Predicting the effects of climate change on reproductive fitness of an endangered montane lizard, Eulamprus leuraensis (Scincidae)

Abstract

A shift in climatic conditions may directly modify critical organismal traits (such as reproductive output and offspring phenotypes), and experimental studies to document such direct effects thus may clarify the impacts of climate change on the species involved. The endangered Blue Mountains Water Skink (Eulamprus leuraensis) exhibits several traits predicted to imperil it under climate change: ectothermy, low reproductive output, specialisation to a restricted habitat type, montane endemicity, and a small geographic range. Congeneric species exhibit temperature-dependent sex determination, increasing potential sensitivity to climate change. We maintained wild-caught female lizards throughout pregnancy under thermal conditions simulating a shift in basking-time availability (3 vs 7 h/day) as might occur under climate change. Females with longer basking opportunities per day gave birth 2 weeks earlier, to slightly smaller offspring, that grew much faster in the first few weeks of life. Importantly, offspring sex ratios were not affected by maternal thermal regimes. Hence, some traits (e.g., offspring size, growth rates, dates of birth) are sensitive to ambient thermal conditions whereas other traits (e.g., offspring sex ratio and sprint speed) are not. On balance, the greatest threat to population persistence for E. leuraensis under climate change is likely to involve indirect effects mediated via habitat degradation (especially, drying-out of the hanging swamps) rather than direct thermal effects on lizard reproductive output or offspring phenotypes.

Effects of night-time warming on temperate ectotherm reproduction: potential fitness benefits of climate change for side-blotched lizards

“…Not only does it appear that climate warming will benefit dams but also there are potential fitness benefits for the hatchlings of temperate ectotherms as a result of thermal effects during incubation. We found that hatchling mass was positively correlated with incubation temperature, as noted previously (Dubey and Shine, 2011), but not significantly affected by ovarian temperature (Fig.3). By what mechanism does incubation temperature influence hatchling traits?…”

“…However, there is not complete maternal control over embryonic developmental conditions ['maternal manipulation hypothesis' (Shine, 1995)], calling into question the effects of temperature variability on the ovarian cycle. While we know of no reports of temperature during the ovarian cycle of oviparous reptiles affecting subsequent hatchling traits (see also Dubey and Shine, 2011), the existence of latent thermal effects during incubation means that we must consider as a possibility both direct and latent effects of asymmetric warming during the ovarian cycle as well as during incubation.…”

“…For example, montane populations of common lizards, Lacerta vivipara, have experienced increases in environmental temperatures that have been linked to increases in survival, body size, clutch size and reproductive output (Chamaillé-Jammes et al, 2006). A positive relationship between warmer incubation temperatures and hatchling size has been observed in multiple other lizard species, including both oviparous and viviparous species (Shine, 2004;Shine and Harlow, 1993;Wapstra, 2000;Dubey and Shine, 2011). In general, the effects of climate warming are predicted to increase fitness in temperate ectotherms because of the limitations imposed by current environmental temperatures in seasonal environments (Bradshaw et al, 2004;Deutsch et al, 2008;Huey et al, 2009) (see also Olsson et al, 2010).…”

Experimental evaluation of reproductive response to climate warming in an oviparous skink

“…Previous studies have indicated that changes in environmental temperatures experienced by gravid females or their eggs can influence embryonic development and the phenotypes of their offspring (e.g. Shine & Harlow 1993;Shine & Downes 1999;Du et al 2005;Dubey & Shine 2011). However, most of these studies involving oviparous species have evaluated the life history effects of constant temperatures rather than the fluctuating temperatures that constitute the natural thermal environment experienced by organisms.…”

Disparity in the timing of vertebrate diversification events between the northern and southern hemispheres

“…Ectothermic vertebrates depend on abiotic conditions to thermoregulate, and thus are extremely vulnerable to climatic fluctuations [14,15]. For example, temperature-dependent sex determination is widespread in reptiles such as lizards, turtles, and crocodiles, making these taxa particularly sensitive to abrupt variations in ambient temperature [16].…”