Understanding the mechanisms that lead to the origin of new species is a primary goal of evolutionary biology. Although new species have traditionally been viewed as originating in isolation from close relatives, recent data suggest that unique evolutionary entities can diverge even with high levels of gene flow. Although both genetic and ecological factors contribute to divergence of new taxa, the balance and roles of connectivity and isolation in diverging populations remain poorly understood. This project uses molecular genetic, ecological, and morphological data to understand patterns of divergence resulting from the balance between isolation and interbreeding in many populations of two endemic Lotus species in the California Channel Islands. These islands are close to each other and mainland California, but contain many unique species not found on the mainland.
This project contributes to the documentation of biodiversity and understanding of the underlying processes that generate new species. Such understanding is needed for effective conservation and management of biological diversity and the ecosystem services it supports. This study will clarify how natural processes influence connectivity and divergence in ecological communities of islands, with applications also to similar continental regions. The research also offers interdisciplinary research training for many undergraduate and graduate students and significant outreach to agencies and NGOs that are charged with conservation and management of biodiversity.
In this collaborative project with the Mississippi State University and the University of South Dakota, genetic and morphological data were analyzed to understand how plant species colonize and evolve on the California Channel Islands. Most of the native flora of the Channel Islands is shared with mainland California, suggesting a high rate of dispersal, but 15% are endemic, suggesting infrequent dispersal and gene flow in at least some species. For this study, genetic variation was measured using three types of molecular markers in 29 populations of Acmispon argophyllus and Acmispon dendroideus, also known as deerweeds, endemic to the Channel Islands and nine populations of related taxa from the islands and mainland California. The resulting data indicate that morphological differences among populations and the species do not always match with levels of genetic divergence, that seeds have dispersed multiple times to the Channel Islands as well as among the islands, and that these species have hybridized when they came into contact on San Clemente and Santa Catalina. Acmispon argophyllus var. niveus is so strongly divergent that it should be recognized as a new species, rather than a variant of A. argophyllus. These data also suggest that conservation of these species should focus on preserving unique variation within populations and across all of the islands. Seven undergraduate students and one graduate student at the University of Northern Colorado participated in the project, thereby contributing to their education. Two undergraduate students successfully moved into graduate and three undergraduate students are working in lab or field based research positions, having been aided by their experience with this project. Two publications and more than 20 research presentations have resulted from this project thus far. An additional two publications are currently in review, with several additional publications in preparation for publication. A workshop on conservation genetics was held at the California Native Plant Society meeting in 2012 and was attended by 24 participants from private, state and federal agencies, including the Denver Botanic Garden, Rancho Santa Ana Botanic Garden, Catalina Island Conservancy, California Department of Fish and Wildlife, San Diego County, Santa Clara County Water District, Point Reyes National Seashore, U.S. Fish and Wildlife Service, U.S. Forest Service, Bureau of Land Management, and, U.S. Navy. Workshop attendees were trained in interpreting genetic data to better manage rare and endangered plants, and have established relationships with the project leaders to ensure correct interpretation of genetic data related to specific management activities.
