NSF-DEB-RAPID: Evolution of reproductive barriers in long-lived conifers

Understanding the mechanisms underlying speciation is a fundamental aim of evolutionary biology with direct implications to conservation and species management in a rapidly changing landscape. This research aims to understand how barriers to reproduction have evolved in a long-lived conifer, Torrey Pine, one of the rarest pines in the world. With a restricted distribution to just two discrete populations, a mainland population and an island population, this research uses a particularly exciting approach to understand the evolution of reproductive barriers in a long-lived species using longitudinal monitoring of plant phenotypes and fitness characteristics within a common environment. Established in 2007, mainland, island and first-generation hybrid seedlings representing island maternal plants fertilized by mainland pollen donors were planted into a single common environment at the Santa Barbara Botanic Garden. Annual monitoring of these trees suggests there is an advantage to being a hybrid in the common environment, with hybrids taller and exhibiting increased fecundity relative to parent trees. However, whether this advantage is maintained across future generations remains a question, which will provide insight into mechanisms that contribute to reproductive isolation. This research will study those factors that define a species, and will have conservation and management implications for rare, endemic species. This project will provide field and database management exposure for students at the undergraduate and graduate level. In addition, this project will bring together partners from governmental (USDA-Forest Service), non-governmental (Santa Barbara Botanic Garden) and research institutions to promote the long-term preservation of these genetic resources, which have fundamental scientific and applied conservation value, and educational impact.

This RAPID project will fund a collection of data and tissue from a long-term provenance trial of Torrey Pine (Pinus torreyana), a rare, endemic California conifer planted at the Santa Barbara Botanic Garden in Santa Barbara, California. The objectives of the project will be to (i) collect cones for processing and planting within a containerized common garden at the Institute of Forest Genetics in Placerville, CA, (ii) collect needle tissue for long-term storage and genomics work, and (iii) assess trait and morphological data for future association analyses with genomic data. The common garden property may be listed for sale shortly, which could restrict access to the mainland, island, and F1 individuals that were established in 2007 and that are only now reproductive and producing an F2 generation. Therefore, this funding provides an opportunity to sample tissue and collect data for the development of a longer term Torrey pine project which will aim to understand the genomic and phenotypic architecture underlying the evolution of population differences in a long-lived conifer.