Long-Distance Dispersal of Planktonic Larvae and the Biogeography and Evolution of Some Polynesian and Western Pacific Mollusks

The wide geographic range of many contemporary marine molluscan species throughout Polynesian and western Pacific islands is accounted for by long-distance dispersal of larvae. Plankton taken in the tropical and temperate central Pacific Ocean between Hawaii and New Zealand and from 160°W to 180° longitude contained teleplanic veligers including, but not restricted to, the gastropod families Neritidae, Architectonicidae, Triphoridae, Ovulidae, Cypraeidae, Naticidae, Cymatiidae, Bursidae, Tonnidae, Muricidae, Thaididae, Coralliophilidae, Columbellidae, Turridae and Conidae, the bivalve families Pinnidae and Teredinidae, and a number of other as yet undetermined taxa. The present study considers some members of three gastropod families with teleplanic larvae (viz. Architectonicidae, Naticidae, and Coralliophilidae) and also some representatives of the bivalve family Pinnidae.

Fossil evidence from western Pacific islands shows that mollusks with a long planktonic life have occurred throughout most of the Tertiary and that contemporary families that have a teleplanic larva are largely the same as those in the fossil record. It is assumed that teleplanic larvae in the geologic past were carried by surface currents as they are today and that the general direction of larval dispersal can be inferred from the paleocirculation.

Fossil species having a long planktonic larval life of many months usually are shown to have had a greater geographic range than species with a shorter duration in the plankton. Concomitantly, fossil species with teleplanic larvae also persist over several geologic epochs whereas those with nonplanktonic development appear to be more restricted in temporal distribution. A different biogeographic and evolutionary outcome may be expected in species with a planktonic life of only a few weeks.

More evidence on the life history of both fossil and contemporary species is required to provide further insights into the evolutionary significance of planktonic and nonplanktonic development and larval dispersal in marine mollusks.