Book Description

The overarching theme of my thesis is to explore patterns of larval dispersal as they relate to management of fished marine species. I employed a case study of two species: Megastraea undosa and Parastichopus parvimensis to investigate patterns of phylogeography and assess relative scales of dispersal for these two species which are fished in both California, USA and Baja California, MEX. To examine how some generalities for many species can be made for a specific geographic area, I reviewed all existing phylogeographic studies around Cape Mendocino, CA. Dispersal at a snail's pace: Strong genetic structure in the fisheries gastropod Megastaea undosa. Information about larval dispersal is necessary for effective management of fisheries. Population genetics are often employed to assess dispersal, but these data also carry artifacts from the evolutionary history of a species. I assessed historical and modern demography of the wavy top snail, Megastraea undosa, a marine snail that is fished in California, USA and Baja California, Mexico. Genetic structure at the COI mtDNA locus is strikingly high, with large shifts in haplotype frequencies between southern Baja and southern California. Coalescent-based modeling of genetic data suggests that the population has limited dispersal throughout the range and underwent a northward range expansion after the last glacial maximum. I conclude that both historical and contemporary processes affect observed patterns of phylogeography in M. undosa. Consideration of the evolutionary history of target species allows for a more accurate interpretation of genetic data for management. iv Subtle genetic structure in the commercially fished warty sea cucumber, Parastichopus parvimensis. The warty sea cucumber, P. parvimensis, is fished commercially in both California, USA and Baja California, Mexico but little is known about the status of the fisheries or if separate stocks exist. P. parvimensis has a long pelagic larval duration of 50-90 days, which may translate to high connectivity throughout the species range (Monterey, CA, USA to Bahía Asuncion, BCS, Mexico). I examined phylogeographic patterns at the COI mtDNA locus and five microsatellite loci throughout the range of P. parvimensis and was particularly interested in patterns associated with the potential phylogeographic barriers of Point Conception, CA, USA and Punta Eugenia, BCS, MEX. I found no structure associated with Point Conception, but subtle genetic structure at both types of loci for Punta Eugenia, which may be mechanistically explained by oceanographic patterns. These data have important implications for management of the sea cucumber fishery and indicate that populations south of Punta Eugenia likely do not receive biologically meaningful input of larvae from northern populations to supplement the local fishery. Concordant phylogeographic patterns associated with the major headland of Cape Mendocino in northern California. Most coastlines are non-linear and headlands such as Cape Mendocino may interact with oceanographic processes to create barriers to dispersal. Though Cape Mendocino is a prominent headland, it has been largely ignored in the phylogeographic literature, which focuses instead on Point Conception in southern California. I reviewed and synthesized phylogeographic studies that include sampling sites north and south of Cape Mendocino and discuss the v oceanography and topography of the cape as potential mechanistic drivers of larval dispersal patterns. Slightly more than half (24 out of 46) of the surveyed species that showed significant genetic structure around this headland, which suggests that this headland may be an important barrier to dispersal and may limit connectivity between northern and central California. If populations north of Cape Mendocino have higher connectivity with populations in Oregon than with those in central California, marine spatial planning must occur at a multi-state scale to reach marine conservation goals.