Hybrid pythons win the invasion of Florida.

Researchers in the US have discovered that hybrids of Burmese and Indian pythons are better adapted to their environment, allowing them to spread and multiply more quickly.

Burmese pythons hang from tree trunks in Everglades National Park. Photo: R. Cammauf — Burmese pythons hang from tree trunks in Everglades National Park. Photo: *R. Cammauf*

Hybridization is creating a major problem in the conflict with invasive pythons in Florida. A few years ago, scientists discovered a large number of giant pythons lurking in the Everglades swamps that were hybrids created by mating two different species: the Burmese python ( Python bivittatus ) and the Indian python ( P. molurus ). Notably, the hybrids appear to adapt better to their new environment than their parents, IFL Science reported on October 21st.

As their names suggest, Burmese and Indian pythons are native to the tropical rainforests of Asia, not the swamps of Florida. Researchers believe they were introduced to the state in the 1970s, most likely through the pet trade. Their population boomed in August 1992 when Hurricane Andrew destroyed a python breeding facility near the Everglades, releasing large numbers of pythons into the wild.

The new swamp environment was well-suited to the pythons. Giant pythons quickly established breeding populations, competing with native animals through their voracious appetites and hunting skills. Since the python population boomed a few decades ago, the numbers of smaller mammals such as marsh hares, cottontail hares, and foxes have almost disappeared from the Everglades. A 2012 study found that raccoon populations in the Everglades had decreased by 99.3%, opossums by 98.9%, and lynxes by 87.5% since 1997.

Efforts to combat the invasive python population have made little progress, but scientists are closely monitoring the python population in search of solutions. In 2018, a research team from the U.S. Geological Survey (USGS) conducted a genetic analysis of approximately 400 Burmese pythons captured in a large area of South Florida. The study, published in the journal Ecology and Evolution, revealed that at least 13 of the pythons were genetically hybrids of Burmese and Indian pythons, demonstrating that they are the product of interspecies hybridization.

"The pythons in South Florida may be identifiable as Burmese pythons visually, but genetically, it's a more complex story," said Margaret Hunter, a geneticist at the USGS and lead researcher.

Typically, when two similar species crossbreed, the offspring are often at a disadvantage. They may be infertile or face numerous challenges that make them less suited to the environment. However, sometimes, a suitable combination can produce a hybrid species that is superior to its non-hybrid counterpart, a phenomenon known as hybrid vigor.

"Interspecific hybridization can lead to heterosis, meaning the best traits of both species are passed on to their offspring. Heterosis can lead to better adaptation to environmental stress and changes. In invasive populations like the Burmese python in South Florida, this can result in a wider distribution or faster spread," Hunter explained.

Meanwhile, the fight against invasive pythons continues. Part of the reason python populations are so difficult to control is their exceptional ability to camouflage themselves in their habitats. Genetic engineering could provide scientists with new tools to better understand the threat. "By using genetic tools and techniques, and continuing to track the movement patterns of invasive pythons, we can better understand their preferred habitats and how they use resources," said ecologist Kristen Hart of the USGS, co-author of the study.

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