The spatial and temporal distribution of females influence the evolution of testes size in Australian rodents

Renee C. Firman, Dustin R. Rubenstein, Bruno A. Buzatto

Research output: Contribution to journalArticlepeer-review

3 Citations (Scopus)
34 Downloads (Pure)


Male-male competition after mating (sperm competition) favours adaptations in male traits, such as elevated sperm numbers facilitated by larger testes. Ultimately, patterns of female distribution will affect the strength of sperm competition by dictating the extent to which males are able to prevent female remating. Despite this, our understanding of how the spatial and temporal distributions of mating opportunities have shaped the evolutionary course of sperm competition is limited. Here, we use phylogenetic comparative methods to explore interspecific variation in testes size in relation to patterns of female distribution in Australian rodents. We find that as mating season length (temporal distribution of females) increases, testes size decreases, which is consistent with the idea that it is difficult for males to prevent females from remating when overlap among oestrous females is temporally concentrated. Additionally, we find that social species (spatially clustered) have smaller testes than non-social species (spatially dispersed). This result suggests that males may be effective in monopolizing reproduction within social groups, which leads to reduced levels of sperm competition relative to non-social species where free-ranging females cannot be controlled. Overall, our results show that patterns of female distribution, in both space and time, can influence the strength of post-mating sexual selection among species.

Original languageEnglish
Article number20220058
Number of pages5
JournalBiology letters
Issue number5
Publication statusPublished - May 2022


  • mating season length
  • net primary productivity
  • post-mating sexual selection
  • sociality
  • sperm competition
  • testes size


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