T. Backeljau et al., GENETIC-VARIATION, SYSTEMATICS AND DISTRIBUTION OF THE VENERID CLAM CHAMELEA-GALLINA, Journal of the Marine Biological Association of the United Kingdom, 74(1), 1994, pp. 211-223
Two morphotypes of the venerid bivalve Chamelea gallina (L.), viz. C.
gallina s.s. and C. striatula, were electrophoretically compared at se
ven polymorphic enzyme loci. In three populations from the Ria Formosa
(southern Portugal), both morphotypes occurred sympatrically. Analyse
s of genotype frequencies in these mixed populations revealed departur
es from Hardy-Weinberg expectations at nearly all loci. These deviatio
ns were mainly attributable to a Wahlund effect, caused by mixing the
two morphotypes. Nei's mean unbiased genetic distance between the two
forms was D=1.138, while the mean genetic distances between population
s within morphotypes were D=0.083 in C. gallina s.s. and D=0.229 in C.
striatula. It is therefore concluded that C. gallina and C. striatula
are reproductively isolated (biological) species, the geographical di
stribution of which is outlined.