Predicting the effects of climate change on incubation in reptiles: methodological advances and new directions

Abstract

The unprecedented advancement of global climate change is affecting thermal conditions across spatial and temporal scales. Reptiles with temperature-dependent sex determination (TSD) are uniquely vulnerable to even fine-scale variation in incubation conditions and are a model system for investigating the impacts of shifting temperatures on key physiological and life-history traits. The ways in which current and predicted future climatic conditions translate from macro- to ultra-fine scale temperature traces in subterranean nests is insufficiently understood. Reliably predicting the ways in which fine-scale, daily and seasonally fluctuating nest temperatures influence embryonic development and offspring phenotypes is a goal that remains constrained by many of the same logistical challenges that have persisted throughout more than four decades of research on TSD. However, recent advances in microclimate and developmental modeling should allow us to move farther away from relatively coarse metrics with limited predictive capacity and towards a fully mechanistic model of TSD that can predict incubation conditions and phenotypic outcomes for a variety of reptile species across space and time and for any climate scenario.

Microclimate, an important part of ecology and biogeography

“…Recent research on ectotherms and insects showcases how microclimate impacts on individuals are reflected on their populations. Ectothermic organisms, in particular, experience the significant influence of microclimates through thermoregulation and temperature‐dependent sex determination (Carter & Janzen, 2021; Sears et al., 2016; Stark et al., 2023). Darker ants tend to dominate tree canopies due to melanism, which provides them protection against UV radiation and reduces moisture loss (Law et al., 2020).…”

“…The impacts of microclimates however extend beyond individuals, populations and single ecosystems, as microclimates have broader implications for global biodiversity (Trew & Maclean, 2021). Consequently, microclimate models have become invaluable tools in the field of biophysical ecology (Briscoe et al., 2022; Carter & Janzen, 2021; Sears et al., 2016), because these tools help understanding and predicting interactions between organisms and their environmental conditions.…”

Geographic variation in incubation temperatures promoting viable offspring production in broadly co‐distributed turtles

“…As such, the OTR has been defined as the range of constant incubation temperatures that yield high hatching success rates (Taylor et al, 2021). The OTR is of particular interest because oviparous reptiles tend to provide little, if any, parental care after depositing eggs in subterranean cavities that are subject to periodic abiotic disturbances (Carter & Janzen, 2021; Telemeco et al, 2016). More broadly, identifying the upper bounds of the OTR (i.e., T opt ) is critical to defining tradeoffs between metabolism (rate of energy conversion) and offspring production (development time) in ectothermic animals responding to warming climates (e.g., developmental cost theory; Marshall et al, 2020; Pettersen et al, 2019).…”

Is the future female for turtles? Climate change and wetland configuration predict sex ratios of a freshwater species

“…Most species display delayed sexual maturity (Ernst & Lovich, 2009), low reproductive output, and a type III survivorship curve (i.e., high juvenile mortality, low adult mortality), and therefore lack the life‐history traits necessary to rapidly respond to critical threats (Stanford et al, 2020). Further compounding the vulnerability of global turtle diversity, most species exhibit TSD, and warming climates are expected to dramatically increase the proportion of females in turtle populations (Carter & Janzen, 2021; Janzen, 1994a). However, while there is an abundance of research regarding the effect of climate change on primary sex ratios (e.g., Hawkes et al, 2007; Valenzuela et al, 2019), empirical information linking adult sex ratios in the wild to climate change has proven elusive (although see Jensen et al, 2018), and thus the magnitude of this threat remains unclear.…”