PARENT SESSION
Poster Session #14: Dispersal.
Monday, August 5. Presentation from 5:00 PM to 6:30 PM. Exhibit Hall B & C, TCC
141
Characterization of larval dispersal within the California Current by two estuarine crabs.
Petersen, Christine*,1, 1 UC Berkeley, Berkeley, CA
ABSTRACT- Measurement of dispersal of marine larvae is a challenging task because of the difficulty of either marking or sampling larvae during migration. Modelling marine dispersal as an entirely passive function of dominant current patterns often produces poor results due to the factors of behavior, and importance of rare events. To support a model of marine larval dispersal within the California Current system of the Eastern Pacific, I carried out a genetic comparative analysis of dispersal between the estuarine shore crabs Hemigrapsus oregonenesis and Rhithropanopeus harrisii. Hemigrapsus oregonensis is ecologically, but not phylogenetically, similar to Rhithropanopeus harrisii, a nonindigenous species introduced around the 1930s. Contrasting the range expansion of the recently introduced species with that of the native (which has existed in longer term equilibrium) provides evidence for selection between alternative hypotheses of mechanisms of dispersal along the coastline. I sequenced cytochrome oxidase I, and generated estimated dispersal rates, and directions using phylogeographic analysis of haplotype locations. Genetic data confirmed the original introduction of R. harrisii into San Francisco Bay and subsequent expansion to sites in Oregon. Migration events are estimated to occur less frequently than annually. The northward range expansion of R. harrisii is evidence for the importance of the unusual northward current regime experienced during El Nino events, or the effects of the northward flowing Davidson current which occurs during Winter. A dispersal kernel for a metapopulation model for either species was developed with a Bayesian approach using both genetic dispersal estimates as well as data from a 2-D current model assuming semi-passive dispersal.
KEY WORDS: dispersal model, range expansion, bayesian, phylogeography