Sexual Selection’s Hidden Genetic Toll on Mammalian Populations
A new study in the Journal of Evolutionary Biology reveals a broader demographic impact of sexual selection than previously recognized. Analyzing mitochondrial DNA diversity across 262 species of non-flying terrestrial mammals, researchers found that species with stronger male-biased sexual dimorphism—a key indicator of intense sexual selection on males—consistently exhibit lower mitochondrial genetic diversity. This finding is significant because mitochondria are maternally inherited, suggesting that sexual selection influences genetic variation beyond just the paternal line. The study posits that intense competition among males can reduce the effective population size of females, leading to a measurable decline in allelic diversity over time. This research provides crucial insights into how mating systems and selection pressures shape population genetic structure and evolutionary potential.
Study Significance: For evolutionary biologists, this work directly connects sexual selection theory with empirical patterns of genetic drift and population genetics. It demonstrates that classic metrics like effective population size must account for the demographic consequences of mating systems. This finding has practical implications for conservation genetics, as species under strong sexual selection may harbor less genetic diversity and thus face greater vulnerability to environmental change.
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