Sympatric Ants Research Articles

Interference Competition for Mutualism between Ant Species Mediates Ant-Mealybug Associations.

Ant-hemipteran mutualism has been well documented, and many studies have reported the interference competition between ant species for the mutualism. However, little is known on how this interference competition impacts the reciprocally beneficial association. Previous studies demonstrated that the invasive mealybug Phenacoccus solenopsis (Tinsley) has established close mutual relationship with the ghost ant Tapinoma melanocephalum (Fabricius). The sympatric ants, Paratrechina longicornis (Latreille) and Tetramorium bicarinatum (Nylander) were frequently observed to compete for nutrient honeydew produced by P. solenopsis with T. melanocephalum. Herein, we investigated the effects of interference competition between the ant species on the ant-mealybug interactions. Phenacoccus solenopsis benefited from the tending by T. melanocephalum and P. longicornis. Interference competition between T. melanocephalum and P. longicornis interrupted the mutualism, suppressed the trailing activity of both species, but negligibly influenced the parasitism of Aenasius bambawalei Hayat, a solitary endoparasitoid of P. solenopsis. Harmonia axyridis, a predator of P. solenopsis, showed a significant avoidance when encountering with T. melanocephalum or P. longicornis, but not T. bicarinatum. Ant workers showed higher aggressiveness and lower exploratory activity when T. melanocephalum encountered P. longicornis. However, competition between T. melanocephalum and T. bicarinatum seldom influenced the trailing and exploratory activity of T. melanocephalum. It is concluded that interference competition for mutualism between ant species can mediate ant-mealybug associations and the fitness of mealybug colony. Our results also demonstrate that the effects of interference competition between ant species on ant-mealybug mutualism are varied among ant species.

Pyrazine emission by a tropical firefly: An example of chemical aposematism?

AbstractAlthough famous for photic courtship displays, fireflies (Coleoptera: Lampyridae) are also notable for emitting strong odors when molested. The identity of volatile emissions and their possible role, along with photic signals, as aposematic warnings of unpalatability have been little explored, especially in tropical species. Pursuant to the observation that the widespread Neotropical fireflies, Photuris trivittata and Bicellonycha amoena, emit pungent odors, glows, and flashes when handled, we investigated their cuticular and headspace chemistry. Gas chromatography–mass spectrometry analyses revealed that both fireflies have species‐specific cuticular hydrocarbon profiles. Photuris trivittata headspace was dominated by 2‐methoxy‐3‐(1‐methylpropyl) pyrazine (hereafter, pyrazine), on the order of 1.59 ng/individual and a suite of sesquiterpenes, while B. amoena emitted 3‐methoxy‐2‐butenoic acid methyl ester and a few ketones. This is the first report of such compounds in fireflies. We investigated the role of pyrazine in P. trivittata's interactions with potential predators: sympatric ants, toads, and bats. Solvent‐washed P. trivittata painted with pyrazine incurred lower ant predation than did their solvent‐washed counterparts. Pyrazine significantly repelled ants at baits in concentrations as low as 9.8 × 10−4 ng/μl. The toad, Rhinella marina, readily accepted intact fireflies, pyrazine‐coated and uncoated mealworms. Both Myotis nigricans and Molossus molossus bats rejected fireflies, but accepted both pyrazine‐coated and uncoated mealworms. While pyrazine repels ants, its role as an aposematic signal warning other potential predators of firefly distastefulness requires further investigation. Our results underscore the idea that multiple enemies exert conflicting selection on firefly defenses.

Nest distribution varies with dispersal method and familiarity-mediated aggression for two sympatric ants

Dispersal mechanisms and competition together play a key role in the spatial distribution of a population. Species that disperse via fission are likely to experience high levels of localized competitive pressure from conspecifics relative to species that disperse in other ways. Although fission dispersal occurs in many species, its ecological and behavioural effects remain unclear. We compared foraging effort, nest spatial distribution and aggression of two sympatric ant species that differ in reproductive dispersal: Streblognathus peetersi, which disperse by group fission, and Plectroctena mandibularis, which disperse by solitary wingless queens. We found that although both species share space and have similar foraging strategies, they differ in nest distribution and aggressive behaviour. The spatial distribution of S. peetersi nests was extremely aggregated, and workers were less aggressive towards conspecifics from nearby nests than towards distant conspecifics and all heterospecific workers. By contrast, the spatial distribution of P. mandibularis nests was overdispersed, and workers were equally aggressive towards conspecific and heterospecific competitors regardless of nest distance. Finally, laboratory experiments showed that familiarity led to the positive relationship between aggression and nest distance in S. peetersi. While unfamiliar individuals were initially aggressive, the level of aggression decreased within 1 h of contact, and continued to decrease over 24 h. Furthermore, individuals from near nests that were not aggressive could be induced to aggression after prolonged isolation. Overall, these results suggest that low aggression mediated by familiarity could provide benefits for a species with fission reproduction and an aggregated spatial distribution.

Behavioural investigation of trail signals specificity in three sympatric species of Messor ants (Hymenoptera, Formicidae)

Trail signals specificity of three sympatric species of Messor ants (M. capitatus, M. minor, and M. wasmanni) was investigated in the laboratory. Interspecific trail‐following tests showed that workers of each species are able to recognize and follow artificial trails obtained from the Dufour's gland secretions of the others. These results indicate that signals mediating trail‐following behaviour in these harvesting ants are not strictly species‐specific. However, using a series of preference tests, some differences among the species were found. The differences and similarities in trail‐following responses and, ultimately, in the chemical communication system of such sympatric ants are discussed taking into account their ecological implications.

Top-down Control by the Red Imported Fire Ant (Solenopsis invicta)

Top-down control by predaceous insects has rarely been demonstrated in terrestrial communities, but invasive species may be particularly suited to exert such control. The red imported fire ant, Solenopsis invicta, has strong interactions with spiders, other ants and phytophageous insects, and we predicted that it would exert top-down control, cascading to plants in early successional plant communities. In forest gaps in South Carolina, we measured levels of folivory, growth and fecundity for five common herbaceous plant species in plots where ants were present vs. excluded (ant exclusion study) and in plots with varying abundance of fire ants and sympatric ants (ant substitution study). For all plant species in the ant exclusion study, folivory was greater when fire ant abundance was low (P < 0.01). Light levels, spider abundance and herbivore abundance were also related to folivory for some plant species in both studies (P < 0.01). Mean folivory over the growing season was low for all plant species (mean amount of leaf tissue removed for the most-chewed species was 11%). Variation in plant growth and fecundity were not well explained or consistent for any plant species in either study (partial R2 ≤ 0.10 for eight significant variables related to aboveground vegetative biomass and three significant variables related to reproductive biomass). Our results indicated that fire ants are important in determining the level of folivory on early successional plants; however, their top-down influence was not enough to cascade and impact plant growth or fecundity.

Tetraponerine-8, an Alkaloidal Contact Poison in a Neoguinean Pseudomyrmecine Ant, Tetraponera sp.

The sting of the Neoguinean pseudomyrmecine ant, Tetraponera sp. (group punctulata) is modified in a structure resembling a drawing pen. These ants do not sting, but smear upon enemies a contact poison. The venom which originates from the poison gland is a mixture of eight alkaloids with an original tricyclic ring system. The structure of the major component, tetra-ponerine-8, has been determined by X-ray diffraction analysis. The poison of Tetraponera is highly efficient in deterring aggressive sympatric ants and tetraponerine-8 shows toxic properties against Myrmica rubra when applied topically, with a LD50 of 5 × 10-4 mg/mg of ants.

Observations on Mantoida maya (Orthoptera: Mantidae)

The Little Yucatan Mantid, Mantoida maya Saussure and Zehntner, is a small (15 mm) ground-dwelling species native to Florida and Mexico (Blatchley 1920; Helfer, 1953), it appears to be relatively abundant at the Archbold Biological Station (Highlands Co., FL.), though live adult specimens are seldom seen and are apparently most active at night (Hubbell, 1945). Two small, continuously operated Townes traps set up in a dense stand-of sand pine (Pinus clausa Chapman) have captured 198 individuals over a period of 3 years. These capture records indicate that the flight period is concentrated in July and August (196 specimens), and strongly suggest that there is one generation per year. A dramatic decrease in number of individuals in 1985 might be related to very dry conditions in fall of 1984, and winter and spring of 1985. Immature Mantoida maya are difficult to see as they run through surface litter in their usual habitat of dimly lit hammocks and thickets of dense scrub. Immature individuals (Fig. 1) probably derive additional protection from their resemblance to ants and wingless ichneumonids. My work on ants at the Archbold Biological Station has led to occasional encounters with immature M. maya which I have mistaken at a distance of a few f for a novel species of ant. The presumed mimetic features of M. maya are: 1) The reu coloration of the head and thorax, contrasting strongly with the black abdomen, as in the abundant sympatric ants Camponotus abdominalisfioridanus (Buckley) and C. tortuganus Emery; 2) the apically expanded oval abdomen, resembling the gaster of an ant; 3) the white band on the first 2 visible abdominal tergites, reducing the visual impact of the petiole area; 4) the white median band on the antennal flagellum, as in females of many ichneumonids. The immature mantids run in a series of short spurts, the antennae quivering rapidly. The visual contrast between adult and young in this species is far more dramatic than in any other U.S. mantid. It is the only mantid I know in which the shape, color, and behavior is defensively mimetic rather than cryptic.

Defensive Ecology of Forelius Foetidus and Its Chemosystematic Relationship to F. (=Iridomyrmex) pruinosus (Hymenoptera: Formicidae: Dolichoderinae)

The alarm pheromone of southern California populations of the ant Forelius foetidus (Buckley) was identified as 2-heptanone. This compound (2.9µg per worker) occurs in an admixture with cis, trans-iridodial and a minor unidentified iridodial isomer, which together constitute a defensive secretion emitted posteriorly from the gaster. Secretory components were isolated and quantified from extracts by gas chromatography and structurally elucidated by 1H and 13C nuclear magnetic resonance analyses. Videorecordings of agonistic encounters with foreign ants revealed a stereotypical defense behavior of F. foetidus workers culminating in aerial transfer of their secretion onto the heterospecific worker. The defensive spray was repellent but not toxic to either Solenopsis maniosa or Crematogaster califomica Chemical and behavioral comparisons between F. foetidus and F. (=Iridomyrmex) pminosus indicate a high degree of similarity between these sympatric ants and support the generic reclassification of the latter species.

The Tramp Ant Wasmannia auropunctata: Autecology and Effects on Ant Diversity and Distribution on Santa Cruz Island, Galapagos

A large-scale ecological experiment is underway on Santa Cruz Island, Galapagos, where an introduced ant (Wasmannia auropunctata) is devastating all sympatric ants. Collecting, observation, and experiments were used to study the extent and mechanisms of Wasmannia's success. Seventeen taxa of ants were collected, of which four were endemic, and most of the rest were well-known tropical tramp species. Current distribution of all species was determined. Greatest species diversity occurred in the arid zone, which was also the area of lowest Wasmannia density. Systematic collecting-transects showed that Wasmannia either exterminates or reduces to very low density all sympatric species on Santa Cruz. In many areas the ant fauna composition changes from 100 percent Wasmannia to 0 percent Wasmannia within 100 m. Experiments with artificial baits arranged in transects perpendicular to sharp boundaries showed that Wasmannia mobilized the greatest number of workers, was very successful in replacing other species, and remained the longest time at baits. Wasmannia ate primarily invertebrates, honeydew, and, in the hot season, plants parts. It was active 24 hr/day during three 24-hour periods. There were no central, intraspecifically defended nests. Nests were small and numerous. No intraspecific aggression was ever observed, either under natural conditions or at bait stations. Wasmannia density increased with altitude up to near the summit of the island. The species is not presently found in either the driest or wettest parts of Santa Cruz. Currently no ant species occurs on Santa Cruz which can coexist with Wasmannia in zones of high Wasmannia density, Because Wasmannia occurs in high density and consumes a variety of invertebrate prey, it is probably causing major ecosystem changes in invertebrate diversity and density.