Ant Pseudomyrmex Research Articles

Two new ant-mimicking spiders (Araneae: Salticidae) from Costa Rica

During a recent investigation of ant-mimicking arthropods in Costa Rica, two new species of salticid spiders were discovered. Here, I provide descriptions of the two species, Myrmapana costaricaensis sp. nov. and Corcovetella galianoae sp. nov. The former species has two forms; the dark form resembles Neoponera ants, while the light form resembles Pseudomyrmex ants. Corcovetella galianoae resembles Camponotus ants.

Three neotropical bird species shift nest‐site preferences from swollen‐thorn acacias to other sites in human‐altered habitats

AbstractNest location is a decision that presumably affects predation probability, thus, it directly impacts offspring survival. Those locations could be near animals that deter potential nest predators, like acacia ants. We tested whether the preference of three neotropical bird species (Icterus pustulatus, Tolmomyias sulphurescens and Pitangus sulphuratus) for nesting in swollen‐thorn acacias (Vachellia) shifted in human‐modified landscapes. Because natural predators deterred by ant‐defended acacias in protected forest may decrease or be replaced by other predators in human‐modified landscapes, we predicted a potential loss of preference for swollen‐thorn acacias in those landscapes. Swollen‐thorn acacias can be inhabited by defending Pseudomyrmex ants (ant‐defended acacias) or by non‐defending ants (non‐defended acacias). Hence, a preference for nesting on ant‐defended acacias was expected in natural habitats but not in anthropogenic habitats. All three bird species preferred to nest in swollen‐thorn acacias in forests, but only P. sulphuratus showed a preference for ant‐defended acacias. However, this nesting preference of all three species was lost in human‐modified landscapes, where birds switched to large trees, and included utility poles or power lines, although acacias remained a common species. The preference of P. sulphuratus for ant‐defended acacias in the forests was also lost in anthropic areas. The habitat‐dependent shift in preference for nesting trees indicates a potential change in the benefits of tree traits and the selective forces (e.g., predators) at those sites. Our results demonstrate that birds who seem strongly dependent on a tree when studied in natural habitats may shift their preferences in altered habitats.Abstract in Spanish is available with online material.

Friend or Foe? Orb-Weaver Spiders Inhabiting Ant-Acacias Capture Both Herbivorous Insects and Acacia Ant Alates.

The orb-weaver spiders Eustala oblonga (Chickering) and Eustala illicita (O. Picard-Cambridge) (Araneae: Araneidae) inhabit the ant-defended acacias Vachellia melanocerus (Beurling) and Vachellia collinsii (Safford) (Fabales: Fabaceae), respectively, in Panama. These spiders do not capture patrolling Pseudomyrmex ants but exploit their plant-protection services to escape predation. What effect the spiders have on the ant-acacia mutualisms is unknown. They may provide an additional layer of plant defense by capturing flying herbivorous insects in their webs. Alternatively, the spiders may disrupt the ant–acacia mutualisms by capturing alate acacia ants during nuptial flights. We evaluated these two hypotheses by sampling insects flying through acacia foliage and by identifying prey remains in webs. The proportions of insects captured on sticky card traps and in webs varied with taxonomic order and ecological role. Herbivorous insects greatly outnumbered other groups captured on sticky cards and were captured in spiders’ webs in both acacia species but made up a minority of prey remains in webs. Instead, insect predators and parasitoids made up the majority of prey remains and were comprised primarily by alate ant mutualists of the host acacias. These results provide indirect support for both hypotheses and suggest that the spiders potentially both benefit and harm their host ant-acacia mutualisms. The net effect of spider exploitation, however, is unclear and is likely based on both the effectiveness of plant protection from herbivory provided by the spiders relative to that provided by acacia ants, as well as the overall proportion of the ant reproductive caste the spiders actually capture.

ANOTHER ONE BREAKING THROUGH AN ANT PLANT MUTUALISM

Ant-plant mutualistic interactions are common and the degree of specialization varies greatly. Some Pseudomyrmex ants maintain an obligate mutualistic relationship with a group of plants in the genus Vachellia. Ants aggressively defend the resources the plants provide (food and shelter) against a wide range of herbivores and food robbers. A few arthropods successfully overcome the ant’s defense, which allows them to access the resources the plant offers. We here report for the first time extrafloral nectar robbing by Notaulacella octicola Sabrosky, 1994 flies (Chloropidae). These flies congregate in large numbers to feed on extrafloral nectar simultaneously with Pseudomyrmex ants, which seem to defend the nectaries against flies. This report suggests that the extrafloral nectar of Vachellia represents an important food resource for N. octicola, particularly during the dry season when small flowers are scarce.

Genus Pseudolepturges Gilmour (1957) (Coleoptera: Cerambycidae: Lamiinae): a new species from Bolivia, key to the species of the genus and first reports of a possible Pseudomyrmex ant mimic in longhorn beetles

A new species of Pseudolepturges from Bolivia is described and illustrated; a key to the species is also provided. Based on the similar body size, orange-yellowish colour, behaviour, and close co-occurrence on a Triplaris americana tree, we suggest that Pseudolepturges triplarinus sp. nov. is a mimic of the ant Pseudomyrmex triplarinus.http://www.zoobank.org/urn:lsid:zoobank.org:pub:6DF38C64-6986-4A79-8D9A-645DA89149F2

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.

Foliage-dwelling ants in a neotropical savanna: effects of plant and insect exudates on ant communities

Ant dominance in tropical ecosystems can be explained by a capacity to exploit liquid foods such as extrafloral nectaries (EFNs) and secretions from honeydew-producing hemipterans (HPHs). Such nutritious exudates may determine ant distribution in space and shape specialization in ant–plant interactions. We provide a first assessment of how EFNs and HPHs mediate the structure of ant assemblages, ant visitation intensity, and characteristics of ant–plant interaction networks across space in Brazilian “cerrado” savanna. We used arboreal pitfall traps to sample visiting ants in four cerrado localities and recorded the presence of lepidopteran larvae to determine their possible response to ant visitation. Ant species composition and richness did not differ regardless of the presence of liquid rewards on plants, and most network patterns did not show consistent differences. However, in two of the four sites, ant densities were higher on plants with HPHs or EFNs due to increased activity by Camponotus and Pseudomyrmex ants. At these two sites, plants with liquid food sources had a more specific ant assemblage (higher specialization d′) than did plants without resources, and caterpillars were more frequently found on plants with fewer workers of Camponotus and Pseudomyrmex. Plants with HPHs had increased ant visitation and accumulated more ant species than did plants with EFNs or without liquid foods. Ant response to such food sources may thus depend on local conditions and identity of ant species, and may determine how ant assemblages are structured. Results highlight how different patterns of ant visitation to liquid resources can produce distinctive effects on herbivore infestation.

Establishing an ant-plant mutualism: foundress queen mortality and acquiring the third partner

In the Neotropics, colonies of the ant Pseudomyrmex dendroicus are found in the hollow stems of Triplaris americana. The ants are obligate inhabitants of the ant-plant and they nest and reproduce exclusively in this myrmecophyte. However, this mutualistic association often involves a third partner, scale insects (Coccoidea, Hemiptera). Established colonies of this ant are always associated with scale insects and ants appear to be dependent on the honeydew excretions of their trophobionts. Acquisition of scale insects is therefore an important step in the successful establishment of a new colony. Domatia of juvenile host-plants were dissected to determine (1) how colonies are founded, (2) if there was evidence of co-dispersal between trophobionts and foundress queens. Colony foundation is claustral. Founding queens of Pseudomyrmex chew their entrance holes at the prostoma and then close the hole with debris. 104 queens were located with few or no workers. Of the 104 foundresses, 69 were found dead and only 32 had at least a single trophobiont. Although the association with trophobionts may prove vital to the establishment of the colony, these results indicate that scale insects do not seem to co-disperse with the foundress queens.

Tree size but not forest basal area influences ant colony response to disturbance in a neotropical ant–plant association

Ant–acacia mutualisms are conspicuous biotic associations in Savannah and neotropical ecosystems; however, the effects of tree size and forest structure on ant behaviour and tree traits are rarely examined. We tested two hypotheses related to these effects: (1) ant responses to disturbance are influenced by tree size and forest basal area; and (2) tree traits important to ants are predictable by tree size and forest basal area. We investigated these hypotheses in a dry tropical forest (Ometepe Island, Nicaragua) with the myrmecophytic Collins acacia ( Vachellia collinsii Saff.) and the ant Pseudomyrmex spinicola (Emery 1890). We measured trees from three size classes and three basal area classes and quantified resources that are important for ants, including food resources (nectaries and Beltian bodies) and domiciles (thorns), as well as a measure of potential tree reproductive fitness (seedpods). We also evaluated ant responses to experimental disturbances. Three important findings emerged: (1) on average, 1140–1173% more ants responded to experimental disturbances of large trees than small- or intermediate-sized trees, respectively; (2) forest basal area did not affect ant responses to disturbance; and (3) neither tree size nor forest basal area was correlated with branch-level mean numbers of nectaries, food bodies or thorns. Our studies support the hypothesis that tree size is an important factor regarding ant behavioural responses to disturbance, but not forest basal area. Our work suggests that future studies of ant behaviour on myrmecophytes should consider tree size.

Contraste en la eficiencia defensiva de dos especies de hormigas del género Pseudomyrmex sobre plantas de Acacia cornigera (Parte III)

One of the most emblematic mutualistic interactions in the Neotropics is that between Acacia plants and Pseudomyrmex ants. In his first studies, D. H. JANZEN (1969) related the functional defensive system by the ants to allelopathic chemical agents, thus this system can be associated to induced defensive systems. Our study system, the interaction between Acacia cornigera and two Pseudomyrmex species (P. gracilis and P. ferrugineus), includes ant colonization patterns and plant behavior after colonization. Previous research on ant defensive roles had mentioned that P. ferrugineus was a good defensive system for Acacia plants, and that P. gracilis was a so-called parasite of the system. Here we suggest that the subsistence mechanism between the two ant species is based on chemical products, clear postdamage signals which, are intrinsic to the plant and promote recruitment and defense by the two species of Pseudomyrmex.

Plant-Inhabiting Ant Utilizes Chemical Cues for Host Discrimination

The Neotropical ant Pseudomyrmex triplarinus is involved in an obligate and complex symbiotic association with Triplaris americana trees. The ants inhabit trunk and branch domatia and respond aggressively to foreign invaders. Their degree of host specificity and basis for recognition of host trees has not been studied. We determined that, in contrast to T. americana seedlings, heterospecific seedlings set around the host trees suffered continuous pruning. Ants also removed 80–100 percent of heterospecific leaves attached to the trunk in contrast to only 10–30 percent of conspecific leaves. True species specificity was demonstrated by the selective removal of leaves from Triplaris poeppigiana pinned to host trees. This selectivity was also observed in a matrix-independent bioassay using leaf cuticular extracts on glass microfiber strips. Strips treated with leaf wax extracts from host trees and pinned to the trunk of host trees received only 42 percent of the number of ant visits recorded on solvent-treated controls by the end of the experiment. Strips treated with extracts of a related species, T. poeppigiana, received 64 percent of the number of ant visits compared with solvent-treated controls. These experiments also suggest that P. triplarinus recognizes surface chemicals of their host tree, independent of the texture or architecture of the carrier material; although these factors may still play some role in recognition. This is the first study that we are aware of to investigate the mechanism of host discrimination related to pruning behavior. Abstract in Spanish is available at http://www.blackwell-synergy.com/loi/btp.

La fuerza del amor en el Neotrópico: contraste en la eficiencia defensiva de dos especies de hormigas del género Pseudomyrmex sobre plantas de Acacia cornigera. (Parte II)

Extensive research conducted so far suggests that the physiological functionality of myrmecophilous Acacia and Pseudomyrmex ants have evolved through a coevolutionay process. This is one of the most recognized myrmecophilous interactions present in the Neotropics. In our system of A. cornigera and the ant P. ferrugineus and P. gracilis, we first reported a neighborhood effect in the colonization of plants by both ant species, a higher proportion of colonization and larger host plants colonized by P. ferrugineus. However, which is the function of P. gracilis, in classic terms of anti-herbivory, were the two ant species Pseudomyrmex equally efficient in defending their Acacias? A first level of observation is based on an index of herbivory per plant. We also used simulated herbivory and found that P. ferrugineus is more efficient, when present on plants less damage is caused by herbivores, and ants were recruited faster in the presence of a potential herbivore. LARS et al. (2008) suggested that the coexistence of both species and especially the persistence of P. gracilis on a similar system whit Acacia hindsii is because they have fast-growing, low-density colonies, suggesting reproductive winged forms as an r - strategy. However, these authors are not including chemical stimuli, only visual or physical stimuli, so which other mechanisms promote the interaction of P. gracilis with Acacia cornigera. We will find out in the next part (part III).

Pseudomyrmex ants and acacia host plants join efforts to protect their mutualism from microbial threats

Plants express numerous ‘pathogenesis-related’ (PR) proteins to defend themselves against pathogen infection. We recently discovered that PR-proteins such as chitinases, glucanases, peroxidases and thaumatin-like proteins are also functioning in the protection of extrafloral nectar (EFN) of Mexican Acacia myrmecophytes. These plants produce EFN, cellular food bodies and nesting space to house defending ant species of the genus Pseudomyrmex. More than 50 PR-proteins were discovered in this EFN and bioassays demonstrated that they actively can inhibit the growth of fungi and other phytopathogens. Although the plants can, thus, express PR-proteins and secrete them into the nectar, the leaves of these plants exhibit reduced activities of chitinases as compared to non-myrmecophytic plants and their antimicrobial protection depends on the mutualistic ants. When we deprived plants of their resident ants we observed higher microbial loads in the leaves and even in the tissue of the nectaries, as compared to plants that were inhabited by ants. The indirect defence that is achieved through an ant-plant mutualism can protect plants also from infections. Future studies will have to investigate the chemical nature of this mechanism in order to understand why plants depend on ants for their antimicrobial defence.

The Triplaria tree (Triplaris spp) and Pseudomyrmex ants: a symbiotic relationship with risks of attack for humans

The authors report a massive attack by Pseudomyrmex ants on a human who touched a Triplaria - novice tree (Triplaris spp). The ants naturally live in these trees and their stings cause intense pain and discrete to moderate local inflammation. The problem is common in some Brazilian regions and can be prevented by identifying the trees.

Polymerase chain reaction primers for polymorphic microsatellite loci in the ant Pseudomyrmex gracilis (Formicidae: Pseudomyrmecinae)

The elongate twig ant Pseudomyrmex gracilis is widely distributed in the New World ranging from southern USA to Brazil and northern Argentina. To investigate its within-colony relatedness, we developed primers for nine polymorphic microsatellite loci. High levels of within-population variation were observed, with number of alleles ranging from two to 13, and heterozygosity from 0.28 to 0.90. The loci showed no deviations from Hardy-Weinberg equilibrium and no linkage disequilibrium.

Strategies of a parasite of the ant–Acacia mutualism

Mutualisms can be exploited by parasites—species that obtain resources from a partner but provide no services. Though the stability of mutualisms in the presence of such parasites is under intensive investigation, we have little information on life history traits that allow a species to be a successful mutualist or rather a parasite, particularly in cases where both are closely related. We studied the exploitation of Acacia myrmecophytes by the ant, Pseudomyrmex gracilis, contrasting with the mutualistic ant Pseudomyrmex ferrugineus. P. gracilis showed no host-defending behavior and had a negative effect on plant growth. By preventing the mutualist from colonization, P. gracilis imposes opportunity costs on the host plant. P. gracilis produced smaller colonies with a higher proportion of alates than did the mutualist and thus showed an “r-like” strategy. This appears to be possible because P. gracilis relies less on host-derived food resources than does the mutualist, as shown by behavioral and stable isotope studies. We discuss how this system allows the identification of strategies that characterize parasites of mutualisms.

Elongate Twig Ant, Mexican Twig Ant (suggested common names), Pseudomyrmes gracilis (Fabricius) (Insecta: Hymenoptera: Formicidae: Pseudomyrmecinae)

EENY-418, a 5-page illustrated fact sheet by Patricia L. Toth, is part of the Featured Creatures collection. It describes this neotropical, arboreal ant best known for its associations with plants and its terrible sting, its synonymy, distribution, description, life cycle, nests, hosts, damage, and management. Includes selected references. Published by the UF Department of Entomology and Nematology, September 2007. EENY-418/IN752: Slender Twig Ant Pseudomyrmex gracilis (Fabricius) (Insecta: Hymenoptera: Formicidae: Pseudomyrmecinae) (ufl.edu)

Look before leaping: foraging selectivity of capuchin monkeys on acacia trees in Costa Rica

Acacia trees in Costa Rica have an obligate mutualism with three species of Pseudomyrmex ants, which vigorously defend their host tree from insect and mammalian herbivores. Depending on the size and species of ant colony, individual acacia trees may be differentially protected. For animals able to discern between weakly and highly aggressive ant colonies, costs of ant stings from less active colonies might be offset by nutritional value acquired from feeding on acacia fruit or ant larvae in swollen thorns. We examined foraging selectivity of capuchin monkeys on acacia trees in Santa Rosa National Park, Costa Rica. We measured four characteristics of the acacia trees from which capuchins fed and of acacias immediately adjacent to those in which the monkeys fed: diameter at breast height (DBH), accessibility, species of closest tree and ant species present. We found that capuchins prefer to forage in acacias that are large and accessible. We also made two measurements of ant colony activity on each tree, one before and one after disturbing the ant colony. We found that the three species of mutualistic ants differ in baseline activity levels and that mutualistic ants are more active than non-mutualistic ant species found in acacia trees. We also found that capuchins foraged more frequently in trees colonized by non-mutualistic ants, but the explanatory value (r (2)) of this model was low. Furthermore, monkeys did not discriminate between acacias on the basis of baseline ant activity or the ant colony's response to disturbance. We conclude that these monkeys select acacia trees in which to forage based on characteristics of the trees rather than the ants. In addition, our study suggests that white-faced capuchins act as predators on the acacia ants but they probably benefit the dispersal and reproductive success of acacia trees. Capuchins may in fact function as an additional mutualistic partner for acacia trees via seed dispersal, but they must overcome the ants' defense of the trees to do so.

Why are there few seedlings beneath the myrmecophyte Triplaris americana?

We compared the relative importance of chemical alellopathy, pruning behaviour of resident ants and other non-related agents to ant-plant mutualism for seedling establishment beneath Triplaris americana L. (Polygonaceae), a myrmecophyte plant. We also included a preliminary analysis of effects of fragmentation on these ecological processes. Seeds and seedlings of Theobroma cacao L. (Sterculiaceae) were used as the target species in all experiments. Leaf-tissue extracts of the myrmecophyte plant did not inhibit germination of cacao seeds. Resident Pseudomyrmex triplarinus Weddell (Pseudomyrmecinae) ants did not remove seeds under the canopy of their host plants. The main seed consumer was the leaf-cutting ant Atta sexdens L. (Myrmicinae). Leaves of cacao seedlings were partially or totally pruned by Pseudomyrmex ants mainly in forest fragments studied. We offer evidence pointing to the possibility that the absence of seedlings beneath Triplaris may result from effects of both ant species. We discuss the benefits of pruning behaviour for the resident ant colony and the effects of ant–ant interactions on seedling establishment beneath this ant-plant system.

Guards and thieves: antagonistic interactions between two ant species coexisting on the same ant‐plant

Abstract. 1. The simultaneous occupation of a rare understorey ant‐acacia Acacia mayana by its guarding ant Pseudomyrmex ferrugineus, and an apparent opportunist parasite of the mutualism, the generalist ant Camponotus planatus is described. The two ant species occur together in 30.7% of the 26 mature A. mayana plants [23.5% of all trees (n = 34)] surveyed, but C. planatus is absent from saplings below 1 m in height (n = 8).2. While P. ferrugineus shows behaviour compatible with effective host‐tree defence, C. planatus does not attack phytophagous insects and appears ineffective as an ant‐guard. Camponotus planatus does, however, occupy swollen thorns (pseudogalls) on the host tree, and harvests nectar from extrafloral leaf nectaries. It is proposed that C. planatus is a parasite of the Acacia–Pseudomyrmex mutualism.3. Camponotus planatus does not harvest the second trophic reward produced by the tree for its Pseudomyrmex ant‐guards, protein‐rich food (Beltian) bodies. Camponotus planatus lack the specialised larval adaptations needed to use Beltian bodies as brood food, suggesting that this resource is potentially more resistant to exploitation by generalists than extrafloral nectar.4. In competition for access to nectaries, C. planatus effectively displaced P. ferrugineus in 99.8% of encounters. These results suggest not only that C. planatus is a parasite of this mutualism, but also that it is able to effectively counteract the aggression shown to other insects by the resident ant‐guards.