The sociometry and sociogenesis of reproduction in the Florida harvester ant, Pogonomyrmex badius.

Abstract

The colony is the functional unit of natural selection for most social insects including the Florida harvester ant, Pogonomyrmex badius. To address reproduction in the species variables were evaluated relevant to the colony-level (sociometry), and social growth (sociogenesis). Colonies become reproductively mature when the worker population reaches ~700 individuals. The production of males and gynes (reproductive females) occurs only in spring, and is highly synchronized from its onset, which in turn allows synchronization of mating in early summer. Worker production follows sexual production, and continues until colonies go dormant in winter. Once mature, colony investment into reproduction is a constant proportion of colony size (isometric), regardless of the sex ratio produced. As individual male body size increases, they become leaner, whereas the amount of fat stored by gynes is highly variable. Larger colonies produce larger males, but gyne size is a constant across the range of colony sizes. As colony size increases, investment into males increases faster than investment into gynes. Therefore, there is a trend of increasing male bias in the sex ratio with increasing colony size (although a single outlier complicates this conclusion). We interpret our results in the light of sexual and natural selection as documented in related species. We also report the first documentation of male production by workers in the genus Pogonomyrmex.