Tri- and tetra-nucleotide microsatellite DNA markers for assessing genetic diversity, population structure, and demographics in the Holmgren milk-vetch (Astragalus holmgreniorum)

We document the isolation and characterization of 17 tri- and tetra-nucleotide microsatellite DNA markers in the Holmgren milk-vetch (Astragalus holmgreniorum) surveyed among plants from three critical habitat units (CHUs) located in southern Utah and northern Arizona, USA. These markers displayed moderate to high levels of allelic diversity (averaging 19.5 alleles/locus) and heterozygosity (averaging 75.1%). No deviations from Hardy- Weinberg equilibrium and limited (1.8%) linkage disequilibrium were observed. A series of analyses identified significant population differentiation among the three CHUs. Demographic analyses suggested that each collection has achieved mutation-drift equilibrium. The microsatellite markers developed for A. holmgreniorum yielded sufficient genetic diversity to: (1) distinguish individuals and delineate kinship; (2) elucidate population structure; (3) define management units; and (4) provide unique demographic perspectives for recovery efforts.