The decoupling of abundance and species richness in lizard communities

1. Patterns of species richness often correlate strongly with measures of energy. The more individuals hypothesis (MIH) proposes that this relationship is facilitated by greater resources supporting larger populations, which are less likely to become extinct. Hence, the MIH predicts that community abundance and species richness will be positively related. 2. Recently, Buckley & Jetz (2010, Journal of Animal Ecology, 79, 358-365) documented a decoupling of community abundance and species richness in lizard communities in south-west United States, such that richer communities did not contain more individuals. They predicted, as a consequence of the mechanisms driving the decoupling, a more even distribution of species abundances in species-rich communities, evidenced by a positive relationship between species evenness and species richness. 3. We found a similar decoupling of the relationship between abundance and species richness for lizard communities in semi-arid south-eastern Australia. However, we note that a positive relationship between evenness and richness is expected because of the nature of the indices used. We illustrate this mathematically and empirically using data from both sets of lizard communities. When we used a measure of evenness, which is robust to species richness, there was no relationship between evenness and richness in either data set. 4. For lizard communities in both Australia and the United States, species dominance decreased as species richness increased. Further, with the iterative removal of the first, second and third most dominant species from each community, the relationship between abundance and species richness became increasingly more positive. 5. Our data support the contention that species richness in lizard communities is not directly related to the number of individuals an environment can support. We propose an alternative hypothesis regarding how the decoupling of abundance and richness is accommodated; namely, an inverse relationship between species dominance and species richness, possibly because of ecological release.     

Community assembly time and the relationship between local and regional species richness

Many previous studies have assumed that a linear relationship between local and regional species richness indicates that communities are limited by regional processes, while a saturating relationship suggests that species interactions restrict local richness. We show theoretically that the relationship between local and regional richness changes in a consistent fashion with assembly time in interacting communities. Communities show saturation in their early assembly stages because only a subset of the regional pool may colonize a locality. At intermediate assembly times, communities will appear unsaturated until significant competitive exclusion occurs. Finally, when communities reach equilibrium, we found saturation as a result of resource competition resulting in the dominance of a limited number of species. We show that habitat size and species fecundity are important in determining the time needed for the community to reach equilibrium and thus affect the relationship between local and regional species richness. Our results suggest the number of coexisting species is a function of local and regional processes whose relative influences might vary over time and that research using the relationship between local and regional species richness to infer mechanisms limiting species richness must have knowledge of the assembly time of the community.     

Richness and species composition of arboreal arthropods affected by nutrients and predators: a press experiment

A longstanding goal for ecologists is to understand the processes that maintain biological diversity in communities, yet few studies have investigated the combined effects of predators and resources on biodiversity in natural ecosystems. We fertilized nutrient limited plots and excluded insectivorous birds in a randomized block design, and examined the impacts on arthropods associated with the dominant tree in the Hawaiian Islands, Metrosideros polymorpha (Myrtaceae). After 33 months, the species load (per foliage mass) of herbivores and carnivores increased with fertilization, but rarified richness (standardized to abundance) did not change. Fertilization depressed species richness of arboreal detritivores, and carnivore richness dropped in caged, unfertilized plots, both because of the increased dominance of common, introduced species with treatments. Herbivore species abundance distributions were more equitable than other trophic levels following treatments, and fertilization added specialized native species without changing relativized species richness. Overall, bird removal and nutrient addition treatments on arthropod richness acted largely independently, but with countervailing influences that obscured distinct top-down and bottom-up effects on different trophic levels. This study demonstrates that species composition, biological invasions, and the individuality of species traits may complicate efforts to predict the interactive effects of resources and predation on species diversity in food webs.     

Dominance–diversity relationships in ant communities differ with invasion

The relationship between levels of dominance and species richness is highly contentious, especially in ant communities. The dominance‐impoverishment rule states that high levels of dominance only occur in species‐poor communities, but there appear to be many cases of high levels of dominance in highly diverse communities. The extent to which dominant species limit local richness through competitive exclusion remains unclear, but such exclusion appears more apparent for non‐native rather than native dominant species. Here we perform the first global analysis of the relationship between behavioral dominance and species richness. We used data from 1,293 local assemblages of ground‐dwelling ants distributed across five continents to document the generality of the dominance‐impoverishment rule, and to identify the biotic and abiotic conditions under which it does and does not apply. We found that the behavioral dominance–diversity relationship varies greatly, and depends on whether dominant species are native or non‐native, whether dominance is considered as occurrence or relative abundance, and on variation in mean annual temperature. There were declines in diversity with increasing dominance in invaded communities, but diversity increased with increasing dominance in native communities. These patterns occur along the global temperature gradient. However, positive and negative relationships are strongest in the hottest sites. We also found that climate regulates the degree of behavioral dominance, but differently from how it shapes species richness. Our findings imply that, despite strong competitive interactions among ants, competitive exclusion is not a major driver of local richness in native ant communities. Although the dominance‐impoverishment rule applies to invaded communities, we propose an alternative dominance‐diversification rule for native communities.     

Experimental Manipulation of Grassland Plant Diversity Induces Complex Shifts in Aboveground Arthropod Diversity

Changes in producer diversity cause multiple changes in consumer communities through various mechanisms. However, past analyses investigating the relationship between plant diversity and arthropod consumers focused only on few aspects of arthropod diversity, e.g. species richness and abundance. Yet, shifts in understudied facets of arthropod diversity like relative abundances or species dominance may have strong effects on arthropod-mediated ecosystem functions. Here we analyze the relationship between plant species richness and arthropod diversity using four complementary diversity indices, namely: abundance, species richness, evenness (equitability of the abundance distribution) and dominance (relative abundance of the dominant species). Along an experimental gradient of plant species richness (1, 2, 4, 8, 16 and 60 plant species), we sampled herbivorous and carnivorous arthropods using pitfall traps and suction sampling during a whole vegetation period. We tested whether plant species richness affects consumer diversity directly (i), or indirectly through increased productivity (ii). Further, we tested the impact of plant community composition on arthropod diversity by testing for the effects of plant functional groups (iii). Abundance and species richness of both herbivores and carnivores increased with increasing plant species richness, but the underlying mechanisms differed between the two trophic groups. While higher species richness in herbivores was caused by an increase in resource diversity, carnivore richness was driven by plant productivity. Evenness of herbivore communities did not change along the gradient in plant species richness, whereas evenness of carnivores declined. The abundance of dominant herbivore species showed no response to changes in plant species richness, but the dominant carnivores were more abundant in species-rich plant communities. The functional composition of plant communities had small impacts on herbivore communities, whereas carnivore communities were affected by forbs of small stature, grasses and legumes. Contrasting patterns in the abundance of dominant species imply different levels of resource specialization for dominant herbivores (narrow food spectrum) and carnivores (broad food spectrum). That in turn could heavily affect ecosystem functions mediated by herbivorous and carnivorous arthropods, such as herbivory or biological pest control.     

Species abundance distributions and numerical dominance in gastrointestinal helminth communities of fish hosts

The abundances of different species in a parasite community are never similar: there is typically one or a few numerically dominant species and many species with low abundance. Here, we determine whether basic features of parasite communities are associated with strong dominance by one or a few species, among 39 component communities of gastrointestinal helminths in marine fishes from Brazil. First, we tested whether the shape of the species abundance distribution in these communities fits that predicted by several theoretical models, using a goodness-of-fit procedure. Only the canonical lognormal model could be rejected for 5 out of 39 communities; all other comparisons of observed and predicted abundance distributions showed no significant differences, although this may be due to limited statistical power. Second, we used the ratio between the abundance of the most abundant species and either the second or third most abundant species, as indices of dominance; these show, for instance, that the dominant species in a community is typically twice, but sometimes over ten times, as abundant as the next most abundant species. We found that these ratios were not influenced by either the community's species richness, the mean number of individual parasites per host, or the taxonomic identity of the dominant species. However, the abundance ratio between the first and third most abundant species in a community was significantly correlated with an independent index of species interactivity, based on the likelihood that the different parasite species in a component community co-occur in the same host individuals: the difference in abundance between the dominant and third most abundant species was greater in communities characterized by weak interactions. These findings suggest that strong interactions may lead to greater evenness in the abundance of species, and that numerical dominance is more likely to result from interspecific differences in recruitment rates.     

宁夏水洞沟湿地昆虫群落多样性分析与评价

水洞沟湿地昆虫计11目84科182种。其中半翅目和双翅目昆虫个体数量和种数较多,占个体总数的60%以上。植食性昆虫较捕食性和中性昆虫多。昆虫物种丰富度较高,群落结构复杂且稳定,群落种-多度曲线符合对数正态分布。捕食性群落的优势度随季节变化较大,植食性和中性昆虫群落的优势度随季节变化基本一致。     

Tree heterogeneity,resource availability,and larger scale processes regulating arboreal ant species richness

Abstract Processes acting on different spatial and temporal scales may influence local species richness. Ant communities are usually described as interactive and therefore determined by local processes. In this paper we tested two hypotheses linked to the question of why there is local variation in arboreal ant species richness in the Brazilian savanna (‘cerrado’). The hypotheses are: (i) there is a positive relationship between ant species richness and tree species richness, used as a surrogate of heterogeneity; and (ii) there is a positive relationship between ant species richness and tree density, used as a surrogate of resource availability. Arboreal ants were sampled in two cerrado sites in Brazil using baited pitfall traps and manual sampling, in quadrats of 20 m × 50 m. Ant species richness in each quadrat was used as the response variable in regression tests, using tree species richness and tree density as explanatory variables. Ant species richness responded positively to tree species richness and density. Sampling site also influenced ant species richness, and the relationship between tree density and tree species richness was also positive and significant. Tree species richness may have influenced ant species richness through three processes: (i) increasing the variety of resources and allowing the existence of a higher number of specialist species; (ii) increasing the amount of resources to generalist species; and (iii) some other unmeasured factor may have influenced both ant and tree species richness. Tree density may also have influenced ant species richness through three processes: (i) increasing the amount of resources and allowing a higher ant species richness; (ii) changing habitat conditions and dominance hierarchies in ant communities; and (iii) increasing the area and causing a species–area pattern. Processes acting on larger scales, such as disturbance, altitude and evolutionary histories, as well as sampling effect may have caused the difference between sites.     

Resource partitioning of sympatric small mammals in an African forest‐grassland vegetation mosaic

It is often hypothesized that two species competing for the same resource cannot stably coexist unless they partition their resources in space and time. More recently stable isotope analyses have complemented traditional, observation‐based niche research by conceptualizing many of the characteristics of communities, for example, trophic niche width and the partitioning of resources. Here we quantify resource partitioning of sympatric small mammal species in an African ecosystem by analysing stable isotope ratios of hair collected from a South African forest‐grassland vegetation mosaic, and combine this with known spatial and temporal behavioural data to interpret community competition and resource partitioning. We observe niche separation to different degrees across the entire community, with different species displaying either unique isotopic dietary preferences, or partitioning resources in space and/or time. δ¹³C values were more enriched in species that inhabited afromontane grassland compared with those that inhabited afromontane forest, a reflection of the dominant vegetation in each habitat. Contrary to expectations, arboreal rodents occupied higher trophic positions than terrestrial rodents and approaching δ¹⁵N values similar to insectivorous shrews, suggesting that arboreal rodents feed on items such as arthropods enriched in ¹⁵N. While grassland species display phenotypic plasticity in terms of dietary preferences, small mammals that occurred in forests display narrow niche preferences, suggesting these species may be particularly sensitive to habitat modifications. Our results illustrate that the use of stable isotopes can be used in conjunction with spatial and temporal behavioural knowledge to elucidate resource partitioning in small African mammal communities.     

新疆农田系统瓢虫资源调查与多样性研究

为全面了解新疆农田系统瓢虫资源组成以及多样性结构差异,本研究采用网捕法于2018年、2019年连续两年对新疆11个地州50个县/市/区15种农作物生境的406个采集点开展了瓢虫资源系统调查.结果表明:共获7001号瓢虫标本,隶属3亚科13属26种,其中多异瓢虫Hippodamia variegata为绝对优势种类,其个...     

Environmental Productivity and Biodiversity Effects on Invertebrate Community Invasibility

Productivity influences the availability of resources for colonizing species. Biodiversity may also influence invasibility of communities because of more complete use of resource types with increasing species richness. We hypothesized that communities with higher environmental productivity and lower species richness should be more invasible by a competitor than those where productivity is low or where richness is high. We experimentally examined the invasion resistance of herbivorous meiofauna of Jamaican rock pools by a competitor crustacean (Ostracoda: Potamocypris sp. (Brady)) by contrasting three levels of nutrient input and four levels of species richness. Although relative abundance (dominance) of the invasive was largely unaffected by resource availability, increasing resources did increase the success rate of establishment. Effects of species richness on dominance were more pronounced with a trend towards the lowest species richness treatment of 2 resident species being more invasible than those with 4, 6, or 7 species. These results can be attributed to a ‘sampling effect associated with the introduction of Alona davidii (Richard) into the higher biodiversity treatments. Alona dominated the communities where it established and precluded dominance by the introduced ostracod. Our experimental study supports the idea that niche availability and community interactions define community invasibility and does not support the application of a neutral community model for local food web management where predictions of exotic species impacts are needed.     

Geological age, ecosystem development, and local resource constraints on arthropod community structure in the Hawaiian Islands

An ongoing debate in evolutionary ecology concerns the relative role of contemporary vs. historical processes in determining local species richness and community structure. At sites along a 4 Mya geological chronosequence on Hawai'i, Moloka'i and Kaua'i, numerous extrinsic factors can be held constant, but ecosystem fertility and nutrient availability are low, both very young and very old sites, peaking at intermediate geological age across islands. Thus, contemporary resource traits are similar among sites with different biogeographical legacies, and these opposing gradients allowed a test of their relative importance for arboreal arthropod community structure. Pyrethrum knockdown was used to sample arboreal arthropods from Metrosideros polymorpha (Myrtaceae), the dominant tree throughout the Hawaiian Islands. Arthropod abundances and sample-based species richness peaked at more productive, intermediate-aged sites, but did not correlate with geological age. The proportions of individuals and biomass in trophic groups and in different taxonomic orders differed widely across sites, but proportions of species in trophic groups were more regular than the chance expectation. Species richness in local communities did not accumulate or pack more tightly with increasing geological age to the oldest island. Intermediate-aged islands may be contemporary peaks of richness, mediated by ecosystem development and senescence. Although historical and evolutionary processes generate diversity at broad scales, local communities converged in trophic structure and composition, and ecosystem resource availability constrained arthropod numbers and richness at local scales.  © 2007 The Linnean Society of London, Biological Journal of the Linnean Society , 2007, 90 , 551–570.     

Dominant species,rather than diversity,regulates temporal stability of plant communities

A growing body of empirical evidence suggests that the temporal stability of communities typically increases with diversity. The counterview to this is that dominant species, rather than diversity itself, might regulate temporal stability. However, empirical studies that have explicitly examined the relative importance of diversity and dominant species in maintaining community stability have yielded few clear-cut patterns. Here, using a long-term data set, we examined the relative importance of changes in diversity components and dominance hierarchy following the removal of a dominant C4 grass, Bouteloua gracilis, in stabilizing plant communities. We also examined the relationships between the variables of diversity and dominance hierarchy and the statistical components of temporal stability. We found a significant negative relationship between temporal stability and species richness, number of rare species, and relative abundance of rare species, whereas a significant positive relationship existed between temporal stability and relative abundance of the dominant species. Variances and covariances summed over all species significantly increased with increasing species richness, whereas they significantly decreased with increasing relative abundance of dominant species. We showed that temporal stability in a shortgrass steppe plant community was controlled by dominant species rather than by diversity itself. The generality of diversity–stability relationships might be restricted by the dynamics of dominant species, especially when they have characteristics that contribute to stability in highly stochastic systems. A clear implication is that dominance hierarchies and their changes might be among the most important ecological components to consider in managing communities to maintain ecosystem functioning.     

Functional and phylogenetic approaches reveal the evolution of diversity in a hyper diverse biota

Ant communities in tropical forests may be governed by varying assembly mechanisms, depending on the particular habitat investigated. We compared phylogenetic diversity and structure across two forest biomes (dry and humid) and two vertical layers (arboreal and terricolous) in ant communities in Madagascar, and assessed the influence of invasive species on this community structure. We estimated phylogenetic signal and correlated evolution for habitat and several functional traits and tested for conservatism in relevant functional and habitat traits. Ancestral states were reconstructed to illuminate the evolution of habitat traits. All analyses utilized phylogenies estimated from newly generated data from three nuclear markers for 290 Malagasy ant taxa. Dry forests, although lower in species richness, were found to support equally high lineage diversity as humid forests. In contrast, phylogenetic diversity was much lower in arboreal than in terricolous communities. We observed significant phylogenetic clustering in the combined humid forest and in the arboreal–humid, arboreal–dry and terricolous–humid communities, whereas the combined dry forest community was overdispersed. Among ant communities in Madagascar, overdispersion and competition therefore may be more prevalent in dry forest, and habitat filtering may be more dominant in humid forest. Excluding invasive ant species had little overall effect on community structure. All investigated traits showed low to intermediate conservatism; strong support for correlated evolution was found for increased eye size and an arboreal lifestyle. Habitat transitions from humid to dry and from terricolous to arboreal occurred more frequently, and ancestors of most lineages were predicted to be terricolous or humid‐forest adapted. We conclude that most Malagasy ant clades first colonized humid forests and subsequently transitioned into dry forests, indicating that previous hypotheses on the evolution of Madagascar's hyperdiverse biota may not apply to ants and other arthropods.     

Dominance determines fish community biomass in a temperate seagrass ecosystem

Biodiversity and ecosystem function are often correlated, but there are multiple hypotheses about the mechanisms underlying this relationship. Ecosystem functions such as primary or secondary production may be maximized by species richness, evenness in species abundances, or the presence or dominance of species with certain traits. Here, we combine surveys of natural fish communities (conducted in July and August 2016) with morphological trait data to examine relationships between biodiversity and ecosystem function (quantified as fish community biomass) across 14 subtidal eelgrass meadows in the Northeast Pacific (54°N, 130°W). We employ both taxonomic and functional trait measures of diversity to investigate whether ecosystem function is best predicted by species diversity (complementarity hypothesis) or by the presence or dominance of species with particular trait values (selection or dominance hypotheses). After controlling for environmental variation, we find that fish community biomass is maximized when taxonomic richness and functional evenness are low, and in communities dominated by species with particular trait values, specifically those associated with benthic habitats and prey capture. While previous work on fish communities has found that species richness is often positively correlated with ecosystem function, our results instead highlight the capacity for regionally prevalent and locally dominant species to drive ecosystem function in moderately diverse communities. We discuss these alternate links between community composition and ecosystem function and consider their divergent implications for ecosystem valuation and conservation prioritization.     

The role of resource dispersion in promoting the co‐occurrence of dominant and subordinate ant species

Dominant competitors govern resource use in many communities, leading to predictions of local exclusion and lower species diversity where dominant species are abundant. However, subordinate and dominant species frequently co‐occur. One mechanism that could facilitate resource sharing and co‐occurrence of dominant and subordinate competitors is fine‐scale resource dispersion. Here, we distributed 6 g of a food resource into 1, 2, 8, 32 or 64 units in small 0.40 m² areas centred on nests of the dominant ant Monomorium sydneyense. We tested three hypotheses. First, we hypothesized that the species richness and abundance of foraging ants would increase with increasing resource dispersion. Accordingly, species richness doubled and total ant abundance was two orders of magnitude higher in high resource dispersion treatments. Secondly, we hypothesized that increasing resource dispersion would reduce competitive interactions such as resource turnover events and lower the probability of food resources being occupied. Substantial support for this hypothesis was observed. Finally, we tested the hypothesis that the foraging time of each species would be proportional to the relative abundance of each species solely in high resource dispersion treatments. Expected and observed foraging times were statistically similar for only the dominant ant M. sydneyense. The subdominant Pheidole rugosula increased its foraging time much more than was expected, while two subordinate ants showed no relationship between observed and expected times. Thus, while increasing resource dispersion significantly increased overall species richness, this increase in co‐occurrence did not correlate with a significant increase in foraging time for the two subordinate species. Rather, changes in resource dispersion appeared to benefit only the subdominant species. Inter‐site variation appeared more important for other subordinate species indetermining co‐occurrence and foraging time. Multiple mechanisms facilitate co‐occurrence and resource sharing in this community, and probably in most other communities.     

Patterns of functional diversity across an extensive environmental gradient: vertebrate consumers, hidden treatments and latitudinal trends

Over the last two decades, although much has been learned regarding the multifaceted nature of biodiversity, relatively little is known regarding spatial variation in constituents other than species richness. This is particularly true along extensive environmental gradients such as latitude. Herein, we describe latitudinal gradients in the functional diversity of New World bat communities. Bat species from each of 32 communities were assigned to one of seven functional groups. Latitudinal gradients existed for the richness, diversity and scaled‐dominance of functional groups. No significant patterns were observed for evenness of functional groups. Measures of functional diversity were different in magnitude and increased towards the equator at a faster rate than expected given the underlying spatial variation in species richness. Thus, latitudinal gradient in species richness alone do not cause the latitudinal gradient in functional diversity. When variation in species composition of the regional fauna of each community was incorporated into analyses, many differences between observed and simulated patterns of functional diversity were not significant. This suggests that those processes that determine the composition of regional faunas strongly influence the latitudinal gradient in functional diversity at the local level. Nonetheless, functional diversity was lower than expected across observed sites. Community‐wide responses to variation in the quantity and quality of resources at the local level probably contribute to differences in functional diversity at local and regional scales and enhance beta diversity.     

Effect of local and regional processes on plant species richness in tallgrass prairie

Historically, diversity in a community was often believed to result primarily from local processes, but recent evidence suggests that regional diversity may strongly influence local diversity as well. We used experimental and observational vegetation data from Konza Prairie, Kansas, USA, to determine if: (1) there is a relationship between local and regional richness in tallgrass prairie vegetation; (2) local dominance reduces local species richness; and (3) reducing local dominance increases local and regional species richness. We found a positive relationship between regional and local richness; however, this relationship varied with grazing, topography and fire frequency. The decline in variance explained in the grazed vegetation, in particular, suggested that local processes associated with grazing pressure on the dominant grasses strongly influenced local species richness. Experimental removal of one of the dominant grasses, Andropogon scoparius , from replicate plots resulted in a significant increase in local species richness compared to adjacent reference plots. Overall all sites, species richness was higher in grazed (192 spp.) compared to ungrazed (158 spp.) areas. Across the Konza Prairie landscape, however, there were no significant differences in the frequency distribution of species occurrences, or in the relationship between the number of sites occupied and average abundance in grazed compared to ungrazed areas. Thus, local processes strongly influenced local richness in this tallgrass prairie, but local processes did not produce different landscape-scale patterns in species distribution and abundance. Because richness was enhanced at all spatial scales by reducing the abundance of dominant species, we suggest that species richness in tallgrass prairie results from feedbacks between, and interactions among, processes operating at multiple scales in space and time.     

Drought resistance increases with species richness in restored populations and communities

It is unknown to what extent or by what mechanisms introducing biodiversity influences stability of high-stress ecosystems undergoing restoration. Opportunity to investigate patterns of biodiversity and resistance to disturbance in a high-stress environment was presented when severe drought struck a restoration experiment underway on abandoned limestone quarry floors in Ontario, Canada. Experimental communities were previously established within small quarry-floor plots by sowing native grass and forb species considered to be characteristic of rare natural limestone pavements called alvars. Despite adding an identical 18-species seed-mixture to all plots, realized communities varied extensively with respect to the numbers of species established (species richness), the total number of individuals established (community abundance), and the number of individuals belonging to each species (population abundances). We investigated the relationship between species richness and resistance of community abundance to drought, while accounting for background richness–abundance correlation, by contrasting slopes and intercepts of the richness–abundance relationship immediately before vs. 6 weeks after the drought. This relationship was significantly positive prior to drought but 72% steeper in slope following drought, while the abundance intercept exhibited a 44% drop. Plots featuring richer, more abundant communities prior to drought thus suffered considerably less damage than species-poor, low-abundance plots. Population abundance was weakly related to richness prior to drought, but strongly and positively related to richness after the drought. At the individual species level, no species experienced greater losses of abundance with increased plot richness, but six species experienced reduced abundance losses where they co-occurred with more neighbour species. Facilitation or other mechanisms capable of increasing population resistance may thus underlie community resistance in high-stress environments. Though controlled experiments are required to establish causes of relationships reported here, the forms of these relationships suggest that managers may be able to promote resistance in high-stress ecosystems by establishing species-rich communities.     

An Ant Mosaic Revisited: Dominant Ant Species Disassemble Arboreal Ant Communities but Co-Occur Randomly

The spatial distributions of many tropical arboreal ant species are often arranged in a mosaic such that dominant species have mutually exclusive distributions among trees. These dominant species can also mediate the structure of the rest of the arboreal ant community. Little attention has been paid to how diet might shape the effects of dominant species on one another and the rest of the ant community. Here, we take advantage of new information on the diets of many tropical arboreal ant species to examine the intra- and inter-guild effects of dominant species on the spatial distribution of one another and the rest of the tropical arboreal ant community in a cocoa farm in Bahia, Brazil. Using null model analyses, we found that all ant species, regardless of dominance status or guild membership, co-occur much less than expected by chance. Surprisingly, the suite of five dominant species showed random co-occurrence patterns, suggesting that interspecific competition did not shape their distribution among cocoa trees. Across all species, there was no evidence that competition shaped co-occurrence patterns within guilds. Co-occurrence patterns of subordinant species were random on trees with dominant species, but highly nonrandom on trees without dominant species, suggesting that dominant species disassemble tropical arboreal ant communities. Taken together, our results highlight the often complex nature of interactions that structure species-rich tropical arboreal ant assemblages.