Meeting Abstract
Temperature is an omnipresent environmental variable influencing survival and reproduction of all living organisms. Understanding how and when species adapt to different thermal regimes can provide insight into the evolution and subsequent maintenance of reproductive isolation via natural selection. We investigated evolutionary patterns of the thermal biology across the genus Xiphophorus using a multifaceted approach. First, thermal niche evolution was reconstructed using phylogenetically-controlled niche modeling. The niche models were used to identify comparisons of interest which included the monophyletic platyfishes which are broadly distributed across a biogeographic divide and three replicated instances of speciation along elevational gradients. For these comparisons, we examined upper and lower thermal limits in common-garden fish to test for adaptive, heritable differences in functional physiology. Patterns of thermal tolerance were further complemented with gene expression assays of candidate genes. Collectively, these three approaches provide insight into adaptive shifts in functional physiology and gene expression that have enabled colonization and speciation across a broad range of environmental conditions (e.g., the platyfishes) as well as maintaining reproductive isolation along stream gradients from high to low elevation.
