Seasonality, division of labor, and dynamics of colony-level nutrient storage in the ant Pheidole morrisi

摘要

Nutritional provisioning is a critical component of life history strategies, and of particular interest in social insect colonies because of the role that division of labor plays in resource allocation. To explore the mechanisms that underlie colony nutritional strategies, I examined three populations of the ant Pheidole morrisi across a gradient of overwinter food scarcity over two seasons. P. morrisi colonies were found to employ a mixed strategy of fat storage with regard to a longer overwinter period: members of both worker castes increase their percent-fat in a graded manner, while the proportion of a specialized subcaste of majors known as "repletes", also increased within the colony. Geographic variation in other colony traits such as mean colony size, mean worker size, and minor/major caste ratio were also found, although not always in a manner clearly relating to fat storage. These results indicate that colony demography responds to seasonal fluctuations in food availability through behavioral alterations (increased fat stores and recruitment of replete workers) rather than physical alterations (changes in lean body sizes or caste ratio). The findings illustrate the dynamic role division of labor plays in the success of insect colonies confronting environmental variability.