Cheaters and removalists: the influence of soil disturbance on ant–seed interactions in roadside vegetation

Abstract

Myrmecochory is an important mutualistic interaction, where ants provide seed dispersal services for many plant species. We examined the influence of soil disturbances associated with roadworks activity on ant–seed interactions in roadside environments in south-eastern Australia. In the study landscape, minor rural road reserves often provide critical habitat for endangered species and woodland ecosystems. We conducted seed-depot experiments to quantify the extent of ant–seed removal, and identified the contribution of different ant species to seed removal and elaiosome consumption (cheating) interactions, in disturbed and non-disturbed roadside zones. Twenty-six ant species were recorded interacting with seeds; however, only a few species were responsible for dispersing most seeds. We found soil disturbance and roadside width influenced observed ant–seed interactions, which was largely explained by individual species habitat and behavioural traits. Iridomyrmex purpureus removed a higher proportion of seeds in soil disturbed zones, while Rhytidoponera metallica carried out more seed removals in narrow roadsides. R. metallica and Melophorus bruneus typically carried out seed removals (only), while Monomorium and Pheidole spp. almost exclusively carried out cheating behaviours. These results highlight the complex nature of ant–plant interactions is association with novel soil disturbance regimes, where ants perform a critical seed dispersal service for myrmecochorous roadside vegetation.