Benoit, Lori , Les, Donald .
Phylogenetic structure in the cosmopolitan aquatic angiosperm Hydrilla verticillata (L.f.) Royle (Hydrocharitaceae): evidence for cryptic speciation in a monotypic genus?
Hydrilla verticillata (L.f.) Royle (Hydrocharitaceae), a submersed, cosmopolitan aquatic plant, currently is recognized as the only species of a monotypic genus. Presumably, its native range includes Australia, India and Southeast Asia; it is invasive in the United States, with two introduced biotypes (dioecious; monoecious). These biotypes are similar morphologically, with much of their vegetative variation attributed to phenotypic plasticity. Here we evaluate phylogenetic and nonparametric network methods to reconstruct complex gene genealogies, determine origins of introduced populations, and identify clades that might be significant taxonomically. Nuclear (nrITS; cloned nrITS; phytoene desaturase - PDS; cloned PDS), and plastid (trnL intron/trnL-F spacer) sequences were evaluated. Maximum parsimony analyses resolved four clades (PDS) or three clades (ITS; trnL/trnL-F). The clades recovered for PDS had greater support than those for ITS, but the topologies were congruent overall. Clades I and II (ITS; PDS) contained 'US dioecious' haplotypes as well as genomic sequences and haplotypes from Burundi, China, India, and Nepal. Accessions from Europe, Japan, and Korea comprised a third clade that was well-supported in all trees. A fourth, broadly Indo-Pacific clade (Australia, Indonesia and Malaysia), was not well-supported in the nuclear gene trees. 'US monoecious' haplotypes were found in clades II and IV in PDS, but only in clade IV in ITS. Plastid data placed the US monoecious haplotype with an uncommon Korean haplotype; neither was part of clade III, which contained the most commonly found Korean nuclear gene sequences. All data indicated that US dioecious plants originated from India, a result consistent with previously published phenetic analyses. Cloned nuclear gene sequences revealed a complex, somewhat reticulate gene history, which for some accessions and relationships was better visualized using network rather than tree-based methods. Phylogeographic patterns indicated genetic divergence over large spatial scales, but additional data will be required to assess whether the clades described here deserve taxonomic recognition, perhaps as cryptic species. Morphological character analyses also are underway for this purpose.
Log in to add this item to your schedule
1 - University Of Connecticut, Ecology & Evolutionary Biology, 75 N. Eagleville Road, Unit 3043, Storrs, CT, 06269-3043, USA
2 - University Of Connecticut, Department Of Ecology & Evolutionary Biology, 75 N. Eagleville Road, Unit 3043, Storrs, CT, 06269-3043, USA
trnL intron/trnL-F spacer.
Presentation Type: Oral Paper:Papers for Sections
Location: Lindell C/Chase Park Plaza
Date: Tuesday, July 12th, 2011
Time: 2:30 PM