Population genetics of Sabatia campestris (Gentianaceae), a state-endangered plant of the Illinois prairie

The role of temporal and spatial gene flow in the genetic structuring of two natural populations of Sabatia campestris (Gentianaceae) was investigated within Illinois using both direct, field methods and indirect, molecular genetic methods. In addition, population genetic structure differences were explored between Illinois and Texas populations of S. campestris.; Field estimates of pollen and seed movements showed highly localized gene dispersal within populations with average dispersal distances of 2.2 m and 0.18 m, respectively. The field estimates of gene movement were consistent with the population genetic data indicating that most populations had a deficiency of heterozygotes and were highly structured. Migration estimates were obtained by extrapolating results of pollen analog movements (m = 0.0009), as well as using genotypic data (m = 0.0035). From a population genetics perspective, the two migration estimates are comparable and taken together, provide a reasonable range of migration between the two populations.; A significant F_ST value (0.0426) indicated genetic differences between the two populations separated by 170 m of prairie vegetation. Further analysis supported isolation by distance patterns between populations and also indicated an isolation by distance trend within populations.; For Illinois S. campestris populations, seed banks are critical for long-term persistence, with plants emerging that reflect the past genetic history of the populations. Seed bank recruitment ranged from 27–100% and, even in the third years of the study, rare alleles were found to originate from the seed bank. In addition, seed bank recruitment influenced fine-scale population structure. This research is unique because it documents seed bank recruitment within the population at the level of the individual plant, providing further evidence for the importance of the seed bank in storing genetic variation over time.; Population genetic structure of peripheral populations of S. campestris from Illinois was investigated both within Illinois and at a regional scale. The results identified isolation by distance patterns indicating that Illinois populations differed genetically from central populations that were collected from Texas. In addition, isolation by distance analyses indicated that genetic differences were present among Illinois populations. These data illustrate the evolutionary importance of peripheral populations.