RODRIGUEZ, A.*; KELLY, R.P.; EERNISSE, D.J.; California State Univ., Fullerton; Columbia Univ. and American Museum of Natural History; California State Univ., Fullerton: Is the Palos Verdes peninsula a barrier to gene flow for chitons and limpets?
The comparative phylogeography of selected chiton and limpet species was analyzed in order to test a recent hypothesis that Palos Verdes Peninsula, California, is an underappreciated biogeographic boundary. In California, the cold and warm temperate Oregonian and Californian provinces are separated at Pt. Conception, which has long been considered a potential barrier for larval dispersal. Recent authors have found phylogenetic breaks that are not concordant with Pt. Conception and its strength as a biogeographic boundary has been questioned. In fact, Dawson (2001; J. Biogeogr. 28:723-736) reviewed available phylogeographic comparisons of various marine animals that have planktonic larvae, including fishes, snails, and clams, and he found more general patterns of genetic separation further south near Los Angeles, California, and argued that the area around Palos Verdes Peninsula might represent a more significant dispersal barrier than Pt. Conception. We have tested this hypothesis by looking for congruent patterns of phylogeographic breaks for multiple chiton and limpet species common to southern California. All have similar ecology and relatively brief pelagic dispersal, especially compared to marine invertebrates with feeding larval stages. Specimens are being collected from up to three populations on either side of the peninsula. DNA from the mitochondrial gene regions 16S and COI have been amplified and sequenced from our current specimens. Preliminary datasets show some species to have little to no genetic structure from sample locations in Los Angeles to northern Baja California which is indicative of gene flow among populations. Other species have been shown to have genetic structure with no consistent separation with respect to Palos Verdes. Thus, the Palos Verdes peninsula does not appear to be an effective barrier to gene flow for chitons and limpets and continued sampling is expected to support this.
