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Keywords:

  • egg incubation;
  • egg size;
  • egg survival;
  • maternal effects;
  • nest moisture;
  • nest temperature;
  • nesting phenology;
  • phenotypic selection;
  • vegetation cover

Summary

1. Maternal and environmental factors influence embryo development and offspring phenotypes in ways that are likely to impact fitness. Most studies that address this issue, however, fail to mimic the complexities of natural environmental parameters and only quantify selection during a single season.

2. In this study, we examined year-to-year variation in how maternal factors (egg mass, nesting phenology and nest-site choice) and external abiotic factors (temperature and precipitation) impact egg survival and hatchling morphology in the painted turtle (Chrysemys picta) over seven nesting seasons in the field. In addition, we quantify annual variation in the strength and form of selection operating on maternal factors.

3. Overall, our results demonstrated very low, if any, consistency in how maternal and environmental factors impact egg survival and hatchling size in the field. That is, different variables had different effects in different years. Accordingly, the strength and form of natural selection operating on egg size, nesting phenology and nest-site choice were inconsistent across years, suggesting low potential for substantive or directional evolutionary shifts in these maternal effects.

4. These results may partially explain why traits like egg size and nest-site choice exhibit variation (i.e. are not perfectly optimized), and highlight the importance of multiyear field studies in gaining a more complete picture of the factors driving variation in critical early life-history events and demographic parameters.