Life in the lee: Local distributions and orientations of honeycomb worms along the California coast

In the rocky intertidal, invertebrates living in dense, intraspecific groups may be particularly important community members because they provide structural habitat for other species. Despite the prevalence of conspecific aggregates, there is scant knowledge of the proximate and ultimate causes of their distributions. Phragmatopoma californica is a gregarious, suspension-feeding tubeworm that forms extensive reefs ("honeycombs") along the California coast. Local distributions and sizes of worm aggregations, tube orientations and worm mass were quantified to identify patterns and generate hypotheses regarding potential structuring processes. Field surveys were conducted at five intertidal boulder fields in northern and southern California, spanning much of this species' range. Observational data were obtained at four ecologically meaningful spatial scales. The most striking patterns occurred at the smallest (