Friday, August 8, 2008

PS 79-83: Correlating genetic variation with life history type in chaparral of the Santa Monica and San Gabriel Mountains

Laura A. Merwin, Stephen D. Davis, Thomas L. Vandergon, and Rodney L. Honeycutt. Pepperdine University

Background/Question/Methods Chaparral species found in the transverse mountain ranges of Southern California are classified according to their response to wildfire. Sprouting species respond by vegetative resprouting from root crowns protected from fire under the soil and thus experience almost no genetic recombination within the population after each fire event. Their seeds are killed by fire. In contrast, adult non-sprouting species are entirely killed by fire and respond by extensive post-fire germination of refractory seeds, leading to an entirely new recombinant population after each fire. In addition, sprouting species experience widespread seed dispersal while seeds of non-sprouting species remain close to the parent plant. We hypothesized that these contrasting reproductive patterns in response to wildfire would result in a greater level of genetic diversity both within and between non-sprouting populations when compared to sprouting populations. We sampled populations of Rhamnus ilicifolia (sprouter) and Ceanothus crassifolius (non-sprouter) in the Santa Monica and San Gabriel Mountains and used Amplified Fragment Length Polymorphisms (AFLPs) to analyze genomic diversity. We assessed sixty alleles in ten to fifteen individuals per population and performed an Analysis of Molecular Variance (AMOVA) and a Principle Coordinates Analysis (PCA) using GenAlEx. We also constructed phylograms using PAUP. Results/Conclusions We found that there was no significant genetic difference between the two R. ilicifolia populations. This finding is consistent with our hypothesis for sprouting species. DNA extraction and AFLP analysis for C. crassifolius are ongoing and will be completed by July 2008.