Cushman, Kevin R. , Burgess, Michael B. , Campbell, Christopher S. .
Characterization of a microspecies in Amelanchier (Rosaceae).
All known Amelanchier polyploids are apomictic, and diversification of polyploid apomicts appears to start with the formation of microspecies. In our view, these locally distributed, morphologically distinct microspecies should not be given formal nomenclatural status in Amelanchier because they are very numerous and often minimally distinct morphologically. However, microspecies are important because of their pivotal role in taxonomic complexity in this genus. Amelanchier "rubra" is an apomictic, tetraploid microspecies known only from a part of coastal Maine and one location in Nova Scotia. This entity is morphologically distinct, but it contains at least two morphological forms that may be the result of separate origins or some sexuality following one origination. Quantitative morphological analyses (Dibble et. al. 1998. Syst. Bot. 23:31) placed A. “rubra” between a cluster of shrubby species (A. nantucketensis and A. spicata) and an arborescent species (A. laevis). This pattern suggested a hybrid origin of A. “rubra”, which was plausible given that hybridization is common in the genus and all three of these potential parental taxa grow in the range of A. "rubra.” One very distinctive feature, leaves that are glabrous upon emerging from overwintering buds, occurs in eastern North America only in A. laevis and A. bartramiana. Nuclear DNA sequences have so far not shown any indication that either A. laevis or A. bartramiana is ancestral to A. “rubra.” Instead, our data link this microspecies with a clade that comprises all western North American members of the genus plus eastern North American A. humilis and A. sanguinea; neither of the latter species is known to grow near A. “rubra.” These DNA sequences in A. “rubra” may have been inherited from allotetraploid A. spicata, for which one of the parents appears to have been A. humilis.
Microspecies, which are narrowly distributed taxa that usually reproduce uniparentally, are a challenge in the systematics of agamic complexes (groups with asexual seed production or apomixis). Understanding microspecies is therefore important in creating sound, usable classifications of agamic complexes.
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1 - University of Maine, School of Biology & Ecology, Orono, ME, 04469-5735, USA
2 - University of Maine, School of Biology and Ecology, Orono, ME, 04469-5735, USA
Presentation Type: Poster:Posters for Sections
Location: Hall A/Convention Center
Date: Monday, August 2nd, 2010
Time: 5:30 PM