Sky islands as natural laboratories for studying eco-evolutionary responses to climate change
S. J. LOVE, J. A. SCHWEITZER, J. K. BAILEY
Department of Ecology and Evolutionary Biology, University of Tennessee at Knoxville, 1416 Circle Drive, Knoxville, TN 37996, USA

Climate-induced evolution will determine population persistence in a changing world. However, finding natural systems in which to study these responses has been a barrier to estimating the impact of global change on a broad scale. Hot, dry, and isolated sky islands (SIs) and adjacent cool and wet mountain chains (MCs) can serve as a comparative natural laboratory for studying the impact of long-term climatic pressures on real populations. We used a comprehensive global literature review and two separate common garden experiments to test the efficacy of the SI-MC natural comparison to examine the effects of climate change and isolation on ecosystems, specifically focusing on long-lived trees and soil microbial communities, that have experienced these different climate regimes since the end of the Pleistocene. Locally, we show SI divergence in quantitative traits of a long-lived tree driven by natural selection and genetic drift. Globally, SI isolation has resulted in lineage formation, reduced genetic variation, and trait evolution, as well as the evolution of novel traits driven by altered species interactions on divergent mountain peaks. Further, we show compositional and functional divergences in soil microbial communities across the comparison. Operable across most continents, the SI-MC comparison may be an advantageous natural laboratory and predictive framework for studying ecological and evolutionary responses to climate change, from genes to ecosystems, across the globe.