Bridgehead effect and multiple introductions shape the global invasion history of a termite

Abstract

Native to eastern Asia, the Formosan subterranean termite Coptotermes formosanus (Shiraki) is recognized as one of the 100 worst invasive pests in the world, with established populations in Japan, Hawaii and the southeastern United States. Despite its importance, the native source(s) of C. formosanus introductions and their invasive pathway out of Asia remain elusive. Using ~22,000 SNPs, we retraced the invasion history of this species through approximate Bayesian computation and assessed the consequences of the invasion on its genetic patterns and demography. We show a complex invasion history, where an initial introduction to Hawaii resulted from two distinct introduction events from eastern Asia and the Hong Kong region. The admixed Hawaiian population subsequently served as the source, through a bridgehead, for one introduction to the southeastern US. A separate introduction event from southcentral China subsequently occurred in Florida showing admixture with the first introduction. Overall, these findings further reinforce the pivotal role of bridgeheads in shaping species distributions in the Anthropocene and illustrate that the global distribution of C. formosanus has been shaped by multiple introductions out of China, which may have prevented and possibly reversed the loss of genetic diversity within its invasive range.

Coordination of movement via complementary interactions of leaders and followers in termite mating pairs

“…In our study of an invasive population, we found less stable tandem runs than those previously observed in a native population of C. formosanus in Japan [19] (electronic supplementary material, figure S4). This suggests modification of tandem coordination following invasion, although such differences may have already existed between the source population and other native ranges [51]. Further investigation is needed to determine what is the cause of evolutionary change in behaviour of C. formosanus from Florida, as invasive populations often have different populational structures from native populations (e.g.…”

“…Further investigation is needed to determine what is the cause of evolutionary change in behaviour of C. formosanus from Florida, as invasive populations often have different populational structures from native populations (e.g. high density or relatively low genetic diversity [51]). Moreover, colony foundation experiments have confirmed that hybrid colonies can last greater than 2 years [52].…”

Coordination of movement via complementary interactions of leaders and followers in termite mating pairs

“…This suggests modification of tandem coordination following invasion, although such differences may have already existed between the source population and other native ranges [43]. Further investigation is needed to determine if properties of the invasive population (e.g., high density or relatively low genetic diversity [43]) are causes of behavioral change in C. formosanus from Florida. Moreover, colony foundation experiments have confirmed that hybrid colonies can last > 2 years [44], raising questions about potential behavioral changes of hybrid adults.…”

A High Soldier Proportion Encouraged the Greater Antifungal Immunity in a Subterranean Termite

“…This study involved the wood-feeding subterranean termite Coptotermes formosanus Shiraki, which is a globally distributed economic pest ( Blumenfeld et al, 2021 ). These termites are endowed with a unique and social immune defense system that strongly limits their biological control ( Bulmer et al, 2009 ; Chouvenc and Su, 2010 ).…”