The Development and Evolution of Division of Labor and Foraging Specialization in a Social Insect (Apis mellifera L.)

Abstract

How does complex social behavior evolve? What are the developmental building blocks of division of labor and specialization, the hallmarks of insect societies? Studies have revealed the developmental origins in the evolution of division of labor and specialization in foraging worker honeybees, the hallmarks of complex insect societies. Selective breeding for a single social trait, the amount of surplus pollen stored in the nest (pollen hoarding) revealed a phenotypic architecture of correlated traits at multiple levels of biological organization in facultatively sterile female worker honeybees. Verification of this phenotypic architecture in "wild-type" bees provided strong support for a "pollen foraging syndrome" that involves increased senso-motor responses, motor activity, associative learning, reproductive status, and rates of behavioral development, as well as foraging behavior. This set of traits guided further research into reproductive regulatory systems that were co-opted by natural selection during the evolution of social behavior. Division of labor, characterized by changes in the tasks performed by bees, as they age, is controlled by hormones linked to ovary development. Foraging specialization on nectar and pollen results also from different reproductive states of bees where nectar foragers engage in prereproductive behavior, foraging for nectar for self-maintenance, while pollen foragers perform foraging tasks associated with reproduction and maternal care, collecting protein.

Stochastic epigenetic variation as a driving force of development, evolutionary adaptation, and disease

“…This epigenetic instability may have been first described while observing individual cancer cells (20), and data show clear epigenetic differences between identical twins (21). In evolutionary biology, social insects show environment-mediated phenotypic differences in social castes, and the distribution of those differences can be selected for (22), leading those authors to speculate that an epigenetic mechanism might be involved (23); the bee would be an outstanding model for testing these ideas. Finally, substantial variations in phenotype of crayfish from an identical genotype have been reported (24).…”

Measuring individual locomotor rhythms in honey bees, paper wasps and similar sized insects

“…Given that age is a major regulator of the circadian system in honey bees (Moore et al, 1998), this may be another source of variation. An additional factor could be that specialized water-, pollen -, nectarand/or propolis-foraging individuals may be present within our sample (Page et al, 2006;Giray et al, 2007). Despite the fact that foraging specialization and age may be different, no studies have dissected the effect of forager age and specialization on circadian periodicity.…”

Modification of feeding circuits in the evolution of social behavior

“…In honey bees, increased levels of circulating Vg are associated with increased foraging for pollen, and by extension, increased provisioning of the colony (Page and Amdam, 2007;Page et al, 2006). Within colonies, nurses have higher Vg expression and more ovarioles than foragers, indicating that nurse bees performing brood care exhibit a reproductive physiology more similar to that of mothers despite being nonreproductive themselves .…”