Cuticular hydrocarbons and defensive compounds ofReticulitermes flavipes (Kollar) andR. santonensis (feytaud): Polymorphism and chemotaxonomy

Abstract

Colonies ofReticulitermes flavipes andR. santonensis were collected from the southeastern United States (Georgia) and the southwest of France (Charente-maritime). Defensive compounds and cuticular hydrocarbons were identified by gas chromatography-mass spectrometry and quantified by gas chromatography using an internal standard for each caste and all colonies. These analyses show that although the cuticular hydrocarbons ofR. santonensis in Europe andR. flavipes in Georgia are identical, their relative proportions are different. However, the defensive compounds synthesized by their soldiers are different. A strong chemical polymorphism between sympatric colonies ofR. flavipes in the SW United States was detected in terms of both the hydrocarbons of the workers and soldiers and in the defensive secretions of the soldiers. The six defensive secretion phenotypes are based on the presence or absence of terpenes whereas the cuticular hydrocarbon phenotypes are based on significant differences in the proportions of the various components. A multivariate analysis (analysis of principal components) clearly permitted discrimination of four phenotypes (three inR. flavipes and one inR. santonensis) without intermediates. The hydrocarbons responsible for these variations were identified, and it was shown that the variations are neither seasonal nor geographic. The phenotypes of the cuticular hydrocarbons (workers and soldiers) and defensive compounds are linked in each colony, forming in three groups inR. flavipes Georgia, one subdivided into four subgroups according to the defensive secretion phenotypes. The role of these polymorphisms is discussed and ethological tests indicate that the chemical polymorphism do not determine aggressive behavior. The taxonomic significance of these results is considered and two hypothesis are formulated: (1) We only detected a strong genetic polymorphism in one unique species, and we believe thatR. santonensis was introduced into Europe in the last century from oneR. flavipes colony. (2) Chemical variability characterizes the sibling species that can be grouped into the same subspeciesR. flavipes. Unknown mechanisms of reproductive isolation separate them.

Effects of Soldier-Derived Terpenes on Soldier Caste Differentiation in the Termite Reticulitermes flavipes

“…The 1 H chemical shift axis was referenced to CHCl 3 , assigned to 7.26 ppm Previously Identified Chemicals. Past research (Zalkow et al, 1981;Bagnères et al, 1990;Nelson et al, 2001;Quintana et al, 2003) Statistical Analyses. In all experiments the number and caste of each termite in each dish was counted every five days.…”

Courtship Pheromones in Parasitic Wasps: Comparison of Bioactive and Inactive Hydrocarbon Profiles by Multivariate Statistical Methods

“…Studies on social insects have shown that subtle quantitative differences in cuticular hydrocarbon profiles can be detected by analyzing chemical data with multivariate statistical methods. By this approach, cuticular hydrocarbon profiles of social insects have been shown to be species-(e.g., Kaib et al, 1991;Page et al, 2002), caste-(e.g., Bagnères et al, 1990;Klochkov et al, 2005), and colony-specific (e.g., Butts et al, 1995;Lorenzi et al, 1997).…”

Endogenous synchronization of the chemical signature of Reticulitermes (Isoptera: Rhinotermitidae) worker termites

“…Th e cuticular compounds may also play a role in caste regulation similar to primer pheromones LeConte & Hefetz 2008). Th erefore, the chemical signature and its variations depend on a wide range of factors: endog-enous factors, such as endocrine or enzymatic factors and the regulation of transport paths, etc (Lengyel et al 2007;Schal et al 2003;Fan et al 2004), as well as exogenous factors, such as climate and season (Bagnères et al 1990), diet (Liang and Silverman 2000), the presence of predators, etc. Th e predominance of these factors varies between insects (VanderMeer & Morel 1998).…”