation
- painted turtle