Isolation, characterization and cross-species amplification of polymorphic microsatellite loci in Asclepias (Apocynaceae)
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Ten polymorphic loci were isolated and characterized from the milkweed, Asclepias syriaca L., of North America. These loci successfully cross-amplified in A. exaltata L. Polymorphism ranged from two to 16 alleles per locus per species in 68 individuals of A. syriaca and 56 individuals of A. exaltata. Expected heterozygosities ranged from 0.017 to 0.851 and significant deviations from Hardy–Weinberg equilibrium were found for two and three loci in A. syriaca and A. exaltata, respectively. No linkage disequilibrium was detected. These markers should prove useful for assessing population genetic structure and interspecific gene flow in these and other species of Asclepias.
KeywordsApocynaceae Asclepias Cross-species amplification Hybridization Microsatellite PCR primers
We appreciate the hard work and amusement contributed during fieldwork by REU students Theresa Stoepler and Andrea Edge, lab assistance from Chris Ellison, microsatellite development and consultation by Genetic Identification Services (especially Mark Todd), and the Cruzan lab at Portland State University (especially David Rosenthal and Trieste Dobberstein) for technical consultation and use of their ABI 310 for fragment analysis. Thanks to Alisa Ramakrishnan and Mitch Cruzan for helpful comments on the manuscript. Funding was provided by US Department of Agriculture-Cooperative State Research, Education and Extension Service award 2003-3456-13768 and US National Science Foundation-Division of Environmental Biology award 0244113.
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