Campbell, Christopher , Burgess, Michael , Cushman, Kevin , Doucette, Eric , Frye, Christopher , Nelson, Gretchen .
Classifying North American Amelanchier polyploids (Rosaceae).
Amelanchier is well known for its taxonomic complexity, which is generated largely through the evolution of polyploid apomicts. Gene flow among polyploids and among polyploids and diploids frequently generates new forms the establishment and spread of which are favored by polyploidy and apomixis. We expect such newly formed polyploid apomicts, which have traditionally been called microspecies, to be common, and our fieldwork indicates that they are common. Amelanchier polyploid apomicts retain some sexuality in egg formation, and the pollen is chromosomally reduced and abundant. Over time, this sexuality can be expected to transform apomicts from microspecies into heterogeneous assemblages with fuzzy boundaries. Amelanchier polyploids can also be taxonomically challenging because both autopolyploids, which represent about 5% of the polyploids we have studied, and allopolyploids are often morphologically cryptic compared to diploids. We follow Hausdorf's (2011) differential fitness species concept and identify Amelanchier polyploid species as phenotypic clusters that are ecogeographically distinct and show some genetic coherence. We also prioritize polyploid groups that are widespread, common, and readily identifiable by people who are interested in these ecologically important plants. Our draft classification includes about eight polyploid species and some well-studied, informally recognized microspecies. We deal with transformed apomicts and cryptic polyploids with about ten species complexes. Each species complex contains a diploid species, one or more polyploid species, or both diploid and polyploid species. All species complexes also encompass plants that are not part of formally recognized taxonomic groups, including microspecies and hybrids. Species complexes provide a name for polyploid morphological diversity that is related to recognized species but that does not meet our criteria for formal nomenclatural status.
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Presentation Type: Oral Paper:Papers for Sections
Location: Delaware D/Hyatt
Date: Wednesday, July 11th, 2012
Time: 10:15 AM