Lost reproductive value reveals a high burden of juvenile road mortality in a long-lived species.

Adult mortality is often the most sensitive vital rate affecting at-risk wildlife populations. Therefore, road ecology studies often focus on adult mortality despite the possibility for roads to be hazardous to juvenile individuals during natal dispersal. Failure to quantify concurrent variation in mortality risk and population sensitivity across demographic states can mislead the efforts to understand and mitigate the effects of population threats.

Long-Term Resilience of Primary Sex Ratios in a Species with Temperature-Dependent Sex Determination after Decades of Climate Warming.

AbstractSpecies with environmental sex determination (ESD) have persisted through deep time, despite massive environmental perturbation in the geological record. Understanding how species with temperature-dependent sex determination (TSD), a type of ESD, persist through climate change is particularly timely given the current climate crisis, as highly biased sex ratios and extinction are predicted. Since 1982, we have studied primary sex ratios of a reptile with TSD ().

Variation in space and time: a long-term examination of density-dependent dispersal in a woodland rodent.

Dispersal is a fundamental ecological process that can be affected by population density, yet studies report contrasting effects of density on propensity to disperse. In addition, the relationship between dispersal and density is seldom examined using densities measured at different spatial scales or over extensive time series. We used 51 years of trapping data to examine how dispersal by wild deer mice (Peromyscus maniculatus) was affected by changes in both local and regional population densities.

Measurement and modelling of primary sex ratios for species with temperature-dependent sex determination.

For many oviparous animals, incubation temperature influences sex through temperature-dependent sex determination (TSD). Although climate change may skew sex ratios in species with TSD, few available methods predict sex under natural conditions, fewer still are based on mechanistic hypotheses of development, and field tests of existing methods are rare. We propose a new approach that calculates the probability of masculinization (PM) in natural nests.

Altered spring phenology of North American freshwater turtles and the importance of representative populations.

Globally, populations of diverse taxa have altered phenology in response to climate change. However, most research has focused on a single population of a given taxon, which may be unrepresentative for comparative analyses, and few long-term studies of phenology in ectothermic amniotes have been published. We test for climate-altered phenology using long-term studies (10-36 years) of nesting behavior in 14 populations representing six genera of freshwater turtles (, , , , , and ).

A new method of estimating thermal performance of embryonic development rate yields accurate prediction of embryonic age in wild reptile nests.

Temperature has a strong effect on ectotherm development rate. It is therefore possible to construct predictive models of development that rely solely on temperature, which have applications in a range of biological fields. Here, we leverage a reference series of development stages for embryos of the turtle Chelydra serpentina, which was described at a constant temperature of 20 °C.

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

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.

Recurrent violations of invariant rules for offspring size: evidence from turtles and the implications for small clutch size models.

Smith and Fretwell's classic model predicts that parents can maximize fitness by dividing the energy available for reproduction into offspring of an optimal size. However, this model breaks down when clutch size is small (~1-10 offspring). Invariant rules are an extension of the Smith-Fretwell model, and these rules predict how offspring size will vary among and within individuals that produce small clutch sizes.

Widespread reproductive variation in North American turtles: temperature, egg size and optimality.

Theory predicts the existence of an optimal offspring size that balances the trade-off between offspring fitness and offspring number. However, in wild populations of many species, egg size can still vary from year to year for unknown reasons. Here, we hypothesize that among-year variation in population mean egg size of freshwater turtles is partly a consequence of their gonadal sensitivity to seasonal temperatures, a physiological mechanism which principally functions to synchronize reproduction with a favorable time of year.

A phylogeographic analysis of populations of the wood turtle (Glyptemys insculpta) throughout its range.

We investigated the phylogeography of wood turtles, Glyptemys insculpta, in North America using 750 bp of the mitochondrial control region from 117 individuals sampled at 29 localities across the species' range. A total of 21 haplotypes were identified and little genetic variation was found. The highest pairwise difference was 2%.

Sexually dimorphic morphology of hatchling snapping turtles (Chelydra serpentina) from contaminated and reference sites in the Great Lakes and St. Lawrence River basin, North America.

Some organochlorine pesticides and industrial chemicals may alter sexually dimorphic traits through endocrine disruption. Therefore, we examined a sexually dimorphic trait, precloacal length, of hatchling snapping turtles (Chelydra serpentina) incubated from 31 clutches from a heavily contaminated site (Hamilton Harbour, ON, Canada; n = 14), a moderately contaminated site (Akwesasne Mohawk Territory; n = 3), and from a reference site (Algonquin Provincial Park, ON, Canada; n = 14). The mean sum polychlorinated biphenyls from Algonquin were low (20.

Octylphenol (OP) alters the expression of members of the amyloid protein family in the hypothalamus of the snapping turtle, Chelydra serpentina serpentina.

The gonadal estrogen estradiol-17beta (E(2)) is important for developing and regulating hypothalamic function and many aspects of reproduction in vertebrates. Pollutants such as octylphenol (OP) that mimic the actions of estrogens are therefore candidate endocrine-disrupting chemicals. We used a differential display strategy (RNA-arbitrarily primed polymerase chain reaction) to isolate partial cDNA sequences of neurotransmitter, developmental, and disease-related genes that may be regulated by OP or E(2) in the snapping turtle Chelydra serpentina serpentina hypothalamus.

Allocation of reproductive effort in female Arrenurus spp. water mites (Acari: Hydrachnidia; Arrenuridae).

Twenty-seven species of water mites of the genus Arrenurus were compared with respect to allocation of reproductive effort. Clutch volume was positively correlated to female volume, female volume was positively correlated with clutch size and with larval volume, while clutch size and larval volume were negatively correlated. In threespace, corresponding to female volume, clutch size and larval volume, species were arranged along two trajectories representing separate reproductive strategies.