Evolution in a Glaciated Landscape: Contribution of Endemism to Great Lakes Biodiversity
Derieg, Nathan , Deprenger-Levin, Michelle , Bruederle, Leo P. .
Speciation mid-stride: diverging lineages in glaciated environments.
The processes of speciation active in glaciated landscapes are hardly idiosyncratic to glacial/interglacial episodes: the literature contains examples of vicariant (and especially peripatric) speciation (e.g., Picea mariana), suggestions of sympatric speciation (e.g., Deschampsia mackenzieana), and discussions centered on hybridization (e.g., Potentilla section Niveae). Population genetic and phylogenetic studies of species pairs, or groups, have provided insight into the origins of some Great Lakes endemics, specifically. Notable among these are: Iris cristata and the threatened I. lacustris; Mimulus glabratus var. jamesii and M. michiganensis; and Cirsium canescens and C. pitcheri. The genus Carex (Cyperaceae) provides additional examples where the trajectory of speciation appears to have been initiated by Pleistocene climate change. Within Carex section Ceratocystis, a yet to be described sedge formerly ascribed to C. cryptolepis is endemic to southern Michigan, Ohio, and eastern Indiana. Several lines of evidence (morphology, habitat, allozyme allele frequency, nrDNA sequence data) suggest a sister-species relationship with the narrow endemic C. lutea of Pender and Onslow Counties, North Carolina. Observed patterns of genetic diversity, although hardly conclusive, are consistent with peripatric speciation. Carex scirpoidea subsp. convoluta (Carex section Scirpinae) is an edaphic endemic restricted in distrubtion to alvar communities of Michigan and Ontario; the putative sister taxon C. scirpoidea subsp. scirpoidea is widely distributed across North America, occupying a wider ecological amplitude. Carex scirpoidea subsp. convoluta, an outcrossing taxon, exhibits relatively low levels of genetic diversity. In combination with limited occurrence on highly specific substrate, this suggests a local origin from a small founding population.
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1 - University of Colorado at Denver and Health Sciences Center, Biology, Campus Box 171, P.O. Box 173364, Denver, Colorado, 80217, USA
Presentation Type: Symposium or Colloquium Presentation
Location: Boulevard A/Hilton
Date: Tuesday, July 10th, 2007
Time: 9:30 AM