Ionta, Gretchen M. , Judd, Walter S. .
Phylogenetic relationships and patterns of morphological evolution in Periplocoideae (Apocynaceae).
Periplocoideae, a small but distinctive subfamily of Apocynaceae, comprises ca. 195 species of mostly lianas centered in the Old World tropics and subtropics, extending into Old World temperate regions. The generally small yet highly complex flowers of species of Periplocoideae exhibit the high degree of synorganization between androecium and gynoecium typical for derived members of Apocynaceae s.l. Distinctive spoon-like translators, which assist in pollen transfer, are unique to the subfamily. Pollinia are found in Orchidaceae and in three subfamilies of Apocynaceae: Periplocoideae, Secomonoideae, and Asclepiadoideae. Within Apocynaceae, Periplocoideae are unique in having both taxa that shed pollen as tetrads and taxa whose pollen is agglutinated into pollinia. Sequence data from nuclear ribosomal DNA and three plastid regions, in conjunction with 65 morphological characters, were utilized to investigate relationships within the subfamily. Resulting phylogenies provided a framework for the exploration of patterns of morphological evolution in the group. The monophyly of most genera represented by more than one species is confirmed, however, the recent amalgamation of several monoptyic and ditypic Asian taxa into Finlaysonia based on similarity of floral form and the presence of pollinia is not supported, thus we recommend the resurrection of Atherolepis and Meladerma, and the transfer of two Finlaysonia species into the genus Streptocaulon, and one species into Decalepis. Several clades are identified, including an Asian pollinial clade, a grooved translator clade, an epiphyte clade and a midvein colleter clade. Pollinial species appear in four distinct, well-defined clades, suggesting either three or four independent origins of pollinia within the subfamily, and indicating that pollinia evolved separately in Periplocoideae and in the common ancestor of Secamonoideae and Asclepiadoideae, a hypothesis supported by differences in pollinial structure in the three subfamilies.
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1 - University of Florida, Department of Biology, 220 Bartram Hall, P.O. Box 118526, Gainesville, FL, 32611-8526, USA
2 - University of Florida, Department of Biology, 220 Bartram Hall, P.O. Box 118526, Gainesville, FL, 32611, USA
Presentation Type: Oral Paper:Papers for Sections
Location: 552B/Convention Center
Date: Wednesday, August 4th, 2010
Time: 9:00 AM