The life history continuum hypothesis links traits of male ants with life outside the nest

Abstract

AbstractAn ant society, headed by a mated queen, can live for decades. Male ants, in contrast, are generally assumed to be ephemeral sperm delivery vessels programmed to die hours after leaving the nest to mate. However, the events from dispersal to mate location have rarely been studied, and the links between male traits and the ecological demands of diverse mating systems remain poorly understood. Here, we propose that interspecific variation in the length of mating flights has generated a life history continuum for male ants, and that the previously proposed ‘male aggregating’ and ‘female calling’ mating syndromes represent the endpoints. We also provide the first evidence for systematic divergence in pre‐mating traits between males that attract females to brief nuptial swarms (Male aggregation syndrome) and those that must survive while searching for patchily distributed females that signal with pheromones (Female calling syndrome). Specifically, female‐calling males tend to have larger eyes and mandibles, but the length of the basal antennal segment (scape) appears relatively constant across body sizes. After exploring these patterns, we review evidence that key components of fitness like mating frequency vary across a male life history continuum, and then explore links between male traits and a colony's per capita reproductive investment. Systematic variation in pre‐flight provisioning of males relative to mating systems may have important ecological implications, given that ants are dominant consumers on a global scale, and colonies ultimately use large fractions of harvested resources to fuel reproduction.