Bolin, Jay F. , Bray, Rebecca D , Taylor, W. Carl , Musselman, Lytton John .
Unraveling the reticulate evolutionary history of the Isoetes hyemalis complex.
Quillworts (Isoetes, Isoetaceae) are cosmopolitan heterosporous fern allies of freshwater aquatic habitats; they consist of slender microphylls and a corm-like root stock. The greatest challenge in species identification is a paucity of usable taxonomic characters. Nonetheless, approximately 200 species of Isoetes are recognized and in North America Isoetes form a species complex of approximately 31 taxa. Allopolyploidy, interspecific hybridization followed by chromosome doubling, has emerged as an important mechanism of speciation in this group. Of the Isoetes in N. America, 16 are diploids (2n = 22) and 15 are polyploids ranging from tetraploids (2n = 44) to decaploids (2n = 110). Molecular techniques were applied to determine parentage in several coastal plain and piedmont populations of the tetraploid plant Isoetes hyemalis in the southeastern US. We amplified the second intron of LEAFY (LFY) homolog, a biparentally inherited nuclear gene, cloned PCR products, screened 10-15 clones per individual, and sequenced the LFY clones. Our LFY sequence data indicated that I. hyemalis is not monophyletic. For I. hyemalis, we present several new parental combinations of diploid Isoetes and others with no extant representatives. Reticulate evolution and morphological convergence present challenges to the useful delimitation species in this complex.
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1 - Old Dominion University, Department of Biological Sciences, Mills Godwin Building, 45th Street, Norfolk, Virginia, 23529-0266, USA
2 - National Science Foundation, Division of Environmental Biology, 4201 Wilson Boulevard, Arlington, Virginia, 22230, USA
Presentation Type: Oral Paper:Papers for Sections
Date: Monday, July 28th, 2008
Time: 9:15 AM