Geographic Variation in the Reproductive Phenology of a Widespread Amphibian
Geographic variation in reproductive phenology can reveal how life history is shaped by the environment. For amphibians, the timing of reproduction has downstream consequences on other life history traits such as larval period and size at metamorphosis. Two-lined Salamanders (Eurycea bislineata species complex) are widespread across the eastern United States and Canada and exhibit dramatic geographic variation in reproductive morphology, reproductive behavior, and larval life history, and thus make compelling models for studying these processes. Here, we compile courtship and nesting records from citizen science data, published literature, museum records, field notes, and social media to describe the geographic variation of reproductive phenology in the E. bislineata species complex. We demonstrate that the date of oviposition is negatively correlated with mean annual temperature and examine how this may interact with the timing of other seasonal behaviors such as migration and overwintering. Finally, we discuss how these geographic patterns may influence the evolution of reproductive tactics through differences in the spatial and temporal clustering of courtship opportunities in terrestrial and aquatic environments.ABSTRACT
Geographic distribution (WGS84) of nest records from the E. bislineata species complex. The land surface is colored by mean annual temperature, and dots representing individual nest records are shaded by date of observation. Nest records from December are coded as negative ordinal dates.
The relationship between mean annual temperature and date of oviposition in the E. bislineata species complex. Blue dots represent observations of nests from the northern clade, and red squares represent observations from the southern clade. The solid black line (and corresponding 95% CI in gray) shows predicted values from our best-fit polynomial regression, with mean annual precipitation set to the mean value and developmental stage set to 0. The dotted line (and corresponding 95% CI barely visible in gray) shows predicted values from a linear regression modeling the ordinal date of first freeze as a function of mean annual temperature.
Contributor Notes
