Climate change could lead to a reptile ‘sexpocalypse’

Image caption: Many reptile species have their sex determined by incubation temperature rather than genes

Lizards, crocodiles and turtles have some rocky times ahead. Warming temperatures have the potential to drastically alter the reproductive ability of reptiles, affecting their genetic breakdown as well as their evolution. With worsening climate change plus habitat degradation, pollution and other human influences, maintaining populations is likely going to be an uphill battle.

Sexual seesaw

Temperature can have a significant effect on reptiles’ diversity. Their sex genetics tend to “differ from typical vertebrates in that their sex is not determined by their genes,” said Scientific American. Rather, the “temperature of their nest pushes them toward becoming male or female.” This is called Temperature-Dependent Sex Determination (TSD). A world of increased heat from climate change means that “entire generations of sexually reproducing reptiles will be dramatically skewed male or female.” This skews the entire balance of species. Some scientists have predicted there could be only one sex of alligators by the year 2100.

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Unfortunately, this development may lead to a “sexpocalypse” that spells the end of some species. “Mating opportunities will decline; populations might become inbred,” said Scientific American. In addition, “surviving members of a species that’s already dwindling from other pressures might not be able to find a partner with whom to make babies.” As a result, “these ancient creatures — who have survived since the era of the dinosaurs — simply won’t be able to find mates to sustain the next generation,” said NBC.

Along with the sex breakdown of reptile species, temperatures can also impact their genetic diversity, according to a study published in the journal PLOS Genetics. The study found that extreme temperatures can “alter the genetic recombination” of the Guibé’s ground gecko (Paroedura guibeae), a “small reptile living in the warm ecosystems of Madagascar,” said a release about the study. Genetic recombination is a process where DNA is exchanged between chromosomes, and it “generates genetic diversity, which increases the probability of a species adapting to climate changes.” It also “influences evolution by determining which genetic combinations are passed on to descendants.”

Downward slide

The survival of reptiles is highly dependent on their ability to adapt. Reptiles are some of the oldest animals on Earth and have outlasted “dramatic climate shifts, living through ice ages and intense heat,” said Scientific American. Reptiles at risk “might be able to keep their eggs cool and their sex ratios steady by nesting earlier in the year or in shadier places or by digging deeper in the ground.” However, this would “depend on the animals perceiving the temperature shift” and “having the capacity to do things differently.”

Many reptiles also face additional dangers, giving them even worse odds of survival. “For reptiles that already face habitat loss and pollution, this genetic sensitivity adds a quiet risk,” said Earth.com. The good news is that “by knowing the genetic makeup of males and females, scientists can predict how changes in temperature might affect sex ratios in the wild.” Global warming “not only affects the climate, but also influences the adaptation mechanisms of animals to survive,” Laura González Rodelas, a co-author of the study, said in a statement.