Hybridization of Two Major Termite Invaders as a Consequence of Human Activity

Abstract

While hybridization of an invasive species with a native species is a common occurrence, hybridization between two invasive species is rare. Formosan subterranean termites (Coptotermes formosanus) and Asian subterranean termites (C. gestroi) are both ecologically successful and are the two most economically important termite pests in the world. Both species have spread throughout many areas of the world due to human activity; however, their distributions overlap in only three narrow areas because of distinct ecological requirements. In south Florida, where C. formosanus and C. gestroi are both invasive, the dispersal flight seasons of both species overlapped for the first time on record in 2013 and 2014. Pairings of heterospecific individuals were readily observed in the field and C. gestroi males preferentially engaged in mating behavior with C. formosanus females rather than females from their own species. In the laboratory, heterospecific and conspecific pairings had an equal colony establishment rate, but heterospecific incipient colonies had twice the growth rate of conspecific incipient colonies, suggesting a potential case of hybrid vigor. As all pre-zygotic barriers were lifted between the two species in the field, the apparent absence of post-zygotic barriers in the laboratory raises the possibility for introgressive hybridization in south Florida. While laboratory observations remain to be confirmed in the field, and the alate hybrid fertility is currently unknown, our results raise a tangible concern about the hybridization of two major destructive pest species. Such hybridization would likely be associated with a new economic impact.

Potential Hybridization between Two Invasive Termite Species, Coptotermes formosanus and C. gestroi (Isoptera: Rhinotermitidae), and Its Biological and Economic Implications

“…Alate collection records up until then showed that C. gestroi alates swarmed from February to mid-April and C. formosanus alates from mid-April to June. In fact, according to Scheffrahn [25], “…as soon as C. formosanus begins its first flights, those of C. gestroi cease…” In 2013, however, Chouvenc et al [8] observed two events of simultaneous flights by these two species in Broward County. A more thorough survey carried out in 2014 at the same location revealed that C. gestroi alates swarmed from late February to early June, while C. formosanus swarmed from mid-March to mid-June.…”

“…A more thorough survey carried out in 2014 at the same location revealed that C. gestroi alates swarmed from late February to early June, while C. formosanus swarmed from mid-March to mid-June. Alates of these two species swarmed on the same nights 24 times between 18 March and 9 June, with five events of major simultaneous swarming, i.e., >100 alates of both species collected from a light trap [8]. …”

“…Coptotermes formosanus is primarily found in subtropical and temperate regions while C. gestroi is found throughout the tropics, and it was estimated that the two allopatric species evolved separately for 15–20 million years [7]. In recent years, however, C. gestroi expanded its range and has increasingly been collected from the subtropics, making it now sympatric to C. formosanus in three areas, Taiwan, Hawaii, and Florida [8]. …”

Dispersal Flights of the Formosan Subterranean Termite (Isoptera: Rhinotermitidae)

“…Two species, C. formosanus and C. gestroi, are particularly invasive (Chouvenc et al 2015a) and have spread far beyond their native range with the help of human maritime activity (Scheffrahn & Crowe 2011;Rust & Su 2012). They contribute in large part to the annual $40 billion cost associated with termite damage and control around the world (Rust & Su 2012).…”

“…However, both species have spread extensively and, with the help of human activity, have established sympatrically within non-native climatic boundaries (Chouvenc et al 2015a) including southern Taiwan, Hainan (China), Oahu (Hawaii), and the metropolitan area of southeastern Florida (Chouvenc et al 2015a; Fig. 1).…”