Ontogenic potentialities of the worker caste in two sympatric subterranean termites in France

Abstract

In termites, the capacity of workers to differentiate into neotenic reproductives is an important characteristic that deserves particular attention. To gain insight into the differentiation pathway, the potentialities of workers and the endocrinal changes during the formation of neotenics were compared in two sympatric termites, Reticulitermes flavipes and Reticulitermes grassei. After 1 year of development, 100% of R. flavipes worker groups produced neotenics against only 63% of R. grassei groups. The average production of female neotenics was significantly higher in R. flavipes worker groups compared with R. grassei groups and R. flavipes produced a greater proportion of female neotenics. Moreover, R. flavipes produced more offspring, not only because there were more females, but also because R. flavipes females were more productive. Moreover, the offspring produced by R. flavipes grew faster than the offspring of R. grassei. Both ecdysteroid and juvenile hormone (JH) titers varied significantly during the development of neotenics. The two species showed similar ecdysteroid titer variation patterns. However, the JH titer variation patterns strongly differed: in R. grassei, the concentration of JH increased in maturing neotenics then dropped in mature neotenics, whereas in R. flavipes, the level of JH was significantly higher than in R. grassei and remained constantly high in mature neotenics. Overall, these results suggest that these two species differ strongly in many life-history traits as well as in the physiological control of their caste differentiation system. Possible origins and mechanisms of such interspecific variations are discussed, as well as their evolutionary and ecological consequences.

Subterranean termite phylogeography reveals multiple postglacial colonization events in southwestern Europe

“…2006, 2009; Leniaud et al. 2011). This study has found that their complex evolutionary histories (marked by some potential hybridization events) and their resulting distributions are also distinct.…”

Brood care and social evolution in termites

“…This changes with the transition to the foraging lifestyle in termites, as in R. flavipes, because they sooner or later have to leave the nest and forage for food. Increased foraging activity of workers seems to be paralleled by an increasing proportion of neotenic reproductives in some Rhinotermitidae, such as Reticulitermes [61].…”

Communication and Social Regulation in Termites

“…Different castes have been found to have different JH levels: levels are low, high, and intermediate in workers, apterous neotenic reproductives, and pre-soldiers, respectively (Chan et al 2011). Isolated workers that develop into soldiers or neotenic reproductives show different levels of JH synthesis depending on the species (Leniaud et al 2011). Workers that become pre-soldiers have higher levels of JH synthesis than workers that develop into neotenics.…”

“…Nevertheless, workers are perfectly able to differentiate between the different types of secondary reproductives and behave so as to enhance their own indirect fitness, as has been seen in Pterotermes (Zimmermann 1983). It is assumed that most neotenics develop from nymphs in Reticulitermes species found in nature; however, apterous neotenics may occur when a colony (or part thereof) is left with only a few workers after a natural accident (e.g., a flood or fire), a predator attack, or displacement by humans (Pichon et al 2007;Leniaud et al 2011).…”