Abstract Detail

Biogeography

Wallace, Lisa Ellen [1], McGlaughlin, Mitchell M [2], Helenurm, Kaius [3].

Island hopping and evolutionary divergence of endemic Lotus on the California Channel Islands.

Isolation has long held a prominent role in speciation models, but empirical data are increasingly revealing that diverging populations can maintain high levels of gene flow while still moving in different directions throughout an adaptive landscape. The Channel Islands are unique in having a high level of plant endemism (15%), despite their closeness to mainland California. The explanation for the strikingly dissimilar patterns of genetic variation may lie in details of dispersal to and subsequent differentiation on the islands. In this project we examine genetic variation in two endemic Lotus species, L. argophyllus and L. dendroideus on the California Channel Islands to quantify the degree of relatedness and gene flow among populations in relation to geographic isolation and to address hypotheses on possible factors that have shaped the distribution and evolution of these species. We collected DNA sequences at three chloroplast regions (cpDNA) for three varieties of L. argophyllus, three varieties of L. dendroideus and several outgroup taxa. The results demonstrate a high level of variability within and between populations but few diagnostic characters indicative of varietal status. The presence of shared cpDNA haplotypes among populations may in some cases be due to interspecific hybridization but the recent divergence of these taxa and retention of ancestral polymorphisms cannot be discounted. Levels of genetic diversity did not consistently follow expected patterns, instead showing that some single-island endemics harbor high levels of genetic variation that are comparable to more wide-ranging taxa. These results are discussed in light of the proposed phylogeographic pathways that could have promoted divergence of Lotus on the Channel Islands and the conservation status of these taxa and will aid in untangling the role of isolation and gene flow during species divergence, which are likely to characterize many continental systems as well.

Broader Impacts:

1 - Mississippi State University, Department of Biological Sciences, P. O. Box GY, Mississippi State, Mississippi, 39762
2 - University of Northern Colorado, Biological Sciences, 501 20th Street, Ross Hall 1560, Greeley, CO, 80639, USA
3 - University of South Dakota, Department of Biology, 414 E. Clark St, Vermillion, SD, 57069, USA

Keywords:
Channel Islands
intraspecific variation
cpDNA sequencing
Lotus
phylogeography.

Presentation Type: Oral Paper:Papers for Topics
Session: 28
Location: 552B/Convention Center
Date: Tuesday, August 3rd, 2010
Time: 8:45 AM
Number: 28004
Abstract ID:260