The spreading potential of polychaete larvae does not predict adult distributions; consequences for conditions of recruitment

We analysed the relationship between the area covered by each generation of larvae and the area of specific distribution containing adult forms. The specific area was defined as the area in which larvae could settle, juveniles could grow, and adults could reach maturity and produce a new generation of propagules. From observations of larval and adult distributions in precise situations, it appears that larvae of numerous species cover a much wider variety of habitats than those in which their adult forms can survive. The discrepancies between the initial area where larvae were found, or the area occupied by first benthic recruits, and the adult habitat, converge to shaw that ecological constraints take on more and more importance as the animal develops from the planktonic larval stage through the juvenile stage to adult maturity. In the same way, sterile populations express a shift in constraints intensity between the benthic stage and the reproductive phase. Based on Atlantic Ocean results, proof is provided hen for the first time that the ability of larvae to cross an ocean does not bring about the panoceanic presence of adults. Finally, suitable conditions of recruitment do not necessarily imply the presence of adults, and conditions of colonisation are related to ecological constraints on adults. Consequently, the suggestion that species with a long planktonic larval development occupy a larger geographic area than species that spend only a short part of their life in the planktonic larval form does not seem to be justified.