42 research outputs found
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The genetic basis of a social polymorphism in halictid bees
The emergence of eusociality represents a major evolutionary transition from solitary to group reproduction. The most commonly studied eusocial species, honey bees and ants, represent the behavioral extremes of social evolution but lack close relatives that are non-social. Unlike these species, the halictid bee Lasioglossum albipes produces both solitary and eusocial nests and this intraspecific variation has a genetic basis. Here, we identify genetic variants associated with this polymorphism, including one located in the intron of syntaxin 1a (syx1a), a gene that mediates synaptic vesicle release. We show that this variant can alter gene expression in a pattern consistent with differences between social and solitary bees. Surprisingly, syx1a and several other genes associated with sociality in L. albipes have also been implicated in autism spectrum disorder in humans. Thus, genes underlying behavioral variation in L. albipes may also shape social behaviors across a wide range of taxa, including humans
Support for maternal manipulation of developmental nutrition in a facultatively eusocial bee, Megalopta genalis (Halictidae)
Developmental maternal effects are a potentially important source of phenotypic variation, but they can be difficult to distinguish from other environmental factors. This is an important distinction within the context of social evolution, because if variation in offspring helping behavior is due to maternal manipulation, social selection may act on maternal phenotypes, as well as those of offspring. Factors correlated with social castes have been linked to variation in developmental nutrition, which might provide opportunity for females to manipulate the social behavior of their offspring. Megalopta genalis is a mass-provisioning facultatively eusocial sweat bee for which production of males and females in social and solitary nests is concurrent and asynchronous. Female offspring may become either gynes (reproductive dispersers) or workers (non-reproductive helpers). We predicted that if maternal manipulation plays a role in M. genalis caste determination, investment in daughters should vary more than for sons. The mass and protein content of pollen stores provided to female offspring varied significantly more than those of males, but volume and sugar content did not. Sugar content varied more among female eggs in social nests than in solitary nests. Provisions were larger, with higher nutrient content, for female eggs and in social nests. Adult females and males show different patterns of allometry, and their investment ratio ranged from 1.23 to 1.69. Adult body weight varied more for females than males, possibly reflecting increased variation in maternal investment in female offspring. These differences are consistent with a role for maternal manipulation in the social plasticity observed in M. genalis
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Ontogeny of division of labor in a facultatively eusocial sweat bee Megalopta genalis
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Foundress polyphenism and the origins of eusociality in a facultatively eusocial sweat bee, Megalopta genalis (Halictidae)
The reproductive (queen) and nonreproductive (worker) castes of eusocial insect colonies are a classic example of insect polyphenism. A complementary polyphenism may also exist entirely among females in the reproductive caste. Although less studied, reproductive females may vary in behavior based on size-associated attributes leading to the production of daughter workers. We studied a bee with flexible social behavior, Megalopta genalis, to better understand the potential of this polyphenism to shape the social organization of bee colonies and, by extension, its role in the evolution of eusociality. Our experimental design reduced variation among nest foundresses in life history variables that could influence reproductive decisions, such as nesting quality and early adulthood experience. Within our study population, approximately one third of M. genalis nests were eusocial and the remaining nests never produced workers. Though they do not differ in survival, nest-founding females who do not attempt to produce workers (which we refer to as the solitary phenotype) are significantly smaller and become reproductive later than females who attempt to recruit workers (the social phenotype). Females with the social phenotype are more likely to produce additional broods but at a cost of having some of their first offspring become nonreproductive workers. The likelihood of eusocial organization varies with body size across females of the social phenotype. Thus, fitness consequences associated with size-based plasticity in foundress behavior has colony level effects on eusociality. The potential for size-based polyphenisms among reproductive females may be an important factor to consider in the evolutionary origins of eusociality. © 2012 Springer-Verlag Berlin Heidelberg