Extrafloral nectaries as a deterrent mechanism against seed predators in the chemically protected weed Crotalaria pallida (Leguminosae)

Abstract In several plants, extrafloral nectaries (EFN) are located close to the reproductive structures, suggesting that ants may act as a defence against specialized seed predators that overcome chemical defences. Alternatively, ants may also deter herbivores in a generalized manner, thereby protecting the whole plant. In this work, we examined the relationship between the chemically protected weed Crotalaria pallida Ait. (Leguminosae) that bears EFN, its specialized seed predator, the larvae of the arctiid moth Utetheisa ornatrix L. (Arctiidae) and ants. We tested two hypotheses related to the type of deterrence caused by ants. The Seed Predator Deterrence Hypothesis predicts that ant deterrence is directed primarily towards herbivores that destroy seeds and other reproductive structures, without attacking herbivores on vegetative structures. The General Deterrence Hypothesis states that ants are general in their effects, equally deterring herbivores in vegetative and reproductive structures. Our results supported the predictions of the Seed Predator Deterrence Hypothesis, namely, that (i) ant activity on EFN was related to the vulnerability of reproductive structures to attack by U. ornatrix; (ii) ant patrolling was restricted almost entirely to racemes; (iii) ants removed termites used as baits more frequently on racemes than on leaves; and (iv) U. ornatrix larvae were often expulsed from the racemes. These results indicate that EFN can act as another deterrent mechanism in chemically protected plants by promoting the expulsion of specialist seed predators.     

Isolation of polymorphic microsatellite loci in the ponerine ant Ectatomma tuberculatum

We report the development of 11 microsatellite markers by an enrichment protocol in the ponerine ant Ectatomma tuberculatum. Polymorphism was explored in two colonies collected from Mexico and two colonies from Brazil. From the 11 loci which amplified, seven loci showed intracolonial polymorphism in Mexican colonies and only six loci were variable in populations from Brazil. Observed heterozygosity ranged from 0.18 to 0.84. The other five loci exhibited different alleles between Mexico and Brazil but geographical variability was not investigated further. Cross‐amplification was tested in another species of the same Tribe (Gnamptogenys striatula) and one locus was revealed to be polymorphic.     

Ants,plant characteristics and habitat conservation status affect the occurrence of myrmecophilous butterflies on an extrafloral nectaried Malpighiaceae

We investigated the occurrence of myrmecophilous florivorous lycaenid larvae in Banisteriopsis malifolia (Malpighiaceae) according to habitat conservation status (disturbed and preserved savanna), plant phenology, height and the presence of tending ants. The abundance and richness of lycaenids were sixfold and fivefold greater, respectively, in the disturbed area than in the protected savanna. Lycaenids occurred mostly on plants visited by Camponotus blandus, a mutualistic partner of larvae. Habitat type was the main factor influencing lycaenid occurrence, as plants in open areas offered more food resources and tending ants. Banisteriopsis malifolia was considered useful as a host for lycaenids in disturbed sites.     

Cleptobiosis in the antEctatomma ruidum in Nicaragua

Summary Observations of the ponerine antEctatomma ruidum suggested that this is a cleptobiotic species which appears to use the pheromone trails of other ant species to locate individual workers carrying food. To test this hypothesis an arena was set up to quantify the position of eachE. ruidum that entered the arena with respect to its position on or off a well-established foraging trail ofPheidole radoszkowskii, a myrmicine. Encounters betweenE. ruidum andP. radoszkowskii are described. Quantitative data and behavioral observations support the cleptobiosis hypothesis. This study adds yet another dimension to the diverse array of foraging strategies of the Ponerinae.     

Novel interactions of non-pollinating ants with pollinators and fruit consumers in a tropical forest

The tropical ants Ectatomma ruidum and E. tuberculatum (Formicidae) regularly patrol leaves, flowers, and fruits of the understory shrub, Psychotria limonensis (Rubiaceae), on Barro Colorado Island, Panama. Ant and pollinator exclusion experiments elucidated both positive and negative effects of ant attendance on plant reproductive success, including pollination, fruit set, fruit loss, and fruit removal. Ants did not pollinate flowers but did contribute to higher pollination success, probably by increasing the relocation frequency of winged pollinators and thus the rate of flower visitation. Ants also prevented fruit loss to herbivorous insects which were common during the early stages of fruit development. Thus, ant attendance strongly improved both pollination and fruit set whereby plants with ants set more fruit per flower and also lost fewer fruits during fruit maturation. In contrast, ants had a negative effect on the removal of ripe fruits by avian frugivores. Thus, ant attendance has a non-trivial influence on plant reproduction, this interaction being beneficial at some stages of the plant reproductive cycle and carrying costs at another stage. A tight ecological or co-evolved relationship between these Ectatomma spp. and P. limonensis is unlikely given that ant attendance of plants is detrimental to fruit removal. Received: 18 May 1998 / Accepted: 1 March 1999     

The egg capitulum of a neotropical walkingstick,Calynda bicuspis,induces aboveground egg dispersal by the ponerine ant,Ectatomma ruidum

Field observations of a walkingstick,Calynda bicuspis, reveal that its eggs are rapidly discovered and transported by the ponerine ant,Ectatomma ruidum during both dry and wet seasons in Costa Rica. The importance of the egg capitulum in inducing ant transport was established by presenting eggs from which the capitulum had been removed or sealed. Untreated eggs, including those initially taken into nests, were moved approximately 1 m and dropped on the surface of the ground, unlike the eggs of several Old World walkingstick species which ants bury. High rates of oviposition following the termination of prolonged copulatory periods appear to lead to the clumping of eggs, perhaps increasing their susceptibility to a specialist egg-parasitoid,Amisega sp. (Chrysididae, Amiseginae).     

Intraspecific Thievery in the Ant Ectatomma ruidum is Mediated by Food Availability

Animals modify their foraging strategies in response to environmental changes that affect foraging performance. In some species, cleptobiosis represents an alternative strategy for resource access. The environmental factors that favor the incidence or prevalence of cleptobiosis, however, are poorly described. The cleptobiotic Neotropical ant Ectatomma ruidum is characterized by a high frequency of thievery behavior, a specific type of intraspecific cleptobiosis, in which specialized thief workers insinuate themselves into nests of neighboring colonies and intercept food items brought into these nests. Here, we evaluate how colonies adjust thievery behavior in response to food availability. We supplemented food availability and measured how the incidence and intensity of thievery responded to resource availability. We found that the incidence and intensity of thievery decline in response to supplemental food, suggesting that thievery behavior is a response to resource limitation at the population scale. This finding indicates that the phenomenon of intraspecific thievery, although a rare strategy in among colonies of social animals, is a viable alternative foraging tactic in the context of competition and food limitation.     

Ambush Predation by the Ponerine Ant Ectatomma ruidum Roger (Formicidae) on a Sweat Bee Lasioglossum umbripenne (Halictidae), in Panama

An individual ambush predation is used by huntresses of the ponerine ant Ectatomma ruidum to capture halictid bees (Lasioglossum umbripenne) in the Panamanian mountains. Workers, which use this strategy and originated from a colony (A) situated within a nest aggregation of halictid bees, capture almost four times more prey than colony (B) with a foraging area which does not include this type of bee's nest. Forty-eight percent of the prey of colony (A) are halictid bees, demonstrating the local importance of this predatory strategy in E. ruidum. A close examination of the behavioral sequence of predation shows that ambush is successful in only 4.8% of cases, a very low success rate in comparison to other predatory strategies described in this species. Nevertheless, due to the high repetition (16.1 ± 5.9 times on average) of very short waiting phases (6.3 ± 1.9 s), the true success rate (i.e., according to the number of individual trips) can reach up to 80%. A review of ambush predation among ant species allows us to distinguish approaches between jumping, long stealth approaches, and true ambushes. Implications of learning and expectation processes are also discussed.