Baldwin, Bruce G. , Wood, Kenneth R. , Motley, Timothy J. .
Molecular evidence for an American origin of Apostates (Compositae), a monotypic endemic of Rapa (Austral Islands).
Molecular phylogenetic analyses of 18S-26S nuclear ribosomal internal and external transcribed spacer sequences of Apostates rapae and other helianthoid members of Compositae indicate that the monotypic, Rapa-endemic genus Apostates belongs within the New World tribe Bahieae and, more specifically, the “Bahia clade.” Analyses based on extensive taxonomic sampling within the “Bahia clade” [Achyropappus, Amauriopsis, Apostates, Bahia (including Picradeniopsis and Schkuhria multiflora), Florestina, Holoschkuhria, Hymenothrix, Palafoxia, Platyschkuhria] resolved a (91%-bootstrap) subclade containing A. rapae and a (100%-bootstrap) sister-clade of western North American taxa in Bahia. Other North American taxa of the non-monophyletic genus Bahia were placed in one of two other robust clades, either with the two South American species of the “Bahia clade,” B. ambrosioides and Holoschkuhria tetramera, or with representatives of the western North American genera Amauriopsis, Hymenothrix, and Platyschkuhria. The simplest biogeographic hypothesis to explain the molecular findings requires two long-distance dispersal events out of southwestern North America; one to South America and one to Rapa, a distance of >7000 km. Although the shrubby, morphologically disparate Apostates has been difficult to place taxonomically, even at the tribal level, its evident phylogenetic position among mostly herbaceous lineages of Bahieae is consistent with phyllotaxy, which is even more conservative in the “Bahia clade” than recognized previously by W. L. Ellison, who treated alternate-leaved and opposite-leaved taxa of Bahia in separate series (Alternifoliae and Oppositifoliae). Apostates and other opposite-leaved genera of the “Bahia clade” (i.e., Achyropappus and Holoschkuhria) constitute a clade with opposite-leaved members of Bahia; alternate-leaved genera of the “Bahia clade” (i.e., Amauriopsis, Florestina, Hymenothrix, and Palafoxia) constitute a clade with alternate-leaved members of Bahia. The value of Apostates rapae as an example of extreme long-distance dispersal and rapid evolution in the Rapa flora adds to the conservation urgency of this endangered species, with two known living individuals.
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1 - University of California, Berkeley, Jepson Herbarium and Department of Integrative Biology, 1001 Valley Life Sciences Building #2465, Berkeley, CA, 94720-2465, USA
2 - National Tropical Botanical Garden, 3530 Papalina Road, Kalaheo, HI, 96741, USA
3 - Old Dominion University, Department of Biological Sciences, 110 Mills Godwin Building/45th St, Norfolk, VA, 23529-0266, USA
Presentation Type: Oral Paper:Papers for Topics
Date: Wednesday, July 30th, 2008
Time: 9:00 AM