Testing the genetic determination of the soldier caste in the silver ant.

Division of labor among workers is a hallmark of social insects that has largely contributed to their ecological success. In a number of species, ants in particular, environmental cues have long been recognized to determine the different phenotypes of workers. Recently, however, a genetic basis for worker polymorphism has been documented in some species. The silver ant Cataglyphis bombycina is characterized by the co-existence of two physiologically distinct castes of non-reproductive individuals: workers and soldiers. Soldiers are not a worker subcaste; they belong to a third caste, along with the queen and the worker castes. Using microsatellite DNA markers, we tested whether soldier caste determination has a genetic component, by comparing the distribution of patrilines between the soldier and the worker castes. Our data show evidence of genotypic variation in caste propensity in only 2 out of 7 colonies sampled. In addition, most patrilines produce both workers and soldiers across all colonies. These results support moderate genotypic influence to soldier caste determination and suggest that non-genetic, likely environmental factors, also influence caste fate among non-reproductive offspring in this species. We also provide new estimates of the queen mating frequency, which support biogeographic variations in mating behavior in C. bombycina. [ABSTRACT FROM AUTHOR]