Livshultz, Tatyana .
Phylogeny of crown clade Apocynaceae: nuclear locus supports surprising milkweed sister-group.
Analysis of chloroplast loci has identified a well-supported “Crown Clade” within Apocynaceae that includes six (6) primary lineages: 1) the pollinium-bearing milkweeds (subfamilies Asclepiadoideae and Secamonoideae), 2) the tetrad-bearing Periplocoideae, and four monad-bearing lineages: 3) tribe Baisseae (Africa), 4) tribe Apocyneae (predominantly Asia), 5) tribes Odontadenieae, Echiteae, and Mesechiteae (predominantly America), and 6) the genus Rhabdadenia (America); the latter four lineages are all currently classified in a paraphyletic subfamily Apocynoideae. Relationships among these six lineages were unresolved or unsupported in densely sampled analyses of chloroplast data except Baisseae were strongly supported as sister to the pollinium-bearing milkweeds, contradicting a long-accepted morphological hypothesis that the tetrad-bearing Periplocoideae are most closely related to the pollinium-bearing milkweeds. To test this unexpected result with an unlinked genetic locus and to better resolve relationships among the Crown Clade lineages, the first exon of phytochrome A was sequenced and analyzed separately and in combination with the chloroplast loci. Also, the monotypic west African genus Dewevrella, previously classified in Apocyneae or Echiteae, was sampled for the first time in a molecular analysis. Analysis of phytochrome A corroborates the sister group relationship of Baisseae and the milkweeds. All loci support inclusion of Dewevrella in Baisseae. Combined analysis of phytochrome A and chloroplast loci provides improved resolution of and support for relationships among the six primary crown clade lineages. The implications of these results for floral evolution and biogeography are discussed.
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1 - Academy of Natural Sciences of Philadelphia, Botany Department, 1900 Benjamin Franklin Parkway, Philadelphia, PA, 19103-1101, USA
Presentation Type: Oral Paper:Papers for BSA Sections
Location: Rendezvous A/Snowbird Center
Date: Tuesday, July 28th, 2009
Time: 8:15 AM