Evolutionary influences on multiple paternity in mammals

Abstract

Multiple paternity is a widespread phenomenon, but the underlying factors that influence the considerable variation across species remain unclear. We examined four hypotheses to explain variation in multiple paternity across 98 populations of 60 mammalian species. We tested whether the log-odds of multiple paternity could be explained by sexual size dimorphism as an indicator of male–male competition, habitat used (aerial, arboreal, terrestrial), feeding groups (carnivores, omnivores, herbivores) and male social organization (males living separately from females, groups with one male or groups with multiple males). Phylogeny and intraspecific variation (random effects) of populations accounted for 8% of the total variation in the log-odds of multiple paternity, with phylogeny and variations within species each explaining about 4% of the total variation. The hypotheses and a litter size covariate (fixed effects) accounted for about 85% of the total variation. After accounting for phylogenetic relationships and within-species variation, the log-odds of multiple paternity exhibited a slight increase with sexual size dimorphism, in the opposite direction to what was expected. Spatial dimensions of habitats that species used were strongly supported as an influence on the probability of multiple paternity. Contrary to predictions, trophic levels did little to explain the odds of multiple paternity. Predictions of influences of male social organization on multiple paternity were only partially supported: species whose male social organization was composed of groups with multiple males averaged greater odds of multiple paternity than species whose main male social organization was composed of social units with one male. The probability of multiple paternity in mammals appears to be little influenced by phylogeny or within-species variation. But, it seems likely that several factors play a role in explaining variation in the probability of multiple paternity within and among species, including habitat use and social behaviour.