Systematics/Phytogeography / Taxonomie/ Section
Hobbs, Christopher , Baldwin, Bruce G. .
Origin of Hawaiian Artemisia (Compositae—Anthemideae).
Molecular phylogenetic analyses of Hawaiian Artemisia (Compositae—Anthemideae) in the context of worldwide diversity in the genus indicate that the three recognized Hawaiian-endemic species (A. australis, A. kauaiensis, and A. mauiensis) constitute a clade that is sister to the East Asian A. chinensis, often treated in the segragate genus Crossostephium (with one species, C. chinense). These robust results from nrDNA ITS and ETS sequences are consistent with morphological similarities between the Hawaiian and East Asian lineages, as previously noted by Asa Gray, who placed A. chinensis together with A. australis in the Synoptical Flora of North America. Like A. chinensis and unlike other members of Artemisia, the Hawaiian endemic A. kauaiensis has a distinct pappus, in addition to the prominently ribbed cypselae that are shared by A. chinensis and all three of the Hawaiian species. Natural occurrence of A. chinensis in littoral habitats of southwestern China, Taiwan, Ryuku, and possibly the Phillipines (where likely introduced) and A. australis in similar situations in the Hawaiian Islands may reflect ancestral ecology of the Hawaiian clade, with subsequent colonization of inland habitats, including subalpine shrubland, where A. mauiensis is endemic. An ecological shift in Hawaiian Artemisia from tropical coastal habitats to subalpine settings, with a temperate to boreal climate, is consistent with evidence from recent studies by Tkach and others showing repeated colonization of the arctic by diverse lineages of Artemisia. Based on available molecular evidence, the clade encompassing A. chinensis and Hawaiian Artemisia may be most closely related to Asian lineages of Artemisia, in keeping with long-distance dispersal of the Hawaiian Artemisia ancestor from East Asia to the Hawaiian archipelago.
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1 - University of California, Berkeley, Integrative Biology, 3060 Valley Life Sciences Bldg. #3140, Berkeley, CA, 94720-3140, USA
2 - University of California, Berkeley, Department of Integrative Biology, University and Jepson Herbaria, 1001 Valley Life Sciences Bldg. #2465, Berkeley, California, 94720, USA
Presentation Type: Oral Paper:Papers for Sections
Date: Wednesday, July 30th, 2008
Time: 5:00 PM