We all know numerous examples for sexual dimorphism as the result of sexual selection. Thinking of mammals and birds, males are very often bigger or more colorful and richly ornamented than females. In some species however, females and males look very much alike, (aside from a minute difference in body size maybe), they are monomorphic. Why is that?
I couldn't find an answer myself in the literature so maybe you can give me a hint!
In primates sexual dimorphism is often driven by intrasex competition, and lack of it implies it is not important for reproductive success
Michael Berthaume Wouldn't a lack of dimorphism mean that the females mate more or less at random with males, without any preferences in regard to their outer appearance?
Never really thought about it. I guess it implies that sexual selection isn't always the strongest player in the field: in cases with strong predation pressure, natural selection could overshadow any potential sexual selection. For instance, consider Zahavi's handicap principle: females will prefer males with conspicuous traits that reduce male survival chance, because it signals their quality ('they can afford it, so they must be good'). But if predation pressure is very high, males may not be able to afford conspicuousness at all (hence not leaving a lot of room for sexual selection).
Just some first thoughts that crossed my mind, I'm not the expert in this.
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