Spotted lanternflies are adapting to the pressures of city life such as heat, pollution, and pesticides, according to genomic analyses of the invasive insects in the US and their native China.
The findings, published in the Proceedings of the Royal Society B: Biological Sciences , show how urbanization may be shaping the spotted lanternfly's spread into new environments.
"Cities can act as evolutionary incubators that may help an invasive species to better deal with pressures like heat and pesticides, which then helps them to better adapt to new environments," said Fallon Meng, a PhD student in NYU's Department of Biology and the study's first author.
Invasive species like the spotted lanternfly can wreak havoc on ecosystems, threatening native plants and animals and causing environmental and economic harm. Estimates show that spotted lanternflies could cause millions of dollars in damage to vineyards in New York State alone. Studying their genomes may provide clues as to how spotted lanternflies so successfully invaded the northeastern US over the past decade.
NYU researchers in New York and Shanghai used whole genome sequencing to analyze the DNA of spotted lanternflies in both their native China (urban and rural locations in Shanghai) and in the US (New York City, Connecticut, and New Jersey).
Mapping the lanternfly's history and genetic diversity
Scientists have long been curious about why some invasive species are so successful at spreading in new environments, despite new populations growing from a small number of newcomers—for instance, a handful of egg masses hitching a ride on cargo traveling to a new place. After these "bottlenecks," populations have much lower genetic diversity, but some still manage to establish and spread, an idea known as the "genetic paradox of invasion."
Comparing the genomes of spotted lanternflies from both China and the US, the researchers confirmed that lanternflies in the US are far less genetically diverse than their counterparts in China.
"We found a really dramatic decrease in genetic variation—US lanternflies were genetically clustered into one big population—but despite that decrease, the lanternflies are still adapting to the local climate," said Anthony Snead, a postdoctoral associate at NYU and study co-author.
In the US, the lanternflies were genetically similar across locations spanning 200 kilometers. This likely reflects a combination of the species' recent arrival, repeated population bottlenecks that reduced genetic diversity, and ongoing connectivity between populations.
"Because evolution happens across generations, it may take much more time for genetic differences to accumulate," explained Snead.
In contrast, lanternflies living in urban vs. forested areas of Shanghai showed clear genetic differences—even a mere 30 or 40 kilometers apart. This may be because, despite their name, lanternflies aren't big fliers. "Lanternflies are really localized in their native range. They can fly, but they tend not to move around much because they rely on specific host trees, such as the tree of heaven, and need to feed continuously using their piercing mouthparts," explained Meng.
The researchers also fed the genomic data into demographic modeling software to reconstruct the history of lanternflies invading new areas. Their modeling points to three bottlenecks, two of which align with what other studies have shown: the lanternfly likely arrived in South Korea from China in 2004 and in Pennsylvania via South Korea in 2014. However, the researchers also discovered a third, previously unknown bottleneck that occurred more than 170 years ago, a period that coincided with Shanghai's rapid urbanization.
The role of cities
Digging into genetic differences between lanternflies from urban and rural areas, the researchers found that adapting to cities may hold the key to understanding the "genetic paradox of invasion" for the spotted lanternfly.
Urban lanternflies in both China and the US showed changes in genes associated with stress response, which may enable the insects to live in the hotter conditions of cities, as well as detoxification and metabolism, which are important for exposure to pesticides and pollution. This raises the possibility that adapting to China's cities primed the lanternfly to tolerate other urban environments.
"We think that these differences may indicate how lanternflies have evolved to survive in hot, polluted, pesticide-heavy cities—and not just in their native China, but in the US as well, which may be helping them spread and creating new potential problems with control in the future," said Meng.
"It's interesting to consider that our own infrastructure in cities may be facilitating invasion—not just because humans move organisms via trade, but also because our presence may drive an organism to adapt and allow them to become invasive," said Snead.
Based on their findings, the researchers encourage conservation and invasive species management efforts to consider the role that cities may be playing—for instance, monitoring for egg masses in cities, diversifying pesticide use, and updating invasion risk maps given that lanternflies are spreading north into colder US climates.
"In our increasingly urban world, we should be studying invasive species and urbanization as interconnected parts of a whole. These two major aspects of global change are too often studied in isolation, but their effects can compound in synergistic and surprising ways, as we are seeing here with the spotted lanternfly," said Kristin Winchell, professor of biology at NYU and the study's senior author. "This perspective may be the key to understanding the success of the spotted lanternfly and how to best predict and manage biological invasions."
Additional study authors include Aria Yang Zhang of NYU Shanghai and Jason Munshi-South of Drexel University. This work was supported in part by NYU IT High-Performance Computing resources, the Zegar Family Foundation, the NYU Center for Genomics and Systems Biology Genomics Core, and the National Science Foundation (NSF-PRFB no. 2305939).
