Genetic consequences of a single-founder population bottleneck in Trifolium amoenum (Fabaceae)

We investigated the genetic consequences of a single-founder bottleneck in a population of showy Indian clover (Trifolium amoenum), a species presumed to be extinct until rediscovered near Occidental, California, in 1993. Electrophoretic variation was evaluated in the bottlenecked population and in a larger population (Dillon Beach) discovered during the course of this study, as well as in populations of two closely related species, T. albopurpureum var. dichotomum and T. macraei. We found a surprisingly high amount of polymorphism in the single-founder T. amoenum population from Occidental (15% of loci polymorphic; an average of 1.1 alleles per locus). However, this represents a 53% reduction in number of polymorphic loci and a 20% reduction in average number of alleles per locus compared to three Trifolium populations with putatively similar mating systems (the Dillon Beach T. amoenum population and both populations of T. albopurpureum var. dichotomum). Expanding the genetic base of the Occidental T. amoenum population is a priority due to concerns about loss of evolutionary potential and the possibility of deleterious effects associated with inbreeding. However, using seed from the Dillon Beach T. amoenum population may not be beneficial due to distinct, presumably adaptive differences between plants from the two populations and concerns about outbreeding depression.