Wasps are better plant-guards than ants in the extrafloral nectaried shrub Ouratea spectabilis (Ochnaceae)

Abstract

In the Cerrado, many plants are patrolled by ants, but in some cases, predatory wasps may also play an important role in herbivore deterrence. Here we examined the effects of the wasp Brachygastra lecheguana and the ant Pseudomyrmex gracilis on the predation of endophytic weevils which develop in the flower buds of Ouratea spectabilis trees. We (i) compared frequency and the abundance of weevils preyed upon by wasps; (ii) possible synergic effects of ants and wasps in decreasing weevil population; and (iii) whether wasps preyed upon weevils in more visible, easy-access inflorescences, i. e. those located in edges of canopy. In contrast to ants, wasps were observed significantly more frequently on O. spectabilis and were responsible for 88% of the weevil larvae preyed upon. Plants visited by both B. lecheguana and P. gracilis had a substantial reduction in weevil larvae compared to plants visited by B. lecheguana only. This indicates a complementary effect of predators with distinct skills in deterring the weevil population; however, ants were responsible for only a small portion of weevils preyed upon. Weevil larvae occurred evenly in both visible and hidden inflorescences; nonetheless, wasps predominantly visited inflorescences located on the edges of the canopy. In this ecological system, predatory wasps played a substantial part in weevil deterrence and can be considered a better plant-guard than ants.