Dominant Ants Research Articles

Fire and ant interactions mediated by honeydew and extrafloral nectar in an australian tropical savanna

Fire is a major disturbance affecting ecosystems globally, but its impact on mutualisms has received minimal attention. Here, we use a long-term field experiment to investigate the impact of different fire regimes on globally important ant–honeydew and ant–extrafloral nectar (EFN) mutualistic interactions in an Australian tropical savanna. These interactions provide ants with a key energy source, while their plant and hemipteran hosts receive protection services. We examined ant interactions on species of Eucalyptus (lacking EFNs) and Acacia (with EFNs) in three replicate plots each of burning every 2 and 3 years early in the dry season, burning late in the dry season every 2 years, and unburnt for > 25 years. The proportions of plants with ant–honeydew interactions in Acacia (44.6%) and Eucalyptus (36.3%) were double those of Acacia plants with ant–EFN interactions (18.9%). The most common ants, representing 85% of all interactions, were behaviourally dominant species of Oecophylla, Iridomyrmex and Papyrius. Fire promoted the incidence of ant interactions, especially those involving EFNs on Acacia, which occurred on only 3% of plants in unburnt plots compared with 24% in frequently burnt plots. Fire also promoted the relative incidence of behaviourally dominant ants, which are considered the highest quality mutualists. Contrary to expectations, frequent fire did not result in a switching of behaviourally dominant ant partners from forest-adapted Oecophylla to arid-adapted Iridomyrmex. Our findings that frequent fire increases ant interactions mediated by honeydew and extrafloral nectar, and promotes the quality of ant mutualists, have important implications for protective services provided by ants in highly fire-prone ecosystems.

Ant communities and their trophobionts shape the incidence of pests and diseases in Indonesia’s coffee agroforestry system

Abstract. Muhammad FN, Rizali A, Rahardjo BT. 2024. Ant communities and their trophobionts shape the incidence of pests and diseases in Indonesia’s coffee agroforestry system. Biodiversitas 25: 1127-1134. Ants play various roles in a coffee agroecosystem, and their presence may impact biological control in coffee plantations. Despite the pantropical economic importance of coffee, most research is focused on the Americas. This study investigates how ant communities and their trophobionts shape the incidences of pests and diseases in the Indonesian shade coffee agroecosystem. Three 30 m x 30 m plots consisting of a total of 256 coffee plants were observed from January to March 2022. Ant communities and their trophobiont were observed using three methods: visual, tuna bait, and live bait. The ants found were classified into dominant and non-dominant based on their nesting behavior and dominance in the bait trap. Pest damage and disease intensity observation were also conducted three times. Generalized linear models were used to test the relationships between ant, hemipteran, coffee berry borer, twig borer damage and leaf rust disease intensity. Twenty-one species of ants were found, and five of them were categorized as dominant ants. Ants correlate coffee pest damage and disease intensity, their hemipteran trophobionts, or both. Dolichoderus thoracicus ant positively correlated with all trophobiont hemipteran and negatively correlated with twig borer damage. Technomyrmex albipes positively correlated with aphids but negatively with flatids. Meanwhile, Tetraponera sp.1 ant only positively correlated with flatids. In trophobiont hemipteran group, all except aphids positively correlated with coffee pests and disease. Scale insect Coccus viridis positively correlated with coffee leaf rust and twig borer infestation intensity, while flatid presence even positively correlated with all coffee plant pest and disease intensity. Indirectly, ants may reduce coffee pests and diseases through hemipteran suppression. The results suggest that the interaction of ants and their trophobiont hemipteran can act as a biological control agent for coffee pests and diseases.

The abundance of ants (Hymenoptera: Formicidae) and their ecological roles as predators in Arabica coffee plantations with different densities of shade trees

Shade-grown coffee, incorporated in an agroforestry system, is a common practice of coffee plantations in Aceh Tengah Regency, Aceh Province, Indonesia. Coffee is grown under the shade of a canopy of surrounding trees. Shade trees reduce excessive light and provide a home for various predatory animals, including predatory ants. Some growers plant a dense population of shade trees, while others plant less shade trees. A study to investigate the diversity of ants and their abundance in different densities of shade trees has been conducted from April until August 2023. Ants were sampled from coffee trees (arboreal ants) in two coffee plantations with dense populations of shade trees and two plantations with sparse shade trees. We found 13 ant species in both categories of plantations (combined). All ant species were found in sparsely shaded coffee plantations, and only five were recorded from densely shaded plantations. However, the abundance of ants was much higher in densely shaded plantations than in sparsely shaded plantations. The ant genera Technomyrmex and Componatus were the dominant ants found in sparsely shaded plantations, while the dominant ants in densely shaded plantations were the genera Componatus and Crematogaster. These ants are known as general predators and potentially are predators of coffee berry borer (CBB), a significant pest in the area. This research has shown how different densities of shade trees in coffee plantations affected the ant fauna, which could be used as a basis for ant conservation to increase their ecosystem service as predators.

Impact of urbanization on the ant diversity: a case study on teak plantation in South Sulawesi, Indonesia

Ant communities play an important role in a teak agroecosystem. However, ant diversity is affected by urbanization. The purpose of this study was to determine the diversity and composition of ants in teak plantations in urban and rural areas. This study was conducted in July 2022 at three plantations in two regencies (Gowa and Maros) and one city (Makassar) in South Sulawesi, Indonesia. Gowa and Maros are located in rural areas, while Makassar is located in urban areas. Ants were sampled using a pitfall canopy. At each plantation, 20 trees were sampled randomly for pitfall installation. Ants were identified to the genera level and morphospecies. Ant’s diversity was analyzed using the Shannon Wiener, Simpson, and Evenness index and analysis of dissimilarity (Anosim). Total 273 individual ants samples were collected from 10 species and four subfamilies from three teak plantations in South Sulawesi. Crematogaster sp.1 was the most abundant ant among all the collected samples. Based upon the different indexes, the highest ant diversity was found in Gowa followed by Maros, while the lowest diversity was found in Makassar. The level of ant dominance in Makassar was higher than other two studied areas. The highest species evenness index was also found in Gowa and followed by Maros. The species composition in the three teak plantations was also not similar. Each location had their unique species composition than the other locations. This indicated that urbanization causes negative impacts on ants diversity and evenness as well as increase the dominance of ant species in teak plantations.

The Effect of Artificial Feeding Treatments on Predatory and Pollinating Ants in Cayenne Pepper Plants

Pests have the potential to reduce the quality and quantity of cayenne pepper production. Pest control is done by utilizing natural enemies, such as ants by being stimulated with artificial food. This study aims to observe the population of dominant species and the effect of various artificial feeding treatments on ants that act as predators or pollinators in chili plants. The study was arranged in a Randomized Group Design (RGD) with 5 treatments, namely P0: Control (no pellet or sugar solution treatment); P1: 10 g artificial feed pellets; P2: 10% sugar solution; P3: 10% sugar solution and 10 g artificial feed pellets; and P4: 10 g artificial feed pellets (put into artificial nest) which was repeated 4 times. Observations were made five times at three-day intervals. Data were analyzed by calculating the species diversity index (H'), species dominance index (C), and ant population. Based on the results, the ant diversity index in this experiment was classified as moderate at 1.17 (H' 1.0-3.0) and the ant dominance index was 0.35 (low: C<0.5). Ant identification revealed four species from three sub-families: Myrmicinae, Dolichodorinae, and Formicinae, namely Pheidole sp., Monomorium sp., Tapinoma sp., and Paratrechina sp. While species that have the potential as predators or pollinators on chili plants are Tapinoma sp.. Artificial feeding with treatment P3 (10 g artificial feed and 10% sugar solution) can have an effect and increase the population of Tapinoma sp. ants with an average of 81.95 heads on chili plants.

The Evolution and Ecology of Interactions Between Ants and Honeydew-Producing Hemipteran Insects

The interactions between ants and certain sap-feeding insects in the order Hemiptera are classic examples of food-for-protection mutualisms. In these associations, herbivorous hemipterans use a highly specialized, straw-like mouthpart to consume sap directly from plant phloem and xylem and, as a result, excrete a sugar-rich waste product called honeydew. Ant foragers use specialized adaptations to collect and share honeydew with nestmates and, in exchange, protect hemipterans against predators. The two key innovations underlying this interaction—hemipteran sap feeding and ant harvesting of honeydew—have driven the evolutionary success and ecological dominance of ants. These interactions also carry unique costs and benefits for each partner and are highly context dependent. Understanding the factors mediating this mutualism is critical, as these interactions have broader ecological consequences for the natural and agricultural ecosystems in which they are embedded.

Positive effects of ants on host trees are critical in years of low reproduction and not influenced by liana presence

Tropical tree-climbing lianas form paths that benefit foraging of dominant ants which might protect the host tree against herbivores. In contrast, lianas are often associated with negative effects on growth and reproduction of host trees due to light obstruction, structural stress and other negative effects. It is unclear if dominant ants could mitigate the negative effects of lianas on host plants. We investigated how lianas and carton nest ants (Azteca chartifex) affected herbivory and reproductive structures of the host tree Byrsonima sericea. Considering 68 trees, almost half of them were naturally colonized by A. chartifex nests (32 trees). We removed lianas from half of the trees (34), establishing a factorial sampling design between A. chartifex and liana presence. We sampled ants and leaf herbivory before and after removing lianas, and measured plant fitness in two consecutive years after removing lianas. Liana removal had no effect on A. chartifex foraging, on leaf herbivory and flower-fruit conversion of host plants. However, A. chartifex decreased leaf herbivory and increased B. sericea flower-fruit conversion irrespective of lianas presence. A noticeable positive effect of ants was detected only in the second year of the experiment, consistently on all plants at each experimental level. The reproductive conditions of the first year resulted in most plants with more than 75% flower-to-fruit conversion success, regardless of the presence of A. chartifex, a success sustained only on those ant-colonized plants in the second year. Our results contribute to understanding multi-trophic interactions in tropical forest canopies as we demonstrated i) that dominant arboreal ants can benefit plants even in a non-obligatory interaction and ii) that the influence of lianas on its host tree is context-dependent, presenting even neutral effects depending on habitat type and species involved.

Abundance and richness of invertebrates in shade-grown versus sun-exposed coffee home gardens in Indonesia

Complex agroforestry systems are suggested as a possible solution to reduce the effects of deforestation in the tropics while enhancing the livelihoods of local human populations. Coffee (Coffea spp.) is one of the most important commodity crops in the world that can easily be cultivated in complex agroforestry systems. Coffee agroforestry systems usually sustain higher biodiversity levels than sun-exposed fields while keeping similar levels of productivity considering the several benefits of growing coffee under a complex system. We aim to explore the richness and abundance of invertebrates in coffee home gardens in West Java, Indonesia by comparing 14 sun-exposed and 14 shade-grown gardens. We collected data in March/April 2019 via pitfall traps, pan traps, and beating tray in each field. We ran generalised linear models to assess whether the number of species and the number of individuals of insects differed between sun-exposed vs. shade-grown coffee gardens, and tested associations between main taxa. Overall, there was no difference in the richness (sun-exposed: 19.86 ± SE1.19; shade-grown: 19.71 ± SE1.19; Z-value = 0.12, p value = 0.904) and abundance (sun-exposed: 141.93 ± SE 3.18; shade-grown: 139.93 ± SE3.16; Z-value = 0.35, p value = 0.706) of invertebrates in coffee gardens, although taxa specific differences were present. Sun-exposed fields had a higher abundance of invertebrates considered as pests (Blattodea: Rhinotermitidae, Ectobiidae; Coleoptera: Scarabaeidae, Lycidae and Tenebrionidae; Diptera: Anisolabididae, Drosophilidae and Sarcophagidae). Camponotus spp. were the most dominant ants in shade-grown gardens while Dolichoderus spp. and Myrmicaria spp. were more abundant in sun-exposed gardens. Despite the fact that sun-exposed coffee fields registered higher abundance of invertebrate pests than shade-grown coffee fields, the richness of invertebrates did not substantially vary between sun-exposed and shade-grown coffee, suggesting that the matrix of gardens offers advanced ecosystem services. It is important to keep the complexity of agroforestry systems that provide key habitats for biodiversity.

Rapid assessment of the three‐dimensional distribution of dominant arboreal ants in tropical forests

Abstract Ants are omnipresent in tropical forests, especially territorially dominant arboreal ants whose territories are spatially segregated forming ‘ant mosaics’. These ecologically important species are rarely used in conservation monitoring because of the difficulty in collecting them. We developed a standardised baitline protocol to study the distribution of dominant ants on canopy trees and also a procedure to objectively define species dominance, even in unknown ant assemblages. Besides eliminating the need to climb trees, this protocol allows live arboreal ant specimens to be sampled at different heights. Behavioural aggressiveness assays between the collected workers provide data on the three‐dimensional distribution of colonies and on interactions between species. We compared the results of the behavioural tests to those from null models. In the New Guinean lowland forest studied, we show that the canopy was either shared by multiple territorial species or inhabited by a single species with a large territory. The baitline protocol collected up to half of the arboreal ant species found in a felling census. However, the proportion of species collected at baits decreased with the increasing spatial dominance of single territorial species. Behavioural observations used in the protocol allowed a more efficient detection of ant mosaics than null models. Territorially dominant ants were active on both understorey and canopy trees. The protocol is fast and easy to replicate. It is a potential tool for understanding and monitoring the spatiotemporal dynamics of arboreal ant assemblages and can detect populous colonies, including those of invasive species.

Conceitos de ecologia aplicada: as redes neotropicais e a manutenção da biodiversidade

A estrutura das florestas neotropicais, determinada pelas interações animal/planta é altamente organizada. O sistema consiste de várias redes paralelas, estruturalmente semelhantes, porém taxonomicamente diferentes, baseado em grupos específicos de plantas. O mutualismo tem um papel crucial na manutenção da diversidade de um sistema. As ligações moveis são representadas por animais requeridos por muitas plantas para sua reprodução e dispersão. Mutualista-chave são as plantas que suportam os organismos de ligação e que mantêm indiretamente as redes de alimentação que dependem de ligações móveis, por toda, ou parte, da abundância de espécies. Finalmente, como as formigas controlam a taxa de herbívoros sobre diversas plantas, a existência de um mosaico de diferentes formigas dominantes, onde certas espécies criam uma forma sutil e importante de locais, é necessária.

Diversity and Distribution of the Dominant Ant Genus Anonychomyrma (Hymenoptera: Formicidae) in the Australian Wet Tropics

Anonychomyrma is a dolichoderine ant genus of cool-temperate Gondwanan origin with a current distribution that extends from the north of southern Australia into the Australasian tropics. Despite its abundance and ecological dominance, little is known of its species diversity and distribution throughout its range. Here, we describe the diversity and distribution of Anonychomyrma in the Australian Wet Tropics bioregion, where only two of the many putative species are described. We hypothesise that the genus in tropical Australia retains a preference for cool wet rainforests reminiscent of the Gondwanan forests that once dominated Australia, but now only exist in upland habitats of the Wet Tropics. Our study was based on extensive recent surveys across five subregions and along elevation and vertical (arboreal) gradients. We integrated genetic (CO1) data with morphology to recognise 22 species among our samples, 20 of which appeared to be undescribed. As predicted, diversity and endemism were concentrated in uplands above 900 m a.s.l. Distribution modelling of the nine commonest species identified maximum temperature of the warmest month, rainfall seasonality, and rainfall of the wettest month as correlates of distributional patterns across subregions. Our study supported the notion that Anonychomyrma radiated from a southern temperate origin into the tropical zone, with a preference for areas of montane rainforest that were stably cool and wet over the late quaternary.

Neither ant dominance nor abundance explain ant-plant network structure in Mexican temperate forests.

BackgroundAnt-plant mutualistic networks tend to have a nested structure that contributes to their stability, but the ecological factors that give rise to this structure are not fully understood. Here, we evaluate whether ant abundance and dominance hierarchy determine the structure of the ant-plant networks in two types of vegetation: oak and grassland, in two temperate environments of Mexico: Flor del Bosque State Park (FBSP) and La Malinche National Park (MNP). We predicted that dominant and abundant ant species make up the core, and submissives, the periphery of the network. We also expected a higher specialization level in the ant trophic level than in plant trophic level due to competition among the ant species for the plant-derived resources.MethodsThe ant-plant interaction network was obtained from the frequency of ant-plant interactions. We calculated a dominance hierarchy index for the ants using sampling with baits and evaluated their abundance using pitfall traps.ResultsIn MNP, the Formica spp. species complex formed the core of the network (in both the oak forest and the grassland), while in FBSP, the core species were Prenolepis imparis (oak forest) and Camponotus rubrithorax (grassland). Although these core species were dominant in their respective sites, they were not necessarily the most dominant ant species. Three of the four networks (oak forest and grassland in FBSP, and oak forest in MNP) were nested and had a higher number of plant species than ant species. Although greater specialization was observed in the ant trophic level in the two sites and vegetations, possibly due to competition with the more dominant ant species, this was not statistically significant. In three of these networks (grassland and oak forest of MNP and oak forest of FBSP), we found no correlation between the dominance hierarchy and abundance of the ant species and their position within the network. However, a positive correlation was found between the nestedness contribution value and ant dominance hierarchy in the grassland of the site FBSP, which could be due to the richer ant-plant network and higher dominance index of this community.ConclusionsOur evidence suggests that ant abundance and dominance hierarchy have little influence on network structure in temperate ecosystems, probably due to the species-poor ant-plant network and a dominance hierarchy formed only by the presence of dominant and submissive species with no intermediate dominant species between them (absence of gradient in hierarchy) in these ecosystems.

Do Dominant Ants Affect Secondary Productivity, Behavior and Diversity in a Guild of Woodland Ants?

The degree to which competition by dominant species shapes ecological communities remains a largely unresolved debate. In ants, unimodal dominance–richness relationships are common and suggest that dominant species, when very abundant, competitively exclude non-dominant species. However, few studies have investigated the underlying mechanisms by which dominant ants might affect coexistence and the maintenance of species richness. In this study, we first examined the relationship between the richness of non-dominant ant species and the abundance of a dominant ant species, Formica subsericea, among forest ant assemblages in the eastern US. This relationship was hump-shaped or not significant depending on the inclusion or exclusion of an influential observation. Moreover, we found only limited evidence that F. subsericea negatively affects the productivity or behavior of non-dominant ant species. For example, at the colony-level, the size and productivity of colonies of non-dominant ant species were not different when they were in close proximity to dominant ant nests than when they were away and, in fact, was associated with increased productivity in one species. Additionally, the number of foraging workers of only one non-dominant ant species was lower at food sources near than far from dominant F. subsericea nests, while the number of foragers of other species was not negatively affected. However, foraging activity of the non-dominant ant species was greater at night when F. subsericea was inactive, suggesting a potential mechanism by which some non-dominant species avoid interactions with competitively superior species. Gaining a mechanistic understanding of how patterns of community structure arise requires linking processes from colonies to communities. Our study suggests the negative effects of dominant ant species on non-dominant species may be offset by mechanisms promoting coexistence.

Environmental drivers of ant dominance in a tropical rainforest canopy at different spatial scales

Tropical trees accommodate a high co‐occurrence of ant species, mainly due to the high diversity of microhabitats available. However, a few ant species are highly abundant, dominating resources and defending territories in tree canopies. Although arboreal ants have been studied extensively, little is known about the structural drivers of ant spatial dominance in tropical rainforest canopies. This study investigated whether canopy tree microhabitats and micro‐environmental factors (given by branch characteristics and spatial position of sampling points within tree crowns) are determinants of ant presence and species composition in a Mexican tropical rainforest. It also analysed whether whole tree characteristics, that is, the tree canopy, given by tree size and epiphyte/climbing plant richness and abundance, could determine ant spatial dominance of food resources. This study found a higher probability of ant presence on baits lower in the canopy, probably a result of ants foraging in the zones between the treetops and the ground layer. No microhabitat or micro‐environmental variables were related to ant species composition. It also observed less dissimilarity of species composition between baits and between trees than between plots, revealing that each plot presents a unique set of species. Moreover, increased tree height and epiphyte/climbing plant abundance (i.e., structural heterogeneity and greater foraging area) and lower epiphyte/climbing plant richness led to decreasing ant dominance. This study's findings reveal that, while micro‐environmental factors have almost no influence on the foraging of dominant ant species within canopy trees, the size and heterogeneity of trees shape ants' spatial dominance.

Can different soil fertilization regimes modify soil fauna to interfere in maize grain yield?

Soil fauna activities transform the soil, but soil organisms are also influenced by changes in the land. We hypothesize that different soil fertilization regimes modify soil fauna and in this way affect maize grain yield. The aim of this study was to evaluate the effects of different soil fertilization regimes on the structure of the soil fauna and the association between these organisms and the maize grain yield. The experiment was conducted in Maranhão State (Brazil), in an alley crop system which was divided into 32 plots of 4×10 m, with four replicates and the following treatments: Gliricidia sepium – gliricidia (G), potassium (K), humic acid (HA), humic acid + potassium (HA + K), potassium + gliricidia (K + G), humic acid + potassium + gliricidia (HA + K + G), humic acid + gliricidia (HA + G) and uncovered soil (US). Soil fauna dominance, abundance, richness, Shannon–Wiener diversity index, and Pielou evenness index and maize grain yield were determined. Fertilization with humic acid and potassium caused the dominance of isopods. The dominance of ants was also related to soil potassium (K treatment). The only taxon associated with yield was Araneae. Although fauna abundance did not show differences between treatments, it was related to yield. This study does not confirm the hypothesis that different soil fertilization regimes affect soil fauna and consequently influence maize grain yield. Nevertheless, we confirm that maize grain yield may be improved by the presence of specific groups and by the increased abundance of soil fauna.

The loss of flight in ant workers enabled an evolutionary redesign of the thorax for ground labour

BackgroundExplanations for the ecological dominance of ants generally focus on the benefits of division of labour and cooperation during foraging. However, the principal innovation of ants relative to their wasp ancestors was the evolution of a new phenotype: a wingless worker caste optimized for ground labour. Ant workers are famous for their ability to lift and carry heavy loads, but we know surprisingly little about the morphological basis of their strength. Here we examine the consequences of the universal loss of flight in ant workers on skeletomuscular adaptations in the thorax for enhanced foraging on six legs.ResultsUsing X-ray microcomputed tomography and 3D segmentation, we compared winged queens and wingless workers in Euponera sikorae (subfamily Ponerinae) and Cataglyphis savignyi (subfamily Formicinae). Workers are characterized by five major changes to their thorax: i) fusion of the articulated flight thorax (queens) into a rigid box optimized to support the muscles that operate the head, legs and abdomen, ii) redesign of internal cuticular structures for better bracing and muscle attachment, iii) substantial enlargement of the neck muscles for suspending and moving the head, iv) lengthening of the external trochanter muscles, predominant for the leg actions that lift the body off the ground, v) modified angle of the petiole muscles that are key for flexion of the abdomen. We measured volumes and pennation angles for a few key muscles to assess their increased efficacy. Our comparisons of additional workers across five genera in subfamilies Dorylinae and Myrmicinae show these modifications in the wingless thorax to be consistent. In contrast, a mutillid wasp showed a different pattern of muscle adaptations resulting from the lack of wing muscles.ConclusionsRather than simply a subtraction of costly flight muscles, we propose the ant worker thorax evolved into a power core underlying stronger mandibles, legs, and sting. This contrasts with solitary flightless insects where the lack of central place foraging generated distinct selective pressures for rearranging the thorax. Stronger emphasis is needed on morphological innovations of social insects to further our understanding of the evolution of social behaviours.

Habitat disturbance modifies dominance, coexistence, and competitive interactions in tropical ant communities

1. Interspecific competition is a major structuring principle in ecological communities. Despite their prevalence, the outcome of competitive interactions is hard to predict, highly context‐dependent, and multiple factors can modulate such interactions.2. We tested predictions concerning how competitive interactions are modified by anthropogenic habitat disturbance in ground‐foraging ant assemblages inhabiting fragmented Inter‐Andean tropical dry forests in southwestern Colombia, and investigated ant assemblages recruiting to baits in 10 forest fragments exposed to varying level of human disturbance.3. Specifically, we evaluated how different components of competitive interactions (patterns of species co‐occurrence, resource partitioning, numerical dominance, and interspecific trade‐offs between discovery and dominance competition) varied with level of habitat disturbance in a human‐dominated ecosystem.4. Multiple lines of evidence suggest that the role of competitive interactions in structuring ground‐foraging ant communities at baits varied with respect to habitat disturbance. As disturbance increased, community structure was more likely to exhibit random co‐occurrence patterns, higher levels of monopolization of food resources by dominant ants, and disproportionate dominance of a single species, the little fire ant (Wasmannia auropunctata). At a regional scale, we found evidence for a trade‐off between dominance and discovery abilities of the 15 most common species at baits.5. Together, these results suggest that human disturbance modifies the outcome of competitive interactions in ground‐foraging ant assemblages and may promote dominant species that reduce diversity and coexistence in tropical ecosystems.

Testing trade‐offs and the dominance–impoverishment rule among ant communities

AbstractAimAnt communities are believed to be structured by competition, with dominant species competitively excluding subordinates (the dominance–impoverishment rule). However, a high number of seemingly similar species coexist, possibly due to interspecific trade‐offs. Here, we examine the evidence for the dominance–impoverishment rule across a broad latitudinal gradient and explore whether trade‐offs explain coexistence within and among ant communities.Location40 sites in 19 countries across Europe, western North America and northern South America.TaxonFormicidae.MethodsWe conducted 2‐hr baiting experiments at each site. Three dominance scores were calculated for each species at each site where it occurred. We then examined the relationship between ant dominance and diversity and tested for the generality of three trade‐offs (dominance–discovery, dominance–thermal tolerance and dominance–generalism) within and among ant communities along with the possible effects of environmental variables on these trade‐offs.ResultsWe found no support for the dominance–impoverishment rule. Instead, overall species richness at baits was positively correlated with the number of dominant species and exhibited a unimodal relationship with the relative abundance of dominant ants. Moreover, we found little consistent evidence for the three interspecific trade‐offs.Main conclusionAlthough total species richness at baits is positively correlated with species richness of dominant species and, to a point, increasing worker numbers of dominants, trade‐offs among species do not appear to shape broad‐scale patterns of coexistence among ants. Species richness declines only when the numbers of dominant workers are very high. Together, these results suggest that while trade‐offs and the dominance–impoverishment rule might promote coexistence or shape ant communities in some locations, the evidence for their being general across communities is scant.

Invasive Ants Affect Spatial Distribution Pattern and Diversity of Arboreal Ant Communities in Fruit Plantations, in Tarakan Island, Borneo

Human activities influence ant community structure. In tropical areas, the habitat characteristics of crop plantations frequently shape the structure of arboreal ant communities. The present study investigated the spatial distribution of arboreal ants dwelling in durian Durio zibethinus and citrus Citrus amblycarpa plantations in the Tarakan Island, North Kalimantan. Specifically, it was investigated whether ant communities are dominated by native or invasive species; and if ant arboreal mosaics occur. This study included two sites (A and C) comprising durian and citrus plantations and one site B with only citrus plantations. Ant workers dwelling on crop trees were collected by branch beating, and subsequently identified and counted. Across all sites, a total of 64,360 workers, from 22 ant species, were collected from 59 durian and 63 citrus trees. In site A, the invasive species Tapinoma melanocephalum and the native species Oecophylla smaragdina were numerically dominant. A null model analysis of species co-occurrence revealed that species segregation existed in this site. Conversely, in sites B and C the invasive species T. melanocephalum and Technomyrmex albipes were dominant, and native arboreal ants almost co-occurred with the two species. Moreover, the number of T. melanocephalum and T. albipes workers was negatively correlated with the species diversity index of arboreal ants. However, the number of O. smaragdina workers showed no significant correlation. The results suggest that the invasion and domination of non-native species dissasemble spatial structures and reduce the species diversity in arboreal ant communities. The community structures of arboreal ants in fruit plantations were varied, depending on the fruit species and the properties of dominant ants.

The Dominance of Tramps Ants in The Settlement Area of Semarang, Central Java

The high rate of urbanization in Semarang have caused the land conversion from forest into various human need spaces. The land conversion is not only affect the life of humans but also the animals, including ants. The objectives of this study were to examine the dominance of tramp ants in the settlement area of Semarang City. The method used was the bait trap method using chicken intestine as a bait. Samples of ants were collected from four habitats, i.e., waste disposal area, traditional markets, house area, and urban parks. This study found four dominant ants, i.e., Anoplolepis gracilipes, Paratrechina longicornis, Solenopsis geminata and Monomorium pharaonis. Two of them were categorized as tramp ants (Anoplolepis gracillipes and Paratrechina longicornis). The highest diversity of ants was found in house (H'= 2.72). The waste area tends to be an ideal habitat for particular species, which was proved by the low value of Simpson's dominance index (iD = 0.06) and a high value of evenness index (E=0 0.89). This study provides new information about tramp ants population as pest in urban area. The findings would be beneficial for controlling the population of tramp ants, which are disturbing humans in the settlement area.