Fehrmann, Susie , Halliburton, Richard , Philbrick, C. Thomas .
Intraspecific variation in Podostemum ceratophyllum.
Few studies have addressed the phylogeography of aquatic plants in the northern hemisphere and the role of climactic oscillations. ¬†Podostemum ceratophyllum (Podostemaceae), a species of eastern North America, Honduras and the Dominican Republic, occupies fast flowing river current. A previous study of isozyme variation indicated that genetic population structure varied relative to the glacial boundary, although limited population sampling was conducted. The purpose of the present study was to re-examine intraspecific variation in P. ceratophyllum using chloroplast DNA over a more extensive geographic range. Nineteen collections were made from Nova Scotia to Arkansas, with one from Honduras. Noncoding chloroplast DNA was sequenced (trnS-trnG, psbD-trnT, ndhJ-trnF, psaI-accD, atpI-atpH and rpoB-trnC¬†regions) to create a 4189bp haplotype for three individuals per population. Nineteen haplotypes were identified with only one found in more than one region. Fourteen populations were monomorphic; four had two haplotypes while the remaining two had three each. When populations were grouped north or south of the glacial boundary, nucleotide diversity was 0.00014 (north) and 0.0019 (south). Results did not change significantly when Arkansas and Honduras populations were excluded; both show no variation. With 4 groups, estimates of pairwise NST ranged from 0.13 (north - southeast) to 1.00 (Arkansas - Honduras). Selective neutrality tests were significant in the north, indicating the possibility of a recent bottleneck and subsequent expansion. We hypothesize that limited variation in northern collections is a result of colonization since the last ice age, a recent bottleneck, and prevalence of asexual reproduction. Higher diversity in the southeast, primarily Southern Appalachia, corresponds to other studies supporting this area as a refugia during Pleistocene climactic changes.
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1 - Western Connecticut State University, Biology and Environmental Sciences, 181 White Street, Danbury
2 - Western Connecticut State University, Biological & Environmental Sciences, 181 White Street, Danbury, CT, 06810, USA
Presentation Type: Oral Paper:Papers for Topics
Location: 552B/Convention Center
Date: Tuesday, August 3rd, 2010
Time: 9:30 AM