Sex-specific responses to competitive environment in the mosquitofish Gambusia holbrooki

Brookes, Samuel; Iglesias‐Carrasco, Maider; Kruuk, Loeske E. B.; Head, Megan L.

doi:10.1007/s10682-020-10080-y

Cited by 2 publications

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“…However, in other cases, the larger sex may be disadvantaged, due to the higher energy requirements of being large (Bonneaud et al., 2016; Laaksonen et al., 2004; Wikelski & Thom, 2000). Although a few studies consider the effect of competitor sex on competitive interactions (Bonisoli‐Alquati, Boncoraglio, Caprioli, & Saino, 2011; Brookes, Iglesias‐Carrasco, Kruuk, & Head, In press), studies typically consider the sex‐specific responses of focal individuals and ignore the role of competitor sex (Nicolaus et al., 2009; Oddie, 2000). This distinction between the sex of focal and competitor individuals is important because by ignoring competitor sex, these studies also ignore the potential for one sex to affect the other sex differently.…”

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confidence: 99%

The effects of competition on fitness depend on the sex of both competitors

Iglesias‐Carrasco

Brookes

Kruuk

et al. 2020

Ecology and Evolution

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In intraspecific competition, the sex of competing individuals is likely to be important in determining the outcome of competitive interactions and the way exposure to conspecifics during development influences 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, influences 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 emerged lighter when competing with another female, while males did not. 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 play a role 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.

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