Competition as possible driver of dietary specialisation in the mushroom harvesting ant Euprenolepis procera (Hymenoptera: Formicidae)

Abstract

Competition between co-existing species for limited resources is considered a main driving force of niche differentiation, including dietary specialization. Responses to interference competition vary, ranging from combat in dominant species to avoidance in submissive ones. Submissive species often show alternative strategies to avoid competition such as quick and efficient resource exploitation or shifts to less competitive resources. In the present study, we have evaluated the potential role of interference competition as driver of dietary specialisation in the mushroom-harvesting formicine ant Euprenolepis procera (Emery, 1900). This ant harvests a broad spectrum of wild-growing mushroom fruiting bodies – an exceptional diet among ants. We asked whether competition avoidance for more typical ant diets could explain the high degree of dietary specialization in E. procera. In baiting experiments at the Ulu Gombak field station, Malaysia, we first showed that E. procera also utilizes alternative food sources (tuna and honey) demonstrating that mushroom-harvesting is not a hard-wired foraging strategy. In contrast to expectations, E. procera's competitive ability for these resources was relatively high compared with other ants in the community. In a second experiment, we offered three resources (honey, tuna, mushroom) simultaneously and close to each other in baiting stations. In the absence of other ants, all three resources were exploited at similarly high rates by E. procera workers. However, E. procera avoided foraging on tuna and honey baits when those baits were utilized by other ants. This context-dependent food choice behaviour in E. procera suggests that the exceptional dietary specialization on wild-growing mushrooms represents a case of competition-induced niche differentiation. Finally, we provide new data about the geographic distribution and about variability in seasonal dietary preferences of E. procera.

Files

Additional details