ABSTRACT
Congeneric species that live in sympatry may have evolved various mechanisms that maintain reproductive isolation among species. However, with the spread of invasive organisms owing to increased global human activity, some species that evolved in allopatry can now be found outside their native range and may have the opportunity to interact, in the absence of mechanisms for reproductive isolation. In South Florida, where the Asian subterranean termite, Coptotermes gestroi (Wamann), and the Formosan subterranean termite, Coptotermes formosanus Shiraki (Blattodea: Rhinotermitidae) are invasive, the two species can engage in heterospecific mating behavior as their distribution range and their dispersal flight season both overlap. Termites rely on semiochemicals for many of their activities, including finding a mate after a dispersal flight. In this study, we showed that females of both species produce (3Z,6Z,8E)-dodeca-3,6,8-trien-1-ol (DTE) from their tergal glands as a shared sex pheromone. We suggest that both species primarily rely on an inundative dispersal flight strategy to find a mate, and that DTE is used as a short distance pheromone or contact pheromone to initiate and maintain the tandem between males and females. The preference of C. gestroi males for C. formosanus females during tandem resulted from the relatively high amount of DTE produced by tergal glands of C. formosanus females, when compared with those of C. gestroi females. This results in confusion of mating in the field during simultaneous dispersal flights, with a potential for hybridization. Such observations imply that no prezygotic barriers emerged while the two species evolved in allopatry for ~18 Ma.
Subject(s)
Isoptera/physiology , Polyenes/metabolism , Sex Attractants/metabolism , Sexual Behavior, Animal , Animal Distribution , Animals , Biological Evolution , Courtship , Female , Florida , Introduced Species , Male , SeasonsABSTRACT
Abstract Trail-following pheromone is one of the most important semiochemical in termites. This pheromone is responsible for the recruitment of individuals from the colony to perform different tasks. The aim of this work was to isolate and identify the trail-following pheromone of Microcerotermes exiguus (Isoptera: Termitidae), a typical termite from the Neotropic, that is considered pest in some crops. Subterranean nest of M. exiguus were collected with a shovel in Caracas, Venezuela in 2010. Different chemical micro-reactions combined with chromatographic analysis of solvent extracts, as well as solid phase microextraction analyses (SPME) were applied to termite sternal glands; besides, some behavioral biossays were undertaken. A peak in the chromatograms from extracts (retention index: 1 483), presented a fragmentation pattern with m/z ions: 41; 55; 67; 79; 91; 105; 119; 135; 142; 180, this result alongside behavioral assays allowed us to conclude that (3Z,6Z,8E)-dodeca-3, 6, 8-trien-1-ol (DTOH) acts as the main component of the trail following pheromone. The estimated optimum concentration for termite recruitment and orientation was around 1 pg/cm, being statistically comparable to the value on trails marked with whole body extracts at concentration of 1 worker/cm. The period of time that this compound takes to recruit other colony members is 13.67 ± 5.76 s and lasts up to two hours. Both analytical and behavioral results provided better understanding on the chemical communication of M. exiguus. This information could be used for the future development of newer pest control methods. Rev. Biol. Trop. 66(1): 303-311. Epub 2018 March 01.
Resumen La feromona de camino es uno de los semioquímicos más importantes en las termitas. Esta feromona es responsable del reclutamiento de individuos de la colonia para realizar diversas tareas. El objetivo de este trabajo fue aislar e identificar la feromona de camino de Microcerotermes exiguus (Isoptera: Termitidae), que es una termita típica del Neotrópico, considerada como plaga en algunos cultivos. Nidos subterráneos de M. exiguus fueron recolectados en Caracas, Venezuela en el 2010. Se realizaron diferentes micro-reacciones químicas combinadas con el análisis cromatográfico de los extractos en solventes, así como el de la microextracción en fase sólida (SPME) de las glándulas esternales de las termitas; además de algunos bioensayos de comportamiento. Un pico en los cromatogramas de los extractos (índice de retención:1 483), presentó un patrón de fragmentación con los iones m/z: 41; 55; 67; 79; 91; 105; 119; 135; 142; 180, este resultado junto con los ensayos comportamentales, nos permitieron concluir que el (3Z,6Z,8E)-dodeca-3, 6, 8-trien-1-ol (DTOH) es el compuesto principal de la feromona de camino. La concentración óptima estimada para el reclutamiento y la orientación se encuentra alrededor de 1 pg/cm, siendo estadísticamente comparable al valor en los caminos trazados con extractos de cuerpo entero de 1 obrera /cm. El tiempo que toma este compuesto para reclutar a otros miembros de la colonia es de aproximadamente 13.67 ± 5.76 s y se mantiene hasta por dos horas. Los resultados analíticos y de comportamiento proporcionan una mejor comprensión de la comunicación química de M. exiguus, y dicha información podría ser utilizada para el desarrollo de nuevos métodos de control de plagas.
