Affiliation:
1. Departamento de Ecología Pontificia Universidad Católica de Chile Santiago Chile
2. Department of Biological Sciences University of Manitoba Winnipeg MB Canada
3. Department of Biological and Medical Sciences Oxford Brookes University Oxford UK
4. Mammal Research Institute, Department of Zoology and Entomology University of Pretoria Pretoria South Africa
Abstract
AbstractSperm production represents a costly reproductive investment by males. High reproductive competition within the female reproductive tract may select for higher sperm counts or quality resulting in selection for larger testes size. In species where females mate multiply or have more offspring per litter (litter size), or more litters per year (litter rate), male reproductive competition may select for larger relative testes size (i.e., scaled by body mass). Given that different mating systems vary in the alternative forms of reproductive investment available to males, sperm production levels may vary with social system. Here, we examined the relationship between testes size and mating systems, litter size, and litter rate while considering male lifespan and investment in paternal care in 224 terrestrial mammalian species in 15 orders. Relative testes size was larger in species where females mated with multiple males. Furthermore, in species with multiple mating females, species with higher litter rates had larger testes compared to species with fewer litters per year. In contrast, in monogamous species, species that had multiple litters per year had smaller relative testes sizes compared to species with fewer litters per year. Neither longevity nor paternal care influenced testes size. Our results elucidate the effect of female reproductive strategies on relative testes size is nuanced and varies between mating systems. Our findings suggest that the interplay between male reproductive investment and female reproductive investment may be different within similar social mating systems.
Funder
Fondo Nacional de Desarrollo Científico y Tecnológico
Natural Sciences and Engineering Research Council of Canada
Subject
Animal Science and Zoology,Ecology, Evolution, Behavior and Systematics