Benoit, Lori K. , Les, Donald H. .
Indications of hybridization between monoecious and dioecious biotypes of Hydrilla verticillata (Hydrocharitaceae).
Hydrilla verticillata (L.f.) Royle (Hydrocharitaceae), the only species of the monotypic genus Hydrilla, is a nonindigenous, invasive aquatic plant found in the U.S. It is widely distributed in the Old World and believed to be native to broad areas throughout southern Asia. Two “strains” or biotypes of H. verticillata (i.e. monoecious and dioecious) have been recognized, and both have been introduced to the U.S. Previous phenetic analyses have indicated that the vast geographical range of H. verticillata is associated with informative genetic divergence. However, phylogenetic analyses of worldwide H. verticillata accessions are lacking. We present the first such analysis of H. verticillata using sequences from nuclear ribosomal DNA internal transcribed spacer (ITS1, 5.8s, ITS2), cloned nrITS and cloned phytoene desaturase (PDS), another nuclear-encoded gene. Maximum parsimony analysis of ITS data resolved two distinct clades that correspond to the known distribution of monoecious and dioecious biotypes in the U.S. The Korean, Indian and Australian accessions clustered with the U.S. monoecious clade. Cloned nrITS and PDS data provide evidence of historical hybridization events involving the monoecious and dioecious biotypes. We explain these incongruencies by hypothesizing that subsequent to hybridization between monoecious and dioecious parents, the nrITS region converted to the genotype of only one parent. Sequencing a cpDNA marker is underway and these data will be used to test this hypothesis further. A precise determination of the hybrid parents’ geographical origins will not be possible until additional material from Old World localities has been studied.
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1 - University of Connecticut, Ecology & Evolutionary Biology, 75 North Eagleville Road, Unit 3043, Storrs, CT, 06269, USA
2 - University of Connecticut, Ecology & Evolutionary Biology, 75 North Eagleville Road, U-3043, Storrs, Connecticut, 062693043, USA
nuclear ribosomal DNA (nrITS)
Presentation Type: Oral Paper:Papers for BSA Sections
Location: Cottonwood A/Snowbird Center
Date: Monday, July 27th, 2009
Time: 1:30 PM