No abstract

Species with large geographical ranges provide an excellent model for studying how different populations respond to dissimilar local conditions, particularly with respect to variation in climate. Maternal effects, such as nest-site choice greatly affect offspring phenotypes and survival. Thus, maternal behaviour has the potential to mitigate the effects of divergent climatic conditions across a species' range. We delineated natural nesting areas of six populations of painted turtles ( Chrysemys picta ) that span a broad latitudinal range and quantified spatial and temporal variation in nest characteristics. To quantify microhabitats available for females to choose, we also identified sites within the nesting area of each location that were representative of available thermal microhabitats. Across the range, females nested non-randomly and targeted microhabitats that generally had less canopy cover and thus higher nest temperatures. Nest microhabitats differed among locations but did not predictably vary with latitude or historic mean air temperature during embryonic development. In conjunction with other studies of these populations, our results suggest that nest-site choice is homogenizing nest environments, which buffers embryos from thermally induced selection and could slow embryonic evolution. Thus, although effective at a macroclimatic scale, nest-site choice is unlikely to compensate for novel stressors that rapidly increase local temperatures. This article is part of the theme issue ‘The evolutionary ecology of nests: a cross-taxon approach’.

Head-start programs have been established to aid in the recovery of Macrochelys temmincki (Alligator Snapping Turtle) throughout the Mississippi River drainage. As the success of the breeding programs increase, additional release sites are needed where suitable habitat persists for reintroduction of Alligator Snapping Turtles, but methods to evaluate habitat suitability remain loosely defined. We developed a standardized field survey and habitat suitability model that can be used to assess and prioritize potential reintroduction sites. We measured important habitat features in the field and indexed them using a simple model that translated continuous data to an ordinal scoring system, resulting in an overall site-suitability score. We developed the model using 2 potential measurements of submerged deadwood density and determined habitat suitability among 17 sites in Kansas, Oklahoma, and Mississippi where Alligator Snapping Turtles were absent, present, and reintroduced. The model using side-scan sonar correctly predicted the presence of good habitat at sites where wild and reintroduced populations of Alligator Snapping Turtles were present, and scores were significantly related to Alligator Snapping Turtle abundance.