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Genetic variation within and among infrapopulations of the marine digenetic trematode Lecithochirium fusiforme

Published online by Cambridge University Press:  07 May 2003

R. VILAS
Affiliation:
Laboratorio de Parasitología, Facultad de Farmacia, Universidad de Santiago de Compostela (USC), Av. Vigo s/n, 15782 Santiago de Compostela, Spain
E. PANIAGUA
Affiliation:
Laboratorio de Parasitología, Facultad de Farmacia, Universidad de Santiago de Compostela (USC), Av. Vigo s/n, 15782 Santiago de Compostela, Spain
M. L. SANMARTÍN
Affiliation:
Laboratorio de Parasitología, Instituto de Investigación y Análisis Alimentarios, Universidad de Santiago de Compostela (USC), 15782 Santiago de Compostela, Spain

Abstract

Allozyme markers were used to study genetic variation in Lecithochirium fusiforme within a natural population of Conger conger. Six of 16 enzyme-coding loci studied were found to be polymorphic. These loci were surveyed in 12 infrapopulations of adult flukes. High levels of genetic variation were detected (P=0·375); Ho=0·048; He=0·085). However, the population did not conform to Hardy-Weinberg expectations, as it showed a significant deficit of heterozygotes. L. fusiforme also exhibited low differentiation between infrapopulations (FST=0·064). Despite significant linkage disequilibrium at Pgm-1 and Pgm-2 (P<0·05), mating system does not appear to be the principal reason for the deficit of heterozygotes detected, because some polymorphic loci were in Hardy-Weinberg equilibrium. Association between FIS and FST statistics suggests the existence of the Wahlund effect. However, all infrapopulations showed a strong deficit of heterozygotes for most polymorphic loci (FIS=0·409). Detection of significant genetic differentiation among temporal samples and the existence of paratenic hosts in the life-cycle suggests the Wahlund effect, caused by the mixture of genetically distinct temporal samples in the infrapopulations. Occasional temporal gene flow also might explain the high estimated genetic polymorphism.

Type
Research Article
Copyright
2003 Cambridge University Press

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