Environmental Sex Reversal Shapes Populations

A field experiment on agile frogs (Rana dalmatina) found that about 20% of phenotypic males in some ponds are genetically female (XX) yet mate, sire viable offspring, and win male–male competitions at rates indistinguishable from genotypic (XY) males. Sex reversal was higher in human‑altered habitats, and all offspring of XX males are XX (female), so local sex ratios and long‑term demography may shift even when reversed individuals remain reproductively successful. — If environmental stressors (pollutants, habitat change, warming) routinely create sex reversal in wild populations, conservation models, regulatory assessments of endocrine disruptors, and forecasts of species' climate resilience must account for altered sex determination and demographic feedbacks.