Population genetics and phylogeography of endangered Oxytropis campestris var. chartacea and relatives: arctic‐alpine disjuncts in eastern North America

Abstract

Fassett's locoweed (Oxytropis campestris var. chartacea, Fabaceae) is an endangered perennial endemic to Wisconsin. Patterns of genetic variation within and among six remaining populations and their relationship to other members of the O. campestris complex were analysed using AFLPs from 140 accessions across northern North America. Within-population measures of genetic diversity were high (mean expected heterozygosity HE = 0.16; mean nucleotide diversity pi = 0.015) compared with other herbaceous plants. Estimates of among-population differentiation were low (FST = 0.12; PhiST = 0.29), consistent with outcrossing. Genetic and geographical distances between populations were significantly correlated within Fassett's locoweed (r2 = 0.73, P < 0.002 for Mantel test) and O. campestris as a whole (r2 = 0.63, P < 0.0001). Individual and population-based phylogenetic analyses showed that Fassett's locoweed is monophyletic and sister to O. campestris var. johannensis. Morphometric analyses revealed significant differences between Fassett's locoweed and populations of var. johannensis. The first chromosome count for Fassett's locoweed indicates that it is tetraploid (2n = 32), unlike hexaploid var. johannensis. High within-population diversity and relatively low among-population differentiation are consistent with populations of Fassett's locoweed being relicts of a more continuous Pleistocene distribution. Our data support the continued recognition of Fassett's locoweed and protection under federal and state regulations. High levels of genetic diversity within populations suggest that maintain-ing the ecological conditions that favour the life cycle of this plant may be a more pressing concern than the erosion of genetic variation.

Landscape Population Genomics of Forsythia (Forsythia suspensa) Reveal That Ecological Habitats Determine the Adaptive Evolution of Species

“…In recent years, research on the influence of environmental variables on spatial structure gradually increased. Identifying the influence of environmental variables on spatial genetic structure remains difficult because of the complex reciprocal interactions of multiple factors (Chung et al, 2004; Ohsawa and Ide, 2008). Our survey demonstrated a significant spatial population genetic structure across the studied populations.…”

Comparative phylogeography of unglaciated eastern North America

“…Phylogeographical studies are also emerging for plants occurring in once‐glaciated and arctic eastern North America (e.g. Tremblay & Schoen 1999; Chung et al . 2004; Godbout et al .…”

Phylogeny and genetic structure of Erophaca (Leguminosae), a East–West Mediterranean disjunct genus from the Tertiary

“…The AFLP (Amplified Fragment Length Polymorphism) technique is appropriate for phylogeographic studies because it allows genotyping of large numbers of loci in many different individuals, and hence the elucidation of genetic population structures and recent phylogenies (Weising et al, 2005). Phylogeographic studies using AFLP have been successfully carried out of legume taxa in Europe and America (e.g., Anthyllis montana; Kropf et al, 2002;Astragalus ampullarioides;Breinholt et al, 2009; Astragalus cremnophylax; Travis et al, 1996;Oxytropis campestris;Chung et al, 2004), as well as in Mediterranean species of diverse plant groups (Ortiz et al, 2008;Piñeiro et al, 2007;Terrab et al, 2008).…”