Modes of dispersal of clonal benthic invertebrates: consequences for species' distributions and genetic structure of local populations

Sexual reproduction is not necessarily correlated with dispersal among epibenthic invertebrates. Clonal animals disperse by both asexual and sexual means, and may often disperse farther by the former. Larvae of aclonal animals typically disperse farther than those of clonal animals, not because they are sexually produced, but because they take longer to develop sufficiently to settle. Dispersal is an inevitable component of planktonic larval development and drift, but not of the crawling or tethered larvae of many clonal and some aclonal species which may travel only a few centimeters before they metamorphose. Because of the preponderance of asexual reproduction and short-distance larval dispersal among clonal animals, local populations of clonal species may be dominated by large numbers of closely related individuals. In these animals larval development has been largely decoupled from exploitation of new distant sites which apparently occurs as an haphazard consequence of "sessile" dispersal. The larval stage is the primary mode of dispersal for most clonal animals over maximum distances of a few hundreds or thousands of meters, and generally much less. Beyond that, rafting may be the most common means of long-distance dispersal for both clonal and aclonal species.