Plastic responses to temperature during embryonic development are common in ectotherms, but their evolutionary relevance is poorly understood. Using a combination of field and laboratory approaches, we demonstrate altitudinal divergence in the strength of effects of maternal thermal opportunity on offspring birth date and body mass in a live-bearing lizard (Niveoscincus ocellatus).Poor thermal opportunity decreased birth weight at low altitudes where selection on body mass was negligible. In contrast, there was no effect of maternal thermal opportunity on body mass at high altitudes where natural selection favored heavy offspring.The weaker effect of poor maternal thermal opportunity on offspring development at high altitude was accompanied by a more active thermoregulation and higher body temperature in highland females. This may suggest that passive effects of temperature on embryonic development have resulted in evolution of adaptive behavioral compensation for poor thermal opportunity at high altitudes, but that direct effects of maternal thermal environment are maintained at low altitudes because they are not selected against. More generally, we suggest that phenotypic effects of maternal thermal opportunity or incubation temperature in reptiles will most commonly reflect weak selection for canalization or selection on maternal strategies rather than adaptive plasticity to match postnatal environments. K E Y W O R D S :Life-history evolution, maternal effect, phenotypic plasticity, selection-natural.

Summary1. Maternal hormones during embryogenesis act as a bridge between the maternal and the offspring environment and consequently may allow maternal pre-programming of offspring phenotype to the environment, assuming that maternal environment is a reliable predictor of offspring environment. 2. We use an orthogonal experimental design in which we increase plasma corticosterone concentration (vs. control) in placentotrophic gravid female spotted skinks (Niveoscincus ocellatus) and their offspring. We hypothesize that high concentrations of maternal corticosterone allow offspring phenotype to be pre-programmed to better cope with high concentrations of corticosterone after birth and, consequently, offspring would not suffer from its deleterious effects. We use growth as a measure of performance as corticosterone typically affects growth in reptiles. 3. High concentrations of maternal corticosterone had significant effects on offspring body condition at birth which could have resulted from corticosterone passing through the complex placenta and ⁄ or from the indirect effects of corticosterone on maternal body condition. 4. There was no indication of maternal pre-programming to high concentrations of corticosterone postpartum: growth rate of offspring placed in the same treatment (corticosterone vs. control) than their mother was not different to growth rate of offspring placed in a different treatment than their mother. 5. Maternal pre-programming to corticosterone may not have been selected for in this species either because maternal chronic stress is not a reliable predictor of offspring chronic stress or because maternal pre-programming does not outweigh the costs of having reduced sensitivity to the hormone, resulting in slower, less appropriate reactions in stressful conditions. This study further demonstrates the highly versatile and context-dependent nature of maternal effects and the trade-offs between costs and benefits of maternal pre-programming.

In reptiles, the thermal environment during embryonic development affects offspring phenotypic traits and potentially offspring fitness. In viviparous species, mothers can potentially manipulate the embryonic thermal environment through their basking behaviour and, thus, may be able to manipulate offspring phenotype and increase offspring fitness. One way in which mothers can maximise offspring phenotype (and thus potentially affect offspring fitness) is by fine-tuning their basking behaviour to the environment in order to buffer the embryo from deleterious developmental temperatures. In widespread species, it is unclear whether populations that have evolved under different climatic conditions will exhibit different maternal behaviours and/or thermal effects on offspring phenotype. To test this, we provided extended or reduced basking opportunity to gravid spotted skinks (Niveoscincus ocellatus) and their offspring from two populations at the climatic extremes of the species' distribution. Gravid females finetuned their basking behaviour to the basking opportunity, which allowed them to buffer their embryos from potentially negative thermal effects. This fine-tuning of female basking behaviour appears to have led to the expression of geographical differences in basking behaviour, with females from the cold alpine regions being more opportunistic in their basking behaviour than females from the warmer regions. However, those differences in maternal behaviour did not preclude the evolution of geographic differences in thermal effects: offspring growth varied between populations, potentially suggesting local adaptation to basking conditions. Our results demonstrate that maternal effects and phenotypic plasticity can play a significant role in allowing species to cope in changing environmental conditions, which is particularly relevant in the context of climate change. KEY WORDS: Maternal effect, Maternal buffering, Climate change, Phenotypic plasticity, Population, Spotted skink INTRODUCTIONMaternal effects are the interactions between a mother and her offspring that affect offspring phenotype independently of the mother's genetic contribution. They have been described as being highly dynamic, and they vary in direction and strength depending on the environment or the context (Uller, 2008;Plaistow and Benton, 2009 et al., 2011). However, perhaps more overlooked is the fact that they can also vary between ultimate contexts (i.e. the environmental conditions under which they have evolved) and may in some cases become locally adapted (Ghalambor et al., 2007;Hof et al., 2011;Hoffmann and Sgrò, 2011). Typically, we would expect to see local adaptation in maternal effects in widespread species in which the immediate maternal environment differs consistently between populations (e.g. Räsänen et al., 2005;Doody et al., 2006;Doody, 2009).In reptiles, the temperature experienced by embryos during development can affect numerous phenotypic traits such as date of birth, size at birth, sex, locomotor performance or beh...

Climate change is already impacting species around the world. Although most focus has been on the effect of temperature, changes in climatic variables other than temperature are also expected to drive biological change. Current models suggest that ectotherms, such as reptiles, will be strongly affected by climate change; however, data from natural populations are rare. Here, we use extensive data from 2 populations of a viviparous lizard (Niveoscincus ocellatus Gray, 1845) at the climatic extreme of the species distribution. We examine the effects of climate at a local, a regional and a global scale (thus, integrating a suite of variables at different spatial and temporal scales) on 2 key life history traits: offspring date of birth and size at birth. Overall, our results show that across 9 years of study, local temperature had strong effects on the offspring date of birth but not on the size at birth. Therefore, a rapid increase in local temperature throughout the species range (as predicted under global warming scenarios) is likely to affect phenological processes with potential concomitant effects on offspring fitness and survival.

SUMMARY Viviparous reptiles have been used as model species for many studies that seek to explain the evolution of viviparity. The vast majority of such studies have focused on the advantage viviparity provides with regards to maternal control of embryonic developmental temperature. However, viviparity may also allow increased control of nutrient transfer, such that mothers adaptively manipulate offspring phenotype through varying maternal nutritional support. Because maternal nutritional transfer is temperature dependent, maternal nutritional strategies may vary between climatically distinct populations. In this study we used an orthogonal experimental design in which mothers and offspring from climatically distinct populations of a viviparous skink (Niveoscincus ocellatus) were allocated randomly to either a protein-rich or a protein-poor diet. Our results suggest that N. ocellatus mothers are able to compensate for sub-optimal nutritional conditions and can adaptively manipulate offspring phenotype to best fit the postnatal nutritional environment. Furthermore, maternal nutritional strategies appear to vary between climatically distinct populations. These results suggest that in viviparous reptiles, matrotrophy provides a means of producing an adaptive offspring phenotype, in addition to maternal control of developmental temperature.