Mechanisms regulating caste and behavior differentiation in social insects

Abstract

Background & Aims: Eusociality is a critical evolutionary innovation. Understanding the origin of eusociality and related regulating mechanisms has theoretical and practical significance to several research fields. A clear hierarchy and division of labor exists among individuals of social insects. The behavioral differentiation and extensive cooperation between castes are beneficial for their adaptation to complicated environmental changes. Understanding how social insects can produce individuals with differences in morphology, behavior and life-history characteristics is an important goal of much evolutionary and developmental biology research. With the rapid development of sequencing technology and bioinformatics, there have been many studies on the mechanisms underlying social insect behavioral differentiation. Here, we present recent advances on the environmental factors and physiological and molecular mechanisms regulating caste and behavioral differentiation in social insects by summarizing the current results of social insect studies, and propose the future research directions. Progresses: Both biotic factors (e.g., nutrients, pheromones, cuticular hydrocarbons) and abiotic factors (e.g., temperature, climate) can directly and indirectly affect the differentiation of insect social behavior and castes. Endocrine hormones, such as juvenile hormone (JH), ecdysteroids (20E), insulin-like peptides (ILPs), and neurohormonal bioamines, also play important roles. In addition, evolutionary changes in gene sequences or genome structure, including heritable differences and novel genes, as well as gene regulatory mechanisms, such as DNA methylation and differential expression of genes, can also affect the caste and behavior differentiation of social insects to different degrees. Prospects: We suggest strengthening the study of social behavior and regulating mechanisms in other social insect lineages, such as aphids and thrips, which are relatively understudied and which will improve the understanding of the origins and evolution of eusociality and social behaviors in insects.