Conservation implications of small population size and habitat fragmentation in an endangered lupine

Abstract

Conservation measures to preserve critically endangered species aim to maintain healthy and self-sustaining populations and often involve reintroductions. Effective introductions must take into account the genetic structure and diversity remaining in the species to inform choices of germplasm for introduction strategies. Lupinus aridorum (McFarlin ex Beckner; Fabaceae) is an endangered plant found on two disjunct ridge systems in central Florida. All plants are found in areas that are favored for human development and agriculture. Few options exist for introduction locations, so the most informed strategies must be used to preserve this species. We used ten microsatellite loci, developed for this species, to determine genetic diversity and genetic differentiation among populations, and to compare L. aridorum with two closely related congeners. Our results show a low level of diversity remaining in the species in comparison with a more abundant congener and similar levels of variability among each L. aridorum population. At least three L. aridorum populations exhibit a genetic signal of partial selfing. Hybridization with a closely-related congener was not apparent; however, additional crossing trials are needed to fully assess the possibility of hybridization. Although some sources list the taxonomy of L. aridorum as a variety of a Florida panhandle species, L. westianus (Small), the genetic differences revealed by our data support listing these two species as separate entities. Our findings can be used to guide sampling strategies for ex situ conservation such as providing a mixture of source populations to improve the probability of successful introductions.