Dominant Ants Research Articles

Pengaruh tipe penggunaan lahan dalam membentuk komunitas semut dan layanan ekosistem yang diberikan

Semut menyediakan berbagai layanan ekosistem, seperti predasi dan penguraian. Layanan ekosistem semut pada berbagai tipe penggunaan lahan dapat dipengaruhi oleh jenis-jenis semut yang dominan di wilayah tersebut. Tujuan penelitian ini adalah mempelajari pengaruh tipe penggunaan lahan dalam membentuk komunitas semut dan layanan ekosistem yang diberikan. Penelitian ini dilakukan pada empat tipe penggunaan lahan, yaitu hutan sekunder, hutan karet, perkebunan karet, dan perkebunan kelapa sawit di Jambi dari bulan April sampai Juni 2014. Pada setiap tipe penggunaan lahan dibuat empat plot berukuran 50 m x 50 m sebagai ulangan. Semut dikoleksi menggunakan metode pengumpanan dengan larva Corcyra cephalonica (Stainton) yang direkatkan pada piring plastik kemudian diletakkan di permukaan tanah dan batang pohon. Layanan ekosistem semut diukur dengan mengamati larva C. cephalonica yang berhasil diangkut oleh semut dalam waktu satu jam. Hasil penelitian menunjukkan bahwa hutan sekunder memiliki jumlah spesies semut tertinggi dibandingkan dengan tipe penggunaan lahan lainnya. Tipe penggunaan lahan tidak berdampak pada jumlah spesies semut, namun berdampak pada komposisi spesies semut. Pengangkutan larva C. cephalonica terbanyak yang dilakukan oleh semut terjadi di hutan sekunder. Semut yang berperan penting dalam layanan ekosistem sebagai predator pada penelitian ini adalah Achantomyrmex sp. 01, Aenictus sp. 01, Carebara sp. 01, dan Tetramorium sp. 02, Odontoponera denticulata, Tetramorium sp. 03 Crematogaster sp. 02. Anoplolepis gracilipes dan Rhoptromyrmex sp. 01.

Long-term responses of desert ant assemblages to climate.

Productivity is a key driver of ecosystem structure and function, so long-term studies are critical to understanding ecosystems with high temporal variation in productivity. In some deserts, productivity, driven by moisture availability, varies immensely over time (rainfall) and space (landscape factors). At high productivity, species richness is expected to be driven in opposing directions by abundance (More Individuals Hypothesis - MIH) and competition. While studies investigating the impacts of spatial variation in productivity on community structure are common, the impacts of temporal variability on productivity are poorly understood. We tested how well rainfall predicted the activity, species numbers and assemblage composition of ants and if responses were moderated by landscape position. We also asked whether the number of species (richness per sampling unit and estimated species richness) responded directly to rainfall or was moderated by ant activity or competition from dominant ants. Over a 22-year period, when annual rainfall fluctuated between 79mm and 570mm, we sampled ants using pitfall traps in paired dune and swale habitats in the Simpson Desert, Australia. We used climate records over this period to model changes in ant assemblages. Activity of dominant ants responded primarily to long-term rainfall, increasing exponentially, while subordinate ants responded to short-term weather and time. Consistent with the MIH, the number of ant species was best predicted by activity, particularly that of subordinate ants. Activity of dominant ants had a declining positive effect on numbers of species. Landscape position strongly predicted species composition, while long-term rainfall determined composition at genus level but not species level. Over time, species composition fluctuated, but several genera consistently increased in activity. Productivity moderators such as long-term rainfall and landscape position are key drivers of ant activity and composition in the study ecosystem, acting indirectly on numbers of species. Numbers of species were explained largely by ant activity, making a strong case for the MIH, but not competition. Longer periods of low rainfall may indirectly reduce species richness in desert ecosystems. However, a trend to increasing richness over time may indicate that conservation management can ameliorate this impact.

Differences in exploitation and interference ability between two dominant ants: the invasive Argentine ant (Linepithema humile) and Tapinoma magnum

The Argentine ant is a highly invasive species that can cause significant ecosystem alterations. Its spread in the invaded areas is usually associated with the displacement of native ant species by means of strong interference competition mechanisms. According to recent studies, Tapinoma nigerrimum s.l., a native Mediterranean ant, can potentially limit the expansion of the Argentine ant. The aim of the present study is to determine the ethological features that discriminate against the ability of L. humile and T. magnum (nigerrimum complex) to exploit a trophic resource both in the presence and in the absence of the competitor. We conducted behavioural assays on experimental colonies using foraging arenas in a laboratory experiment. Linepithema humile colonies showed the ethological profile typical of the species, as they carried out more intense recruitment, initially concentrated on the whole foraging site rather than on the bait. Linepithema humile workers were more aggressive and fought cooperatively during inter-specific interactions. Tapinoma magnum colonies apparently showed a more food-oriented profile as they were faster in the search for food and concentrated the recruitment on it rather than on the whole foraging site. Tapinoma magnum workers tried to avert the competitor using threat postures rather than physical aggression. Tapinoma magnum colonies were systematically excluded by L. humile colonies from the trophic resource and underwent a visible reduction in surface activity. These results suggest that L. humile used a different and more effective interference competition strategy compared to T. magnum.

Biotic and abiotic determinants of the formation of ant mosaics in primary Neotropical rainforests

1. Ants are widespread in tropical rainforests, including in the canopy where territorially dominant arboreal species represent the main part of the arthropod biomass.2. By mapping the territories of dominant arboreal ant species and using a null model analysis and a pairwise approach this study was able to show the presence of an ant mosaic on the upper canopy of a primary Neotropical rainforest (c. 1 ha sampled; 157 tall trees from 28 families). Although Neotropical rainforest canopies are frequently irregular, with tree crowns at different heights breaking the continuity of the territories of dominant ants, the latter are preserved via underground galleries or trails laid on the ground.3. The distribution of the trees influences the structure of the ant mosaic, something related to the attractiveness of tree taxa for certain arboreal ant species rather than others.4. Small‐scale natural disturbances, most likely strong winds in the area studied (presence of canopy gaps), play a role by favouring the presence of two ant species typical of secondary formations: Camponotus femoratus and Crematogaster levior, which live in parabiosis (i.e. share territories and nests but lodge in different cavities) and build conspicuous ant gardens. In addition, pioneer Cecropia myrmecophytic trees were recorded.

Humans and scavenging raptors facilitate Argentine ant invasion in Doñana National Park: no counter-effect of biotic resistance

Biotic resistance by native communities could have a role in the spread of invasive species. This seems to be the case in the invasion of the Argentine ant, Linepithema humile, but only when the environment is unfavorable for the survival of the invader. We studied the progress of Argentine ant invasion through favorable and unfavorable habitats of Donana National Park across three temporal snapshots covering three decades (1992, 2000, 2016). We assessed biotic resistance of the native community using species richness, as well as dominance and community structure. We also explored the role of abiotic factors (quality of surrounding habitat and spatial variables) and of potential vectors of Argentine ant dispersal across unfavorable areas. We found no evidence of biotic resistance after examining native ant species richness, proportion of native dominant ants, or community structure. On the contrary, invasion proceeded from trees with higher ant species richness, probably because those trees are larger and provide more resources and better protection from aridity. Furthermore, we found evidence that the invasion of new trees across a matrix of unfavorable habitat could be influenced not only by humans, but also by scavenging avian predators, which could act as vectors of ant dispersal through transport of carrion also exploited by the ants. Such leapfrog expansion through mobile predators could represent an overlooked mechanism that would enrich our understanding of invasion dynamics and provide potential opportunities for management of invasive species.

Effect of agricultural land-use change on ant dominance hierarchy and food preferences in a temperate oak forest.

BackgroundThe discovery-dominance trade-off is the inverse relationship between the ability of a species to discover resources and the species’ dominance of those resources; a paradigm used to explain species coexistence in ant communities dependent on similar resources. However, factors such as stress (e.g., temperature) or disturbance (e.g., removal of biomass) associated with the change in land use, can modify this trade-off. Here, we aimed to determine the potential effects of land use change on dominance hierarchy, food preferences and on the discovery-dominance trade-off.MethodsAn experiment with baits was used to investigate the dominance hierarchies of ant communities in a temperate mountain habitat in central Mexico. We evaluated the dominance index (DI), food preferences and discovery-dominance trade-offs of ants inhabiting two types of vegetation: a native oak forest and agricultural land resulting from agricultural land use and grazing.ResultsThe ant communities in both environments were comprised of three species of ants (Monomorium minimum, Myrmica mexicana, and Camponotus picipes pilosulus), four morphospecies (Pheidole sp.1 and Pheidole sp.2, Temnothorax sp. and Lasius sp.) and one genus (Formica spp.). All Formicidae showed values of intermediate to low DI, and this factor did not seem to be influenced by the change in land use. Ants in the modified vegetation (i.e., agricultural land) were found to be numerically greater. Overall, a higher number of visits were registered to the tuna bait, although the duration of foraging events to the honey baits was longer. However, foraging times were dependent on the species considered: the generalized Myrmicinae, M. minimum, the ant species with highest DI, foraged for longer periods of time in the agricultural land and on the tuna bait. Meanwhile, the cold-climate specialist Formica spp., with a lower DI, foraged for longer periods of time in the oak (although not significant) and on the honey bait. We found little evidence of the discovery-dominance trade-off; instead, we found considerable diversity in the strategies used by the different species to access resources. This range of strategies is well represented by the generalized Myrmicinae M. minimum, the cold-climate specialists Formica spp. and Temnothorax sp., and the rare species, as the cold climate specialist Lasius sp. (insinuators).ConclusionsOur evaluation shows that transformation of the original habitat does not appear to affect the hierarchical dominance of the ant communities, but it does affect their food preferences. Species with higher DI values such as the generalized Myrmicinae are more skilled at resource acquisition in modified habitats. Our results suggest that change in land use promotes an increase in the diversity of foraging strategies used by different ant species. This diversity may contribute to resource partitioning which favors coexistence.

Grazing by large savanna herbivores indirectly alters ant diversity and promotes resource monopolisation.

In savannas, grazing is an important disturbance that modifies the grass layer structure and composition. Habitat structural complexity influences species diversity and assemblage functioning. By using a combination of natural sites and manipulated experiments, we explored how habitat structure (grazing lawns and adjacent bunch grass) affects ant diversity and foraging behaviour, specifically the efficiency of resource acquisition, resource monopolisation and ant body size. We found that in the natural sites there was no difference in the amount of time ants took to locate resources, but in the manipulated experiments, ants were faster at locating resources and were more abundant in the simple treatments than in the more complex treatments. Ant body size was only affected by the manipulated experiments, with smaller ants found in the more complex treatments. In both the grazing lawn and bunch grass habitats there were differences in assemblage patterns of ants discovering resources and those dominating them. Seasonality, which was predicted to affect the speed at which ants discovered resources and the intensity of resource monopolisation, also played a role. We show that ants in winter monopolised more baits and discovered resources at a slower rate, but only at certain times within the experiment. Grazing in conjunction with season thus had a significant effect on ant diversity and foraging behaviour, with dominant ants promoted where habitat complexity was simplified when temperatures were low. Our results indicate that structural complexity plays a major role in determining ant assemblage structure and function in African savannas.

Correlates of ecological dominance within Pheidole ants (Hymenoptera: Formicidae)

1. In any group of organisms, one can almost invariably find some species that are ecologically dominant (i.e. disproportionately more abundant and widespread), whereas others are comparatively less prevalent. Understanding of the causes of variation in ecological dominance has been elusive, particularly given that dominant and subordinate species often lack obvious features that could predict their abundance in nature.2. In this study, physiological, behavioural, morphological, and phylogenetic information is integrated in an effort to understand the mechanisms underlying ecological dominance in ants using the hyperdiverse ant genus Pheidole (Formicidae: Myrmicinae) as a model system. Field estimates of the relative abundance of 10 Pheidole species were compared with potential correlates, which included behavioural (walking velocity), physiological (tolerance to high and low temperatures and desiccation), and morphological traits (body size and degree of dimorphism in the worker caste). A molecular phylogeny of the tested species was also generated to account for potential confounding effects of phylogenetic non‐independence.3. Dominant Pheidole species were characterised by higher environmental tolerance with respect to temperature and humidity, as well as faster walking speeds. On the other hand, no morphological correlates of ecological dominance were detected. Interestingly, subordinate species showed no evidence of trade‐off in performance, being both more fragile to environmental challenges and slower in their walking speeds.4. These results provide important insights into the mechanisms involved in local species coexistence in Pheidole.

The Ant Mosaic Distribution of Oecophylla smaragdina and Dominant Ant Species: Effects on Ants Communities in Agroforestry in Tarakan Island

Agroforestry system enhanced ant biodiversity. Ant structure in the ecosystem has been driven by many factors, e.g., competition and predation among species. Dominant species and predator may give impact to species diversity in the ecosystem. We had field research to examine the interactions among dominant ant species, predator Oecophylla smaragdina, and other ants in Tarakan, North Kalimantan. In agroforestry system as the study site, ants and other insects on 66 crop trees were collected by sweeping and beating. The obtained number of two species Tapinoma melanocephalum and Oecophylla smaragdina occupied more than 60% of all collected ants. Two dominant ants tended to be separately distributed. The community structure may be ant mosaic pattern. Furthermore, the densities of the two dominant ants were higher, but their diversities in the tree were lower than dominant species and predator absence. Probably, the tendency seems to be active on the distribution of other ants.

Influences of Species Interactions With Aggressive Ants and Habitat Filtering on Nest Colonization and Community Composition of Arboreal Twig-Nesting Ants.

Ant community assembly is driven by many factors including species interactions (e.g., competition, predation, parasitism), habitat filtering (e.g., vegetation differences, microclimate, food and nesting resources), and dispersal. Canopy ant communities, including dominant and twig-nesting ants, are structured by all these different factors, but we know less about the impacts of species interactions and habitat filters acting at the colonization or recruitment stage. We examined occupation of artificial twig nests placed in shade trees in coffee agroecosystems. We asked whether species interactions-aggression from the dominant canopy ant, Azteca sericeasur Longino (Hymenoptera: Formicidae)-or habitat filtering-species of tree where nests were placed or surrounding vegetation-influence colonization, species richness, and community composition of twig-nesting ants. We found 20 species of ants occupying artificial nests. Nest occupation was lower on trees with A. sericeasur, but did not differ depending on tree species or surrounding vegetation. Yet, there were species-specific differences in occupation depending on A. sericeasur presence and tree species. Ant species richness did not vary with A. sericeasur presence or tree species. Community composition varied with A. sericeasur presence and surrounding vegetation. Our results suggest that species interactions with dominant ants are important determinants of colonization and community composition of twig-nesting ants. Habitat filtering at the level of tree species did not have strong effects on twig-nesting ants, but changes in coffee management may contribute to differences in community composition with important implications for ant conservation in agricultural landscapes, as well as biological control of coffee pests.

Food source quality and ant dominance hierarchy influence the outcomes of ant-plant interactions in an arid environment

In this study, we conducted a series of experiments in a population of Vachellia constricta (Fabaceae) in the arid Tehuacan-Cuicatláan valley, Mexico, in order to evaluate if the food source quality and ant dominance hierarchy influence the outcomes of ant-plant interactions. Using an experiment with artificial nectaries, we observed that ants foraging on food sources with higher concentration of sugar are quicker in finding and attacking potential herbivorous insects. More specifically, we found that the same ant species may increase their defence effectiveness according to the quality of food available. These findings indicate that ant effectiveness in plant protection is context-dependent and may vary according to specific individual characteristics of plants. In addition, we showed that competitively superior ant species tend to dominate plants in periods with high nectar activity, emphasizing the role of the dominance hierarchy structuring ant-plant interactions. However, when high sugar food sources were experimentally available ad libitum, the nocturnal and competitively superior ant species, Camponotus atriceps, did not dominate the artificial nectaries during the day possibly due to limitation of its thermal tolerance. Therefore, temporal niche partitioning may be allowing the coexistence of two dominant ant species (Camponotus rubritorax during the day and C. atriceps at night) on V. constricta. Our findings indicate that the quality of the food source, and temporal shifts in ant dominance are key factors which structure the biotic plant defences in an arid environment.

Keanekaragaman dan Kelimpahan Semut sebagai Predator Hama Tanaman Padi di Lahan Sawah Organik dan Anorganik Kecamatan Karanganom Kabupaten Klaten

Ants potentially as predators that become natural enemies of insect pests in rice fields with paddy cultivation. This study aims to know the diversity and abundance of ants, the role of ants, the population of ants, and the influence of physical and chemical factors in organic and inorganic rice fields. The ants were collected using pit fall trap method with insect bait, fish meat, and sugar solution. The results showed that the number of species and the number of individuals in organic rice fields was higher (429 individuals, 11 species) than inorganic rice fields (193 individuals, 10 species). In general, the index of diversity in organic rice fields was higher (ranging from 0.73 to 1.65) compared to inorganic rice fields (ranging from 0 to 1.28). The index of evenness in organic rice fields ranged from 0.63 to 0.99 (evenly distributed), whereas in inorganic rice fields ranged from 0 to 0.99 (uneven until evenly distributed). The dominant ants in organic rice fields were Camponotus sp, Solenopsis geminata, Anoplolepis gracilipes, and Paratrechina longicornis, whereas in the inorganic rice fields were Tapinoma sp, Solenopsis geminata, and Camponotus sp. The index of similarity between organic and inorganic rice fields showed a high and very high degree of similarity based on the type of feed. Physical factors of high soil and air humidity environment, high soil and air temperature increased the diversity and abundance of ants in the rice fields ecosystem. Factors soil pH in accordance with the growth of soil Arthropods were neutral or slightly acidic. Chemical factors of organic matter content, Nitrogen (N), the content of C organic, and a high P total content increased the diversity and abundance of ants. Keywords: diversity and abundance, ants, organic and inorganic rice fields

Reversing functional extinction of mammals prompts a rethink of paradigms about seed fate in arid Australia.

Functional extinction of once abundant species has frequently preceded understanding of their ecological roles. Consequently, our understanding of ecosystems is prone to shifting baselines because it often relies on observations made on depauperate species assemblages. In Australian deserts, current paradigms are that ants are the dominant granivores, mammals are unimportant seed predators and that myrmecochory in many Australian shrubs is an adaptation to increase dispersal distance and direct seeds to favourable germination sites. Here, we ask whether these paradigms could be artefacts of mammal extinction. We take advantage of a predator-proof reserve within which locally extinct native mammals have been reintroduced to compare seed removal by ants and mammals. Using foraging trays that selectively excluded mammals and ants we show that a reintroduced mammal, the woylie (Bettongia penicillata) was at least as important as ants in the removal of seeds of two shrub species (Dodonaea viscosa and Acacia ligulata). Our results provide evidence that the dominance of ants as granivores and current understanding of the adaptive benefit of myrmecochory in arid Australia may be artefacts of the functional extinction of mammals. Our study shows how reversing functional extinction can provide the opportunity to rethink contemporary understanding of ecological processes.

Polygyny does not explain the superior competitive ability of dominant ant associates in the African ant-plant, Acacia (Vachellia) drepanolobium.

The Acacia drepanolobium (also known as Vachellia drepanolobium) ant‐plant symbiosis is considered a classic case of species coexistence, in which four species of tree‐defending ants compete for nesting space in a single host tree species. Coexistence in this system has been explained by trade‐offs in the ability of the ant associates to compete with each other for occupied trees versus the ability to colonize unoccupied trees. We seek to understand the proximal reasons for how and why the ant species vary in competitive or colonizing abilities, which are largely unknown. In this study, we use RADseq‐derived SNPs to identify relatedness of workers in colonies to test the hypothesis that competitively dominant ants reach large colony sizes due to polygyny, that is, the presence of multiple egg‐laying queens in a single colony. We find that variation in polygyny is not associated with competitive ability; in fact, the most dominant species, unexpectedly, showed little evidence of polygyny. We also use these markers to investigate variation in mating behavior among the ant species and find that different species vary in the number of males fathering the offspring of each colony. Finally, we show that the nature of polygyny varies between the two commonly polygynous species, Crematogaster mimosae and Tetraponera penzigi: in C. mimosae, queens in the same colony are often related, while this is not the case for T. penzigi. These results shed light on factors influencing the evolution of species coexistence in an ant‐plant mutualism, as well as demonstrating the effectiveness of RADseq‐derived SNPs for parentage analysis.

Positive Relation Between Abundance of Pericarpial Nectaries and Ant Richness in Tocoyena formosa (Rubiaceae)

Ants can interact with plants in several ways, being one of the most common visitors of extrafloral nectaries (EFNs). However, pericarpial nectars (PNs) may represent to the ant community a similar resource as EFN would do. Here, we investigate how an ant community interacts with PNs by an individual-based network, using Tocoyena formosa as a model. We hypothesized that plants with more PN’s would present a higher ant richness in comparison to plants with less PNs and will occupy a central position in the network interaction. We observed 36 individuals of T. formosa in November of 2016. We recorded both the ant species and abundances on each plant, as well as the number of active PNs. To test our hypothesis, we performed a linear regression between PNs and ant richness. We performed a bipartite network analysis to obtain both the specialization and centrality metrics of each plant, and we also conducted linear regressions between the number of PNs and both the specialization and centrality. We confirmed our hypothesis, in which the ant community was more rich in individuals of T. formosa with more active PNs, and these individuals were more central, being important for the maintenance of the interactions with ants. We believe that coexistence between ants foraging is possible in T. formosa due to the seasonality and short time prevalence of the PNs, whose dominant ants do not have able time to master the resource and exclude the others, allowing different species to use the same plant.

Ant–aphid relations in the south of Western Siberia (Hymenoptera: Formicidae; Hemiptera: Aphididae)

Aphids, the main suppliers of energy-rich honeydew, play an important role in the life of ants. However, the data on the trophobiotic ant–aphid associations in the majority of regions are still limited. We present the first data on the ant–aphid relations in the south of Western Siberia. Investigations were carried out in the most typical biotopes of forest-steppe and steppe zones in the territory of Novosibirsk and Kurgan regions (Russia) during 1993–2014. There were revealed 35 species of ants and 198 species of aphids. Detected 456 ant–aphid associations involved 28 ant species and 134 myrmecophilous aphids. Seven ant species were found to consume honeydew of 9 non-myrmecophilous aphids, scraping it from the plant. This behaviour is typical of subdominant and subordinate ants which do not protect their foraging areas. Ants associate with various numbers of aphid species. About 36% of ants attended aphid colonies of less than 5 species. The largest number of myrmecophilous aphids is associated with L. niger (Linnaeus, 1758) (103 species), Formica pratensis Retzius, 1783 (50), Formica rufa group (25–33), F. (Serviformica) fusca Linnaeus, 1758 (26) and F. (S.) cunicularia Latreille, 1798 (27). Different ants play unequal roles in the formation of trophobiotic interactions with aphids. Due to complex territorial and foraging behaviour, including high functional specialization among honeydew collectors, dominant ants of Formica s. str. are one of the leaders in this process. The role of L. niger and Formica ants of the subgenus Serviformica requires further detailed investigation.

Separating effects of species identity and species richness on predation, pathogen dissemination and resistance to invasive species in tropical ant communities

Abstract Ants are abundant in natural and managed tropical ecosystems and can have an impact on herbivorous arthropods, as well as plant pathogens. Although it has been shown for plants that the diversity of communities can result in improved ecosystem functioning, it remains uncertain how the species richness of ants affects multiple ecosystem services and disservices. In the present study, we used experimentally enhanced natural gradients in ant species richness on 100 cacao trees in a plantation aiming to analyze the effect of ant species identity and species richness on predation pressure and the incidence of cacao pod borer (CPB), as well as the spread of black pod disease (BPD). Ant species richness did not significantly improve predation of experimentally exposed insects, and was not associated with a reduction in the incidence of CPB. However, the incidence of BPD was higher in ant species rich trees, presumably because more ant species were pathogen vectors. The identity of the dominant ant species affected the incidence of CPB and BPD, as well as predation pressure. Although both ant species richness and identity affected ecosystem services and disservices delivered by the ant community, the results of the present study suggest that the identity of dominant ants is the main driver for ecosystem services in these systems.

Strong influences of a dominant, ground‐nesting ant on recruitment, and establishment of ant colonies and communities

AbstractMany factors drive the organization of communities including environmental factors, dispersal abilities, and competition. In particular, ant communities have high levels of interspecific competition and dominance that may affect community assembly processes. We used a combination of surveys and nest supplementation experiments to examine effects of a dominant ground‐nesting ant (Pheidole synanthropica) on (1) arboreal twig‐nesting, (2) ground‐foraging, and (3) coffee‐foraging ant communities in coffee agroecosystems. We surveyed these communities in high‐ and low‐density areas of P. synanthropica over 2 years. To test for effects on twig ant recruitment, we placed artificial nesting resources on coffee plants in areas with and without P. synanthropica. The first sampling period revealed differences in ant species composition on the ground, in coffee plants, and artificial nests between high‐ and low‐density sites of P. synanthropica. High‐density sites also had significantly lower recruitment of twig ants and had species‐specific effects on twig ant species. Prior to the second survey period, abundance of P. synanthropica declined in the high‐density sites, such that P. synanthropica densities no longer differed. Subsequent sampling revealed no difference in total recruitment of twig ants to artificial nests between treatments. Likewise, surveys of ground and coffee ants no longer showed significant differences in community composition. The results from the first experimental period, followed by survey results after the decline in P. synanthropica densities suggest that dominant ants can drive community assembly via both recruitment and establishment of colonies within the community.

Combined effects of temperature and interspecific competition on the mortality of the invasive garden ant, Lasius neglectus: A laboratory study

The invasive garden ant, Lasius neglectus, is a dominant species due to its capacity to form large supercolonies. This species was assumed to possess a wide thermal niche since it is able to adapt to cold climates, which is a factor that boosted its rapid expansion from south to many central-northern European Countries. However, the effect of variations in environmental temperatures on its competitive ability against other species has still not been investigated. In this paper, we analyzed the change in survival ability of Lasius neglectus during encounters with two Mediterranean dominant ants (Crematogaster scutellaris and Tapinoma nigerrimum) at four different temperatures (15, 20, 25 and 30°C). Firstly, control tests were performed to provide the baseline survival ability of the three species at different temperatures. Secondly, competition tests were carried out at the same temperatures. Lasius neglectus survival was negatively affected by high temperature (30°C) in control tests, and this impairment was much more pronounced in competition tests. On the contrary, the two opponent species were only marginally affected by temperatures in control tests. Crematogaster scutellaris was a better competitor than L. neglectus, particularly at high temperatures. Tapinoma nigerrimum was a weaker competitor and was always outcompeted by L. neglectus, particularly at low temperatures. This result could suggest that L. neglectus is at a disadvantage during interspecific encounters when temperatures are high and that the predicted future increase in environmental temperatures may potentially enhance this handicap.

Patterns of floral resource use by two dominant ant species in a biodiversity hotspot

Ecological dominance in ants is often fuelled by carbohydrate intake. Most studies have focused on the importance of invasive ant mutualistic associations with trophobionts whereas few studies have investigated the importance of floral nectar on invasion success. In this study, utilisation of temporarily available floral nectar by the invasive Argentine ant, Linepithema humile, was compared to that of the dominant native ant, Anoplolepis custodiens, within the Cape Floristic Region (CFR), a biodiversity hotspot. The effect of these two focal ant species on species composition and abundance of ground foraging ants as well as floral arthropod visitors in inflorescences of Proteacea species was assessed. Foraging activity, and trophic ecology inferred from the abundance of natural stable isotopes of Carbon (δ13C) and Nitrogen (δ15N), and the ratio of Carbon to Nitrogen (C:N) were compared between the two ant species during three flowering periods. Linepithema humile significantly reduced the abundance and species diversity of both above-ground and floral arthropod species abundance and composition. Linepithema humile increased its foraging activity with increasing nectar availability, switching its diet to a more herbivorous one. Anoplolepis custodiens did not respond as effectively to increasing floral nectar or negatively impact floral arthropod visitors. This study showed that the availability of floral nectar and ability of L. humile to more effectively utilise this temporarily available resource than native ants, can contribute significantly to the further spread and persistence of L. humile in natural environments in the CFR.