The spotted orchid fly has invaded the United States. They may have acquired evolutionary superpowers in Chinese cities.

Spotted Lambo spread across the United States with relentless speed. And now we have a clue as to why. Living in cities appears to have made these invasive insects more resistant to stress.

“Cities may act as evolutionary incubators that allow invasive species to better cope with pressures such as heat and pesticides, which may allow them to better adapt to new environments,” lead author Fallon (Fang) Meng, a biologist at New York University, told Live Science.

Lycorma delicatula is a planthopper that uses long mouthparts to suck sap from plants. The insect is native to China but has spread to South Korea, Japan and the United States, and was first discovered in Pennsylvania in 2014, but has now been confirmed in 19 states in the eastern United States.

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Its preferred host plant is the tree of heaven (Ailanthus altissima), which is also an invasive species, but can feed on a wide range of plants, including economically valuable plants such as vines, hops, maples, fruit trees, and hardwoods.

Spotted orchid flies can weaken plants and, as they feed, they also expel a sticky, sweet liquid that promotes sooty mold growth. Additionally, when bees choose to scavenge this sweet waste rather than visiting flowers, they give the honey they produce a smoky flavor and a lingering aftertaste, although the honey is still safe to eat.

All of this adds up to a potentially huge economic impact. For example, a 2019 study estimated that Pennsylvania alone could face $324 million in annual losses if the impact of this insect is not controlled.

Lanternfly genetics

To better understand how Lambo flies have adapted so well to life in the United States, researchers sequenced the genomes of Lambo flies from urban and rural areas of Shanghai, China, as well as New York City, Connecticut, and New Jersey. The study was published on Wednesday (February 4) in the journal Proceedings of the Royal Society B: Biological Sciences.

In China’s Rambo fly population, clear genetic differences were found between urban and rural Rambo flies. “Even though it’s only 30km [19 miles] There is very strong demographic discrimination in remote areas,” Meng said.

This is probably because, although they can fly, they need to continuously feed, so they stick close to the host trees on which they depend. This means groups are more likely to remain separated, Meng added.

This separation means that Shanghai’s urban Rambo flies have evolved genetic tolerance to stress that rural Rambo flies do not have, adapted to the hotter conditions of the city, and enhanced their ability to detoxify and metabolize toxins and pesticides.

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But in the U.S., lamb flies were genetically similar everywhere, even though some originated 124 miles (200 kilometers) apart. The same genes that evolved for urban living were further adapted in the American population, according to the study.

The researchers used demographic modeling based on genomic data to reconstruct the recent history of the lambfly and uncovered three genetic bottlenecks in establishing the population from a limited pool of insects. The first was more than 170 years ago, when Shanghai was undergoing rapid urbanization. The second time coincided with the lantern butterfly’s migration from China to South Korea in 2004, and the third time in 2014 when the insect arrived in Pennsylvania, likely hitchhiking on merchandise shipped from overseas.

Meng said adapting to Chinese cities may have made the lanterns better able to withstand other hot, polluted environments. “We should study invasive species and urbanization as interconnected parts of a whole. Too often these two major aspects are studied in isolation, but in reality their impacts can compound in synergistic and surprising ways.”

Zach Radin, an ecologist at the University of Delaware who was not involved in the study, said the ability to handle a wider range of toxins may be helping the spotted fly spread in the United States.

The relatively high density of tree-of-heaven provides a foothold for the spotted fly in many cities, he told LiveScience. “But some of the genes they discovered that are associated with overcoming exposure to toxic chemicals could actually help them switch hosts and take advantage of other plants.”

Radin added that the new genetic information could help slow or stop the spread of the spotted fly. “From a chemical management perspective, there are a number of genes that could be targeted that could be important in making sure that we’re not just building resistance to certain chemicals,” he said.