Determination of Genetic Relationships Among Populations ofAsclepias tuberosa(Asclepiadaceae) Based on ISSR Polymorphisms

Abstract

Asclepias tuberosa L., or butterflyweed, is a native plant species occurring throughout much of North America, and is a valued horticultural plant most known for its ability to attract butterflies. Three subspecies, A.t. interior, A.t. rolfsii, and A.t. tuberosa, have been identified based on leaf shape, but their overall genetic variability is not known. The current study investigated the genetics of this plant from populations located in six different geographic areas in the United States. Because there is very little knowledge of the genetics of this plant, as a first approach, analyses based on ISSR polymorphisms were used to determine genetic structure. A total of 115 ISSR bands, of which 96.5% were polymorphic, were scored from 82 samples. The Exact Test for population differentiation showed that populations from all six geographic locations were genetically distinct from one another. UPGMA analysis determined that the populations from the different geographic locations did not cluster into three different groups representing the three subspecies. These results do not support the separation of A. tuberosa into three subspecies. Instead, they suggest that each of the individual populations studied are relatively genetically isolated. However, there is potential for gene flow, which may allow the populations of A. tuberosa to maintain variability.