Sexual selection’s hidden genetic toll on mammalian populations
A new study in the Journal of Evolutionary Biology reveals a surprising link between sexual selection and genetic diversity. By analyzing mitochondrial DNA from 262 species of non-flying terrestrial mammals, researchers found that species with stronger male-biased sexual dimorphism—a classic indicator of intense sexual selection on males—consistently have lower mitochondrial genetic diversity. This finding is significant because mitochondria are inherited solely through the maternal line, suggesting that sexual selection’s demographic effects extend beyond just reducing the male effective population size. The study posits that intense competition among males can indirectly shrink the female effective population size, thereby reducing allelic diversity in maternally inherited genes across entire species.
Why it might matter to you: For geneticists focused on population genetics and evolutionary genomics, this work underscores that demographic forces like sexual selection are critical, non-neutral drivers of genetic diversity patterns. It suggests that models interpreting mitochondrial diversity for phylogenomics or inferring population history must account for mating system intensity, not just neutral drift or female dispersal. This finding could refine how you interpret genetic diversity data in conservation genetics or when tracing the evolutionary trajectories of species with pronounced sexual selection.
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