US EPA

1775601 

Journal Article 

GENETIC-STUDIES OF ASIATIC CLAMS, CORBICULA, IN THAILAND - ALLOZYMES OF 21 NOMINAL SPECIES ARE IDENTICAL 

Kijviriya, V; Upatham, ES; Viyanant, V; Woodruff, DS 

1991 

Yes 

American Malacological Bulletin
ISSN: 0740-2783 

8 

2 

97-106 

WOS:A1991FN79900001 

Freshwater clams of the genus Corbicula, collected from 40
sites up to 1500 km apart in Thailand, and representing 21 nominal species, show no significant
geographic variation at 24 electrophoretically detected allozyme loci and are most probably all
referable to the widespread Asian species, C. fluminea (Muller, 1774). Thai Corbicula have very
little genetic variability: mean number of alleles per locus (A) was very low: no variation (ABAR
= 1.0) was detected in 30% of the samples, in the remainder, ABAR less-than-or-equal-to 1.1; mean
percentage of loci polymorphic in each sample, PBAR = 4.59% (range: 0.0-12.5%); mean individual
heterozygosity, HBAR = 0.011 (range: 0.000-0.025) with one outlier where HBAR = 0.058). The low
level of population variability and very low individual heterozygosity suggest that most of the
Corbicula in Thailand are facultative self-fertilizers. The small amount of genic diversity
detected, and the observed genotype frequencies, are apparently maintained by limited
outcrossing, at random with respect to shell phenotype, internal shell color and allozyme
genotype. Eighty-eight percent of the samples, including one referable to Corbicula fluminea,
cluster at Nei's genetic distance values of D < 0.01. Only five samples from northeast Thailand
stand slightly apart from the others. These very high genetic similarities, coupled with a lack
of significant anatomical variation, provide no support for the recognition of more than one
species in our samples. Twenty nominal Thai species are synonymized accordingly with C. fluminea;
another seven nominal species are candidates for synonymy.