Climate variability, thermal physiology, and species distributions

Cameron Ghalambor Professor Department of Biology Colorado State UniversityFort Collins, CO 80523 [email protected] [email protected] Climate variability, thermal physiology, and species distributions: Are mountain streams higher in the tropics? It has long been recognized that species diversity is higher in the tropics, but the mechanisms that generate geographic variation in species diversity remain unresolved. One hypothesis to explain higher tropical biodiversity relates to reduced climate variability. Lower climate variability in the tropics is predicted to favor narrower physiological tolerance to temperature, reduced dispersal capacity and higher species turnover across elevational gradients. These outcomes in turn could favor greater population genetic divergence and higher speciation rates. In this presentation, we present results from a comparative study of temperate and tropical aquatic insects that tests the assumptions and predictions of the climate variability hypothesis. While we find support for many aspects of this hypothesis, we also find interesting deviations that suggest greater complexity in the mechanisms that favor latitudinal and elevational variation in species diversity.