Jah. Benzie et St. Williams, PHYLOGENETIC-RELATIONSHIPS AMONG GIANT DAM SPECIES (MOLLUSCA, TRIDACNIDAE) DETERMINED BY PROTEIN ELECTROPHORESIS, Marine Biology, 132(1), 1998, pp. 123-133
Analyses of allozyme variation at 26 loci in eight species of giant cl
ams, collected from the Western Pacific between 1989 and 1991, have co
nfirmed the major groupings currently recognised within the family Tri
dacnidae on the basis of morphological characters: the two genera Hipp
opus and Tridacna, and the subgenera within Tridacna; i.e. Chametrache
a (comprising T. squamosa, T. crocea and T. maxima), Tridacna sensu st
ricto (containing only T. gigas), and Persikima (comprising T. derasa
and T, tevoroa). All these groupings were each supported by several sh
ared characters. In contrast to previous views, Persikima was found to
be intermediate between Chametrachea and T. gigas. Although statistic
al support for branch lengths linking Chametrachea and T. gigas was li
mited in maximum-likelihood analyses, the occurrence of several shared
alleles between these groups, and none shared between only Chametrach
ea and Persikima, suggests a closer relationship between Chametrachea
and T. gigas or, at least, an unresolved trichotomy. Morphological dat
a traditionally assumed to support a closer association of Chametrache
a and Persikima demonstrated that only one shared character linked sub
genera, and this character supported an evolutionary association betwe
en Chametrachea and T. gigas. These findings, together with the number
of shared characters supporting the subgenus Persikima, suggest that
Persikima is the most basal offshoot of the Tridacna line, and that th
e group may deserve generic status.