Heafner, Kerry D. , Hickey, R. James , Watson, Linda E. .
Taxonomic and Systematic Studies of the Isoetes melanopoda Gay & Durieu Assemblage in North America.
Isoetes melanopoda is a binomial first applied to quillworts collected in central Illinois from agricultural fields in the late 1800s, and characterized by the formation and retention of blackened leaf bases (phyllopodia) toward the end of their phenological cycle. Subsequent to Durieu's 1864 description of I. melanopoda, other populations inhabiting a variety of generally acidic habitats and ranging throughout most of the eastern two-thirds of the U.S. have been subsumed under I. melanopoda. These habitats include upland depression swamp forests and intermittent, low woodland streams in the southeastern U.S. Piedmont region, low wet edges of agricultural fields, water-filled depressions and wet edges of rock outcrops, and other seasonally wet areas. We have analyzed data sets from cytological, morphological, anatomical, and allozyme studies to delineate and characterize cryptic species in I. melanopoda, and performed phylogenetic analyses using both nuclear and plastid-encoded DNA sequences in an attempt to arrive at a phylogenetic hypothesis regarding this group. The diploid (2n=22) I. melanopoda exhibits distinct genetic differences between those populations east of the Appalachian Mountains and those west of the Appalachians, especially at TPI-2. Morphological analyses substantiate this pattern, and we propose that I. melanopoda actually consists of at least two species: an eastern, woodland diploid and a western diploid of various habitats. A similar genetic pattern is observed for populations subsumed under I. piedmontana. This taxon my consist of as many as four distinct entities. Phylogenetic analyses weakly support this geographic pattern and further suggest that these species are relatively recently derived.
1 - Miami University, Department of Botany, 316 Pearson Hall, Oxford, Ohio, 45056, USA
Presentation Type: Paper
Location: Superior B (Cliff Lodge)
Date: Monday, August 2nd, 2004
Time: 11:15 AM