Sexual conformism through imprinting in Bicyclus anynana females mating preferences

Details

Supervisors

Nieberding, Caroline M.

Faculty

Faculté des sciences

Degree label

Master [120] en biologie des organismes et écologie, à finalité approfondie

Abstract

Learning is a central mechanism in the adaptation and evolution of species, particularly social learning, which can be divided into three main forms, namely imitation, teaching and imprinting. The latter is a process of self-recognition that occurs rapidly, irreversibly and during a critical period of development. The notion of imprinting is central to this thesis, which deals with the conformism of sexual preferences of females Bicyclus anynana following imprinting. The African butterfly Bicyclus anynana was chosen in view of the ecological relevance of imprinting and the knowledge of sexual selection in this species. Indeed, B. anynana shows seasonal polyphenism with a wet and a dry form during the respective seasons, and females are exposed to different proportions of these seasonal forms depending on the time of the year. Climatic disruption leads to the early emergence of wet season individuals. A change in the sexual preference of females towards this phenotype could compromise the survival of the population due to the reduced fitness offered. This thesis therefore attempts to demonstrate conformist modifications of the sexual preferences of B. anynana females, characterised by a preference superior to the presence of this phenotype during imprinting. The data collected confirm that females learn from early exposure to different proportions of wet and dry season males. Density-dependent learning is clear for dry season males, indicating a decrease in reproduction with this phenotype as its proportion decreases in the environment. This learning compromises population survival as the proportion of dry season males decreases, and therefore matings with this phenotype too, even though they offer superior fitness. Females develop conformism towards wet season males when they are present in ecologically relevant proportions (25-75%), indicating that females prefer this phenotype more abundantly than its presence during imprinting. Conformism is counterproductive to population survival as females will largely favour reproduction with the wet season phenotype, whose presence is increasing in the environment, while the fitness offered is lower. A learning bias still appears to be present when a single seasonal form is present during the imprint, resulting in a strong preference for wet season males when they are absent, and vice versa. In a nutshell, females have developed phenotypic-specific learning, but neither learning is consistent with population persistence over time.