Jah. Benzie et St. Williams, GENE FLOW AMONG GIANT CLAM (TRIDACNA-GIGAS) POPULATIONS IN PACIFIC DOES NOT PARALLEL OCEAN CIRCULATION, Marine Biology, 123(4), 1995, pp. 781-787
Tridacna gigas (L.) populations were sampled from 13 locations through
out the west Pacific in 1990-1491 and screened for allozyme variation
at seven polymorphic loci. Significant genetic differences were found
between the few large stocks of T. gigas remaining in the world. Clust
er analysis identified two major regional groups of populations: a ''C
entral Pacific'' group consisting of Kiribati and the Marshall Islands
, and a ''West Pacific'' group comprising all other populations. Withi
n the latter group, the Great Barrier Reef populations were significan
tly differentiated from those in the Solomon Islands. The main routes
of gene flow did not run parallel with known major surface currents as
might be expected, but crossed them. Gene exchange was limited east-w
est between the Central and West Pacific groups and the GBR and the So
lomon Islands. The lack of correspondence between the major surface cu
rrents and the routes of gene flow suggests that the genetic structure
of T. gigas reflects historical patterns of migration that no longer
occur, rather than present-day dispersal. These findings raise fundame
ntal questions concerning the origin and maintenance of genetic divers
ity in Pacific faunas, and have important implications for the maricul
ture and conservation of T. gigas.