The best plant-guarding ants in extrafloral nectaried plants and myrmecophytes according to baiting tests

Abstract

Extrafloral nectaried plants and myrmecophytes offer resources to ants that may engage in protective mutualisms. The role of different ant species in herbivore deterrence has long been analyzed by using herbivore baits, and ants are regarded as effective plant guards if they attack and/or remove the baits (mostly termites) from plants. Here, we conducted a comparative investigation on which ants display aggression toward baits, which ants are better plant guards, and which plants (extrafloral nectaried plants or myrmecophytes) are better defended by ants. Data from the literature revealed that baiting studies have been performed on 37 extrafloral nectaried plant species and 19 myrmecophytes, and have involved over 30 genera of ants. Extrafloral nectaried plants and myrmecophytes rely on specific ant fauna to defend them from herbivores. In extrafloral nectaried plants,CamponotusandCrematogasterwere regarded as the best plant protectors, as they attacked baits in nearly all plants. In myrmecophytes,Azteca, PheidoleandPseudomyrmexwere the most important bait attackers. Myrmecophytes were better protected by ants, as all baits were attacked; in extrafloral nectaried plants, some ants failed to attack the baits. Plants can be patrolled by several different ants, but there is a core of ants that excel in protection, and this varies according to plant type (extrafloral nectaried plants and myrmecophytes). With this knowledge, it may be possible to label different ants as effective plant guards, to anticipate their effects on plant performance and even to understand their potential role as biological control agents.

Emerging Trends in Ant–Pollinator Conflict in Extrafloral Nectary-Bearing Plants

“…In general, we propose a conceptual framework for understanding the impacts of different levels of ant aggressiveness on factors related to the protection and reproduction of plants; see [ 28 , 92 ]. Docile ants ( point a in Figure 3 ) with low levels of aggressiveness tend to show a low effect on protection effectiveness ( Figure 3 A), pollinator deterrence ( point a in Figure 3 B), and the probability of cross-pollination ( Figure 3 D) but high effects on self-pollination probability ( Figure 3 C) and pollen removal/deposition ( Figure 3 E).…”

“…In this region, 25% of woody plant species and 30% of individuals at a site were found to have EFNs [ 93 , 94 , 95 ]. The main group of numerically and behaviorally dominant ants foraging on these plants is Camponotus [ 60 , 92 , 94 , 96 , 97 , 98 ], with great emphasis on C. crassus , which has been recorded as the most abundant and protective ant on EFN-bearing plants in different areas of the Brazilian savanna [ 2 , 63 , 64 , 68 , 92 , 94 , 96 , 97 , 99 ]. For instance, Souza et al [ 92 ] showed that Camponotus ants are the best EFN-bearing plant protectors according to baiting tests.…”

“…The main group of numerically and behaviorally dominant ants foraging on these plants is Camponotus [ 60 , 92 , 94 , 96 , 97 , 98 ], with great emphasis on C. crassus , which has been recorded as the most abundant and protective ant on EFN-bearing plants in different areas of the Brazilian savanna [ 2 , 63 , 64 , 68 , 92 , 94 , 96 , 97 , 99 ]. For instance, Souza et al [ 92 ] showed that Camponotus ants are the best EFN-bearing plant protectors according to baiting tests. Studying Qualea multiflora plants, we tested how ants’ presence on flowers can impact pollinator deterrence and plant fitness (Calixto et al in review) and whether this impact is contingent on ant and floral visitor identity.…”

“…Supported by these studies, we suggest that C. crassus is a species aggressive enough to protect plants against herbivore attack but leads to low negative impacts on pollination processes ( point c in Figure 3 ). Therefore, Camponotus ants, specifically C. crassus , might represent the suggested “optimal protective mutualist” ( Figure 3 ) in some areas of the Brazilian savanna where they are dominant on EFN-bearing plants; also see [ 28 , 92 ].…”

“…In this region, 25% of woody plant species and 30% of individuals at a site were found to have EFNs [93][94][95]. The main group of numerically and behaviorally dominant ants foraging on these plants is Camponotus [60,92,94,[96][97][98], with great emphasis on C. crassus, which has been recorded as the most abundant and protective Point a represents a docile ant (usually small and non-aggressive compared to other ants in the same system), point b represents a very aggressive ant (compared to other ants in the same system, it is usually large and very aggressive toward herbivores and pollinators), and point c represents an aggressive ant (compared to other ants in the same system, it is usually medium-size and aggressive toward herbivores but not pollinators). Point c represents the optimal balance between ant aggressiveness and the impacts on plant protection and pollination processes.…”