International Journal of Molecular Evolution and Biodiversity 2024, Vol.14, No.5, 252-262 http://ecoevopublisher.com/index.php/ijmeb 255 Figure 1 Effect sizes (Hedges’ g) for differences in the thermal sensitivity of development time (time from oviposition until hatching) and metabolic (heart) rate across cold and warm-adapted populations for 15 species of reptiles across 8 families (± variance) (Adopted from Pettersen, 2020) Image caption: For development time (D; green data points and variance bars), positive Hedges’ g values indicate positive Cov(G,E), or cogradient variation, where cold-adapted populations have longer D, relative to warm-adapted populations. Negative values of D indicate negative Cov(G,E), or countergradient variation, where genotypic differences oppose environmental temperature effects – in these instances, cold-adapted populations develop faster than warm-adapted populations. For metabolic rates (MR; orange data points and variance bars), negative Hedges’ g values indicate positive Cov(G,E), or cogradient variation, where cold-adapted populations have lower MR, relative to warm-adapted populations, while positive values of MR indicate negative Cov(G,E), or countergradient variation – here cold-adapted populations maintain higher MR, relative to warm-adapted populations (Adopted from Pettersen, 2020) 5 Evolutionary Adaptations to Climate Change 5.1 Genetic Mechanisms and Natural Selection The role of genetic mechanisms and natural selection in shaping the evolutionary adaptations of reptiles to climate change is a critical area of study. Natural selection acts on genetic variation within populations, leading to changes in gene frequencies that enhance survival and reproduction in changing environments (Burggren and Mendez-Sanchez, 2023). This process is fundamental to the adaptive evolution of species facing new climatic conditions. For instance, the study by Radchuk et al. highlights that while phenotypic changes in response to climate change are well-documented, the adaptive nature of these changes remains uncertain, particularly in terms of maintaining a good match between phenotype and environment. This underscores the importance of understanding the genetic basis of these adaptations. Moreover, the research on lacertid lizards and other vertebrates by the functional genomics approach reveals that specific subsets of genes are under positive diversifying selection, which are involved in physiological and morphological adaptations to climate (Bairos-Novak et al., 2021; Valero et al., 2021). This indicates that certain genes play a pivotal role in enabling reptiles to cope with environmental stressors induced by climate change. The identification of these genes and their functions can provide insights into the genetic mechanisms that facilitate adaptation and highlight the selective pressures that shape gene frequencies in reptile populations.
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