Climate change drives frog sex reversal, threatening extinction

UPDATE - follow-up to Global warming is turning frogs' sex reversal into an extinction risk: Heat-driven sex reversal in agile frogs is driving lower mating success and vulnerable offspring, accelerating population decline and the risk of extinction. Researchers studying agile frogs in Hungary published these findings in Science Advances on September 3. While chromosomes normally determine sex, excessive heat in the tadpole stage can override this recipe and turn genetically female tadpoles into fertile males.

Mating and Offspring

Veronika Bokony, the study's lead author at the HUN-REN Centre for Agricultural Research, noted that while theoretical models suggest climate threats can be mitigated if sex-reversed males sire all-female offspring, this benefit is lost if they cannot reproduce successfully. Field studies showed that while sex-reversed males made up about 20% of wild populations, only 4% of egg clutches belonged to them. About one-third of females paired with them used a split clutch strategy to save eggs for a better mate. Furthermore, 61% of offspring from sex-reversed males underwent sex reversal themselves, compared to only 17% of offspring from normal males.

Disease and Computer Models

When exposed to heat waves and the pathogen ranavirus, tadpoles of sex-reversed males carried higher viral loads. Computer models showed that when factoring in ranavirus mortality, population decline began roughly 10 years earlier and extinction came about 9.5 years sooner. Without ranavirus, populations still declined about eight years earlier, with extinction occurring two years sooner. Around 40% of amphibian species face extinction risks, making them the most threatened vertebrates on earth.

Context

Climate change continues to alter natural habitats and disrupt species survival patterns across the globe. Researchers rely on field observations and computer models to project how these environmental pressures impact vulnerable animal populations over time.