NSF Award
2423013
This project will study how changes in population numbers and the process of adaptation contribute the to formation of new species in pines. Species represent the basic units by which biodiversity is quantified. It is thus paramount to understand the processes affecting the formation of new species, especially as accelerated environmental change threatens numerous species with extinction. A key component to the formation of new species is the development of reproductive isolation, defined as the reduction and eventual cessation of genetic mixing among populations. Despite more than a century of research into the the ecological, genetic, and developmental drivers of speciation across diverse organisms, there remains gaps in our understanding of the processes that lead to the formation of reproductive isolation. This project attempts to fill these gaps for pines, a group of ecologically dominant and economically important temperate plants displaying enormously variable levels of reproductive isolation. Filling these gaps is crucial to ensure the long-term survival of pines as changes to their habitats continue to accelerate. As such, the next generation of forest scientists must be diverse, multidisciplinary, and well trained. This project will train the next generation of diverse forest scientists in cutting edge methodologies, develop teaching modules about pine and tree diversity for local elementary schools, and expand existing resources and training for forest managers to better understand the role of hybridization (i.e., the lack of reproductive isolation) during evolutionary responses to changing environments.<br/><br/>The relative roles of demography and adaptation to standing levels of reproductive isolation for pines will be quantified using a two-tiered combination of phylogenetics, genomics, demographic inference, and landscape genomics. First, phylogenetically informed meta-analyses will relate interspecific crossing rates to climate niche similarities (adaptation surrogate) and range size (demography surrogate) across the entire genus. Existing data suggest that each predictor significantly affects reproductive isolation for pines. Second, exon-based, pull-down sequencing of tens of thousands of genic regions in a reduced set of species will be used to test the hypothesis that climate adaptation and accumulation of deleterious genetic load within species as a function of demographic history are the primary determinants of crossing rate variability for pines. These efforts capitalize on the unique biology of pines (e.g., large genome size, rapid decay of linkage disequilibrium, polyembryony) relative to other well-studied plant systems and will provide foundational information for further comparative studies across long-lived plants.<br/><br/>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.
