Climate-induced patterns of activity and nest conditions select for genes associated with growth and maturation in a widespread lizard species

How species adapt to local climates across their ranges remains a central question in ecology and evolutionary biology. Though phenotypic responses to climate are well documented, the genetic basis for these adaptive responses remains largely unresolved. Here, we integrate biophysical and genomic methods to identify genomic variants associated with climate-induced patterns of activity and nest conditions across the range of the Eastern fence lizard (Sceloporus undulatus). We first use a biophysical model to estimate potential annual activity and incubation temperatures for nests across the species’ range. The biophysical parameters were then used in gene-environmental association models to identify candidate genes underlying adaptation to climate. The biological functions of candidate genes were assessed through enrichment analyses. Lastly, we use genome-wide linkage disequilibrium to identify evidence of co-selection or epistatic interactions on candidate genes. In general, activity time decreased with latitude, while the range of nest temperatures increased with latitude. However, mean nest temperatures do not correlate with latitude, longitude, or elevation. Genomic analyses identified 2040 candidate genes, of which 48 enriched for two KEGG pathways: the calcium signaling pathway and the gonadotropin-releasing hormone pathway. Calcium signaling dictates cell proliferation and migration through the effects of growth factors (e.g., growth and development), while gonadotropin-releasing hormone dictates the development of sexual traits and the timing of sexual maturity. Phenotypic evidence from previous studies indicates that selection on life history traits, such as body size and age at maturation, underlie adaptation to climate in ectotherms, and our results provide genetic support for this notion.