Effects Of Species Interactions Research Articles

On their best behavior: how animal behavior can help determine the combined effects of species interactions and climate change

The increasingly appreciated link between climate change and species interactions has the potential to help us understand and predict how organisms respond to a changing environment. As this connection grows, it becomes even more important to appreciate the mechanisms that create and control the combined effect of these factors. However, we believe one such important set of mechanisms comes from species' behavior and the subsequent trait-mediated interactions, as opposed to the more often studied density-mediated effects. Behavioral mechanisms are already well appreciated for mitigating the separate effects of the environment and species interactions. Thus, they could be at the forefront for understanding the combined effects. In this review, we (1) show some of the known behaviors that influence the individual and combined effects of climate change and species interactions; (2) conceptualize general ways behavior may mediate these combined effects; and (3) illustrate the potential importance of including behavior in our current tools for predicting climate change effects. In doing so, we hope to promote more research on behavior and other mechanistic factors that may increase our ability to accurately predict climate change effects.

Is feedback control effective for ecosystem-based fisheries management?

We investigate the effects of species interactions on the robustness of feedback control of the harvesting of prey species. We consider the consequences of feedback control of fishing effort. If a prey species is exploited, increasing fishing effort decreases predator abundance more than it does the prey abundance. Feedback control of fishing effort may cause the extinction of the predator, even if the prey population is well controlled. Even when fishing effort is controlled by predator density, it is difficult for the fishery and the predator to coexist, and, if they do so, the system exhibits complex dynamic behaviors. If the predator and fishery coexist, feedback control of fishing effort converges to a stable equilibrium, a synchronous cycle, or an asynchronous cycle. In the last case, the system undergoes more complex cycling with a longer period than that when the fishing effort is kept constant. These analyses suggest that there is no effective strategy that is robust against measurement errors, process errors and complex interactions in ecosystem dynamics.

Food webs in Mediterranean rivers

River food webs are subject to two regimes of longitudinally varying ecological control: productivity and disturbance. Light-limited productivity increases as channels widen downstream. Time windows for growth, however, shrink as discharge increases, substrate particle size decreases, and the frequency of flood-driven bed mobilization increases downstream. Mediterranean rivers are periodically reset by hydrologic events with somewhat predictable timing. Typically, a rainy winter with high river discharge is followed by summer drought with little or no rainfall and slowly declining river flow. The magnitude and timing of winter floods and severity of subsequent summer drought can vary considerably from year to year, however. Episodic scouring floods or prolonged periods of drought are experienced as disturbances, stressors, or opportunities by river biota. The timing, duration, and intensity of these hydrologic controls affect performances of individuals, distribution and abundances of populations, and outcomes and consequences of species interactions. These interactions in turn determine how river food webs will assemble, develop, and reconfigure after disturbance. We discuss how spatial variation in solar radiation and spatial and temporal variations in disturbance affects river food webs under Mediterranean climate seasonality, focusing primarily on long-term observations in the Eel River of northwestern California, USA.

Complex Species Interactions Lead to Unpredictable Outcomes inPlethodon

Evolutionary and ecological theory generates testable predictions concerning the effects of species interactions on ecological, behavioral, and morphological traits. Throughout Ohio, two closely related and ecologically similar salamander species, Plethodon cinereus and P. electromorphus, occur in similar habitats and in many localities are found in sympatry. Geographic and behavioral patterns previously described between these two species could be the result of interspecific competition, a hypothesis that also predicts distinct patterns of resource use, morphological variation, or both when the two species occur in sympatry. Here we tested these predictions by examining patterns of resource use and morphology in sympatry and compared them to patterns observed in allopatric populations of each species. We found that morphological differences in head shape between species were location-specific, with morphological divergence occurring at some sympatric locations and convergence occurring at others. The degree of food-use overlap was also variable between locations but, in general, the two species used similar food resources.

Local filters limit species diversity, but species pools determine composition

Abstract In a series of three experiments, we tested for effects of species pools, resource stress, and species interactions on four aspects of community structure: species richness, evenness, species composition, and functional group composition. We also examined whether the impacts of species interactions on the community varied with resource availability or species pool. Communities of sand dune annuals grew from seed bank samples collected from two sites in three different years, so that the species pool differed at two levels: the source site and the year of seed bank collection. Communities experienced one of three irrigation treatments and a range of sowing densities, which varied resource supply (stress) and the potential for species interactions, respectively. Species richness and evenness were most affected by local factors: higher densities and lower water availability decreased species diversity. In contrast, species composition was influenced most by the species pool. Functional group composition had an intermediate response, and was affected by both species pools and local filters. Resource stress and species interactions strongly filtered species from the community, but the identity of species remaining was variable. Furthermore, the magnitude of species interaction effects on richness and evenness varied with species pools. Thus, the outcome of species sorting among biotic and abiotic environments was dependent on the pool of available species. Contrary to predictions from theory, the effects of species interactions on the community did not vary consistently with resource levels.

Niche incumbency, dispersal limitation and climate shape geographical distributions in a species‐rich island adaptive radiation

AbstractAimTo test the role of climate, dispersal limitation and biotic interactions in limiting species' distributions within an island adaptive radiation by integrating species traits, phylogeny and estimates of dispersal cost into climate‐based species distribution models.LocationHispaniola.MethodsFocusing on 26 species of Anolis lizards, we used multivariate adaptive regression splines to evaluate the contribution of climate, species interactions, phylogenetic history and dispersal limitation to species distributional limits. For each species, we mapped the morphological similarity of congenerics using traits of known ecological import and predicted that species would be less likely to occur in climatically suitable areas if they were inhabited by ecologically similar species. Dispersal limitation was incorporated by generating spatially explicit estimates of dispersal cost, based on inferred habitat suitability. We compared models including morphological similarity, dispersal cost, phylogeny and climate with climate‐only models. Results were evaluated against a null model that conserved the spatial structure of species occurrences.ResultsClimate had a dominant role in shaping species distributions. However, for over one‐third of species we also found evidence consistent with supplemental effects of species interactions, i.e. ecological niche incumbency. These species were less likely to occur in climatically suitable areas inhabited by a morphologically similar species. Dispersal limitation also supplemented climatic limits in most species. These results were robust to co‐variation with phylogeny and to comparison with our null model.ConclusionsThese results suggest that, rather than act as mutually exclusive alternatives, multiple dimensions of the ecological niche, including climatic limits, biotic interactions and dispersal capacity, interact to shape species distributions and that local interactions can influence the broad‐scale geography of species in a predictable way.

Seasonal effect on rooting behaviour of important bamboo species by culm cuttings

We investigated the influence of season on the rooting behaviour of eight important bamboo species viz., Bambusa balcooa, B. bambos, B. nutans, B. tulda, B. vulgaris, Dendrocalamus giganteus, D. hamiltonii and D. strictus. We collected 2–3 node culm cuttings in three growing seasons viz. spring (March), summer (June) and rainy (August) from superior candidate plus clumps (CPCs) centralized in the germplasm garden. Cuttings were placed horizontally in sand and were provided with intermittent misting at regular intervals. Bamboo species exhibited differential rhizogenesis behavior in different seasons. The study reveals significant variation in sprouting and rooting behaviour in different bamboo species. B. bambos had maximum rooting (78.89%), followed by B. vulgaris (74.44%). In general, the potential of different bamboo species for rooting was found to be in the order: B. bambos > B. vulgaris > B. balcooa > D. hamiltonii > B. tulda > D. strictus > D. giganteus >B. nutans. The maximum rooting was recorded in spring (56.67%), which was closely followed by summer (54.58%). In winter season, minimum rooting (36.67%) was observed. The interaction effect of species × season was also significant on sprouting and rooting parameters. In B. balcooa, B. nutans, B. vulgaris, D. hamiltonii and D. strictus, cuttings collected in summer season showed maximum sprouting and rooting, whereas, B. bambos, B. tulda and D. giganteus had maximum rooting in spring. The maximum number of roots developed per cutting was observed in B. tulda (43.8) during spring season.

Interactions for pollinator visitation and their consequences for reproduction in a plant community

Competition and facilitation in species interactions attract much attention in ecology, but their relative importance has seldom been evaluated in a community context. We assessed competitive and facilitative interactions for pollinator visitation among co-flowering species in a plant community, investigated the subsequent consequences for plant reproduction, and investigated whether effects could be trait-based. We removed the flowers of two species attractive to pollinators, in two separate experiments and assessed the effects on pollinator visitation rates and components of reproductive success in 11 co-flowering focal herb species. Overall, most focal species appear not to interact with the removal species with respect to pollinator visitation and subsequent reproduction (neutral interactions). Three focal species in the community had significantly higher reproductive responses (fruit production and seed weight) in the presence of the attractive removal species (facilitative interactions), but species interaction effects were less pronounced in species' flower visitation rates. A community-wide meta-analysis demonstrated that the two experiments did not have a significant effect on either facilitation or competition, and that there was no overall correlation between effect sizes for visitation and reproduction. Based on species-specific responses, it seems likely that floral traits such as similar flower colors contribute to interspecific facilitation of pollinator visitation and, in particular, that high pollinator dependence for plant reproduction, and associated pollen limitation, may contribute to subsequent interaction effects on reproduction in the focal species.

Effect of competition on habitat utilization in two temperate climate gecko species

AbstractCompetition over spatial niche utilisation is one of most common competitive interactions between species in sympatry. Moreover, competitive interactions may involve age classes, and can fluctuate temporally. Consequently, evasive strategies that enable co‐existence are likely to be important in the evolution of species assemblages. Here we investigate a system of two co‐existing species of temperate geckos with similar ecologies (the house gecko, Hemidactylus turcicus and the wall gecko, Tarentola mauritanica), providing an opportunity to study the effect of species interactions. Juveniles and adults of both species were investigated throughout their daily and annual cycle to explore the effect of inter‐ and intra‐specific interactions on microhabitat use. The two species showed differences in habitat use for both age classes in sympatry. In sympatry, T. mauritanica uses more open habitats and is more active. In contrast, H. turcicus is found in more closed habitats, closer to the ground and to vegetation cover. In allopatry, H. turcicus was observed in more open habitats, closer to the ground, and to vegetation cover, when compared to the population in sympatry with T. mauritanica. These differences in habitat usage were significant for both age classes. Moreover, there were differences, both in sympatry and in allopatry, between age classes that were dependent on season. In conclusion, the presence of a competitor induces a spatial shift in individuals of both age classes of H. turcicus. Observed plasticity in habitat utilisation in both age classes of H. turcicus is used to argue for the invasive potential of this species.

Distinct Growth Strategies of Soil Bacteria as Revealed by Large-Scale Colony Tracking

Our understanding of microbial ecology has been significantly furthered in recent years by advances in sequencing techniques, but comprehensive surveys of the phenotypic characteristics of environmental bacteria remain rare. Such phenotypic data are crucial for understanding the microbial strategies for growth and the diversity of microbial ecosystems. Here, we describe a high-throughput measurement of the growth of thousands of bacterial colonies using an array of flat-bed scanners coupled with automated image analysis. We used this system to investigate the growth properties of members of a microbial community from untreated soil. The system provides high-quality measurements of the number of CFU, colony growth rates, and appearance times, allowing us to directly study the distribution of these properties in mixed environmental samples. We find that soil bacteria display a wide range of growth strategies which can be grouped into several clusters that cannot be reduced to any of the classical dichotomous divisions of soil bacteria, e.g., into copiotophs and oligotrophs. We also find that, at early times, cells are most likely to form colonies when other, nearby colonies are present but not too dense. This maximization of culturability at intermediate plating densities suggests that the previously observed tendency for high density to lead to fewer colonies is partly offset by the induction of colony formation caused by interactions between microbes. These results suggest new types of growth classification of soil bacteria and potential effects of species interactions on colony growth.

Effects of pure and mixed plantations of Populus deltoides with Alnus glotinosa on growth and soil properties: A case study of Foman Region, Iran

Plantation and application of fast-growing species, such as Populus deltoides increasingly, are common in the northern part of Iran. Concerns about decline in soil fertility and long-term productivity of fast-growing plantations have promoted interest in using nitrogen-fixing trees in mixed species plantations. P. deltoidesand Alnus glutinosa were planted in five proportions (100P, 70P:30A, 50P:50A, 30P:70A, 100A) in Foman, Iran. After 13 years, the effects of species interactions on tree growth and nutrient concentration in live and senescent leaves and soil properties were assessed. Diameter at breast height and total height of individualPopulus trees were positively affected by the presence of Alnus. Nitrogen concentrations in fully expanded and senescent leaves of Populus were higher in mixed plantations than monoculture plantations. The results of nutrition and nutrient return and growth indicated that mixed plantations of these two species were more productive and sustainable than their monoculture plantations. Within the framework of this experiment, it appeared that production was maximized when these two species were grown together in the relative proportions of 30% Populus and 70% Alnus. Key words: Mixed plantation, Alnus, Populus, growth, soil.

Species composition and interspecific association of plants in primary succession of Mount Merapi, Indonesia

Sutomo, Faradila D, Putri LSE (2011) Species composition and interspecific association of plants in primary succession of Mount Merapi, Indonesia. Biodiversitas 12: 212-217. Primary succession refers to the establishment of plant species and subsequent changes in composition following major disturbance such as volcanic activity. The study of succession may assist in recognizing the possible effects of species interactions (i.e. facilitation or inhibition). The barren landscapes created by volcanic disturbance on Mount Merapi, Java, Indonesia, provide excellent opportunities to study primary succession. Fifty-six species belonging to 26 families were recorded in the five nuées ardentes deposits. The highest number of species belonged to the Asteraceae, then Poaceae, followed by Fabaceae andRubiaceae. In Mount Merapi primary succession, the ecosystem may be developing with time as indicated by the increase in the number of species associations. The number of positive associations was generally higher than the number of negative associations, except in the 2001 deposit where it was equal. Native and alien invasive species had different patterns of interspecific associations. This research demonstrates that in primary succession sites on Mount Merapi, positive interspecific association increased as time progressed, which may support the view that facilitation is more prominent in a severely disturbed habitat as compared to competition.

Seed fate and seedling dynamics after masting in two African rain forest trees

How the effects of biotic factors are moderated by abiotic factors, and their consequences for species interactions, is generally understudied in ecology. A key abiotic feature of forests is regular canopy disturbances that create temporary patches, or “gaps,” of above-average light availability. Co-occurring in lowland primary forest of Korup National Park (Cameroon), Microberlinia bisulcata and Tetraberlinia bifoliolata are locally dominant, ectomycorrhizal trees whose seeds share predator guilds in masting years. Here, we experimentally tested the impact of small mammal predators upon seedling abundance, growth, and survivorship. In 2007, we added a fixed density of seeds of each species to exclosures at 48 gap–understory locations across 82.5 ha within a large Microberlinia grove, and at 15 locations outside it. For both species, small mammals removed more seeds in gaps than in understory, whereas this was reversed for seeds killed by invertebrates. Nonetheless, Microberlinia lost twice as many seeds to small mammals, and more to invertebrates in exclosures, than Tetraberlinia, which was more prone to a pathogenic white fungus. After six weeks, both species had greater seedling establishment in gaps than understory, and in exclosures outside compared to exclosures inside the grove. In the subsequent two-year period, seedling growth and survivorship peaked in exclosures in gaps, but Microberlinia had more seedlings' stems clipped by animals than Tetraberlinia, and more than twice the percentage of leaf area damaged. Whereas Microberlinia seedling performance in gaps was inferior to Tetraberlinia inside the grove, outside it Microberlinia had reduced leaf damage, grew taller, and had many more leaves than Tetraberlinia. No evidence was found for “apparent mutualism” in the understory as seedling establishment of both species increased away from (>25 m) large stems of either species, pointing to “apparent competition” instead. In gaps, Microberlinia seedling establishment was lower near Tetraberlinia than conspecific adults because of context-dependent small mammal satiation. Stage-matrix analysis suggested that protecting Microberlinia from small mammals could increase its population growth rate by 0.06. In the light of prior research we conclude that small mammals and canopy gaps play an important role in promoting species coexistence in this forest, and that their strong interaction contributes to Microberlinia's currently very poor regeneration.

Investigating the drivers of maturation dynamics in Barents Sea haddock ( Melanogrammus aeglefinus)

Changes in size and age at maturation of many exploited fish stocks have been investigated and the influences of environmental factors and exploitation have often been inferred, but not explicitly investigated. Here we determine probabilistic maturation reaction norms (PMRNs) for Barents Sea haddock ( Melanogrammus aeglefinus) using generalized linear models (GLMs) and mixed effect models (GLMMs), which account for the correlation among samples within a tow station, and investigate the effects of fishing mortality, environmental factors (NAO, water temperature, and salinity), and potential density dependence or species interaction effects. We found little evidence of a consistent trend in maturation tendencies for Barents Sea haddock for cohorts 1983–2003, ages 4–6 years. Female haddock matured at larger lengths for a given age than males, but overall patterns were similar for both sexes. The GLMM approach gave consistently higher PMRN midpoint estimates than the GLM approach, which indicated that PMRNs that do not account for correlations within the data may bias estimates. Environmental factors, rather than exploitation, density dependence, or species interactions, were responsible for the observed changes in size and age at maturation in Barents Sea haddock during the late 1980s through early 2000s. Little evidence of fisheries-induced evolution was found in these fish over the time period investigated. The lack of a significant temporal trend in maturation may be due to several challenges in estimating representative population parameters for this stock, the trait change being in a period of stasis or reversal, or adaptation by the fish to higher exploitation in the past resulting in negligible evolutionary selection during the study period when exploitation has been more moderate.

Understanding the relative roles of disturbance and species interactions in shaping Mississippi River island plant communities

In order to better understand the factors governing community assembly on riverine islands, we conducted a greenhouse experiment that examined the effects of species interactions in combination with flooding that mimicked hydrologic gradients found on Mississippi River islands. Specifically, we examined the effects of inter and intra-specific competition and three disturbance treatments (drained, drought, and flood) on the growth performance of three island-ubiquitous herbaceous plant species (Amaranthus palmeri, Cyperus strigosus. and Xanthium strumarium). We predicted a decrease in interspecific competitive effects in disturbance treatments. Specifically, we expected A palmeri to be most affected by flooding treatment based on its facultative upland status suggesting that it should be a poor tolerator of flooded conditions. X. strumarium and C. strigosus both facultative wetland species in their status, should tolerate flooding, but we predict that C. strigosus should have greater stress tolerance due to its perennial life history. Because we find these species coexisting at the same elevation zones on riverine islands, we also predicted stronger intraspecific competition effects. Our results indicate that disturbance indeed affected competitive interactions, but the effects were species-specific. X. strumarium showed stronger competitive effects when grown with conspecifics while C. strigosus experienced greater competition with heterospecifics under drought treatments. Based on its wetland indicator status and life history characteristics, we expected A palmeri to exhibit a facilitative effect, as it is typically an upland species, but instead it was impacted most by interspecific competition. Our study indicates that factors other than competition, facilitation, and flood tolerance (e.g., priority effects) may be controlling island plant community dynamics, further studies are required.

Indirect effects of species interactions on habitat provisioning

Species that shelter in a biogenic habitat can influence their refugia and, in turn, play an essential role in shaping local patterns of biodiversity. Here we explore a positive feedback loop between the provisioning rate of habitat-forming branching corals and their associated fishes and show how interactions between two groups of fish—the planktivorous damselfish and predatory hawkfish—altered the feedback. A field experiment confirmed that skeletal growth of branching coral (genus Pocillopora) increased substantially with increasing numbers (biomass) of resident fishes, likely because they greatly increased the interstitial concentrations of nutrients. Because there is a positive relationship between colony size and number (biomass) of associated fishes (primarily damselfishes in the Family Pomacentridae), a structure–function feedback loop exists in which increasing numbers of damselfish enhance coral growth and larger corals host greater abundances (and species richness) of fish. However, interactions between damselfishes and arc-eye hawkfish, Paracirrhites arcatus, a largely solitary resident, can disrupt this positive feedback loop. Field surveys revealed a marked pattern of fish occupancy related to coral size: Pocillopora colonies of sufficient size to host fish (>40 cm circumference) had either groups of damselfish or an arc-eye hawkfish; only larger colonies (>75 cm) were occupied by both the damselfish and hawkfish. Subsequent short- and long-term experiments revealed that on intermediate-sized Pocillopora colonies, arc-eye hawkfish prevented the establishment of damselfish by suppressing their recruitment. The demographic consequences to the host coral were substantial; in a 1-year-long experiment, intermediate-size Pocillopora occupied by hawkfish grew at half the rate of corals that hosted groups of damselfish. These findings indicate that: (1) species which occupy a biogenic habitat can enhance the provisioning rate of their habitat; (2) such positive feedbacks between community structure and ecosystem function can be disrupted by a strong interactor; (3) even substantial consequences on ecosystem processes that arise can be difficult to discern.

Emergence and dynamics of influenza super-strains

BackgroundInfluenza super-strains can emerge through recombination of strains from birds, pigs, and humans. However, once a new recombinant strain emerges, it is not clear whether the strain is capable of sustaining an outbreak. In certain cases, such strains have caused major influenza pandemics.MethodsHere we develop a multi-host (i.e., birds, pigs, and humans) and multi-strain model of influenza to analyze the outcome of emergent strains. In the model, pigs act as “mixing vessels” for avian and human strains and can produce super-strains from genetic recombination.ResultsWe find that epidemiological outcomes are predicted by three factors: (i) contact between pigs and humans, (ii) transmissibility of the super-strain in humans, and (iii) transmissibility from pigs to humans. Specifically, outbreaks will reoccur when the super-strain infections are less frequent between humans (e.g., R0=1.4) but frequent from pigs to humans, and a large-scale outbreak followed by successive dampening outbreaks will occur when super-strain infections are frequent between humans (e.g., R0=2.3). The average time between the initial outbreak and the first resurgence varies from 41 to 82 years. We determine the largest outbreak will occur when 2.3 <R0 < 3.8 and the highest cumulative infections occur when 0 <R0 < 3.0 and is dependent on the frequency of pig-to-human infections for lower R0 values (0 <R0 < 1.9).ConclusionsOur results provide insights on the effect of species interactions on the dynamics of influenza super-strains. Counter intuitively, epidemics may occur in humans even if the transmissibility of a super-strain is low. Surprisingly, our modeling shows strains that have generated past epidemics (e.g., H1N1) could resurge decades after they have apparently disappeared.

Defining environmental risk assessment criteria for genetically modified fishes to be placed on the EU market

Defining environmental risk assessment criteria for genetically modified fishes to be placed on the EU market

Projecting climate change impacts on species distributions in megadiverse South African Cape and Southwest Australian Floristic Regions: Opportunities and challenges

AbstractIncreasing evidence shows that anthropogenic climate change is affecting biodiversity. Reducing or stabilizing greenhouse gas emissions may slow global warming, but past emissions will continue to contribute to further unavoidable warming for more than a century. With obvious signs of difficulties in achieving effective mitigation worldwide in the short term at least, sound scientific predictions of future impacts on biodiversity will be required to guide conservation planning and adaptation. This is especially true in Mediterranean type ecosystems that are projected to be among the most significantly affected by anthropogenic climate change, and show the highest levels of confidence in rainfall projections. Multiple methods are available for projecting the consequences of climate change on the main unit of interest – the species – with each method having strengths and weaknesses. Species distribution models (SDMs) are increasingly applied for forecasting climate change impacts on species geographic ranges. Aggregation of models for different species allows inferences of impacts on biodiversity, though excluding the effects of species interactions. The modelling approach is based on several further assumptions and projections and should be treated cautiously. In the absence of comparable approaches that address large numbers of species, SDMs remain valuable in estimating the vulnerability of species. In this review we discuss the application of SDMs in predicting the impacts of climate change on biodiversity with special reference to the species‐rich South West Australian Floristic Region and South African Cape Floristic Region. We discuss the advantages and challenges in applying SDMs in biodiverse regions with high levels of endemicity, and how a similar biogeographical history in both regions may assist us in understanding their vulnerability to climate change. We suggest how the process of predicting the impacts of climate change on biodiversity with SDMs can be improved and emphasize the role of field monitoring and experiments in validating the predictions of SDMs.

Macroecological signals of species interactions in the Danish avifauna.

The role of intraspecific and interspecific interactions in structuring biotic communities at fine spatial scales is well documented, but the signature of species interactions at coarser spatial scales is unclear. We present evidence that species interactions may be a significant factor in mediating the regional assembly of the Danish avifauna. Because >95% of breeding species (n = 197) are migratory, we hypothesized that dispersal limitation would not be important and that breeding distributions would largely reflect resource availability and autecological habitat preferences. Instead, we detected a striking pattern of spatial segregation between ecologically similar species at two spatial scales with a suite of null models that factored in the spatial distribution of habitats in Denmark as well as population size and biomass of each species. Habitat utilization analyses indicated that community-wide patterns of spatial segregation could not be attributed to the patchy distribution of habitat or to gross differences in habitat utilization among ecologically similar species. We hypothesize that, when habitat patch size is limited, conspecific attraction in concert with interspecific territoriality may result in spatially segregated distributions of ecologically similar species at larger spatial scales. In the Danish avifauna, the effects of species interactions on community assembly appear pervasive and can be discerned at grain sizes up to four orders of magnitude larger than those of individual territories. These results suggest that species interactions should be incorporated into species distribution modeling algorithms designed to predict species occupancy patterns based on environmental variables.