Early learning and speciation : the effects of early experience on sexual and aggressive behaviour in Lake Victoria cichlid fish

The great Lakes of East Africa are inhabited by a great number of haplochromine cichlid species, which form a diverse group in both ecology and nuptial coloration. The large number of sympatrically occuriring closely related species has raised questions about the underlying mechanism for reproductive isolation. In this thesis I describe experiments that test for the effects of early experience on their species assortative behaviour in the contexts of mate choice and male territorial interactions. The maternal care in haplochromine cichlids provides the opportunity for early learning, but do the young cichlids take this opportunity to learn:? And, if so, can this promote reproductive isolation under sympatric conditions? With cross-fostering experiments, I found that young female cichlid fish are affected by experiences with their mothers__ phenotype in their later mate preferences. Maternal imprinting proved to be a mechanism favourable for sympatric speciation in a mathematical comparison of female preference development. This indicates that the propensity that the Lake Victoria cichlid fish appear to have for assortative mating may be fuelled by learning. The behaviour of the males, in contrast, was not affected by learning about their mothers__ phenotype, but male-male interactions were influenced by experiences with siblings.LEI Universiteit LeidenALW: 810.64.012Gedragsbiologi