The macroevolution of sexual size dimorphism in birds

Fernanda S Caron, Marcio R Pie

Research output: Contribution to journalArticle (journal)peer-review


There is considerable variation of sexual size dimorphism (SSD) in body mass among animal groups, yet the drivers of interspecific variation in SSD are still poorly understood. Possible mechanisms have been suggested, including sexual selection, selection for fecundity in females, niche divergence between sexes, and allometry, yet their relative importance is still poorly understood. Here, we tested predictions of these four hypotheses in different avian groups using a large-scale dataset on SSD of body mass for 4761 species. Specifically, we estimated the probability of transition between male- and female-biased SSD, tested for differences in evolutionary rates of body mass evolution for males and females, and assessed the potential ecological and spatial correlates of SSD. Our results were consistent with the sexual selection, fecundity, and niche divergence hypotheses, but their support varied considerably among avian orders. In addition, we found little evidence that the direction of SSD affected the evolution of male or female body mass, and no relationship was detected between SSD and environmental predictors (i.e. temperature and precipitation seasonality, productivity, species richness, and absolute latitude). These results suggest that avian evolution of SSD is likely to be multifactorial, with sexual selection, fecundity, and niche divergence playing important roles in different avian orders.
Original languageEnglish
Pages (from-to)1-14
Number of pages14
JournalBiological Journal of the Linnean Society
Early online date19 Mar 2024
Publication statusE-pub ahead of print - 19 Mar 2024


  • Ecology
  • Evolution
  • Behaviour and Systematics
  • body size
  • evolutionary rates
  • phylogenetic comparative methods
  • Sexual selection


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