Discovery-exploitation tradeoffs in a multispecies ant-treehopper mutualism: foraging strategy differences and temporal changes across ant attendance behaviors

Abstract

The discovery-exploitation tradeoff posits that ant colonies decide between investing in scouts (individual foraging and discovery) or recruits (collective foraging and exploitation) in order to optimize gains. Although this tradeoff has been thoroughly examined through theoretical modelling, research linking model findings to empirical comparative data in ant communities is lacking. We explore the discovery-exploitation tradeoff within an old field ant community in the novel context of a multispecies mutualism with the treehopper Publilia concava. Specifically, we examine the relationship between foraging strategy and ant attentiveness to their treehopper partner, changes in foraging strategy in response to dynamic resources, and how different attendance phenotypes affect partner fecundity. We categorized ants via behavioral assays into “attentive” and “non-attentive” behavioral groups. Foraging strategy differed between ant groups during treehopper oviposition, with “attentive” and “non-attentive” ants favoring collective and individual foraging strategies, respectively. As treehopper nymphs emerged, “non-attentive” Formica subsericea shifted to collective foraging, with a corresponding rapid increase in ant recruitment, while ant recruitment in “attentive” ants remained constant. Treehopper fecundity, however, did not differ when tended by either “attentive” or “non-attentive” ants. We suggest that differences in foraging strategy could be due to residual honeydew left by maternal treehoppers on egg masses, which “attentive” ants exploit. Early recruitment in “attentive” and behaviorally subordinate ants might lead to priority effects, allowing them to persist on host plants and deter invasion from competing ants, which could ultimately lead to species coexistence.