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1 January 2011 Geographic Origins and Genetic Diversity of Air-Potato (Dioscorea bulbifera) in Florida
Matthew D. Croxton, Michael A. Andreu, Dean A. Williams, William A. Overholt, Jason A. Smith
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In Florida, air-potato is an invasive weed with high management priority, which may soon be targeted using classical biological control. This yam was introduced during the early 20th century by the United States Department of Agriculture (USDA) from areas throughout its extensive range. Our objectives were to characterize the genetic diversity of the invasive population in Florida and to identify the source regions of introduction. Authorities have often asserted the African provenance of the species in Florida, but our analyses, conducted using chloroplast markers, indicate that Florida air-potato is more similar to specimens examined from China than to those from Africa. Low intraspecific genetic diversity in Florida indicates that the invasive population was the result of at least two introductions becoming established in Florida.

Nomenclature: Air-potato, Dioscorea bulbifera L

Interpretive Summary: Two distinct, but genetically similar, chloroplast haplotypes were identified in the Florida population of the invasive yam vine, air-potato. Assuming no contribution of somatic mutation in the invasive population, these data are consistent with a minimum of two introductions into Florida. This study contributes baseline information regarding the diversity of air-potato before implementation of biological control in Florida. In the course of examining plant material to locate a putative source population, we characterized the genetic diversity of African air-potato, sampling six haplotypes on that continent. Three of the most prevalent African haplotypes were also geographically widespread, being found in both East Africa and West Africa. These three are also the most genetically distant from Florida and Chinese haplotypes, relative to other African haplotypes, as determined by parsimonious network analysis. A neighbor-joining analysis supported the relationships inferred in a statistical parsimony network. Our study did not find evidence that haplotypes were geographically structured in Africa. Despite a small number of microsatellite markers employed, this methodology confirmed the similarity of Chinese and Florida samples. Future work using a greater number of markers is expected to reveal greater intraspecific diversity, whereas further sampling in Asia and Oceania may localize Florida's source population to a regional, rather than a continental, level. Integrative taxonomic approaches are needed to synthesize morphological treatments of this species with more recent molecular studies, including the present work.

Matthew D. Croxton, Michael A. Andreu, Dean A. Williams, William A. Overholt, and Jason A. Smith "Geographic Origins and Genetic Diversity of Air-Potato (Dioscorea bulbifera) in Florida," Invasive Plant Science and Management 4(1), 22-30, (1 January 2011).
Received: 11 April 2010; Accepted: 1 August 2010; Published: 1 January 2011
biological control
chloroplast DNA
invasive yam
pantropical distribution
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