Plastic rates of development and the effect of thermal extremes on offspring fitness in a cold‐climate viviparous lizard

Abstract

Populations at the climatic margins of a species' distribution can be exposed to conditions that cause developmental stress, resulting in developmental abnormalities. Even within the thermal range of normal development, phenotypes often vary with developmental temperature (i.e., thermal phenotypic plasticity). These effects can have significant consequences for organismal fitness and, thus, population persistence. Reptiles, as ectotherms, are particularly vulnerable to thermal effects on development and are, therefore, considered to be at comparatively high risk from changing climates. Understanding the extent and direction of thermal effects on phenotypes and their fitness consequences is crucial if we are to make meaningful predictions of how populations and species will respond as climates warm. Here, we experimentally manipulated the thermal conditions experienced by females from a high-altitude, cold-adapted population of the viviparous skink, Niveoscincus ocellatus, to examine the consequences of thermal conditions at the margins of this population's normal temperature range. We found strong effects of thermal conditions on the development of key phenotypic traits that have implications for fitness. Specifically, we found that offspring born earlier as a result of high temperatures during gestation had increased growth over the first winter of life, but there was no effect on offspring survival, nor was there an effect of developmental temperature on the incidence of developmental abnormalities. Combined, our results suggest that advancing birth dates that result from warming climates may have positive effects in this population via increased growth.

Degrees of change: between and within population variation in thermal reaction norms of phenology in a viviparous lizard

“…Because of differences in temperatures between sites during this period, this contributed to parturition occurring later in the highlands than in the lowlands across years. An effect of temperature on parturition date is not surprising in this species because, as ectotherms, snow skink metabolism and, therefore, development rates are temperature dependent (Wapstra 2000, Cunningham et al 2017, 2018). Indeed, for this reason, birth or hatching dates generally advance with increasing environmental temperatures in reptilian taxa (Noble et al 2018).…”

“…Whether altered climate and its effects on parturition dates have a positive or negative effect on population persistence in N. ocellatus in the short term will depend on the net effect of a range of factors. These include the frequency, duration, and magnitude of extreme temperatures, the extent to which advanced phenology allows for increased time for growth and survival (Uller et al 2011, Cunningham et al 2018), rates of temperature‐induced developmental stress, the extent to which increased temperatures select for responses to avoid thermal extremes (e.g., Monasterio et al 2011) and differences in the effect of temperature on the phenologies of other components of the ecosystem, which may lead to the emergence of trophic mismatches (e.g., Mayor et al 2017, Noble et al 2018). Importantly, the differences between populations we found in among‐individual variation in the elevation and, possibly, the slopes of reaction norms suggest that the consequences of altered phenology may differ among populations.…”

“…The cold highland site is located on Tasmania’s Central Plateau (41°86' S, 146°53' E, elevation: 1,150 m), and the warm lowland site is on Tasmania’s East Coast (42°55' S, 147°87' E, elevation: 30 m). Both sites are surrounded by either unsuitable habitat or road and there is, consequently, little immigration or emigration in either population (Cadby et al 2010, Uller et al 2011, Cunningham et al 2018). Each year the majority (90–95%) of pregnant females were captured late in the gestation period but prior to birth (mid‐December and mid‐January for the lowlands and highlands, respectively, because of differences in the timing of birth; Cadby et al 2010, Uller et al 2011, Gruber et al 2018).…”

Markers for Global Climate Change and Its Impact on Social, Biological and Ecological Systems: A Review

“…Fluctuation in temperature severely affects reproductive behavior in animals due to mate limitation (McEwan et al, 2019). Thermal extremes effect growth in animals (Nishizaki & Carrington, 2015) and reduce offspring fitness in a cold-climate mainly in viviparous lizards (Cunningham et al, 2018). It also affects emergence of insect and its interaction with plant because of delay in flowering (Kehrberger et al, 2019).…”

Introduction to the special issue—Developmental plasticity in reptiles: Physiological mechanisms and ecological consequences

“…() exposed embryos of two sympatric lizard species (that occupy different microhabitats) to climate warming scenarios and show that the impact of climate warming on these species is dependent upon preferred microhabitats. Lastly, Cunningham, Fitzpatrick, While, and Wapstra () examined the consequences of thermal conditions at the margins of the population's temperature range in a viviparous skink, and suggest that advancing birth dates due to warming climates could have positive effects for their montane population. All of these studies have important implications for making predictions about the impacts of environmental change at global and regional scales.…”