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Abstract Detail



Biogeography

Wallace, Lisa [1], Mcglaughlin, Mitchell [2], Wheeler, Gregory [1], Bresowar, Gerald [3].

Phylogeography of Acmispon (Fabaceae) on the California Channel Islands.

Insular plant taxa show varied evolutionary patterns reflecting dispersal and allopatric divergence. In discrete archipelagos far from a mainland source, radiation from a single ancestor is commonly observed and speciation often follows in a stepping stone fashion from older to younger islands. Less is known about dispersal patterns in island systems that are closer to mainland systems and in islands that have complex geological histories. In this study, we used multiple genetic data sets to reconstruct patterns of seed dispersal and gene flow in Acmispon argophyllus and Acmispon dendroideus throughout the California Channel Islands. This archipelago is comprised of eight islands that vary in distance from the mainland, size, and geological history. Based on these factors, we hypothesized that dispersal/gene flow is primarily dictated by distance from a source. Taxa on islands close to the mainland are predicted to have dispersed from the mainland, whereas inter-island dispersal is expected for taxa on the most distant islands. We also predicted that dispersal between the northern and southern groups of islands is very limited and that populations on the northern islands would show little evidence of divergence given that they were connected during the Last Glacial Maximum. Populations of A. argophyllus on the northern islands are strongly divergent from conspecific southern island populations, but the same is not true of A. dendroideus. Additionally, A. dendroideus populations on the northern islands are genetically indistinguishable despite those on San Miguel considered to represent a unique variety. Patterns on the southern islands are more complex and reflect mainland-to-island dispersal as well as inter-island dispersal. On Santa Catalina and San Clemente, convarietal populations are often highly divergent, a finding that likely reflects a combination of multiple independent dispersal events and historical introgression from congeneric species. In summary, oceanic barriers between islands and topographic barriers on islands appear to have a strong influence on population genetic structure in both species. These results have implications for species conservation and provide a contrasting pattern of dispersal on a near island system that does not follow the traditional stepping stone model found on far island systems.

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1 - Mississippi State University, PO Box GY, Mississippi State, MS, 39762, USA
2 - University of Northern Colorado, 501 20th St, Box 92, Greeley, CO, 80639, USA
3 - University of Northern Colorado, 501 20th Street, Greeley, CO, 80639, USA

Keywords:
Phylogeography
Island Evolution
genetic diversity.

Presentation Type: Oral Paper:Papers for Topics
Session: 50
Location: Magnolia/Riverside Hilton
Date: Wednesday, July 31st, 2013
Time: 2:00 PM
Number: 50003
Abstract ID:756
Candidate for Awards:None


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