Systematics Section / ASPT
Smith, Tyler , Waterway, Marcia .
Combing morphological and molecular data in taxonomic revision: an evaluation of Carex section Porocystis.
CAREX section Porocystis is a group of 2 to 8 species of eastern North America. They can be informally divided into two complexes: the C. virescens complex (C. virescens, C. swanii, C. aestivalis, and the globally rare C. roanensis), primarily Appalachian in distribution, and the C. hirsutella complex (C. hirsutella, C. complanata, C. bushii, C. caroliniana), which is broadly distributed across the southeast. Recent treatments have raised doubts about the appropriate circumscription of these taxa, with various authors suggesting that each complex should be recognised as one to four species. The purpose of our study was to clarify this situation by examining morphological and molecular variation in the section. We sampled populations of each putative taxon from across their range, focusing on areas of sympatry. Our samples included more than 400 samples from 100 populations, with each individual being scored for morphological characters and subjected to amplified fragment length polymorphism (AFLP) assays. The morphological data shows clear separation of four taxa corresponding to C. aestivalis, C. roanensis, C. bushii, and C. caroliniana. The distinction between C. swanii and C. virescens and between C. complanata and C. hirsutella is more problematic, with intermediate specimens confounding otherwise discrete entities. All eight taxa are clearly separated by AFLP markers, although there is some evidence of introgression between C. bushii and C. hirsutella. Surprisingly, the species-pairs that are most difficult to separate morphologically are the most distant genetically, confirming recent sequence-based phylogenetic analysis showing that they are not sister species. The combined data strongly supports recognizing all eight taxa as distinct species, and we identified new characters to improve field-identification of morphologically ambiguous individuals. This highlights the value of pairing molecular and morphological samples in elucidating taxonomic patterns that would not be clear from either data set alone.
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1 - McGill University, Department of Plant Science, 21,111 Lakeshore Road, Ste-Anne-de-Bellevue, Québec, H9X 3V9, Canada
Presentation Type: Oral Paper:Papers for Sections
Date: Wednesday, August 2nd, 2006
Time: 1:30 PM