The Distribution of Genetic Diversity Within and Among Populations of the Rocky Mountain Columbine: The Impact of Gene Flow, Pollinators, and Mating System

Abstract

The distribution of genetic diversity of a plant species over the landscape provides insight into the evolutionary process and affects conservation strategies. We used both conventional methods (F statistic and analysis of molecular variance) and more recently developed methods (Structure and Population Graphs) to describe the genetic structure of 13 Aquilegia coerulea populations across four geographic areas. Gene flow played an important role in explaining the distribution of genetic diversity over the landscape in A. coerulea populations. We detected significant isolation by distance and identified long-distance dispersal events and instances of restricted gene flow. The long-distance dispersal events explained some of the genetic similarities observed among populations from different regions. Restricted gene flow contributed to the genetic differentiation detected among populations within some regions. Populations in Utah represented the most likely center of the range for this group of populations. The mating system had little influence on the distribution of genetic diversity, and the abundance of the two main pollinators did not explain differences among populations from different regions. Fire and differences in flowering phenology with altitude, combined with aggregated populations, limited gene flow and increased the genetic differentiation of some geographically close populations.