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

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

Nestmate Recognition in the Amazonian Myrmecophyte Ant Pseudomyrmex concolor Smith (Hymenoptera, Formicidae)

Nestmate recognition is fundamental to colonial cohesion in social insects, since it allows altruistic behavior towards relatives, recognition of intruders, territorial monopoly and resources defense. In ants, olfactory cues is a key factor in this process. Pseudomyrmex concolor is a highly aggressive ant that defends their host plant Tachigali myrmecophila against herbivores. However, this defense depends on the ant ability to discriminate in order to treat differentially between  members of their own colony and intruders . In this study we investigated “whether” and “how” P. concolor recognizes nestmates from non-nestmates. We hypothesized that P. concolor is skillful in recognizing nestmates and tested it in field with experiments using nestmates and non-nestmates. Additionally, to test the efficiency of resident ants against intraspecific competition during colony foundation, we simulate the plant occupation by a competitor queen, introducing non-nestmates queens in plants previously occupied by P. concolor. For the issue of the "how", we hypothesized that the main cue used by this ant in nestmate recognition is olfactory signal. Thus, we tested adaptive threshold model, which predicts that, if the individual odor and colony’s internal template are discrepant enough, the resident nestmate will behave aggressively towards incoming individuals. In this case, we confined nestmates with non-nestmates odors, and then, we reintroduced them in its host plants. In each experiment the frequency of aggressive behaviors were recorded and compared. Results showed that P. concolor recognize and discriminate nestmates from non-nestmates workers (biting and stinging them) and exclude potential competitors queens. Workers reintroduced in their own colony after impregnated with non-familiar odor were treated as non-nestmates. The adaptive threshold hypothesis was confirmed, the main cue used by this ant species in nestmate recognition is olfactory signals

Availability of food and nesting-sites as regulatory mechanisms for the recovery of ant diversity after fire disturbance

Nest-site is an important resource for cavity-nesting ants, what limits colony establishment and structures ant community composition through competition. In ecosystems frequently disturbed by firecontinuous establishment of new colonies is crucial to the process of natural succession.  Based on this perspective, we tested the hypothesis that fire reduces the amount of cavities for nesting (e.g., hollow branches, dry leaves curled, and galls), with negative impact on ant biodiversity. We searched for natural cavities and added artificial-nests to assess whether the occupancy rate and its consequences for colony growth. We also evaluated the availability of food sources for ants (EFN plants, honeydew-hemipterans and preys). We found that burned areas had less diverse and structurally simple vegetation. The occupation of natural and artificial nests was the same between the areas, but the reduced availability of nesting-sites in the burned area indicates higher limitation after the fire. This effect was even stronger in foliage habitat compared to the ground. In fact, most of the 11 cavity-nesting species found were typically arboreal. Species richness was lower in burned area, possibly due to lower nesting-sites availability, but the abundance was higher, which may be explained by the greater availability of food resources, mainly EFN-bearing plants. The high food availability may also explain the bigger colony size in burned area, since nectar and honeydew boosts colony growth and low richness prevents competition. In summary, our results show that changes in the availability of nesting sites and food resources may be key mechanisms by which fire changes the ant fauna, specifically cavity-nesting ants in the Brazilian Savanna

Influence of Camponotus blandus (Formicinae) and flower buds on the occurrence of Parrhasius polibetes (Lepidoptera: Lycaenidae) in Banisteriopsis malifolia (Malpighiaceae)

In the Brazilian savanna, myrmecophilous lycaenids are often found in many shrubs feeding on plant reproductive structures while are tended by ants, but only recently the role of both ants and food on the occurrence of lycaenids have received attention. In this study, we investigated the influence of Camponotus blandus (Formicinae) and flower bud abundance on the occurrence of Parrhasius polibetes, a florivorous lycaenid species that occurs in Banisteriopsis malifolia(Malpighiaceae). We also examined to what extent larval florivory was deleterious to plant reproductive outputs. Ant-exclusion experiments revealed that most P. polibetes individuals were found on branches with free C. blandus access. Nonetheless, the occurrence of larvae was not related to the abundance of these ants and flower buds, indicating that the presence, rather than the abundance of mutualistic ants and food, influenced the occurrence of P. polibetes. Larvae were attended by C. blandus, which antennated frequently the dorsal nectary organ of larvae. Larval florivory was not deleterious to the plant. Banisteriopsis malifolia produces thousands of buds simultaneously and larvae feed only on a small portion of flower buds. The occurrence of P. polibetes inB. malifolia is advantageous for the larvae, since this plant supports mutualistic ants and plenty of food resources

A New Extrafloral Nectary-Bearing Plant Species in the Brazilian Savanna and its Associated Ant Community: Nectary Structure, Nectar Production and Ecological Interactions

Brazilian Savanna stands out for the large number of species with extrafloral nectaries (EFNs) with high morphological diversity. In Smilax polyantha (Smilacaceae), the base of the petiole showed a slight secretion and great visitation by ants suggesting the presence of an EFN. In this way, we aimed to determine the ant community associated with this plant, as well as to identify and characterize this unsuspected structure and determine the phenology and liquid production of this tissue. The study was carried out in a Cerrado area, in Uberlândia, Brazil. Ten individuals were used for the anatomical analysis and histochemical tests and the EFNs secretory activity was monitored, being categorized into active and non-active EFN. In addition, the volume and sucrose concentration were determined from three nectaries of ten individuals, and individuals of ants found foraging on these nectary were collected, day and night. Results showed a large amount of extrafloral nectar secretion and the EFN tissue is composed of a few cell layers that showed positive reactions for proteins and reducing sugars. We recorded a significantly correlation between percentage of EFNs activity and abundance of ants. The secretory activity is concentrated in September and ten ant species, of five subfamilies, were identified foraging on the EFNs

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The journal Sociobiology announces the adoption of a series of editorial innovations that aim to speed up review and publication time, to select high quality articles for publication, to adopt transparent and ethical editorial standards and to reinforce the culture of open acess scientific publishing

The Influence of Fire and Deforestation on the Floral Symmetry and Fitness of Adenocalymma nodosun (Bignoniaceae)

Burnings and deforestation are severe disturbances to plants and may represent a stressful situation for plant growth, and they can also affect plant-pollinator interactions and the reproductive success of plants. In this study, we verified the variation in floral symmetry of Adenocalymma nodosum (Bignoniacea) in two areas, one post-fire and other after deforestation. We also verified the effects on plant-pollinator interactions and fruit set production. Results showed that A. nodosum flowers were more asymmetric in mowing areas than in fire areas. Asymmetrical flowers presented low nectar concentration and bee visitation rates. Although mowed environments produce fewer fruits and seeds than areas affected by fire, the change was not significant. Soil from the burnt area showed higher nutrient and organic matter concentration and less aluminum than that of mowed areas. Our results showed that A. nodosum flowers in the deforestation area are more asymmetric than those in the post-fire area. This result suggest that Cerrado plants may be less adapted to deforestation than to fire, since they have been facing fire events for thousand years in this biome. We suggest that the effects of environmental stress on the development and fitness of plants may provide an important breakthrough to the understanding of insect-plant interactions in Cerrado savanna, where burnings and deforestation are frequent anthropogenic effects