Did Two Florida Populations of Conehead Termites Come up From a Single Colonization Occasion?

Bernard Dupont, CC BY-SA 2.0)

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The conehead termite (Nasutitermes corniger) is an aggressive pest of crops, wooden structures, and forests in 13 countries in Central and South America and on many Caribbean Islands. Only two populations have ever been found in the United States, both on the west coast of southern Florida: one in Dania Beach and one in nearby Pompano Beach. A group of researchers has conducted a genetic analysis of these two populations to test whether or not these populations in the U.S. arose from one colonization event or if the populations arose independently. (Photo credit: Flickr/Bernard Dupont, CC BY-SA 2.0)

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The conehead termite (Nasutitermes corniger) is an aggressive pest of crops, wooden structures, and forests in 13 countries in Central and South America and on many Caribbean Islands. Only two populations have ever been found in the United States, both on the east coast of southern Florida: one in Dania Beach and one in nearby Pompano Beach. A group of researchers has conducted a genetic analysis of these two populations to test whether or not these populations in the U.S. arose from one colonization event or if the populations arose independently. (Photo credit: Flickr/Bernard Dupont, CC BY-SA 2.0)

By John P. Roche, Ph.D.

The conehead termite (Nasutitermes corniger) is an aggressive pest of crops, wooden structures, and forests in 13 countries in Central and South America and on many Caribbean Islands. Only two populations have ever been found in the United States, both on the east coast of southern Florida: one in Dania Beach and one in nearby Pompano Beach. A group of researchers has conducted a genetic analysis of these two populations to test whether or not these populations in the U.S. arose from one colonization event or if the populations arose independently.

The study, led by Barbara Thorne, Ph.D., of the University of Maryland with colleagues Edward Vargo, Ph.D., and Laura Johnson at Texas A&M University and Eldridge Adams, Ph.D., at the University of Connecticut, was published in late August in the Journal of Economic Entomology.

Nasutitermes corniger is abundant in tropical forests, savannahs, and in areas of secondary plant growth. Whereas many pest termites are subterranean, foraging and nesting in soil, conehead termites live primarily above ground. They generally nest in trees, bushes, logs or stumps, structures, or on the ground. Their nests and foraging tunnels are easy to spot, which helps with their control.

Conehead termites provide the ecosystem-function role of recycling nutrients. As pests, though,these termites are aggressive, causing extensive damage to crops such as sugar cane and fruit trees, and to buildings and forests. Their ecological characteristics contribute to their ability to cause damage. They have a varied diet and can nest in a variety of substrates, so they can survive in a range of habitats. And their populations grow rapidly and disperse easily.

Conehead termites disperse in swarms, often after the first heavy rain of the spring. In one season, over 20,000 winged conehead termites can disperse from a single large colony. After dispersing, a new queen and king—or multiple queens and kings—start a new colony. Conehead termite colonies sampled in regions where they are native show a mixture of some nests with one queen and one king and some with multiple queens or multiple kings. However, in samples of the invasive conehead termite colonies in Florida by Thorne and colleagues since 2012, all colonies with reproductive individuals had multiple queens, and the number of queens per nest was as high as 52! The presence of multiple queens and kings in conehead termites helps create very high reproductive rates in this species.

In samples of invasive conehead termite (Nasutitermes corniger) colonies in Florida conducted by researchers since 2012, all colonies with reproductive individuals had multiple queens, as in this sample with multiple queens from a nest in Pompano Beach, Florida. (Photo credit: Barbara Thorne, Ph.D.)

In May 2001, conehead termites were spotted in Dania Beach Florida. Termiticide treatments were begun on populations there in April 2003. In 2016, conehead termites were spotted in Pompano Beach as well. Were these two populations the result of separate colonization events, or did a single colonization lead to both populations? Answering this question was the goal of Thorne’s study.

Thorne and colleagues sampled conehead termites from eight nests in Dania Beach in 2015 and 2017 and collected individuals from eight nests in Pompano Beach in 2016. They focused their genetic analysis on microsatellite markers within the termites’ DNA. Microsatellite markers are sections of DNA that repeat the same short sequence of from one to 10 nucleotides over and over again. Microsatellite markers are useful for genetic analyses because they mutate at a rate orders of magnitude higher than simple point mutations do. Being highly variable, they provide investigators with an increased ability to discern the degree of evolutionary relationship among biological samples.

The researchers determined the genotype of sample termites at seven out of eight of the microsatellite loci that had been previously identified as being very variable. They discovered that, for all the samples they analyzed, there were four or fewer alleles at each microsatellite locus. In contrast, in a sample of 140 colonies in Panama in another study, genetic analysis found from nine to 32 alleles at the same microsatellite loci. Because so little variation was found in the microsatellite DNA, the data from the two Florida populations supported the hypothesis that all termites in both colonies were so closely related that they arose from one colonization event. They probably arose from a single queen and king, or from offspring from a single queen and king. In their paper, Thorne and her colleagues concluded that the two populations “almost certainly descended from the same founder population.”

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