Influences of landscape and pollinators on population genetic structure: examples from three Penstemon (Plantaginaceae) species in the Great Basin.

PREMISE OF THE STUDY: Despite rapid growth in the field of landscape genetics, our understanding of how landscape features interact with life history traits to influence population genetic structure in plant species remains limited. Here, we identify population genetic divergence in three species of Penstemon (Plantaginaceae) similarly distributed throughout the Great Basin region of the western United States but with different pollination syndromes (bee and hummingbird). The Great Basin's mountainous landscape provides an ideal setting to compare the interaction of landscape and dispersal ability in isolating populations of different species.
METHODS: We used eight highly polymorphic microsatellite loci to identify neutral population genetic structure between populations within and among mountain ranges for eight populations of P. deustus, 10 populations of P. pachyphyllus, and 10 populations of P. rostriflorus. We applied traditional population genetics approaches as well as spatial and landscape genetics approaches to infer genetic structure and discontinuities among populations. KEY
RESULTS: All three species had significant genetic structure and exhibited isolation by distance, ranging from high structure and low inferred gene flow in the bee-pollinated species P. deustus (F(ST) = 0.1330, R(ST) = 0.4076, seven genetic clusters identified) and P. pachyphyllus (F(ST) = 0.1896, R(ST) = 0.2531, four genetic clusters identified) to much lower structure and higher inferred gene flow in the hummingbird-pollinated P. rostriflorus (F(ST) = 0.0638, R(ST) = 0.1116, three genetic clusters identified).
CONCLUSIONS: These three Penstemon species have significant yet strikingly different patterns of population genetic structure, findings consistent with different interactions between landscape features and the dispersal capabilities of their pollinators.