(full paper is archived in the Miller Library)
Title: Small-scale population structure in Nucella emarginata and Nucella ostrina
Student Author(s): Freed, Emily
Faculty Advisor(s): Palumbi, Stephen
Location: Final Papers Biology 175H
Date: June 2003
Abstract: The cryptic gastropod species Nucella emarginata and Nucella ostrina are distributed along the northeastern Pacific coast from Alaska to Baja, California. N. emarginata is found primarily in the south and N. ostrina is found primarily in the north, with their ranges overlapping in central California. Snails (7 34 individuals) from four locations in the overlap zone were collected and their population structures were studied using an approximately 500 bp fragment of the mitochondrial gene cytochrome c oxidase subunit I (COI). Contrary to what might be expected, analysis showed snails from the southern locations of Soberanes Point and San Luis Obispo are both N. ostrina (the northern species), while snails from the northern locations at Hopkins Marine Station in Pacific Grove and Point Joe are both N. emarginata. Although populations in each location are fairly homogenous, small amounts of variation do exist within each population (i.e. some polymorphisms are present). Of particular note is the variation that exists between snails collected from a wave exposed area at Hopkins Marine Station and snails in a wave protected area on the other side of the same point. Despite this intra-population variation, each location forms a genetically distinct group. Further sampling in central California will give more insight into the distribution of Nucella over short geographical distances and will hopefully elucidate more of these species’ evolutionary histories, as well as possibly helping to determine what factors are important in Nucella distribution.