DOI: 10.5061/dryad.kj5t8j8
title: Data from: Altered spring phenology of North American freshwater turtles and the importance of representative populations

description: 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 (Chelydra, Chrysemys, Kinosternon,
 Malaclemys, Sternotherus, and Trachemys). Nesting season initiation occurs
 earlier in more recent years, with 11 of the populations advancing
 phenology. The onset of nesting for nearly all populations correlated well
 with temperatures during the month preceding nesting. Still, certain
 populations of some species have not advanced phenology as might be
 expected from global patterns of climate change. This collection of
 findings suggests a proximate link between local climate and reproduction
 that is potentially caused by variation in spring emergence from
 hibernation, ability to process food, and thermoregulatory opportunities
 prior to nesting. However, even though all species had populations with at
 least some evidence of phenological advancement, geographic variation in
 phenology within and among turtle species underscores the critical
 importance of representative data for accurate comprehensive assessments
 of the biotic impacts of climate change.
description: First nesting date for
 all populations with all possible covariates."First Day" is
 the day of the year when the first nest was laid from a given population.
 Heating degree days (HDD) were calculated from NCDC dailys provided by the
 given "WeatherStation". Latitude and longitude are given for
 each "Site". Columns 12-24 contain climate indices summary
 statistics as indicated by the standardized column name
 abbreviations.TurtlePhenology_FirstNestDay.txtFirst date of observed snapping turtle hibernation and spring emergence from a single population with all possible covariates"FirstDayEmergence" and "FirstDayHibernate" are the day of the year when the first individual to emerge or to enter hibernacula were observed. "FirstDayEmergenceLag" is "FirstDayEmergence" with a 1-year lag useful for evaluating the effect of "FirstDayHibernate" on emergence date. Heating degree days (HDD) and cooling degree days (CDD) were calculated from NCDC dailys provided by the given "WeatherStation". Columns 16-19 contain monthly mean temperature in degrees F. Latitude and longitude are given for the "Site". Columns 26-38 contain climate indices summary statistics as indicated by the standardized column name abbreviations.TurtlePhenology_Chelydra_Emergence_and_Hibernation.txtFirst date of observed turtle emergence or basking for all populations with all possible covariates"FirstDayEmergenceOrBasking" is the day of the year when the first individual was observed to have emerged from hibernation or to be basking. Heating degree days (HDD) were calculated from NCDC dailys provided by the given "WeatherStation". Columns 11-23 contain climate indices summary statistics as indicated by the standardized column name abbreviations.TurtlePhenology_Emergence_and_Basking.txt