Doffitt, Chris , Wallace, Lisa .
Phylogenetic relationships within the genus Amsonia (Apocynaceae) in North America based on chloroplast and nuclear markers.
Amsonia is one of the few genera in the Apocynaceae with a primarily holoarctic distribution. The approximately 20 species are found in four geographic regions: southeastern and southwestern North America, the Mediterranean, and Japan. This distribution represents a disjunct pattern that is also observed in many other taxonomic groups. Currently the genus is recognized as having four sub-genera Euamsonia (includes species from the southeastern U.S. and Japan), Articularia, Longiflora,and Spinctosiphon (all from the Southwestern U.S.). The groups of species found in southeastern and southwestern North America appear to be complexes of closely related species,several of which are rare or of conservation concern. This work examines the relationships of the species within southeastern and southwestern North America with an emphasis on the members of the sub-genus Euamsonia. In addition, it examines the relationship of Amsonia orientalis (Mediterranean) and Amsonia elliptica (Japan) to the North American members of the genus based on phylogenetic analyses of cpDNA sequences derived from trnH-psbA, trnD-trnT, rpi14-rpl36 intergenic spacers,and nuclear sequences of the ribosomal DNA Internal Transcribed Spacer (ITS)region. The resulting phylogenies suggest that Amsonia is not monophyletic if A.orientalis and A. elliptica are included in the genus. Additionally, A. ciliata, a southeastern U.S. species, is closely related to the southwestern species,which suggests that the sub-genus Euamsonia is not monophyletic. Also, some southeastern taxa are nested within a clade containing the wide-ranging species A.tabernaemontana, providing evidence that A.tabernaemontana is not monophyletic and is perhaps a wide-ranging polymorphic species. The morphology and apparent affinity of A. ciliata with the southwestern U.S.taxa seem to suggest aridification has provided a selective pressure that has influenced speciation. It is likely that similar abiotic influences have shaped morphological features in the southeastern species, with the species occurring on drier sites tending to have narrower leaves and more trichomes.
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1 - Mississippi State University, Department Of Biological Sciences, PO Box GY, Mississippi State, MS, 39762-5759, USA
2 - Mississippi State University, PO Box GY, Mississippi State, MS, 39762, USA
Presentation Type: Oral Paper:Papers for Sections
Location: Lindell A/Chase Park Plaza
Date: Tuesday, July 12th, 2011
Time: 2:15 PM