Cushman, Kevin , Doucette, Eric , Burgess, Michael , Frye, Christopher , Campbell, Christopher .
Morphological and molecular relationships of Nantucket shadbush (Amelanchier nantucketensis, Rosaceae).
Amelanchier nantucketensis Bickn. was named in 1911 based on plants from Nantucket Island, Massachusetts. This species is the only taxon in the genus with andropetaly: the presence of microsporangia on small spatulate petals. The expression of this feature varies greatly, but almost all plants of this taxon have some andropetaly. This shrub is known only as a tetraploid and usually grows on acidic sands and rock outcrops from the southeastern United States through much of New England and southern Nova Scotia. The origin of Nantucket shadbush is unclear. Weigand, in his 1912 treatment of Eastern North American Amelanchier, considered this taxon to be a hybrid of A. canadensis (L.) Medic.var. oblongifolia Michx. and A. spicata (Lamarck) K. Koch. In his 1946 monograph of North American Amelanchier, Jones lumped A. nantucketensis with A. humilis Wiegand, a diploid, and A.spicata, a taxonomically complex tetraploid. Distinguishing non-flowering A. nantucketensis and A.spicata is difficult. Allpolyploid Amelanchier studied are aposporous, pseudogamous apomicts capable of creating morphologically discrete microspecies. Hybridization and occasional sex within some microspecies have spawned a bewildering array of forms and, over time, generated loosely connected, morphologically similar, and widely dispersed species complexes. Amelanchier nantucketensis is morphologically rather uniform, but unlike many microspecies that we have observed in the genus, it has a relatively broad distribution. Sequence data from nrDNA ETS and ITS show that Nantucket shadbush is strongly tied to A.canadensis and weakly linked to a clade that includes A. arborea (Michx. f.) Fern., A.canadensis, A. laevis Wiegand, and A.bartramiana (Tausch) M. Roemer. An ITS pseudogene shared by Nantucket shadbush and taxa related to A. humilis, but not A. humilis itself, suggests a member of the clade that includes A. humilis was an ancestor of A. nantucketensis. It appears that A. nantucketensis has had a complex history that has partially obscured its diploid progenitors.
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1 - University of Maine, School of Biology and Ecology, 5751 Murray Hall, Orono, Me, 04469, USA
2 - University Of Maine, Department Of Biological Sciences, 261 HITCHNER HALL, ORONO, ME, 04469-5735, USA
4 - Maryland Wildlife And Heritage Service, 909 Wye Mills Road, PO Box 68, Wye Mills, MD, 21679, USA
Presentation Type: Oral Paper:Papers for Sections
Location: Lindell A/Chase Park Plaza
Date: Wednesday, July 13th, 2011
Time: 2:45 PM