Developmental plasticity of thermal ecology traits in reptiles: Trends, potential benefits, and research needs

A variety of phenotypic traits in reptiles are affected by conditions during embryonic development, a phenomenon known as developmental plasticity. In particular, many traits in which expression changes with temperature, such as locomotor performance or growth rates, are also developmentally plastic. However, much less is known about the extent to which traits associated with thermal ecology, such as thermal tolerance and behavioral thermoregulation, are developmentally plastic. Here, we review the literature on developmental plasticity in physiological and behavioral traits associated with thermal ecology in reptiles. Most studies on developmental plasticity of thermal traits have assessed plasticity in behavioral traits, such as selected temperature or time spent basking, and these studies have found mixed support for the presence of developmental plasticity in behavioral thermal traits. In contrast, very few studies have assessed developmental plasticity in physiological traits, yet these studies generally support a developmentally plastic basis for thermal tolerance. Most studies have only tested for developmental plasticity in thermal ecology traits at the hatchling stage, which limits our understanding of the benefits of developmental plasticity to individuals, or the adaptive significance of developmental plasticity in populations. We recommend that research on developmental plasticity in reptile thermal ecology be expanded to include incubation conditions other than mean temperature, consider traits associated with cold-tolerance, and endeavor to understand how developmental plasticity in thermal ecology traits is beneficial. In particular, determining how long differences persist over ontogeny, and testing for benefits of developmental plasticity across multiple life stages, are crucial first steps towards understanding the adaptive significance of developmental plasticity in thermal ecology traits.