Genetic components to caste allocation in a multiple-queen ant species (original) (raw)

Genetic determination of the queen caste in an ant hybrid zone

Proceedings of the …, 2002

The question of how reproductives and sterile workers differentiate within eusocial groups has long been a core issue in sociobiology because it requires the loss of individual direct fitness in favor of indirect or group-level fitness gains. The evolution of social behavior requires ...

Report Maternal Effect on Female Caste Determination in a Social Insect

2000

Caste differentiation and division of labor are the hallmarks of social insect colonies [1, 2]. The current dogma for female caste differentiation is that female eggs are totipotent, with morphological and physiological differences between queens and workers stemming from a developmental switch during the larval stage controlled by nutritional and other environmental factors (e.g., [3-8]). In this study, we tested whether maternal effects influence caste differentiation in Pogonomyrmex harvester ants. By conducting crossfostering experiments we identified two key factors in the process of caste determination. New queens were produced only from eggs laid by queens exposed to cold. Moreover, there was a strong age effect, with development into queens occurring only in eggs laid by queens that were at least two years old. Biochemical analyses further revealed that the level of ecdysteroids was significantly lower in eggs developing into queens than workers. By contrast, we found no significant effect of colony size or worker exposure to cold, suggesting that the trigger for caste differentiation may be independent of the quantity and quality of resources provided to larvae. Altogether these data demonstrate that the developmental fate of female brood is strongly influenced by maternal effects in ants of the genus Pogonomyrmex. Results and Discussion Effect of Cold Exposure, Queen Age, and Colony Size on Queen Production in Pogonomyrmex Lineages Some Pogonomyrmex lineages produce queens and workers that differ genetically [9-14]. In these lineages, queen-destined eggs abort at periods when only workers are raised [15, 16], whereas the same eggs hatch and develop into adult queens at periods of reproduction. We conducted crossfostering

Worker caste polymorphism has a genetic basis in Acromyrmex leaf-cutting ants

Proceedings of The National Academy of Sciences, 2003

Division of labor is fundamental to the success of all societies. The most striking examples are the physically polymorphic worker castes in social insects with clear morphological adaptations to different roles. These polymorphic worker castes have previously been thought to be a classic example of nongentically controlled polymorphism, being mediated entirely by environmental cues. Here we show that worker caste development in the leaf-cutting ant Acromyrmex echinatior has a significant genetic component. Individuals of different patrilines within the same colony differ in their propensities to develop into minor or major workers. The mechanism appears to be plastic, with caste destiny resulting from interplay between nurture and nature. Unlike the few other recently discovered examples of a genetic influence on caste determination, the present result does not relate to any rare or exceptional circumstances, such as interspecific hybridization. The results suggest that a significant role of genetics may have been overlooked in our understanding of other complex polymorphisms of social insects.

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

Insectes Sociaux, 2015

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 coexistence 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 nonreproductive offspring in this species. We also provide new estimates of the queen mating frequency, which support biogeographic variations in mating behavior in C. bombycina.

Clonal ant societies exhibit fertility-dependent shifts in caste ratios

Behavioral Ecology, 2011

Caste differentiation leading to reproductive division of labor is the hallmark of insect societies. Insect colonies typically contain mated queens that reproduce and workers with reduced fertility that undertake the tasks required for colony maintenance and development. Despite the prediction that the proportion of morphological castes should vary to enhance the fitness of colony members in response to environmental conditions, shifts in caste ratios have so far only been reported in a competitive situation. Societies of the ant Cerapachys biroi have evolved in an extraordinary way, in that queens and all workers reproduce through obligatory thelytokous parthenogenesis. Because workers of C. biroi represent the main reproductive force of the colony, the presence of such unmated queens seems puzzling. Here, we show that societies of C. biroi alter caste ratios by considerably increasing the production of queens when larvae are reared by sterile individuals in 2 situations: when senescent colonies are faced with food shortage or when well-fed larvae are reared by callow workers due to persisting plentiful resources. In the absence of these opposite conditions, larvae mostly develop into workers. Additional experiments suggest that these results are consistent with a contact pheromone to which larvae could be exposed when cared for by fertile individuals. In this species in which reproduction mainly relies on young workers with finite fertility, a self-regulated mechanism of caste differentiation could allow the enhancement of colony growth through worker production in fertile conditions or the restoration of colonial fertility through queen production in senescent societies.

Maternal effect on female caste determination in a social insect

Current Biology, 2008

Caste differentiation and division of labor are the hallmarks of social insect colonies . The current dogma for female caste differentiation is that female eggs are totipotent, with morphological and physiological differences between queens and workers stemming from a developmental switch during the larval stage controlled by nutritional and other environmental factors (e.g., ). In this study, we tested whether maternal effects influence caste differentiation in Pogonomyrmex harvester ants. By conducting crossfostering experiments we identified two key factors in the process of caste determination. New queens were produced only from eggs laid by queens exposed to cold. Moreover, there was a strong age effect, with development into queens occurring only in eggs laid by queens that were at least two years old. Biochemical analyses further revealed that the level of ecdysteroids was significantly lower in eggs developing into queens than workers. By contrast, we found no significant effect of colony size or worker exposure to cold, suggesting that the trigger for caste differentiation may be independent of the quantity and quality of resources provided to larvae. Altogether these data demonstrate that the developmental fate of female brood is strongly influenced by maternal effects in ants of the genus Pogonomyrmex.

Maternal Effect on Female Caste Determinati in a Social Insect

2015

that differ genetically [9–14]. In these lineages, queen-destined eggs abort at periods when only workers are raised [15, 16], whereas the same eggs hatch and develop into adult queens at periods of reproduction. We conducted crossfostering more females (queens and workers) than smaller recipient colonies (Kruskall-Wallis test; X21 = 177.5, p < 0.0001; 26.2 6 15.0 females in smaller versus 54.3 6 35.3 females in larger recipient colonies). Queens produced in larger colonies were as large as the mother queens, whereas smaller colonies typically produced very small queens (data not shown). The finding that small colonies readily produced new queens in the laboratory is in apparent contrast with the observation that new queens and males are produced only in colonies