Eco-evolutionary forces responsible for patterns of micro-endemism in an island biodiversity hotspot

Biodiversity hotspots are places with high concentrations of species found nowhere else in the world (i.e., “endemic” species) that are threatened by human activities. The processes that generate unique concentrations of species remain poorly understood. Madagascar exemplifies biodiversity hotspots: it is home to an extraordinary number of species restricted to small, localized areas on this Indian Ocean island. This project will test three possible explanations of how these biodiversity hotspots formed in members of the tree genus Diospyros (the source of valuable ebony wood) by examining their evolutionary relationships and calculating how sensitive a species is to environmental conditions. A better understanding of these processes will help explain why some parts of the world have exceptionally high levels of biological diversity, why so many species only occur in very limited areas, and how we can better conserve them. This project will also provide educational and training opportunities to graduate students and high school students, giving them foundational tools to contribute to the scientific workforce and develop into future leaders in STEM fields. This research will leverage existing DNA bank material and conduct targeted field sampling to generate a robust, time-calibrated phylogeny of Diospyros (Ebenaceae) from Madagascar and surrounding regions using the Angiosperm 353 target enrichment probe set. The resulting phylogeny will be used to: 1) determine the biogeographic origins of Malagasy Diospyros, 2) produce a unifying taxonomic framework for all Malagasy Diospyros species along with practical, interactive digital identification tools, and 3) conduct the very first head-to-head comparison of three competing hypotheses of island biodiversity and microendemism on Madagascar. Specifically, researchers will assess support for these hypotheses by: 1) quantifying species niche breadth using novel phylogenetically-informed species distribution models, 2) conducting phylo-spatial tests of endemism and phylogenetic turnover, and 3) examining patterns of niche conservatism and shifts in the rate of diversification through time. The project will enrich herbarium collections and contribute sequence data to genomic data repositories, facilitating future systematic research on Ebenaceae, and will provide a model framework for understanding species diversification in other speciose, tropical groups and elucidating how distributions may be impacted under future scenarios. 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.