[Show abstract][Hide abstract] ABSTRACT: Very large colonies of territorially dominant arboreal ants (TDAAs), whose territories are distributed in a mosaic pattern in the canopies of many tropical rainforests and tree crop plantations, have a generally positive impact on their host trees. We studied the canopy of an old Gabonese rainforest (ca 4.25 ha sampled, corresponding to 206 "large" trees) at a stage just preceding forest maturity (the Caesalpinioideae dominated; the Burseraceae were abundant). The tree crowns sheltered colonies from 13 TDAAs plus a co-dominant species out of the 25 ant species recorded. By mapping the TDAAs' territories and using a null model co-occurrence analysis, we confirmed the existence of an ant mosaic. Thanks to a large sampling set and the use of the self-organizing map algorithm (SOM), we show that the distribution of the trees influences the structure of the ant mosaic, suggesting that each tree taxon attracts certain TDAA species rather than others. The SOM also improved our knowledge of the TDAAs' ecological niches, showing that these ant species are ecologically distinct from each other based on their relationships with their supporting trees. Therefore, TDAAs should not systematically be placed in the same functional group even when they belong to the same genus. We conclude by reiterating that, in addition to the role played by TDAAs' territorial competition, host trees contribute to structuring ant mosaics through multiple factors, including host-plant selection by TDAAs, the age of the trees, the presence of extrafloral nectaries, and the taxa of the associated hemipterans.
The Science of Nature 06/2015; 102(5-6):1282. DOI:10.1007/s00114-015-1282-7 · 2.10 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Ants figure prominently among the worst
invasive species because of their enormous ecological
and economic impacts. However, it remains to be
investigated which species would be behaviourally
dominant when confronted with another invasive ant
species, should two species be introduced in the same
area. In the future, many regions might have suitable
environmental conditions for several invasive ant
species, as predicted under climate change scenarios.
Here, we explored interactions among several highly
invasive ant species, which have been shown to have
overlapping suitable areas. The aim of this study was
to evaluate the performance in interference competition
of seven of the world’s worst invasive ant species
(Anoplolepis gracilipes, Paratrechina longicornis,
Myrmica rubra, Linepithema humile, Lasius neglectus,
Wasmannia auropunctata and Pheidole megacephala).
We conducted pairwise confrontations,
testing the behaviour of each species against each of
the six other species (in total 21 dyadic confrontations).
We used single worker confrontations and
group interactions of 10 versus 10 individuals to
establish a dominance hierarchy among these invasive
ant species. We discovered two different behavioural
strategies among these invasive ants: three species
displayed evasive or indifferent behaviour when
individuals or groups were confronted (A. gracilipes,
Pa. longicornis, M. rubra), while the four remaining
species were highly aggressive during encounters and
formed a linear dominance hierarchy. These findings
contrast with the widespread view that invasive ants
form a homogeneous group of species displaying the
‘invasive syndrome’, which includes generally
aggressive behaviour. The dominance hierarchy
among the four aggressive species may be used to
predict the outcome of future competitive interactions
under some circumstances. Yet, the existence of
several behavioural strategies renders such a prediction
[Show abstract][Hide abstract] ABSTRACT: Ants, the most abundant taxa among canopy-dwelling animals in tropical rainforests, are mostly represented by territorially-dominant arboreal ants (TDAs) whose territories are distributed in a mosaic pattern (arboreal ant mosaics). Large TDA colonies regulate insect herbivores, with implications for forestry and agronomy. What generates these mosaics in vegetal formations, which are dynamic, still needs to be better understood. So, from empirical research based on three Cameroonian tree species (Lophira alata, Ochnaceae; Anthocleista vogelii, Gentianaceae; and Barteria fistulosa, Passifloraceae), we used the Self-Organizing Map (SOM, neural network) to illustrate the succession of TDAs as their host trees grow and age. The SOM separated the trees by species and by size for L. alata, which can reach 60 m in height and live several centuries. An ontogenic succession of TDAs from sapling to mature trees is shown, and some ecological traits are highlighted for certain TDAs. Also, because the SOM permits the analysis of data with many zeroes with no effect of outliers on the overall scatterplot distributions, we obtained ecological information on rare species. Finally, the SOM permitted us to show that functional groups cannot be selected at the genus level as congeneric species can have very different ecological niches, something particularly true for Crematogaster spp. which include a species specifically associated with B. fistulosa, non-dominant species and TDAs. Therefore, the SOM permitted the complex relationships between TDAs and their growing host trees to be analyzed, while also providing new information on the ecological traits of the ant species involved. This article is protected by copyright. All rights reserved.
This article is protected by copyright. All rights reserved.
[Show abstract][Hide abstract] ABSTRACT: Myrmecophytism occurs in plants that offer ants a nesting space and, often, food rewards in exchange for protection from predators and competitors. Such biotic protection by ants can, however, interfere with the activity of pollinators leading to potential negative consequences for the plant’s reproduction. In this study, we focused on the association between the understory myrmecophyte, Hirtella physophora (Chrysobalanaceae), and its obligate ant partner, Allomerus decemarticulatus (Myrmicinae). We investigated the reproductive biology of H. physophora and the putative mechanisms that may limit ant–pollinator conflict. Our results show that H. physophora is an obligate outcrosser, self-incompatible, and potentially insect-pollinated species. The reproduction of H. physophora relies entirely on pollen transfer by pollinators that are likely quite specific. Potential interference between flower-visiting insects during pollination may also be lessened by a spatial and temporal segregation of ant and pollinator activities, thus enabling pollen transfer and fruit production.
[Show abstract][Hide abstract] ABSTRACT: In members of the cricket subfamily Eneopterinae (Orthoptera, Grylloidea), songs with powerful high-frequency (HF) harmonics have evolved, which likely represents a distinctive acoustic adaptation. In this study, we analysed or reanalysed the songs of the three eneopterine genera present in the Neotropics to evaluate whether they also possess high-amplitude HF components. We present new data and combine several lines of evidence to interpret or reinterpret the calling signals of a representative species for each genus. We used new recordings in order to detect and analyse potential HF components of the songs. Stridulatory files were measured, and stridulation was studied using high-speed video recordings. The results suggest that all eneopterine genera from the Neotropics use HFs to communicate, based on the rich harmonic content of their songs. Strikingly, the Neotropical eneopterines possess high dominant frequencies, recalling the patterns observed in the tribe Lebinthini, the most speciose tribe of the subfamily distributed in the Western Pacific region and in Southeast Asia: Ligypterus and Ponca show dominant harmonic peaks, whereas Eneoptera possesses unique features. The three species under study, however, deal differently with HFs.
[Show abstract][Hide abstract] ABSTRACT: How species with similar ecological requirements avoid competitive exclusion remains contentious, especially in the species-rich tropics. Niche differentiation has been proposed as a major mechanism for species coexistence. However, different niche dimensions must be studied simultaneously to assess their combined effects on diversity and composition of a community. In most terrestrial ecosystems, ants are among the most abundant and ubiquitous animals. Since they display direct, aggressive competition and often competitively displace subordinate species from resources, niche differentiation may be especially relevant among ants. We studied temporal and trophic niche differentiation in a ground ant community in a forest fragment in French Guiana. Different baits were presented during day and night to assess the temporal and dietary niches of the local species. They represented natural food resources such as sugars, carrion, excrements, seeds, and live prey. In addition, pitfalls provided a background measure of ant diversity. The communities attracted to the different baits significantly differed from each other, and even less attractive baits yielded additional species. We detected species specialized on living grasshoppers, sucrose, seeds, or dead insects. Community-level differences between day and night were larger than those between baits, and many species were temporally specialized. In contrast to commonness, foraging efficiency of species was correlated to food specialization. We conclude that many ant species occupy different temporal or dietary niches. However, for many generalized species, the dietary, and temporal niche differentiation brought forward through our sampling effort, cannot alone explain their coexistence.
[Show abstract][Hide abstract] ABSTRACT: Allomerus ants ensure that they have sufficient nitrogen in their diet by trapping and consuming other insects. In order to construct their traps, like the more extensively studied leaf cutter ants, they employ fungal farming. Pest management within these fungal cultures has been speculated to be due to the ants' usage of actinomycetes capable of producing antifungal compounds, analogous to the leafcutter ant mutualism. Here we report the first identification of a series of antifungal compounds, the filipins, and their associated biosynthetic genes isolated from a bacterium associated with this system.
[Show abstract][Hide abstract] ABSTRACT: Ants (Hymenoptera: Formicidae) represent a taxonomically diverse group of arthropods comprising nearly 13,000 extant species. Sixteen ant subfamilies have individuals that possess a stinger and use their venom for purposes such as a defence against predators, competitors and microbial pathogens, for predation, as well as for social communication. They exhibit a range of activities including antimicrobial, haemolytic, cytolytic, paralytic, insecticidal and pain-producing pharmacologies. While ant venoms are known to be rich in alkaloids and hydrocarbons, ant venoms rich in peptides are becoming more common, yet remain understudied. Recent advances in mass spectrometry techniques have begun to reveal the true complexity of ant venom peptide composition. In the few venoms explored thus far, most peptide toxins appear to occur as small polycationic linear toxins, with antibacterial properties and insecticidal activity. Unlike other venomous animals, a number of ant venoms also contain a range of homodimeric and heterodimeric peptides with one or two interchain disulfide bonds possessing pore-forming, allergenic and paralytic actions. However, ant venoms seem to have only a small number of monomeric disulfide-linked peptides. The present review details the structure and pharmacology of known ant venom peptide toxins and their potential as a source of novel bioinsecticides and therapeutic agents.
[Show abstract][Hide abstract] ABSTRACT: Mutualistic, commensalistic or parasitic interactions are unevenly distributed across the animals and plants: in certain taxa, such interspecific associations evolved more often than in others. Within the ants, associations between species of the genera Camponotus and Crematogaster evolved repeatedly and include trail-sharing associations, where two species share foraging trails, and parabioses, where two species share a nest without aggression. Camponotus and Crematogaster may possess life-history traits that favour the evolution of associations. To identify which traits are affected by the association, we investigated a neotropical parabiosis of Ca. femoratus and Cr. levior and compared it to a paleotropical parabiosis and a trail-sharing association. The two neotropical species showed altered cuticular hydrocarbon profiles compared to non-parabiotic species accompanied by low levels of interspecific aggression. Both species occurred in two chemically distinct types. Camponotus followed artificial trails of Crematogaster pheromones, but not vice versa. The above traits were also found in the paleotropical parabiosis, and the trail-following results match those of the trail-sharing association. In contrast to paleotropical parabioses, however, Camponotus was dominant, had a high foraging activity and often fought against Crematogaster over food resources. We suggest three potential preadaptations for parabiosis. First, Crematogaster uses molecules as trail pheromones, which can be perceived by Camponotus, too. Second, nests of Camponotus are an important benefit to Crematogaster and may create a selection pressure for the latter to tolerate Camponotus. Third, there are parallel, but unusual, shifts in cuticular hydrocarbon profiles between neotropics and paleotropics, and between Camponotus and Crematogaster.
[Show abstract][Hide abstract] ABSTRACT: The rise of integrative taxonomy, a multi-criteria approach used in characterizing species, fosters the development of new tools facilitating species delimitation. Mass spectrometric (MS) analysis of venom peptides from venomous animals has previously been demonstrated to be a valid method for identifying species. Here we aimed to develop a rapid chemotaxonomic tool for identifying ants based on venom peptide mass fingerprinting. The study focused on the biodiversity of ponerine ants (Hymenoptera: Formicidae: Ponerinae) in French Guiana. Initial experiments optimized the use of automated matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) to determine variations in the mass profiles of ant venoms using several MALDI matrices and additives. Data were then analyzed via a hierarchical cluster analysis to classify the venoms of 17 ant species. In addition, phylogenetic relationships were assessed and were highly correlated with methods using DNA sequencing of the mitochondrial gene cytochrome c oxidase subunit 1. By combining a molecular genetics approach with this chemotaxonomic approach, we were able to improve the accuracy of the taxonomic findings to reveal cryptic ant species within species complexes. This chemotaxonomic tool can therefore contribute to more rapid species identification and more accurate taxonomies.
This is the first extensive study concerning the peptide analysis of the venom of both Pachycondyla and Odontomachus ants. We studied the venoms of 17 ant species from French Guiana that permitted us to fine-tune the venom analysis of ponerine ants via MALDI-TOF mass spectrometry. We explored the peptidomes of crude ant venom and demonstrated that venom peptides can be used in the identification of ant species. In addition, the application of this novel chemotaxonomic method combined with a parallel genetic approach using COI sequencing permitted us to reveal the presence of cryptic ants within both the Pachycondyla apicalis and Pachycondyla stigma species complexes. This adds a new dimension to the search for means of exploiting the enormous biodiversity of venomous ants as a source for novel therapeutic drugs or biopesticides.
Journal of proteomics 01/2014; 105. DOI:10.1016/j.jprot.2014.01.009 · 3.89 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Supercolonies of the red fire ant Solenopsis saevissima (Smith) develop in disturbed environments and likely alter the ant community in the native range of the species. For example, in French Guiana only eight ant species were repeatedly noted as nesting in close vicinity to its mounds. Here, we verified if a shared set of biological, ecological and behavioral traits might explain how these eight species are able to nest in the presence of S. saevissima. We did not find this to be the case. We did find, however, that all of them are able to live in disturbed habitats. It is likely that over the course of evolution each of these species acquired the capacity to live syntopically with S. saevissima through its own set of traits, where colony size (four species develop large colonies), cuticular compounds which do not trigger aggressiveness (six species) and submissive behaviors (four species) complement each other.
[Show abstract][Hide abstract] ABSTRACT: We compared the ant assemblages from four very heterogeneous habitats over a short-distance elevational gradient of vegetation (due to the presence of an inselberg) at the Nouragues Research Station, French Guiana. We focused on litter-dwelling ants, combining the use of pitfall traps and the Winkler method according to the Ants of the Leaf Litter Proto-col. This permitted us to note (1) a high leaf-litter ant diversity overall and a decreasing diversity gradient from the lowland rainforest to the top of the inselberg, and (2) differences in species density, composition and functional struc-ture. While the ant assemblages on the plateau and inselberg can be considered functionally similar and typical of an Amazonian rainforest, that of the transition forest, relatively homogenous, rather corresponded to an ant fauna typical of open areas. By contrast, the liana forest assemblage was unexpectedly richer and denser than the others, sheltering a litter-dwelling ant fauna dominated by numerous and abundant cryptic species. These taxonomical and functional dissi-milarities may reflect the influence of the environmental heterogeneity, which, through variable abiotic conditions, can contribute to maintaining a notably rich ant biodiversity in these Neotropical habitats.
[Show abstract][Hide abstract] ABSTRACT: Key evolutionary events associated with invasion success are traditionally thought to occur in the introduced, rather than the native range of species. In the invasive ant Wasmannia auropunctata, however, a shift in reproductive system has been demonstrated within the native range, from the sexual non-dominant populations of natural habitats to the clonal dominant populations of human-modified habitats. Because abiotic conditions of human- modified habitats are hotter and dryer, we performed lab experiments on workers from a set of native and introduced populations, to investigate whether these ecological and genetic transitions were accompanied by a change in thermotolerance and whether such changes occurred before establishment in the introduced range. Thermotolerance levels were higher in native populations from human-modified habitats than in native populations from natural habitats, but were similar in native and introduced populations from human-modified habitats. Differences in thermotolerance could not be accounted for by differences in body size. A scenario based on local adaptation in the native range before introduction in remote areas represents the most parsimonious hypothesis to account for the observed phenotypic pattern. These findings highlight the importance of human land use in explaining major contemporary evolutionary changes.
[Show abstract][Hide abstract] ABSTRACT: Mutualisms, or interactions between species that lead to net fitness benefits for each species involved, are stable and ubiquitous in nature mostly due to "byproduct benefits" stemming from the intrinsic traits of one partner that generate an indirect and positive outcome for the other. Here we verify if myrmecotrophy (where plants obtain nutrients from the refuse of their associated ants) can explain the stability of the tripartite association between the myrmecophyte Hirtella physophora, the ant Allomerus decemarticulatus and an Ascomycota fungus. The plant shelters and provides the ants with extrafloral nectar. The ants protect the plant from herbivores and integrate the fungus into the construction of a trap that they use to capture prey; they also provide the fungus and their host plant with nutrients. During a 9-month field study, we over-provisioned experimental ant colonies with insects, enhancing colony fitness (i.e., more winged females were produced). The rate of partial castration of the host plant, previously demonstrated, was not influenced by the experiment. Experimental plants showed higher δ(15)N values (confirming myrmecotrophy), plus enhanced vegetative growth (e.g., more leaves produced increased the possibility of lodging ants in leaf pouches) and fitness (i.e., more fruits produced and more flowers that matured into fruit). This study highlights the importance of myrmecotrophy on host plant fitness and the stability of ant-myrmecophyte mutualisms.
PLoS ONE 03/2013; 8(3):e59405. DOI:10.1371/journal.pone.0059405 · 3.23 Impact Factor