Colonization and Connectivity of Habitat Patches for Coastal Marine Species Distant from Source Populations

Abstract

Abstract:The exchange of propagules or mobile adults between isolated habitat patches is of critical importance for some types of preserves, especially for species that cannot propagate locally. In the marine realm, the role of planktonic dispersal in maintaining viable local populations can be tested by examining life‐history traits of species that colonize ( or do not colonize ) isolated habitat patches. We compared the abundances of benthic species on an exposed rocky jetty surrounded by dissimilar habitats on the coast of Washington ( U.S.A. ) with those of species at distant bedrock sites within potential source areas. Despite its isolation, the jetty lacked only a small proportion of the potential algal species; these absences could result from the 40‐ to 100‐km distances to larger source areas or from subtle habitat differences at the jetty. Coralline algae are expected to be poor dispersers, both because propagules are short‐lived and because adults are unlikely to float. These algae were absent on the study jetty, although they occur on other isolated jetties on this coast. Short‐term transplant experiments indicated that corallines can survive locally once they colonize. Few animals were absent; one was a chiton that settles and feeds on coralline algae. Animals with obligate dispersal of offspring were abundant on the jetty despite their inability to propagate locally and despite dilution of larvae dispersing in the plankton from distant sources. Conversely, some animal species with no planktonic phase were also present; thus, organisms with a wide range of life‐history traits can persist at this distant and small patch of suitable habitat. Isolation along this shoreline did not eliminate either poor dispersers or obligate dispersers.