By Richard Levine
Formosan subterranean termites (Coptotermes formosanus) and Asian subterranean termites (Coptotermes gestroi) are the most damaging pest species in the world. Both are highly invasive and have spread throughout many areas of the world due to human activity, and their distributions overlap in some areas.
Now scientists in Florida have observed Formosan males mating with Asian females — in fact, they seem to prefer the Asian females more than females from their own species — and their hybrid offspring seem to grow colonies twice as fast as their parents. Their findings are published in the journal PLOS ONE, and are described in the following video:
Many hybrids are unable to reproduce (the mule, for example, which is the sterile hybrid offspring of a male donkey and a female horse). And many hybrids that actually can reproduce tend to lose vigor after one or more generations, which is why farmers often buy new hybrid seeds each growing season.
But so far that doesn’t seem to be the case for these termite hybrids. In the laboratory, the Florida researchers are raising a hybrid colony that is growing twice as fast as same-species colonies, suggesting a potential case of hybrid vigor.
“Our hybrid colony is still showing high vigor, can potentially live up to 20 years, and can still cause a significant amount of damage,” said Dr. Thomas Chouvenc, a co-author from the UFL’s Ft. Lauderdale Research and Education Center.
While these laboratory observations remain to be confirmed in the field, the results still raise a tangible concern about the hybridization of these incredibly destructive pests, which could have significant economic impacts, according to the authors.
To get an idea of how potentially destructive they could be, watch this video of University of Florida researchers observing both termite species swarming simultaneously, including some shots of inter-species boot-knocking:
Don’t Panic … Yet … At least not too much
Right now we’ve got a vigorous hybrid colony in the lab, and we know that in the field both species swarm at the same time, which is when termites look for mates. However, we’ll have to wait and see whether the hybrids actually become established outside of the lab, and whether they can produce multiple generations.
“If our hybrid colony matures in 5-6 years, it MAY produce reproductives,” Dr. Chouvenc said. “This remains a mystery so far, because it’s too early for us to observe. The fertility of the reproductives will determine whether the hybrid is a ‘mule’ or not. If the hybrid vigor and viability that we observed in workers and soldiers also apply to the reproductives, then we will have introgression. If not, they will be sterile, with no chance of gene transfer from one population to the other.”
However, even if they do not produce viable reproductives, the hybrids could still be problematic in the wild. A C. formosanus colony can grow to contain millions of individuals within five to eight years, and since the hybrid colony in the UFL lab is growing at least as fast as its parental species, it’s reasonable to assume that hybrid colonies will also contain millions of termites after five years or so.
“Even if they don’t produce reproductives, you still have a million mouths to feed, and the colonies can be extremely long lived,” Dr. Chouvenc said.
“What we are dealing with here is a termite colony that acts like a super organism,” said Dr. Nan-Yao Su, another UFL professor and co-author of the study. “Whether or not it produces reproductives, the colony itself poses a serious threat to a homeowner.”
UPDATE (March 27, 2015): The following video features Dr. Chouvenc describing their discovery in his own words. He and his UFL colleagues encourage Florida residents to send them termite specimens if they see swarms so they can be identified and mapped:
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Richard Levine is Communications Program Manager at the Entomological Society of America and editor of the Entomology Today Blog.