Isolation and characterization of microsatellite markers from the acacia-ant Crematogaster mimosae

We describe 10 microsatellite loci developed from Crematogaster mimosae, an ant species that nests mutualistically in Acacia drepanolobium trees in east Africa. Polymorphism ranged from 4 to 16 alleles per locus (mean = 7.3). Observed and expected heterozygosities ranged from 0.485 to 0.813 (mean 0.626), and from 0.502 to 0.894 (mean 0.674), respectively. These markers will foster studies of the population structure, colony structure, and reproductive strategies of these ants.     

Spatial patterns of the ant Crematogaster scutellaris in a model ecosystem

1. The spatial arrangement of individuals and populations may have deep influences on all the biotic interactions within a community. 2. The spatial distribution of nests of the ant Crematogaster scutellaris Olivier was analysed in an olive orchard in central Italy. As this species nests inside tree trunks, the regular structure of this simplified ecosystem may help to reduce the confounding effect of habitat heterogeneity on the spatial distribution of nests. In total, 531 trees were mapped and their shape (size and structure of the trunk) recorded. The presence of C. scutellaris nests in each tree was assessed in spring–summer and autumn 2006 and 2007. 3. The number of occupied trees changed in time, from a maximum of 129 (summer 2006) to a minimum of 60 (autumn 2007). Occupancy of tree was related to its shape, with larger trees being more frequently and more steadily occupied than smaller ones. 4. Nests were spatially aggregated, forming well‐defined clusters, but aggregation was not explained by a corresponding clumping of larger trees. Nests belonging to the same cluster were usually not aggressive to each other, whereas aggression was more common between nests belonging to different clusters. The dynamic nature of the system coupled with the clustered distribution of nests, is consistent with a hypothesis of seasonal polydomy, and suggest that whereas some trees are steadily occupied (core) others are opportunistically colonised when new resources are discovered (satellites). 5. Clusters size distribution was shown to follow a truncated power‐law, a finding consistent with the idea that clusters are self‐organised structures dependent on local interactions. These results suggest that spatial self‐organisation in ant colonies may in principle be more common than previously thought, although the mechanisms generating these patterns still need to be clarified.     

The Rules of Aggression: How Genetic,Chemical and Spatial Factors Affect Intercolony Fights in a Dominant Species,the Mediterranean Acrobat Ant Crematogaster scutellaris

Nest-mate recognition plays a key role in the biology of ants. Although individuals coming from a foreign nest are, in most cases, promptly rejected, the degree of aggressiveness towards non nest-mates may be highly variable among species and relies on genetic, chemical and environmental factors. We analyzed intraspecific relationships among neighboring colonies of the dominant Mediterranean acrobat ant Crematogaster scutellaris integrating genetic, chemical and behavioral analyses. Colony structure, parental relationships between nests, cuticular hydrocarbons profiles (CHCs) and aggressive behavior against non nest-mates were studied in 34 nests located in olive tree trunks. Bayesian clustering analysis of allelic variation at nine species-specific microsatellite DNA markers pooled nests into 14 distinct clusters, each representing a single colony, confirming a polydomous arrangement of nests in this species. A marked genetic separation among colonies was also detected, probably due to long distance dispersion of queens and males during nuptial flights. CHCs profiles varied significantly among colonies and between nests of the same colony. No relationship between CHCs profiles and genetic distances was detected. The level of aggressiveness between colonies was inversely related to chemical and spatial distance, suggesting a ‘nasty neighbor’ effect. Our findings also suggest that CHCs profiles in C. scutellaris may be linked to external environmental factors rather than genetic relationships.     

Behavioural and chemical mechanisms behind a Mediterranean ant–ant association

1. Interspecific competition among ants is common, and so is competitive exclusion among dominant ant species. In contrast, specific associations between non‐parasitic ant species are rare, especially in the temperate zones. As an exception, the subordinate ant Camponotus lateralis frequently co‐occurs with the dominant Crematogaster scutellaris but rarely with other dominant ants. 2. This association is one of various associations between Camponotus and Crematogaster species across the world. However, the mechanisms behind these co‐occurences are largely unknown. 3. In the present study, we therefore investigated the association of Ca. lateralis and Cr. scutellaris. We studied the spatial association of the nests, interspecific aggression, both species' cuticular hydrocarbon profiles, and their propensity to follow the other species' pheromone trails. 4. Crematogaster scutellaris usually attacked and displaced the generally submissive Ca. lateralis, but was significantly less aggressive at jointly used trails. Camponotus nests were always in close proximity to Crematogaster nests. 5. The cuticular hydrocarbons of both species consisted of alkanes with chain lengths between C21 and C35. The two species had 25 hydrocarbons in common, including mono‐, di‐, and tetramethyl alkanes. Despite this qualitative similarity, however, the quantitative hydrocarbon composition differed between the two species. 6. Camponotus lateralis followed artificial trails containing trail pheromones of Cr. scutellaris, but the latter did not follow Ca. lateralis trail pheromones. Interspecific trail‐following by Camponotus, but not vice versa, has been observed in another Camponotus–Crematogaster association and may be a more general mechanism that facilitates associations between the two ant genera.     

Behavioural Interactions Between <Emphasis Type="Italic">Crematogaster brevispinosa rochai</Emphasis> Forel (Hymenoptera: Formicidae) and Two <Emphasis Type="Italic">Nasutitermes</Emphasis> Species (Isoptera: Termitidae)

In the savanna-like Brazilian biome caatinga, the arboreal and polydomous ant Crematogaster brevispinosa rochai can be found cohabiting with two closely related Nasutitermes species (N. corniger and N. ephratae). This ant occupies variably sized portions of the termite nests and maintains a physical separation with its hosts by plugging the cells of the boundary areas with fibrous material. Although all the analysed cohabiting C. b. rochai nests were queenless, they always contained brood, especially from male and female reproductive castes. Interaction experiments between workers of C. b. rochai and workers or soldiers of N. ephratae revealed a low level of aggressiveness between the two species that contrasts with the aggressiveness of both C. b. rochai and N. ephratae in encounters with other ant (Azteca cf. chartifex, Cephalotes pusillus) or termite (M. cf. indistinctus) species. The association could benefit both ants (additional nesting sites, brood rearing places) and termites (protection against predators, dead ants or ant refuses as source of nitrogen).     

Crematogaster chiarinii ants as a potential biological control agent for protecting honeybee colonies from attack by Dorylus quadratus driver ants in Ethiopia (Hymenoptera: Formicidae)

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A reassessment of the relations in Malaysia between ants (Crematogaster) on trees (Leptospermum and Dacrydium) and epiphytes of the genus Dischidia (Asclepiadaceae) including 'ant-plants'

Three species of epiphytic Dischidia have been investigated in terms of their relationship to ants on trees. Two species, D. parvifolia and D. astephana , are associated with ants and trees in montane areas. A clear association has been found between ants of the genus Crematogaster and the tree Leptospermum flavescens. This relationship is complex and probably both organisms benefit from the association. The ants live in tunnels in the wood of the major branches and the trunk, and the entire tree is occupied by one ant colony. Trees occupied by ants are maintained by the ants substantially clear of epiphytes other than the two species of Dischidia. The potential benefits to the tree and to the ants of this association are noted. The roots of D. astephana and D. parvifolia penetrate into the cavities of these ant nests and presumably gain nutrients from waste in the ant nests. Both Dischidia species are effectively scavenging upon the waste material from the ant-tree association. The leathery dome-shaped leaves of D. astephana are not vital to the development of the scavenging habit as D. parvifolia has lens-shaped leaves, but may offer some advantage to D. astephana by the uptake of nutrients from waste deposited by the ants under the dome-shaped leaves by interception of stem flow and by uptake of gaseous waste. Ants do not nest under these leaves. Seeds of these species of Dischidia are taken by ants into the central woody area of the ant nest where they germinate. Both Leptospermum and Dischidia can be visualized as showing adaptations to a nutient-deficient tropical montane environment. These adaptations are discussed as is the need for reassessment in this genus of the term 'ant-plant', and the need for wider recognition of the 1ant-tree' relationship between Crematogaster and Leptospermum.     

Predation by ants controls swallow bug (Hemiptera: Cimicidae: Oeciacus vicarius) infestations

The swallow bug (Oeciacus vicarius) is the only known vector for Buggy Creek virus (BCRV), an alphavirus that circulates in cliff swallows (Petrochelidon pyrrhonota) and house sparrows (Passer domesticus) in North America. We discovered ants (Crematogaster lineolata and Formica spp.) preying on swallow bugs at cliff swallow colonies in western Nebraska, U.S.A. Ants reduced the numbers of visible bugs on active swallow nests by 74‐90%, relative to nests in the same colony without ants. Ant predation on bugs had no effect on the reproductive success of cliff swallows inhabiting the nests where ants foraged. Ants represent an effective and presumably benign way of controlling swallow bugs at nests in some colonies. They may constitute an alternative to insecticide use at sites where ecologists wish to remove the effects of swallow bugs on cliff swallows or house sparrows. By reducing bug numbers, ant presence may also lessen BCRV transmission at the spatial foci (bird colony sites) where epizootics occur. The effect of ants on swallow bugs should be accounted for in studying variation among sites in vector abundance.     

Application of CO2 carbon stable isotope analysis to ant trophic ecology

Stable isotope analysis of animal tissues is commonly used to infer diet and trophic position. However, it requires destructive sampling. The analysis of carbon isotopes from exhaled CO₂ is non-invasive and can provide useful ecological information because isotopic CO₂ signatures can reflect the diet and metabolism of an animal. However, this methodology has rarely been used on invertebrates and never on social insects. Here, we first tested whether this method reflects differences in δ¹³C-CO₂ between workers of the Mediterranean ant Crematogaster scutellaris (Olivier) (Hymenoptera: Formicidae, Crematogastrini) fed with sugar from beet (C3; Beta vulgaris L., Amaranthaceae) or cane (C4; Saccharum officinarum L., Poaceae). We found that a significant difference can be obtained after 24 h. Consequently, we used this technique on wild co-occurring ant species with different feeding preferences to assess their reliance on C3 or C4 sources. For this purpose, we sampled workers of C. scutellaris, the invasive garden ant Lasius neglectus (van Loon et al.) (Lasiini), and the harvester ant Messor capitatus (Latreille) (Stenammini). No significant differences in their carbon isotopic signatures were recorded, suggesting that in our study site no niche partitioning occurs based on the carbon pathway, with all species sharing similar resources. However, further analysis revealed that M. capitatus, a seed-eating ant, can be regarded as a C3 specialist, whereas L. neglectus and C. scutellaris are generalists that rely on both C3 and C4 pathways, though with a preference for the former. Our results show that this methodology can be applied even to small animals such as ants and can provide useful information on the diets of generalist omnivores.     

Predatory Behavior in Dominant Arboreal Ant Species: The Case of Crematogaster sp. (Hymenoptera: Formicidae)

Crematogaster sp. is a dominant arboreal ant species that captures and retrieves very large prey. Hunting workers forage collectively thanks to short-range recruitment. They detect prey by contact, then rapidly attack, seizing small prey by the body and large prey by a leg. In this study, almost all the active prey were spread-eagled by several workers, even when small enough to permit a single worker to easily master them. While certain workers spread-eagled the prey, others deposited venom on the prey body using their spatulated sting (topical action of the venom). The well-developed arolia on the pretarsus of workers' legs have crucial importance for the success of prey capture (spread-eagling) and transport in an arboreal habitat. These results are compared with those known for other arboreal-dwelling generalist predator ant species.     

Studies of a South East Asian ant-plant association: protection of Macaranga trees by Crematogaster borneensis

Summary In the humid tropics of SE Asia there are some 14 myrmecophytic species of the pioneer tree genus Macaranga (Euphorbiaceae). In Peninsular Malaysia a close association exists between the trees and the small, non-stinging myrmicine Crematogaster borneensis. These ants feed mainly on food bodies provided by the plants and have their colonies inside the hollow internodes. In a ten months field study we were able to demonstrate for four Macaranga species (M. triloba, M. hypoleuca, M. hosei, M. hulletti) that host plants also benefit considerably from ant-occupation. Ants do not contribute to the nutrient demands of their host plant, they do, however, protect it against herbivores and plant competition. Cleaning behaviour of the ants results in the removal of potential hervivores already in their earliest developmental stages. Strong aggressiveness and a mass recruiting system enable the ants to defend the host plant against many herbivorous insects. This results in a significant decrease in leaf damage due to herbivores on ant-occupied compared to ant-free myrmecophytes as well as compared to non-myrmecophytic Macaranga species. Most important is the ants' defense of the host plant against plant competitors, especially vines, which are abundant in the well-lit pioneer habitats where Macaranga grows. Ants bite off any foreign plant part coming into contact with their host plant. Both ant-free myrmecophytes and non-myrmecophytic Macaranga species had a significantly higher incidence of vine growth than specimens with active ant colonies. This may be a factor of considerable importance allowing Macaranga plants to grow at sites of strongest competition.     

Polymorphic microsatellite loci for the ant-garden ant, Crematogaster levior (Forel)

Throughout Amazonia, the ant Crematogaster levior is known for its participation in a complex ant-garden mutualism with the ant Camponotus femoratus and several species of epiphytic plants for which it plays an important role in seed viability. We isolated nine polymorphic microsatellite loci for C. levior from a genomic library enriched for di-, tri-, and tetra-nucleotide repeats. Two to 14 alleles were detected per locus, with levels of observed heterozygosity ranging from 0.103 to 0.785.     

Not all ants are equal: obligate acacia ants provide different levels of protection against mega‐herbivores

In obligate ant–plant mutualisms, the asymmetric engagement of a single plant species with multiple ant species provides the opportunity for partners to vary in their behaviour. Variation in behaviour has implications for the interactions with third‐party species such as herbivores. This study assessed the effect of obligate ant‐mutualists (Crematogaster mimosae, Crematogaster nigriceps and Tetraponera penzigi) inhabiting the African ant‐acacia (Acacia drepanolobium) on three mega‐herbivore browsers: the Maasai giraffe (Giraffa camelopardalis tippelskirchi), the reticulated giraffe (Giraffa c. reticulata) and the black rhino (Diceros bicornis). Giraffes are abundant and wide‐ranging herbivores of the acacias, whereas black rhinos are localized and perennial herbivores of the acacias. Multiyear field studies comparing the ants’ aggressive behaviour and browsing by mega‐herbivores suggested differences between the tending abilities of the primary ant species inhabiting A. drepanolobium. Trees occupied by the aggressive ant species C. mimosae had significantly less browsing by giraffes and black rhino than trees occupied by other ant species. The results of this study provide evidence that ant‐mutualists on African acacias can serve as deterrents to mega‐herbivores and that different ant species vary in their tending abilities.     

Parasitism <Emphasis Type="Italic">versus</Emphasis> mutualism in the ant-garden parabiosis between <Emphasis Type="Italic">Camponotus femoratus</Emphasis> and <Emphasis Type="Italic">Crematogaster levior</Emphasis>

Ant-gardens represent a special type of association between ants and epiphytes. Frequently, two ant species can share the same nest in a phenomenon known as ‘parabiosis’, but the exact nature (i.e., mutualistic or parasitic) of this interaction is the subject of debate. We thus attempted to clarify the mutual costs and benefits for each partner (ants and plants) in the Crematogaster levior/Camponotus femoratus ant-garden parabiosis. The ants’ response to experimental foliar damage to the epiphytes and to the host tree as well as their behavior and interactions during prey capture were investigated to see if the purported parasitic status of Cr. levior could be demonstrated in either the ant-ant or in the ant-plant interactions. The results show that both species take part in protecting the epiphytes, refuting the role of Cr. levior as a parasite of the ant-garden mutualism. During capture of large prey Ca. femoratus took advantage from the ability of Cr. levior to discover prey; by following Cr. levior trails Ca. femoratus workers discover the prey in turn and usurp them during agonistic interactions. Nevertheless, the trade-off between the costs and benefits of this association seems then to be favorable to both species because it is known that Cr. levior benefits from Ca. femoratus building the common carton nests and furnishing protection from vertebrates. Consequently, parabiosis can then be defined as the only mutualistic association existing between ant species, at least in ant-gardens. Received 31 August 2006 ; revised 8 December 2006 ; accepted 12 December 2006     

Courtship Behaviour and Mating in Two Cow Dung Inhabiting Sphaerocerid Flies (Diptera: Sphaeroceridae)

Adults and larvae of Coproica lugubris and Chaetopodella scutellaris (Diptera: Sphaeroceridae) occur in great numbers on cow droppings. Courtship behaviour and copulation were analyzed and compared. Striking differences were found in the complexity and number of courtship patterns. In contrast to C. lugubris, where males usually mount females without performing any displays, courtship of Ch. scutellaris is rather complex: a male approaches a female and positions himself facing her; he then starts to circle her in a fashion very similar to a male courtship pattern in Drosophila species. Females usually respond to circling with a typical behaviour pattern I called swaying. Its function is discussed. The complex courtship behaviour of Ch. scutellaris is interpreted as a mechanism for female choice. In Ch. scutellaris copulation takes about 60 min longer than in C. lugubris, but the mechanism based upon this obvious difference is not understood. Females of both species can effectively prevent males from copulating.     

Successional patterns of the insect fauna on a pig carcass in southern Italy and the role of Crematogaster scutellaris (Hymenoptera,Formicidae) as a carrion invader

The sarcosaprophagous fauna plays a key role in organic matter decomposition. Moreover, the biological, ecological and behavioral specificities of the taxa are useful to reconstruct the decay history of a corpse or carcass, often back to the lethal event. Here we report the seasonal succession of the insect fauna on a pig carcass exposed in a rural area in Calabria (southern Italy) during summer 2007 and 2008. The aim is to identify and qualitatively assess the major taxa of forensic importance in this region. The principal fly invaders were Lucilia caesar (L.), L. sericata (Meigen, 1826), Chrysomya albiceps (Wiedemann, 1819), Sarcophaga (Meigen, 1826) spp. and Amobia (Robineau‐Desvoidy, 1830) spp., Musca domestica (L.) and Muscina stabulans (Fallen, 1817). The primary beetle species collected in summer belonged to Dermestidae, Dermestes maculatus (De Geer, 1774) and Cleridae, Necrobia rufipes (De Geer, 1775). This paper also examined the ecological role of ants in the insect succession and describes the evidence of skin injuries directly inflicted by the acrobat ant Crematogaster (Acrocoelia) scutellaris (Olivier, 1791) (Hymenoptera Formicidae) while feeding on pig carrion. Ants belonging to two other species were also collected: Camponotus aethiops (Latreille, 1798) and Tetramorium semilaeve (André, 1881). Ants can invade carcasses and corpses directly, disrupting blowfly egg laying or preying on their larvae. Our data on the carrion faunal composition and role of ants as invaders should be useful for further forensic cases in Calabria (southern Italy). This is among the few reports of ants as forensically relevant species.     

Description and DNA barcoding of Crematogaster fraxatrix Forel, 1911 and two new closely related species from Cambodia and Indonesia (Hymenoptera,Formicidae)

Crematogaster fraxatrix Forel, 1911 and two new species, C. chhangi sp. n. and C. simboloni sp. n., are described from Cambodia and Indonesia, respectively. DNA sequences were generated for C. fraxarix and the two newly described species using 3 amplications of two regions of the mitochondrial gene COI with a total of 1129 bp. The mean interspecific divergences are 9.4% and 23.5% for C. fraxatrix vs. C. chhangi, C. simboloni, respectively. DNA sequences reveal that C. simboloni is found to be genetically distinct from the other two species, but C. chhangi is not distinct from C. fraxatrix.     

Diel and seasonal patterns of foraging activity in the arboreal ant Crematogaster matsumurai Forel

The foraging habits of the arboreal ant Crematogaster matsumurai Forel were studied in natural and captive colonies in southern Kyushu, Japan. The nests of C. matsumurai are made mainly in the trunks of living trees. In the natural environment, the species mainly lives in decayed parts of relatively tall trees, such as Acer palmatum, Prunus jamasakura and Prunus yedoensis. Observation over a 24 h period showed that C. matsumurai foraged actively at night as well as during the day. The foraging of the workers out of the nest was seen from early spring to late autumn, both on the tree and on the ground. As protein sources, aphids were mainly collected by foragers from the tree, while small parts of dead insects or other arthropods were mainly collected from the ground surface. The foraging activity of workers is assumed to be influenced by the quantity and quality of food rather than seasonality.     

The rove beetle Drusilla sparsa (Coleoptera: Staphylinidae) is a myrmecophilous species associated with a myrmicine ant,Crematogaster osakensis (Hymenoptera: Formicidae)

The rove beetle genus Drusilla includes some myrmecophilous species. The Japanese species Drusilla sparsa (Sharp, 1874) has been regarded as a non‐myrmecophilous beetle. In Kagawa Prefecture, Shikoku Island, western Japan, however, we often observed that D. sparsa adults were walking in the vicinity of foraging workers of the myrmicine ant Crematogaster osakensis Forel, 1990. The body color of the beetle is similar to C. osakensis as in other myrmecophilous beetles found near the trails of the host ants. To examine whether D. sparsa is myrmecophilous, we investigated the distribution of D. sparsa and C. osakensis in the field, as well as their behavior including prey preference of the beetle in the laboratory. Drusilla sparsa beetles were collected only in sites where C. osakensis ants occurred. When the beetles encountered the ant workers, they bent the abdominal tip toward the ants. The ants licked the abdominal tip, and then the beetles usually walked away. Such behavioral reaction of the ants was not observed when the beetles encountered workers of the formicine ant Nylanderia flavipes (Smith, 1874) that continuously attacked the beetles. Drusilla sparsa preferred to feed on dead workers of C. osakensis even when other ants were available as food, indicating that D. sparsa is a myrmecophilous species associated with C. osakensis. Crematogaster osakensis was frequently found in the stomach in the ant predator, the Japanese treefrog Hyla japonica Günther, 1859. Thus, the significance of body color similarity between the host ants and beetles is not a case of Batesian mimicry.