Ant Assemblage Composition Research Articles

The impacts of fire vary among vertical strata: Responses of ant communities to long-term experimental burning.

Fire is a powerful tool for conservation management at a landscape scale, but a rigorous evidence base is often lacking for understanding its impacts on biodiversity in different biomes. Fire-induced changes to habitat openness have been identified as an underlying driver of responses of faunal communities, including for ants. However, most studies of the impacts of fire on ant communities consider only epigeic (foraging on the soil surface) species, which may not reflect the responses of species inhabiting other vertical strata. Here, we examine how the responses of ant communities vary among vertical strata in a highly fire-prone biome. We use a long-term field experiment to quantify the effects of fire on the abundance, richness, and composition of ant assemblages of four vertical strata (subterranean, leaf litter, epigeic, and arboreal) in an Australian tropical savanna. We first document the extent to which each stratum harbors distinct assemblages. We then assess how the assemblage of each stratum responds to three fire-related predictors: fire frequency, fire activity, and vegetation cover. Each stratum harbored a distinct ant assemblage and showed different responses to fire. Leaf litter and epigeic ants were most sensitive to fire because it directly affects their microhabitats, but they showed contrasting negative and positive responses, respectively. Subterranean ants were the least sensitive because of the insulating effects of soil. Our results show that co-occurring species of the same taxonomic group differ in the strength and direction of their response to fire depending on the stratum they inhabit. As such, effective fire management for biodiversity conservation should consider species in all vertical strata.

Comparing Ant Assemblages and Functional Groups across Urban Habitats and Seasons in an East Asia Monsoon Climate Area.

China's East Asia monsoon zone is undergoing rapid land-use conversion and urbanization. Safeguarding remaining biodiversity requires reducing, mitigating, and/or eliminating the negative impacts of human-induced landscape modification. In this study, we sampled ground-dwelling ants at 40 plots over 12 continuous months in a suburban area in southwestern China to examine whether and how vegetation composition and habitat fragmentation affected species richness and assemblage composition for the general ant community and, specifically, for principal functional groups (including Opportunists and Generalized Myrmicinae). Warmer seasons were associated with a higher capture rate for all functional groups. Patterns of ant species richness among Opportunists were more sensitive to vegetation and fragmentation than for Generalized Myrmicinae, and these effects generally varied with season. Patterns of ant assemblage composition for Opportunists were exclusively sensitive to vegetation, whereas Generalized Myrmicinae were sensitive to both vegetation and fragmentation with variation among seasons. Overall, our findings highlight the important role of seasonality, vegetation composition, and habitat fragmentation in mediating the impacts of human-induced landscape modification on urbanized ant communities, which make an essential functional contribution to biodiversity in the East Asia monsoon zone.

The Ground-Dwelling Ant Fauna from a Cerrado Reserve in Southeastern Brazil: Vegetation Heterogeneity as a Promoter of Ant Diversity.

Ants represent one of the most diverse and ecologically important group of insects in tropical ecosystems, including in highly threatened ones such as the Brazilian Cerrado. Yet, a detailed understanding of the species diversity and composition of local Cerrado ant assemblages is lacking in many cases. Here we present the results of a comprehensive ant inventory performed within a region of the Cerrado (in São Paulo state) where most of the original vegetation has already been lost and where few conservation units exist. We performed consecutive surveys of the ant fauna that forage on the ground in replicated plots established in open savanna (campo sujo), dense savanna (cerrado sensu stricto), and forest (cerradão). Our surveys, with an estimated sample coverage of 99.4%, revealed a total of 219 species of ants from 60 genera, of which 36.1% were found in all the three vegetation types and 29.7% in just one. Rarefied species richness did not differ between vegetation types, but species composition differed markedly, especially between the two savannas in one hand and the forest in the other. Several species (60.1% of the 128 species analyzed) were significant "indicator" species due to their strong association with a given vegetation type. Overall, our findings reinforce the idea that habitat heterogeneity enhances ant diversity and that the mosaic of vegetation types that characterizes the Cerrado biome is one of the main factors explaining the elevated number of species that can be found at relatively small scales.

Ant assemblages (Hymenoptera: Formicidae) from areas under the direct influence of two small hydropower plants in Brazil

Current energy production has been the subject of studies on environmental impacts and the need to adequately understand that the relationship to biodiversity loss is growing. One of the ways of assessing environmental changes is the use of bioindicator species, and ants represent an alternative in this regard. This study aimed to evaluate ant assemblages occurring in different environments in areas under the direct influence of two small hydropower plants (SHPP). Sampling was carried out using pitfall traps in forest and agricultural fragments, as well as pasture areas, along the Andrada River, municipality of Cascavel, state of Paraná, in July 2016 and March 2017. The sampled ant assemblages were evaluated for richness, abundance, and composition. The rarefaction analysis was used to compare the richness sampled in the two areas under direct influence. Abundance was analyzed based on the number of occurrences. The nonmetric multidimensional scaling (NMDS) was applied to test whether the abundance and composition of ant assemblages differ at the same site when sampled in both seasons. In total, 63 species belonging to 23 genera and 6 subfamilies were identified. The subfamily Myrmicinae was the most speciesrich (S = 25), followed by the subfamily Formicinae (S = 21). The most species-rich genus was Camponotus (S = 15) followed by Pheidole (S =11). A total of 41.3% richness was registered concurrently in the two assemblages. The study contributes to the expansion of knowledge of the ant fauna occurring in the state of Paraná and serves as a basis for monitoring impacts caused by the implementation of SHPP and other developments.

Functional composition of ant assemblages in habitat islands is driven by habitat factors and landscape composition

Fragmented natural habitats within human-transformed landscapes play a key role in preserving biodiversity. Ants as keystone species are essential elements of terrestrial ecosystems; thus, it is important to understand the factors influencing their presence. In a large-scale multi-site study, we surveyed ant assemblages using sweep netting and D-vac sampling on 158 ancient burial mounds preserving grassland habitats in agricultural landscapes in East-Hungary. We asked the following questions: (1) How do habitat factors and landscape composition affect species richness and functional diversity of ants? (2) Which ant traits are affected by habitat factors and landscape composition? Despite their small sizes, mounds as permanent and relatively undisturbed landscape elements could provide safe havens for diverse ant assemblages even in transformed agricultural landscapes. The complex habitat structure of wooded mounds supported high species and functional diversity of ant assemblages. Ant species on wooded mounds had small or medium-sized colonies, enabling the co-existence of more species. The effect of landscape composition on ant assemblages was mediated by habitat factors: steep slopes buffered the negative effect of the cropland matrix and enabled higher ant diversity.

Ant diversity and composition patterns along the urbanization gradients in an arid city

ABSTRACT The dramatic increased rates of uncontrolled urbanisation in various parts of the World have resulted in loss of native species and overall threats to biodiversity. Over the last few decades Saudi Arabia has witnessed a remarkably rapid population growth and unparalleled levels of urbanisation, leading to threats to biodiversity. In this study we focused on arid city (Riyadh, Saudi Arabia) where ant assemblages cross an urban-rural gradient. Ants were collected by pitfall traps from 15 sites along three different urbanisation gradients at 3-monthly intervals throughout 1 year. Ant abundance, species richness, evenness, and α diversity were consistent across the urbanisation gradient. However, significant differences were observed in ant β diversity and assemblage composition between rural and urban, suburban and urban, but not between rural and suburban sites. Eleven ant species were identified as indicator species (IV values between 50.7% and 80.7%). These ant assemblages were influenced by flora, ground cover, soil variables, and urbanisation characteristics. To conclude, we found a significant effect of urbanisation on the β diversity and composition of ant assemblages.

Secondary forest succession buffers extreme temperature impacts on subtropical Asian ants

AbstractSecondary forest succession may restore microclimatic refugia for ectotherms and play a fundamental role in mitigating the combined effects of deforestation and climate warming on biodiversity; however, empirical evidence remains limited by short‐term, coarse‐scale, and solely taxonomic‐based approaches. We hypothesize that ant assemblage composition will respond differently to an increased frequency of extreme heat events between sites with and without microclimatic refugia provided by secondary forest’s regrowth. We test this hypothesis by integrating comprehensive historic surveys (1992–1994) and contemporary resampling (2015–2017) of ant assemblages to investigate how soil surface temperatures (estimated by microclimatic models [30 × 30 m]) and physical parameters (e.g., canopy cover) over the past >20 yr drive changes in their taxonomic, functional, and phylogenetic diversity for open (grasslands and shrublands) and closed (secondary forests) habitat types. Our results show a significant spatial turnover in the ant assemblage composition in both habitat types over the past two decades. Furthermore, for taxonomic, functional and phylogenetic spatial beta diversity, temperature became the primary variable explaining the differences in species composition among sites in open habitats, but not in closed habitats. Nevertheless, leaf litter cover may, to a certain extent, provide some thermal buffer for litter‐dwelling species exposed to extreme heat. On the contrary, within forests, canopy cover mitigated the adverse impact of extreme heat on ant assemblages, with a shift toward smaller body size observed over time only in sites with lower canopy cover. These findings highlight the importance of restored canopy in providing thermal buffering for understory ectotherms. While tropical forest restoration represents an essential component in enhancing species resilience under climate warming, additionally we considered that the restoration of microclimatic regimes across different land use types is essential to conserve tropical biodiversity across the deforested landscape.

Changes in Epigaeic Ant Assemblage Structure in the Amazon during Successional Processes after Bauxite Mining

Environmental impact studies often involve monitoring and using bioindicators to evaluate the restoration stage of impacted areas. We aimed to assess ant assemblages’ response to the ecological succession of previously disturbed areas in the Brazilian Amazon. We sampled epigeic ant assemblages in five bauxite mining areas, representing different restoration stages, and compared them with two pristine areas. We also compared trends in species richness at the same mine site investigated 14 years earlier. Ten pitfall traps and four Winkler samples of litter were taken along a 100-m transect in each area. We expected that ant species richness would increase with the amelioration in habitat condition (i.e., environmental surrogates of ecological succession, including litter depth, soil penetrability, the circumference of trees, the distance of trees to adjacent trees, and percentage of ground cover). We also compared the efficacy of both sampling methods. Due to more significant sampling effort, pitfall traps captured more ant species than Winkler sacks. However, Winkler samples’ addition allowed the collection of more cryptic species than by pitfall traps alone. We sampled a total of 129 ant species, with increases in ant species richness in more mature rehabilitation. Nevertheless, similarity analysis indicated a significant difference between ant assemblages of rehabilitated areas and pristine ones. Assemblages differed mainly by the presence of specialist and rare species, found only in pristine plots. Rehabilitated areas exhibited a significant increase in tree circumference as they reached more ecologically advanced stages, which contributed to increasing ant species richness. These trends and comparison with the earlier study indicate that although there are favorable increases in ant species richness, in terms of species composition, rehabilitated areas were far from achieving an ant assemblage composition or environmental status that closely resembles pristine areas.

Repeated surveying over 6\xa0years reveals that fine-scale habitat variables are key to tropical mountain ant assemblage composition and functional diversity

High-altitude-adapted ectotherms can escape competition from dominant species by tolerating low temperatures at cooler elevations, but climate change is eroding such advantages. Studies evaluating broad-scale impacts of global change for high-altitude organisms often overlook the mitigating role of biotic factors. Yet, at fine spatial-scales, vegetation-associated microclimates provide refuges from climatic extremes. Using one of the largest standardised data sets collected to date, we tested how ant species composition and functional diversity (i.e., the range and value of species traits found within assemblages) respond to large-scale abiotic factors (altitude, aspect), and fine-scale factors (vegetation, soil structure) along an elevational gradient in tropical Africa. Altitude emerged as the principal factor explaining species composition. Analysis of nestedness and turnover components of beta diversity indicated that ant assemblages are specific to each elevation, so species are not filtered out but replaced with new species as elevation increases. Similarity of assemblages over time (assessed using beta decay) did not change significantly at low and mid elevations but declined at the highest elevations. Assemblages also differed between northern and southern mountain aspects, although at highest elevations, composition was restricted to a set of species found on both aspects. Functional diversity was not explained by large scale variables like elevation, but by factors associated with elevation that operate at fine scales (i.e., temperature and habitat structure). Our findings highlight the significance of fine-scale variables in predicting organisms’ responses to changing temperature, offering management possibilities that might dilute climate change impacts, and caution when predicting assemblage responses using climate models, alone.

Distribution of epigeic and hypogeic ants (Hymenoptera: Formicidae) in ombrophilous forests in the Brazilian Amazon

In the Amazon basin, ants are often associated with environmental or edaphic factors. However, these associations may vary between the epigeic and hypogeic strata. Here, we investigated differences in richness and composition of epigeic and hypogeic ant assemblages along an environmental gradient in the Brazilian Amazon. The four studied sites cover different topographic and soil characteristics. We sampled 25 plots of 250 m2 using 10 samples of epigeic pitfalls and 10 samples of hypogeic pitfalls installed at two depths (10 and 30 cm). The pitfalls remained in the fi eld for 48 hours. In the same plots, soil clay content and terrain altitude were also measured. We collected 219 species or morphospecies, of which 14 were exclusively hypogeics. We found higher local richness in the epigeic compared to hypogeic assemblages. We also found an interaction between clay content and strata for ant species composition. Overall, the species turnover was related to clay content, but the eff ect depended on the strata, with hypogeic fauna being more heterogeneous, compared with epigeic fauna. Despite the relationship between clay content and ant´s assemblage’s composition, we did not find strong environment predictors for both strata, which suggests that other factors may structure ant assemblages in these sites. This reinforces the need for studies to defi ne which environmental gradiente determines the distribution of Amazonian epigeic and hypogeic ants.

Fatores associados à ocorrência de formigas em escolas urbanas

As escolas consistem em ambientes que oferecem condições favoráveis para acolonização por formigas. Este estudo objetiva identificar os fatores associadosà ocorrência de formigas em quatro ambientes escolares localizados em áreasurbanas. A amostragem foi realizada em cozinhas, almoxarifados, refeitóriose áreas externas em doze escolas de quatro municípios da região oeste doestado de Santa Catarina, Brasil. Foram utilizadas iscas e coleta manual naamostragem. Variáveis ambientais foram obtidas em cada local. A similaridadeentre as amostras quanto à composição e a abundância de formigas foiavaliada por meio de uma escala multidimensional não métrica (non-metricmultidimensional scaling — NMDS). Foram amostrados 1.478 exemplaresde formigas e identificados 45 espécies. Foi observada uma similaridade de60% na abundância e composição das assembleias de formigas entre escolasde pequenas cidades (Caxambu do Sul, Guatambú e Palmitos). A presençade áreas externas com vegetação e áreas verdes no entorno, o tamanho daárea construída e a frequência de eventos de controle de insetos contribuempara a abundância desses insetos nos ambientes escolares. As formigas nãosão reconhecidas como potenciais vetores de micro-organismos patogênicosnas escolas e são negligenciadas se considerada a periodicidade do controlede insetos.

Termite mounds create heterogeneity in invertebrate communities across a savanna rainfall gradient

Termite mounds create nutrient hotspots that serve as key resource areas for savanna vegetation and mammalian herbivores. However, despite the key ecological roles performed by termite mounds, few studies have investigated their influence on invertebrate communities, and none have examined such effects across environmental gradients. We hypothesised that termite mounds would support greater numbers of invertebrates than the surrounding savanna matrix and that assemblages would differ in composition due to the enhanced nutritional quality of vegetation on mounds. We also predicted that the differences between on-mound and off-mound invertebrate diversity would be more pronounced in areas where the difference in nutritional value between mounds and the savanna matrix vegetation was most prominent. We tested these hypotheses in Kruger National Park, South Africa, by sampling ground- and grass-dwelling invertebrate herbivores, omnivores and detritivores on and at various distances away from termite mounds at three savanna sites of varying vegetation quality across a rainfall gradient. All invertebrate groups sampled responded to termite mounds, but mound influence varied across trophic groups (Orthoptera showed the clearest patterns), diversity measures (changes in abundance rather than species richness) and with mean annual rainfall (strongest effects at the highest rainfall site). Orthoptera were more abundant on mounds, particularly at the wettest site, and there was a positive relationship between mound size and Orthoptera species richness. Ant assemblage composition on mounds differed from that off mounds and beetle abundance was greater on mounds, possibly as a result of concentrated mammalian herbivore activity and faecal deposition on mounds. Our results suggest that termite mounds are not only important nutrient and foraging hotspots for vertebrates, but that they also introduce heterogeneity in invertebrate communities, especially in nutrient-poor savannas.

Ant assemblage composition explains high predation pressure on artificial caterpillars during early night

1. Predator–prey interactions, especially those involving herbivorous insects, are of great importance in maintaining biodiversity. Predation pressure varies temporally in response to prey availability and activity. However, little is known about the patterns and drivers of fluctuations in predation pressure at fine temporal scales.2. Artificial caterpillars (placed on plant leaves at breast height) were used to assess changes in predation pressure across four time intervals of the day in a monsoonal tropical rainforest in south‐west China. The study examined how assemblage composition of arboreal ants, the dominant predators, changed across the same time intervals. The potential linkages between biotic (arboreal ants) and abiotic (temperature and light intensity) factors with predation rate were evaluated.3. Predation rate on caterpillars during the early part of the night (19.00–01.00 hours) was significantly higher than in the morning, afternoon, or late night. Ant assemblage composition, rather than species richness or total abundance, best explained the variations in predation rate on artificial caterpillars.4. The results help to strengthen understanding of trophic interactions by demonstrating that predation pressure fluctuates at finer timescales than previously tested, and that a particular set of ant species may play major roles in predation on caterpillars and possibly other organisms.

Links between prey assemblages and poison frog toxins: A landscape ecology approach to assess how biotic interactions affect species phenotypes.

Ecological studies of species pairs showed that biotic interactions promote phenotypic change and eco‐evolutionary feedbacks. However, it is unclear how phenotypes respond to synergistic interactions with multiple taxa. We investigate whether interactions with multiple prey species explain spatially structured variation in the skin toxins of the neotropical poison frog Oophaga pumilio. Specifically, we assess how dissimilarity (i.e., beta diversity) of alkaloid‐bearing arthropod prey assemblages (68 ant species) and evolutionary divergence between frog populations (from a neutral genetic marker) contribute to frog poison dissimilarity (toxin profiles composed of 230 different lipophilic alkaloids sampled from 934 frogs at 46 sites). We find that models that incorporate spatial turnover in the composition of ant assemblages explain part of the frog alkaloid variation, and we infer unique alkaloid combinations across the range of O. pumilio. Moreover, we find that alkaloid variation increases weakly with the evolutionary divergence between frog populations. Our results pose two hypotheses: First, the distribution of only a few prey species may explain most of the geographic variation in poison frog alkaloids; second, different codistributed prey species may be redundant alkaloid sources. The analytical framework proposed here can be extended to other multitrophic systems, coevolutionary mosaics, microbial assemblages, and ecosystem services.

Ant assemblage composition and structure in different land uses in Santa Fe de Antioquia, Colombia

The Agrarian Station Cotove is located in Santa Fe de Antioquia, an area of tropical dry forest in which agricultural activities have been carried out for more than 40 years, which have transformed their original ecosystems and modifi ed the environmental conditions. Therefore, this study aims to evaluate the composition and structure of ants in five sites with different land uses: fruit trees, silvopasture, secondary forest, grass for cutting, and pastures with low density of trees. In each land use, three transects of 100m each were located, inside, inside-edge, and edge, taking a sample every 20m to a depth of 10cm. In each site, the ants were identified to morphospecies, and classified by trophic guilds and by functional groups. The diversity index for each land uses were determined. We collected 5239 ants, grouped in 253 colonies, belonging to 23 genera and 37 morphospecies of subfamilies Myrmicinae, Ponerinae, Formicinae y Ecitoninae. Species diversity was highest in secondary forest and fruit trees, while the dominance was higher in silvopasture and pastures with low density of trees. Secondary forest and fruit trees showed the highest value of shared morphospecies. The omnivorous and predator’s trophic guilds were the best represented, and regarding functional groups, we found a high proportion of tropical climate specialists and Myrmicinae generalists.

Direct evidence of native ant displacement by the Argentine ant in island ecosystems

Ecological impacts associated with ant introductions have received considerable attention, but most studies that report on these impacts contrast species assemblages between invaded and uninvaded sites. Given the low inferential power of this type of space-for-time comparison, alternative approaches are needed to evaluate claims that ant invasions drive native species loss. Here, we use long-term data sets from two different Argentine ant eradication programs on the California Channel Islands to examine how the richness and composition of native ant assemblages change before and after invasion (but prior to the initiation of treatments). At four different sites on two different islands, pre-invasion native ant assemblages closely resembled those at uninvaded (control) sites in terms of species richness, species composition, and the presence of multiple indicator species. Invader arrival coincided with large (> 75%) and rapid (within 1 year) declines in species richness, shifts in species composition, and the loss of indicator species. These impacts will hopefully be reversed by the recolonization of formerly invaded areas by native ant species following Argentine ant treatment, and long-term studies of native ant recovery at these sites are ongoing. Unchecked spread of the Argentine ant on other islands in this archipelago, however, poses a grave threat to native ants, which include a number of endemic taxa.

Mirmecofauna em áreas de preservação permanente e plantios florestais no noroeste do Rio Grande do Sul

As formigas compreendem um táxon muito diverso de insetos, apresentam elevada riqueza e são ecologicamente importantes nos diferentes ecossistemas terrestres. A riqueza e diversidade de formigas tendem a aumentar de acordo com a complexidade dos ambientes no que se refere à vegetação e ao estágio de conservação da biodiversidade. Este estudo visou caracterizar as assembleias de formigas que ocorrem em duas áreas de preservação permanente, descritas como fragmentos de vegetação nativa circundados por lavouras e, dois plantios de eucalipto, cercados por lavouras e pastagens. O estudo foi realizado no município de Frederico Westphalen (27°21′27″; 53°23′ 40″O), noroeste do Rio Grande do Sul. Foram utilizadas 10 armadilhas de queda (pitfall) e 20 iscas, 10 de sardinha e 10 de glicose em cada área. A riqueza foi definida como o número de espécies que ocorreram em cada uma das amostras e foi comparada por meio de análise de rarefação baseadas no número de ocorrências. A relação entre as espécies de formigas e os diferentes ambientes foi verificada através da Análise de Componentes Principais (PCA). A riqueza de formigas amostrada foi de 71 espécies, pertencentes a 19 gêneros, cinco subfamílias e, sete espécies ocorreram nos quatro ambientes amostrados. A subfamília Myrmicinae e os gêneros Pheidole e Camponotus foram os mais ricos no estudo. Observou-se diferença significativa quanto à riqueza, abundância e a composição das assembleias de formigas entre os ambientes amostrados. Os resultados apontam diferenças entre as assembleias de formigas dos fragmentos florestais e das plantações de eucalipto, e acrescentam informações acerca da biodiversidade da região do estudo.

Can environmental complexity predict functional trait composition of ground-dwelling ant assemblages? A test across the Amazon Basin

Environmental gradients may influence species distributions by filtering their functional traits, resulting in a correspondence between community functional composition and local environmental conditions. We used a vegetation gradient as an indicator for environmental complexity to test whether it predicted the morphological composition of ground-dwelling ant assemblages across geographic extents. The sampling design covered 126 plots distributed across eight sampling sites along a broad environmental gradient in the Amazon Basin. Plots covered different phytophysiognomies that have a strong relation with forest biomass and, consequently, litter production. We selected six morphological traits related to ant foraging strategies and behavior. Generalized linear mixed models were used to predict how environmental complexity affects trait composition of ground-dwelling ant assemblages. Structurally less complex environments (eg. Amazonian savannah) harboured more species of smaller ants, with relatively smaller mandibles and relatively larger eyes. In more complex environments (eg. dense ombrophylous forest), there were more ant species of larger size, with relatively larger mandibles and relatively smaller eyes. No relationship was detected between relative femur length and the environmental gradient investigated. The functional approach focused on individual traits may illuminate which ant foraging strategies are best adapted to a particular habitat. Our data reveal that the morphological composition of ground-dewelling ant assemblages responds clearly to environmental complexity suggesting that certain ant characteristics offer ecological advantages to particular species in particular habitats.

Effects of Urbanization on the Diversity, Abundance, and Composition of Ant Assemblages in an Arid City.

Cities within arid regions make up a significant but understudied subset of the urban ecosystems of the world. To assess the effects of urbanization, fragmentation, and land-use change in an arid city, we sampled the ant assemblages in three habitat types in Tucson, Arizona: irrigated neighborhood parks, urban desert remnants, and preserved desert. We analyzed the abundance, species richness, evenness, as well as the species and functional group composition of ant assemblages. We found no significant differences in species richness or evenness. However, irrigated parks had significantly greater ant abundances. Although some exotic species were present in the urban habitats, they did not have significant effects on ant diversity. Ant assemblages from all three habitat types were distinct from each other in their composition. Irrigated parks included a significantly higher proportion of species typically found in cooler and wetter climates. The differences in abundance and species composition between irrigated parks and the other habitats are likely the effect of irrigation removing water as a limiting factor for colony growth and increasing resource availability, as well as producing a localized cooling effect. Our results show that arid urban ecosystems may include considerable biodiversity, in part thanks to increased landscape heterogeneity resulting from the irrigation of green areas.

Habitats shape taxonomic and functional composition of Neotropical ant assemblages.

Determining assembly rules of co-occurring species persists as a fundamental goal in community ecology. At local scales, the relative importance of environmental filtering vs. competitive exclusion remains a subject of debate. In this study, we assessed the relative importance of habitat filtering and competition in structuring understory ant communities in tropical forests of French Guiana. Leaf-litter ants were collected using pitfall and Winkler traps across swamp, slope and plateau forests near Saül, French Guiana. We used a combination of univariate and multivariate analyses to evaluate trait response of ants to habitat characteristics. Null model analyses were used to investigate the effects of habitat filtering and competitive interactions on community assembly at the scale of assemblages and sampling points, respectively. Swamp forests presented a much lower taxonomic and functional richness compared to slope and plateau forests. Furthermore, marked differences in taxonomic and functional composition were observed between swamp forests and slope or plateau forests. We found weak evidence for competitive exclusion based on null models. Nevertheless, the contrasting trait composition observed between habitats revealed differences in the ecological attributes of the species in the different forest habitats. Our analyses suggest that competitive interactions may not play an important role in structuring leaf-litter ant assemblages locally. Rather, habitats are responsible for driving both taxonomic and functional composition of ant communities.