JOHNSON, R.F.; California Academy of Sciences/Univ. of California, Santa Cruz: Phylogenetics, phylogeography and biogeography: Where and how do they meet?

The increasing ease and speed at which DNA sequences (especially mtDNA) can be obtained from large numbers of individuals has revolutionized biology. One of the unexpected findings of this revolution was that intra-specific gene trees often have phylogenetic structure that corresponds to geography (phylogeography). Phylogeography has been described as a bridge between the isolated disciplines of population genetics and systematics. Since the term was coined in 1987, the number of phylogeographic studies has dramatically increased. Simultaneously, but mostly independently, the number of systematic studies using molecular data has swelled. There can be considerable overlap in the questions asked by phylogeographers and systematists (especially those related to biogeography), although their primary goals are very different. Many phylogeographers do not take phylogenetic information into account when framing their questions or analyzing their results and many systematists do not look at intraspecific variation. Phylogeographers have found genetic discontinuities are often coincident with established biogeographic boundaries. Conversely, genetic discontinuities have not been found across all biogeographic boundaries. In some regions, diverse sympatric taxa have been found to have concordant phylogeographic patterns. In other regions with well-known biogeographic boundaries, unexpected phylogeographic patterns have been uncovered. Should we expect to find genetic discontinuities across all biogeographic boundaries? How does phylogenetic evidence change our interpretation of phylogeographic results? I will focus on marine taxa and discuss how the integration of phylogenetic and phylogeographic methods can help answer biogeographic and evolutionary questions.