| The Great Basin region of the western U.S. provides an ideal setting to study the interacting effects of geographic isolation, distance, topography, climate, and pollination syndrome on population genetic differentiation of plant species. I used three ecological genetics tools (microsatellite DNA analysis, common garden studies, and experimental crosses) to understand the causes and effects of population genetic divergence for three species of Penstemon (Plantaginaceae) in the Great Basin. All species are common and widespread throughout the western United States, share most life history traits thought to affect population genetic structure, but have very different primary pollinators, ranging from small and large bees to hummingbirds. If these pollinators have different abilities to connect disjunct populations, particularly in the mountainous landscape of the Great Basin, the evolutionary trajectory of each species will be altered via impacts on its population genetic structure.;My results revealed significant genetic diversity and divergence among populations in both neutral and potentially adaptive quantitative traits for all three species, but results were strikingly different depending upon the primary pollinator of each species. The hummingbird-pollinated species had much greater gene flow among populations than the two bee-pollinated species, but this greater gene flow did not translate to lower divergence in quantitative traits. However, the first generation of experimental crosses spanning increasing geographic and genetic distances revealed both inbreeding and outbreeding depression in progeny of the bee-pollinated P. pachyphyllus, which had the highest degree of population divergence. No negative fitness effects were identified in the hummingbird-pollinated P. rostriflorus .;These results can be directly applied to understanding important genetic considerations in ecological restoration in the Great Basin. Taken together, they indicate that the broad-scale movement and mixing of seeds for restoration purposes may lead to both short and long-term restoration failure in both bee and hummingbird-pollinated species. Additional research on these and similar species is needed to help direct restoration efforts now and into the future. |
