Meeting Abstract

62.5  Saturday, Jan. 5  Vicariance or pseudocongruence? Multispecies phylogeography in the northeastern Pacific MCGOVERN, TM*; HART, MW; SASKI, C; MARKO, PB; Clemson Univ.; Simon Fraser Univ.; Clemson Univ.; Clemson Univ. tmcgove@clemson.edu

Comparative phylogeography often reveals the existence of shared phylogeographic breaks across co-distributed species, consistent with a hypothesis of vicariance, in which a single event simultaneously disrupted the geographic ranges of many species. The hypothesis of vicariance, however, not only requires geographic concordance, but also temporal congruence with respect to the disruption of gene flow. Pinpointing the timing of divergence not only contributes to our understanding of the historical processes shaping spatial patterns of genetic variation, but also has great significance to community ecology given the potential for testing hypotheses about the geographic responses of groups of interacting species to environmental change. Because most comparative phylogeography typically involves a single (mtDNA) locus, variation in inferred divergence times across taxa has been difficult to ascribe to either true temporal differences in divergence time or simply the expected high inter-locus variance in the coalescent process. Although maternal inheritance, high mutation rates, and small effective population size make mtDNA ideal for phylogeography, additional data from multiple loci are necessary to distinguish true temporal discordance in divergence times from the idiosyncratic histories of individual loci. We therefore investigated the use of anonymous nuclear loci in phylogeographic studies of two co-distributed taxa representing several that share a spatially congruent mtDNA break in the northeastern Pacific. In additional to traditional population genetic analyses, we have employed Bayesian/Markov chain Monte Carlo methods to compare mtDNA-based estimates of divergence to combined mtDNA/nDNA data sets. We use these analyses to discuss broader issues of phylogeographic evidence and congruence as well as implications for community responses to environmental change.