(full paper is archived in the Miller Library)
Title: Habitat niches of acsidians in the rocky intertidal of Pacific Grove, California
Student Author(s): Pulliam, William M.
Location: Final Papers Biology 175H
Date: June 1981
Abstract: The habitat niches of the different species of ascidians which occur in a rocky intertidal region of Cabrillo Point, Pacific Grove, Monterey County, California appear to be largely delimited by the physical factors of intertidal height, degree of exposure to wave action, and slope of substrate. Strength of current flow was also investigated and was found to be closely correlated with wave action. Species which overlap broadly along gradients of one of these parameters are usually fairly well separated along gradients of the other two factors. Interactions between paramenters are frequent, as in cases of species which occur higher, lower or on different slopes in areas with differing wave actions. Several pairs of species show distinct boundaries between their ranges, which is probably a result of interspecific competition. The growth forms of the species occuring in different sites is strongly correlated with the degree of wave action at these sites. Species with sheet-like growth forms dominate heavily exposed areas, and species with erect growth forms more protected areas. The relative resistances of the different growth forms to pounding and shearing forces form waves could be responsible for this trend.