I am currently studying the Stickleback Fish which has a tendency to do a mating ritual. One of the steps requires the fish to dance in front of his partner (zig-zag back and forth). Sexual selection implies “By providing more chances to mate, it ensures that genes related to skillful execution of the dance are more represented in the next generation” (Russem et. al 2023).
If this has been occurring for multiple generations, how is it, not a normal standard, wouldn’t this part of the process of selection be redundant? Is their proof that it has changed over time for other animals?
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If there is variability in the trait, then there will always be some individuals who are really bad and some that are excellent– think about it like a bell curve; most individuals are average but there are extreme outliers on either side. Over time, you might expect the entire species to move the average towards the “best” dance. Except that…
There may be a trade-off. Maybe the fish that dance the best are also more likely to be spotted by predators and eaten. Maybe every few years, their food source wanes and the big fancy swimmers waste too much energy dancing and die before mating. Those trade-offs would likely maintain diversity in the gene pool because occasionally it’s good to be a bad dancer.
In addition to the trait being beneficial and detrimental in different environments/circumstances, another reason for variation could be the gene for dancing is linked to another gene where variation is helpful to the species, like age at maturity or metabolic rate. If the genes are highly linked, you won’t see the response you expected on the trait you’re studying unless you consider both genes.
Also, there could be random variation because there is no selection on that trait. Maybe all the fish have equal chances of having offspring regardless of their dancing. There are lots of examples where a trait or behavior looks like it’s important for natural selection, but the nice story doesn’t actually match the biology.
There are still other reasons that variation is maintained, like immigration from other populations or random mutations.
Nature is amazing.
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