Early environments can profoundly influence an organism in ways that persist over its life. In reptiles, early thermal environments (nest temperatures) can impact offspring phenotype and survival in important ways, yet we still lack an understanding of whether general trends exist and the magnitude of impact. Understanding these patterns is important in predicting how climate change will affect reptile populations and the role of phenotypic plasticity in buffering populations. We compiled data from 175 reptile studies to examine, and quantify, the effect of incubation temperature on phenotype and survival. Using meta-analytic approaches (standardized mean difference between incubation treatments, Hedges' g), we show that across all trait types examined there is, on average, a moderate to large magnitude of effect of incubation temperatures (absolute effect: |g| = 0.75). Unsurprisingly, this influence was extremely large for incubation duration, as predicted, with warmer temperatures decreasing incubation time overall (g = -8.42). Other trait types, including behaviour, physiology, morphology, performance, and survival experienced reduced, but still mostly moderate to large effects, with particularly strong effects on survival. Moreover, the impact of incubation temperature persisted at least one-year post-hatching, suggesting that these effects have the potential to impact fitness in the long term. The magnitude of effect increased as the change in temperature increased (e.g. 6°C versus 2°C) in almost all cases, and tended to decrease when temperatures of the treatments fluctuated around a mean temperature compared to when they were constant. The effect also depended on the mid-temperature of the comparison, but not in consistent ways, with some traits experiencing the greatest effects at extreme temperatures, while others did not. The highly heterogeneous nature of the effects we observe, along with a large amount of unexplained variability, indicates that the shape of reaction norms between phenotype and temperature, along with ecological and/or experimental factors, are important when considering general patterns. Our analyses provide new insights into the effects of incubation environments on reptile phenotype and survival and allow general, albeit coarse, predictions for taxa experiencing warming nest temperatures under climatic change.

How temperature influences development has direct relevance to ascertaining the impact of climate change on natural populations. Reptiles have served as empirical models for understanding how the environment experienced by embryos can influence phenotypic variation, including sex ratio, phenology and survival. Such an understanding has important implications for basic eco-evolutionary theory and conservation efforts worldwide. While there is a burgeoning empirical literature of experimental manipulations of embryonic thermal environments, addressing widespread patterns at a comparative level has been hampered by the lack of accessible data in a format that is amendable to updates as new studies emerge. Here, we describe a database with nearly 10, 000 phenotypic estimates from 155 species of reptile, collected from 300 studies manipulating incubation temperature (published between 1974–2016). The data encompass various morphological, physiological, behavioural and performance traits along with growth rates, developmental timing, sex ratio and survival (e.g., hatching success). This resource will serve as an important data repository for addressing overarching questions about thermal plasticity of reptile embryos.

Aim Predicting the distribution of species relies increasingly on understanding the spatially explicit constraints of environmental conditions on an organism's physiological traits. We combined an empirical model of temperature‐dependent embryonic development with a mechanistic model of soil temperatures to examine potential thermal limitations on the distribution of a nocturnal, oviparous skink, Oligosoma suteri, a range‐restricted endemic. Location New Zealand. Methods We estimated a thermal requirement for successful embryonic development as 616 degree‐days above a threshold of 13.8°C. We then modelled soil temperatures at representative sites across New Zealand and predicted duration of incubation to map the distribution of potentially viable oviposition sites, given variation in the timing of egg‐laying under even temperature increases. Results Successful development of O. suteri embryos is possible in locations outside their current distribution. Increasing temperatures increased the species’ potential range, reducing incubation duration and lengthening the oviposition window. However, due to the disconnected nature of their rocky shore habitat, individuals may not be able to disperse to currently uninhabited sites within that extended range. Additionally, although locations may be thermally suitable for incubation, predation by introduced mammals, competition and habitat modification may prevent successful establishment of populations. Main conclusions Our models contribute to understanding fundamental physiological constraints on an important life history stage that will inform conservation management actions, including potential future translocations.

<p>Predicting species distributions relies on understanding the fundamental constraints of climate conditions on organism’s physiological traits. Species distribution models (SDMs) provide predictions on species range limits and habitat suitability using spatial environmental data. Species distribution modelling is useful to estimate environmental conditions in time and space and how they may change in future climates. Predicting the distribution of terrestrial biodiversity requires an understanding of the mechanistic links between an organism’s traits and the environment. Implementation of mechanistic species distribution models requires knowledge of how environmental change influences physiological performance. Mechanistic modelling is considered more robust than correlative SDMs when extrapolating to novel environments predicted with climate change. I examined the spatial distribution and the impact of climate change on incubation duration of an endemic, nocturnal skink, Oligosoma suteri. My research focused on the ways a microclimate model with local weather data and degree-days can predict O. suteri’s distribution and affect incubation duration. Using a microclimate model (NicheMapR), I generated hourly soil temperatures for three depths in two substrate types (rock and sand) at a 15 km spatial resolution for the entire coastline of New Zealand and for seven depths for one substrate type (rock) for the coastline of Rangitoto/Motutapu Island at a 20 m spatial resolution. I estimated the minimum number of degree days required for successful embryonic development using a minimum temperature threshold for O. suteri eggs. I apply the incubation duration predicted by the model to map potential distribution for the two different spatial resolutions (15 km and 20 m) and I also include a climate change component to predict the potential effects on incubation duration and oviposition timing. My results from the New Zealand wide model indicate that embryonic development for O. suteri may be possible beyond their current distribution, and climate warming decreases incubation duration and lengthens the oviposition period for the New Zealand wide map. I generated maps of predicted incubation duration with depth for a coastal habitat at a higher resolution for Rangitoto/Motutapu Island. Incubation duration varied by depth with higher number of days to hatch predicted for greater depths. Temperature data loggers were installed at two different sites at three depths and were compared to the Rangitoto/Motutapu Island microclimate model. Modelled incubation durations were consistently shorter than data logger incubation durations across all three depths at both data logger sites. Species distribution model with coarse spatial and climate data can predict where soil temperatures would be suitable for successful development. A higher spatial resolution can reveal variation in incubation duration within sites indicated as suitable from the coarse resolution map. By using two different spatial extents initial starting points can be identified for which a higher resolution model can be applied to better inform management decisions relating to conservation actions and the effects of climate change for O. suteri and other species.</p>