THE GENETIC BASIS OF LOCAL ADAPTATION ACROSS AN ISLAND ADAPTIVE RADIATION

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Many species originate in dramatic bursts called adaptive radiations. How adaptive radiations generate spectacular numbers of species over short time periods is a fundamental question in evolutionary biology. Adaptive radiations in remote islands are especially fascinating, given that such radiations originate from founder populations with limited genetic variation, which is the raw material for evolution. Understanding the genetic basis of adaptive radiations on remote islands allows insight into not only the origin of species (and, hence, biodiversity), but also how species will respond to rapid climate change. This project will uncover the genetic basis of adaptation to extreme water availability (drought and flooding) in Metrosideros, an adaptive radiation of woody species that dominate Hawaii’s forests. The results will reveal how often recurring adaptation to very wet and very dry environments relies on the recycling of ancient genes present in the founder population versus new genes arising through mutation. Repeated adaptation through the recycling of ancient genes would help to explain how adaptive radiations occur and would suggest that species are able to adapt to rapid climate change. In particular, this project will reveal insights into how trees will cope with the increased drought and flooding expected with climate change. The project will also train one technician, 2 Ph.D. students, and several undergraduates in cutting-edge technologies and analyses, provide bioinformatics training to federal and state agency staff and students, faculty, and staff at two Minority-Serving Institutions, and develop G6-12 curriculum related to plant adaptation and response to climate change.The proposed research will apply an evolutionary systems biology approach to Hawaii’s landscape-dominant woody genus, Metrosideros, to characterize the genetic basis of local adaptation to water availability across an island adaptive radiation. The project will take advantage of the relatively small genome size and high-quality chromosome-level reference genome; parental, F1, and F2 lines; and population-level resequencing data available for Metrosideros to accomplish 3 aims: Aim 1) contrast seedling physiology and patterns of gene expression between replicate dry- and wet-adapted taxa in response to drought and water-logging, Aim 2) identify phenotypic traits and quantitative trait loci (QTL) for resistance to drought or water-logging and identify QTL that colocalize with differentially expressed genes (DEGs), and Aim 3) examine the evolution of the colocalized DEG-QTL regions (and non-intersecting, but significant QTL) across the Hawaiian Metrosideros adaptive radiation to test the prediction that recurring adaptation to parallel environments involves recurring selection on shared genomic regions of predominantly ancestral origin. By investigating the genetic basis of local adaptation across an island adaptive radiation, this project will help to solve the long-standing evolutionary problem of how spectacular phenotypic and ecological diversity can arise from founder populations with limited genetic variation. Specifically, results will reveal the degree to which recurring adaptation to parallel environments draws on the same genomic regions in different taxa and the relative importance of shared ancestral variation, introgression, and de novo mutations for parallel evolution within an isolated radiation.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.