Sexual selection and conservation: a Palearctic-African perspective

Møller, A. Pape. 2000. Sexual selection and conservation: a Paleartic-African perspective. Ostrich 71 (1): 361

Sexual selection may give rise to an increased general level of stress, either because intense directional selection reduces the ability of individuals to control the stable development of their phenotype, or because extravagant secondary sexual characters by themselves impose stress on their bearers. Sexual selection often acts against individuals with deviant, asymmetric phenotypes, particularly if such phenotypic deviance occurs in secondary sexual characters. Such characters also appear to be more affected by adverse environmental conditions than ordinary morphological characters. Sexual selection may give rise to relatively large body size, exaggeration of costly secondary sexual characters, an overall increase in body size within a lineage, and an increased risk of extinction. Reduced stress resistance caused by intense sexual selection may contribute to this trend. In accordance with this hypothesis, introductions of birds to islands are more likely to fail if the species is sexually dichromatic. Species that have gone extinct worldwide and threatened species are also more often dichromatic than expected by chance. These observations suggest that sexual selection may increase the risks of extinction, and that highly sexually selected may birds deserve more attention in conservation.