Moore, Abigail , Baldwin, Bruce G. .
Biogeography and evolutionary history of Grindelia (Asteraceae: Astereae).
Grindelia is among the most taxonomically challenging groups of North American composites. Estimates for the number of species in North America north of Mexico range from 18 to 30, with many of those species difficult to delimit, even though they are morphologically distinct at their extremes. The genus as a whole has an amphitropical distribution, with approximately half of the species native to North America and Mexico and the remainder native to South America. We used DNA sequence data from the nuclear ribosomal ITS and ETS and chloroplast psaI-accD regions to revisit hypotheses on biogeographic history and character evolution across the genus. Grindelia as a whole is well-supported and is composed of two sister clades, one native to South America and the other native to North America, including Mexico. The South American taxa are much more diverse in habit than the North American members. The North American taxa constitute two clades that largely occur on different sides of the Continental Divide. The diverse radiation of Grindelia in the California Floristic Province appears to be most closely related to species from the Great Basin and Colorado Plateau and evidently descended from drought-adapted ancestors. Although Steyermark’s hypotheses about the relationships of North American Grindelia are not all supported, we did recover a clade corresponding to his Pacific radiation and many of the Mexican and Texan species that he hypothesized to be basal in the genus represent early diverging lineages in our trees. Major taxonomic difficulties posed by endemics of the California Floristic Province in part appear to reflect extreme youth of the Pacific clade, which Steyermark represented as highly nested within North American Grindelia. Dunford’s detailed cytogenetic data for North American Grindelia are largely congruent with our phylogeny, although two origins of one chromosomal arrangement are necessary to fit the interchange data on the molecular trees.
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1 - University of California Berkeley, Department of Integrative Biology, University and Jepson Herbaria, 3060 Valley Life Sciences Building, Berkeley, California, 94720, USA
2 - University of California, Berkeley, Jepson Herbarium and Department of Integrative Biology, 1001 Valley Life Sciences Building #2465, Berkeley, CA, 94720-2465, USA
Presentation Type: Oral Paper:Papers for Sections
Location: 556A/Convention Center
Date: Tuesday, August 3rd, 2010
Time: 3:15 PM