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Data from: The effects of competition on fitness depend on the sex of both competitors

Cite this dataset

Head, Megan; Brookes, Samuel; Iglesias Carrasco, Maider; Kruuk, Loeske (2021). Data from: The effects of competition on fitness depend on the sex of both competitors [Dataset]. Dryad.


In intraspecific competition, the sex of competing individuals is likely to be important in determining the consequences of competition, both for the immediate outcome of competitive interactions, and for long-term effects of competition during development on adult fitness traits. Previous studies have explored differences between males and females in their response to intraspecific competition. However, few have tested how the sex of the competitors, or any interactions between focal and competitor sex, influence the nature and intensity of competition. We set up larval seed beetles Callosobruchus maculatus to develop either alone or in the presence of a male or female competitor, and measured a suite of traits: development time, emergence weight; male ejaculate mass, copulation duration and lifespan; and female lifetime fecundity, offspring egg-adult survival and lifespan. We found effects of competition and competitor sex on the development time and emergence weight of both males and females, and also of an interaction between focal and competitor sex: females but not males responded differently to competitor sex. There was little effect of larval competition on male and female adult fitness traits, with the exception of the effect of a female competitor on a focal female’s offspring survival rate. Our results highlight the importance of directly measuring the effects of competition on fitness traits, rather than distant proxies for fitness, and suggest that competition with the sex with the greater resource requirements (here females) might have a strong effect in driving trait evolution. We also found that male-male competition during development resulted in shorter copulation times than male-female competition, a result that remained when controlling for the weight of competitors. Although it is difficult to definitively tease apart the effects of social environment and access to resources, this result suggests that something about the sex of competitors other than their size is driving this pattern.


Details of data collection methods and data analysis can be found in the paper associated with this data.

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A description of column headings can be found in the data files.


Australian Research Council, Award: FT160100149