Genetic Structure of the Common Milkweed, Asclepias syriaca L.

Abstract

Premise of the study: Microsatellite primers were developed for the common milkweed, Asclepias syriaca, to assist in genet identification and the analysis of spatial genetic structure. • Methods and Results: Using an enrichment cloning protocol, eight microsatellite loci were isolated and characterized in a North American population of A. syriaca. The primers amplified di- and tri-nucleotide repeats with 4-13 alleles per locus. • Conclusions: The primers will be useful for studies of clonality and gene flow in natural populations. Abstract: Chapter 3 Spatial genetic structure (SGS) is largely determined by the reproductive strategies of species. Many plant species, including Asclepias syriaca, the common milkweed, reproduce both sexually and asexually and there can be great variation in SGS among species that reproduce by both methods. SGS was assessed within an old field population of A. syriaca in northern Michigan. Strong SGS was detected to 38 m when multiple identical genotypes were included in the analysis; this signal was lost when identical genotypes were removed. This suggests that clonal reproduction in A. syriaca has a greater impact on spatial genetic structure than does sexual reproduction over the spatial scale of an old field.