Torrey pine (Pinus torreyana) is one of the rarest pine species in the world. Restricted to one mainland and one island population in California, Torrey pine is a species of conservation concern under threat due to low population sizes, lack of genetic variation, and environmental stochasticity. Previous research points to a lack of within population variation that is unprecedented among conifer species, although a few fixed genetic differences between the populations contribute to subspecies classification. Given this, development of best conservation practices requires a combination of genetic and trait evaluation tools to conserve this keystone species. To evaluate phenotypic differences between populations, a provenance trial was established in 2007 at the Santa Barbara Botanic Garden. The trial consists of seeds established from cones collected within a mainland progeny trial of mainland and island individuals and includes mainland, island, and hybrid individuals, the result of natural hybridization within the progeny trial. Genetic ancestry of individuals was evaluated using allozyme markers as fixed genetic differences were observed between populations. We evaluated phenotypic differences between mainland, island and hybrid individuals, comparing early germination traits and annual fitness metrics height and fecundity following establishment. Preliminary results indicate admixed individuals exhibit increased fitness relative to mainland and island individuals at all development stages, suggesting a potential role for genetic rescue via intraspecific hybridization in this genetically depauperate species. However, unidirectional hybridization within the F1s indicates extrinsic or intrinsic barriers to reproduction have evolved between these populations, indicating between-population crosses may not represent a viable option to conserve evolutionary potential. This long term dataset provides an invaluable resource to test predictions regarding the use of genetic rescue in rare, long-lived species.
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