Macroecological diversification of ants is linked to angiosperm evolution.

Abstract

Ants are abundant, diverse, and occupy nearly all habitats and regions of the world. Previous work has demonstrated that ant diversification coincided with the rise of the angiosperms, and that several plant traits evolved as ants began to expand their nesting and foraging habits. In this study, we investigate whether associations with plants enabled niche expansion and are linked to climatic niche evolution in ants. Our analysis of over 1,400 ant species reveals that ancestral expansion from forest floors into the canopy and out into non-forested habitats closely followed evolutionary innovations in angiosperms. Several Paleogene-Neogene ant lineages independently diversified in non-forested habitats on multiple continents, tracking the evolution and expansion of elaiosome-bearing and arid-adapted angiosperms. The evolution of arboreal nesting tracked shifts in angiosperm physiology associated with the onset of everwet tropical rainforests, and climatic optima and rates of climatic niche evolution were linked to nesting location, with arboreally nesting groups having warmer and less seasonal climatic optima, and lower rates of climatic niche evolution. Our work further underscores the varied paths by which niche diversification occurred in ants, and how angiosperms influenced the ecological and evolutionary trajectories of interacting lineages.