Molecular mechanisms of environmental adaptation in the Western Canaries Lizard (Gallotia galloti)

This research aims to elucidate evolutionary and plastic molecular processes that allows Gallotia galloti to inhabit a range of environmental conditions. It specifically investigates evolutionary processes in promoter regions of environmentally-adaptive genes, telomere dynamics, and the expression of heat-shock proteins and oxidative stress biomarkers in relation to microclimate. This has broader implications for understanding climate adaptation and ectotherm resilience.By using a dataset spanning a decade and the entire elevational breadth of G. galloti’s distribution, signatures of selection in promoter regions upstream from environmentally-adaptive genes were detected. Outlier single nucleotide polymorphisms (SNPs) linked to elevation-induced climate factors including in aquaporin and Electron Transfer Flavoprotein Subunit Alpha (ETFA) gene promoters demonstrated roles in local climate adaptation. At the temporal scale, some gene promoters (AQP1, MAPKAP1, ODC1) demonstrated balancing selection supporting survival in a range of environments, while other promoters were under positive selection (ACAT2, HSP90B1, SLC25A33), revealing a selective sweep in specific extreme environments. Elevation-based ancestry groups, which were decoupled from population structure, demonstrated a response to previous extreme weather events; over approximately one generation. At the functional level, selection on promoter regions indicated evolution of the aryl hydrocarbon receptor pathway (AhR-ARNT) transcription factor binding motif, which has previously been demonstrated to play a role in cellular stress tolerance. This chapter reveals the role of climate in driving local adaptation across the landscape, and short-term rapid evolution to extreme weather conditions, both with a functional basis.The investigation of telomere length determined that the sex and the size of the lizards were more pertinent that the microclimate conditions, with bigger males having the shortest telomeres. However, temporal patterns demonstrated that in drier years telomeres were shorter, indicating that acute changes in the environment are still important in shaping relative telomere length. Overall, telomere dynamics in G. galloti are largely shaped by intrinsic factors as opposed to extrinsic environmental factors across the landscape, however extreme climate fluctuations, such as those associated with climate change, may still play a role. A comparison of telomere length to other published datasets revealed G. galloti along with sister lineages display less variable telomere lengths than other lizard taxa, potentially related to ecological versatility across elevations.Examining the expression of heat-shock proteins and oxidative stress markers revealed that the expression of GRP94, but not of HSP70, vary with slope angle and elevation, with greater expression at higher, steeper slopes. GRP94 was also more highly expressed with decreasing radiant sky temperature. Carbonylation, a marker of oxidative stress, decreased at greater elevations interacting with solar radiation. The sex of the lizards also played a role, with females displaying more carbonylation than males. Carbonylation and GRP94 were found to have a tight correlation, which was also influenced by the available microclimates in the form of operative temperature. Warmer temperatures demonstrated increased GRP94 and lower carbonylation, and vice versa, emphasising the importance of thermoregulatory opportunities in maintaining internal biochemistry.The findings from these chapters contribute significant insights into the molecular basis of environmental adaptation, which can have practical applications for the conservation and preservation of organisms during the Anthropocene. These chapters highlight the importance of seldom explored molecular mechanisms in explaining environmental adaptation, and demonstrate them acting at different time scales, and pivoting around the mitigation of oxidative stress.