MORPHOLOGICAL AND GENETIC DIFFERENTIATION OF THE AFRICAN CLUPEID LIMNOTHRISSA-MIODON 34 YEARS AFTER ITS INTRODUCTION TO LAKE KIVU

The evolutionary consequences of an artificial introduction of the clu peid Limnothrissa miodon from Lake Tanganyika into Lake Kivu, East Afr ica were examined. In 1959, 57 400 fry (mixture of Limnothrissa and th e related clupeid, Stolothrissa tanganicae), were released into Lake K ivu to boost fisheries production. Comparisons were made between respe ctive source and transplant populations 34 years later (1993) using mo rphometrics ('truss' method), allozymes (29 enzyme-coding loci) and mi tochondrial (mt) DNA variation (RFLP analysis of PCR-amplified ND5/6 g enes). Significant morphological and genetic differentiation between s ource and transplant samples was detected, with a distinct clustering of Kivu Limnothrissa on respective dendrograms, especially at the morp hometric and mtDNA levels. Differentiation within Lake Tanganyika was, however, consistently higher than that between lakes. Allozymic diver sity was similar in samples from both lakes (Lake Tanganyika: heterozy gosity=0.0658, mean number of alleles=1.44; Lake Kivu: heterozygosity= 0.0655; mean number of alleles=1.48), however, a significantly lower m tDNA haplotype diversity was detected in Lake Kivu (Lake Tanganyika: 0 .905; Lake Kivu: 0.755). Data suggest that high post-introduction mort ality and various demographic factors reduced the effective population size of the introduced population to tens rather than thousands of in dividuals, resulting in a reduction in genetic diversity and founder e ffect. (C) 1995 The Fisheries Society of the British Isles