Development of 15 microsatellite loci in the endangered Streptanthus glandulosus subsp. niger (Brassicaceae)

Premise of the study: The endangered Streptanthus glandulosus subsp. niger (Brassicaceae) is endemic to a single peninsula in California and threatened by fragmentation. We developed microsatellite markers to investigate genetic diversity in the two extant populations and the degree to which they have diverged from one another.

Methods and results: We used Illumina HiSeq high-throughput sequencing to develop 15 microsatellite markers, 14 of which were polymorphic. These di- and trinucleotide repeats yielded one to 11 alleles per locus in 61 plants across the two populations. Levels of observed and expected heterozygosities ranged from 0.108 to 0.946 and 0.257 to 0.839, respectively. We demonstrated cross-amplification in a second rare subspecies, S. glandulosus subsp. secundus, and in the widespread congener S. tortuosus.

Conclusions: These are the first microsatellites reported for this subspecies, and they will aid in the inclusion of genetic information in conservation planning. Cross-amplification was demonstrated in two related taxa, including one of conservation concern.