Effects of life‐history requirements on the distribution of a threatened reptile

Abstract

Survival and reproduction are the two primary life-history traits essential for species' persistence; however, the environmental conditions that support each of these traits may not be the same. Despite this, reproductive requirements are seldom considered when estimating species' potential distributions. We sought to examine potentially limiting environmental factors influencing the distribution of an oviparous reptile of conservation concern with respect to the species' survival and reproduction and to assess the implications of the species' predicted climatic constraints on current conservation practices. We used ecological niche modeling to predict the probability of environmental suitability for the alligator snapping turtle (Macrochelys temminckii). We built an annual climate model to examine survival and a nesting climate model to examine reproduction. We combined incubation temperature requirements, products of modeled soil temperature data, and our estimated distributions to determine whether embryonic development constrained the northern distribution of the species. Low annual precipitation constrained the western distribution of alligator snapping turtles, whereas the northern distribution was constrained by thermal requirements during embryonic development. Only a portion of the geographic range predicted to have a high probability of suitability for alligator snapping turtle survival was estimated to be capable of supporting successful embryonic development. Historic occurrence records suggest adult alligator snapping turtles can survive in regions with colder climes than those associated with consistent and successful production of offspring. Estimated egg-incubation requirements indicated that current reintroductions at the northern edge of the species' range are within reproductively viable environmental conditions. Our results highlight the importance of considering survival and reproduction when estimating species' ecological niches, implicating conservation plans, and benefits of incorporating physiological data when evaluating species' distributions.

Detection, occupancy, and abundance of the alligator snapping turtle in Texas

“…First, the zone of high forest cover in eastern Texas could simply represent a climatic zone that delineates the range of the species. Forest cover in eastern Texas is associated with increased precipitation (Griffith et al 2007), and it is expected that an obligate inhabitant of aquatic habitats would fare optimally under such conditions (Thompson et al 2016). High precipitation and flooding in watersheds of this region increase potential for permanence and connectivity of the alligator snapping turtle's preferred habitat (Griffith et al 2007), which would in turn increase its dispersal potential throughout aquatic habitats of these watersheds.…”

A Standardized Field Method and Habitat Suitability Model to Assess Reintroduction Sites for Alligator Snapping Turtles

“…Additional variables that could be important in describing suitable habitat for Alligator Snapping Turtles that were not incorporated into the model include food availability and flow rate (Shipman 1993, Riedle et al 2009), water depth (Howey and Dinkelacker 2009, Riedle et al 2006, Townsend 2016), flood frequency and dispersal barriers (Riedle et al 2008a), and climate (Thompson et al 2017). Many of these variables have been included in large-scale niche models spanning the current distribution of Alligator Snapping Turtles in the United States (Thompson et al 2017, USGS 2017). All of these factors should be considered alongside the output of the HSI model before a site is deemed suitable for reintroductions.…”

Distribution and Demography of the Alligator Snapping Turtle (Macrochelys temminckii) in Texas: A 20-Year Perspective

“…Sites that were resurveyed confirmed that occupancy and demography of M. temminckii within these areas remained generally stable over the past 2 decades. Higher CPUE than in Oklahoma and Louisiana may attest to benefits of more stringent protection of the species in Texas (Texas Register 1987). D.…”