Co‐occurrence methods are increasingly utilized in ecology to infer networks of species interactions where detailed knowledge based on empirical studies is difficult to obtain. Their use is particularly common, but not restricted to, microbial networks constructed from metagenomic analyses. In this study, we test the efficacy of this procedure by comparing an inferred network constructed using spatially intensive co‐occurrence data from the rocky intertidal zone in central Chile to a well‐resolved, empirically based, species interaction network from the same region. We evaluated the overlap in the information provided by each network and the extent to which there is a bias for co‐occurrence data to better detect known trophic or non‐trophic, positive or negative interactions. We found a poor correspondence between the co‐occurrence network and the known species interactions with overall sensitivity (probability of true link detection) equal to 0.469, and specificity (true non‐interaction) equal to 0.527. The ability to detect interactions varied with interaction type. Positive non‐trophic interactions such as commensalism and facilitation were detected at the highest rates. These results demonstrate that co‐occurrence networks do not represent classical ecological networks in which interactions are defined by direct observations or experimental manipulations. Co‐occurrence networks provide information about the joint spatial effects of environmental conditions, recruitment, and, to some extent, biotic interactions, and among the latter, they tend to better detect niche‐expanding positive non‐trophic interactions. Detection of links (sensitivity or specificity) was not higher for well‐known intertidal keystone species than for the rest of consumers in the community. Thus, as observed in previous empirical and theoretical studies, patterns of interactions in co‐occurrence networks must be interpreted with caution, especially when extending interaction‐based ecological theory to interpret network variability and stability. Co‐occurrence networks may be particularly valuable for analysis of community dynamics that blends interactions and environment, rather than pairwise interactions alone.
Mesophotic coral ecosystems (i.e., deep coral reefs at 30–120 m depth) appear to be thriving while many shallow reefs in the world are declining. Amid efforts to understand and manage their decline, it was suggested that mesophotic reefs might serve as natural refuges and a possible source of propagules for the shallow reefs. However, our knowledge of how reproductive performance of corals alters with depth is sparse. Here, we present a comprehensive study of the reproductive phenology, fecundity, and abundance of seven reef‐building conspecific corals in shallow and mesophotic habitats. Significant differences were found in the synchrony and timing of gametogenesis and spawning between shallow and mesophotic coral populations. Thus, mesophotic populations exhibited delayed or protracted spawning events, which led to spawning of the mesophotic colonies in large proportions at times where the shallow ones had long been depleted of reproductive material. All species investigated demonstrated a substantial reduction in fecundity and/or oocyte sizes at mesophotic depths (40–60 m). Two species ( Seriatopora hystrix and Galaxea fascicularis ) displayed a reduction in both fecundity and oocyte size at mesophotic depths. Turbinaria reniformis had only reduced fecundity and Acropora squarrosa and Acropora valida only reduced oocyte size. In Montipora verrucosa , reduced fecundity was found during one annual reproductive season while, in the following year, only reduced oocyte size was found. In contrast, reduced oocyte size in mesophotic populations of Acropora squarrosa was consistent along three studied years. One species, Acropora pharaonis , was found to be infertile at mesophotic depths along two studied years. This indicates that reproductive performance decreases with depth; and that although some species are capable of reproducing at mesophotic depths, their contribution to the replenishment of shallow reefs may be inconsequential. Reduced reproductive performance with depth, combined with the possible narrower tolerance to environmental factors, further suggests that mesophotic corals may in fact be more vulnerable than previously conceived. Furthermore, we posit that the observed temporal segregation in reproduction could lead to assortative mating, and this, in turn, may facilitate adaptive divergence across depth.
In the absence of broad‐scale disturbance, many temperate coniferous forests experience successful seedling establishment only when abundant seed production coincides with favorable climate. Identifying the frequency of past establishment events and the climate conditions favorable for seedling establishment is essential to understanding how climate warming could affect the frequency of future tree establishment events and therefore future forest composition or even persistence of a forest cover. In the southern Rocky Mountains, USA, research on the sensitivity of establishment of Engelmann spruce ( Picea e ngelmannii ) and subalpine fir ( Abies lasiocarpa )—two widely distributed, co‐occurring conifers in North America—to climate variability has focused on the alpine treeline ecotone, leaving uncertainty about the sensitivity of these species across much of their elevation distribution. We compared annual germination dates for >450 Engelmann spruce and >500 subalpine fir seedlings collected across a complex topographic‐moisture gradient to climate variability in the Colorado Front Range. We found that Engelmann spruce and subalpine fir established episodically with strong synchrony in establishment events across the study area. Broad‐scale establishment events occurred in years of high soil moisture availability, which were characterized by above‐average snowpack and/or cool and wet summer climatic conditions. In the recent half of the study period (1975–2010), a decrease in the number of fir and spruce establishment events across their distribution coincided with declining snowpack and a multi‐decadal trend of rising summer temperature and increasing moisture deficits. Counter to expected and observed increases in tree establishment with climate warming in maritime subalpine forests, our results show that recruitment declines will likely occur across the core of moisture‐limited subalpine tree ranges as warming drives increased moisture deficits.
Binomial N ‐mixture models have proven very useful in ecology, conservation, and monitoring: they allow estimation and modeling of abundance separately from detection probability using simple counts. Recently, doubts about parameter identifiability have been voiced. I conducted a large‐scale screening test with 137 bird data sets from 2,037 sites. I found virtually no identifiability problems for Poisson and zero‐inflated Poisson (ZIP) binomial N ‐mixture models, but negative‐binomial (NB) models had problems in 25% of all data sets. The corresponding multinomial N ‐mixture models had no problems. Parameter estimates under Poisson and ZIP binomial and multinomial N ‐mixture models were extremely similar. Identifiability problems became a little more frequent with smaller sample sizes (267 and 50 sites), but were unaffected by whether the models did or did not include covariates. Hence, binomial N ‐mixture model parameters with Poisson and ZIP mixtures typically appeared identifiable. In contrast, NB mixtures were often unidentifiable, which is worrying since these were often selected by Akaike's information criterion. Identifiability of binomial N ‐mixture models should always be checked. If problems are found, simpler models, integrated models that combine different observation models or the use of external information via informative priors or penalized likelihoods, may help.
Niche differences are key to understanding the distribution and structure of biodiversity. To examine niche differences, we must first characterize how species occupy niche space, and two approaches are commonly used in the ecological literature. The first uses species traits to estimate multivariate trait space (so‐called functional trait diversity, FD); the second quantifies the amount of time or evolutionary history captured by a group of species (phylogenetic diversity, PD). It is often—but controversially—assumed that these putative measures of niche space are at a minimum correlated and perhaps redundant, since more evolutionary time allows for greater accumulation of trait changes. This theoretical expectation remains surprisingly poorly evaluated, particularly in the context of multivariate measures of trait diversity. We evaluated the relationship between phylogenetic diversity and trait diversity using analytical and simulation‐based methods across common models of trait evolution. We show that PD correlates with FD increasingly strongly as more traits are included in the FD measure. Our results indicate that phylogenetic diversity can be a useful surrogate for high‐dimensional trait diversity, but we also show that the correlation weakens when the underlying process of trait evolution includes variation in rate and optima.
Latitudinal gradients in species interactions are widely cited as potential causes or consequences of global patterns of biodiversity. However, mechanistic studies documenting changes in interactions across broad geographic ranges are limited. We surveyed predation intensity on common prey (live amphipods and gastropods) in communities of eelgrass ( Zostera marina ) at 48 sites across its Northern Hemisphere range, encompassing over 37° of latitude and four continental coastlines. Predation on amphipods declined with latitude on all coasts but declined more strongly along western ocean margins where temperature gradients are steeper. Whereas in situ water temperature at the time of the experiments was uncorrelated with predation, mean annual temperature strongly positively predicted predation, suggesting a more complex mechanism than simply increased metabolic activity at the time of predation. This large‐scale biogeographic pattern was modified by local habitat characteristics; predation declined with higher shoot density both among and within sites. Predation rates on gastropods, by contrast, were uniformly low and varied little among sites. The high replication and geographic extent of our study not only provides additional evidence to support biogeographic variation in predation intensity, but also insight into the mechanisms that relate temperature and biogeographic gradients in species interactions.
In recent years, it has been argued that the effect of predator fear exacts a greater demographic toll on prey populations than the direct killing of prey. However, efforts to quantify the effects of fear have primarily relied on experiments that replace predators with predator cues. Interpretation of these experiments must consider two important caveats: (1) the magnitude of experimenter‐induced predator cues may not be realistically comparable to those of the prey's natural sensory environment, and (2) given functional predators are removed from the treatments, the fear effect is measured in the absence of any consumptive effects, a situation which never occurs in nature. We contend that demographic consequences of fear in natural populations may have been overestimated because the intensity of predator cues applied by experimenters in the majority of studies has been unnaturally high, in some instances rarely occurring in nature without consumption. Furthermore, the removal of consumption from the treatments creates the potential situation that individual prey in poor condition (those most likely to contribute strongly to the observed fear effects via starvation or reduced reproductive output) may have been consumed by predators in nature prior to the expression of fear effects, thus confounding consumptive and fear effects. Here, we describe an alternative treatment design that does not utilize predator cues, and in so doing, better quantifies the demographic effect of fear on wild populations. This treatment substitutes the traditional cue experiment where consumptive effects are eliminated and fear is simulated with a design where fear is removed and consumptive effects are simulated through the experimental removal of prey. Comparison to a natural population would give a more robust estimate of the effect of fear in the presence of consumption on the demographic variable of interest. This approach represents a critical advance in quantifying the mechanistic pathways through which predation structures ecological communities. Discussing the merits of both treatments will motivate researchers to go beyond simply describing the existence of fear effects and focus on testing their true magnitude in wild populations and natural communities.
Successional dynamics in plant community assembly may result from both deterministic and stochastic ecological processes. The relative importance of different ecological processes is expected to vary over the successional sequence, between different plant functional groups, and with the disturbance levels and land‐use management regimes of the successional systems. We evaluate the relative importance of stochastic and deterministic processes in bryophyte and vascular plant community assembly after fire in grazed and ungrazed anthropogenic coastal heathlands in Northern Europe. A replicated series of post‐fire successions ( n = 12) were initiated under grazed and ungrazed conditions, and vegetation data were recorded in permanent plots over 13 years. We used redundancy analysis ( RDA ) to test for deterministic successional patterns in species composition repeated across the replicate successional series and analyses of co‐occurrence to evaluate to what extent species respond synchronously along the successional gradient. Change in species co‐occurrences over succession indicates stochastic successional dynamics at the species level (i.e., species equivalence), whereas constancy in co‐occurrence indicates deterministic dynamics (successional niche differentiation). The RDA shows high and deterministic vascular plant community compositional change, especially early in succession. Co‐occurrence analyses indicate stochastic species‐level dynamics the first two years, which then give way to more deterministic replacements. Grazed and ungrazed successions are similar, but the early stage stochasticity is higher in ungrazed areas. Bryophyte communities in ungrazed successions resemble vascular plant communities. In contrast, bryophytes in grazed successions showed consistently high stochasticity and low determinism in both community composition and species co‐occurrence. In conclusion, stochastic and individualistic species responses early in succession give way to more niche‐driven dynamics in later successional stages. Grazing reduces predictability in both successional trends and species‐level dynamics, especially in plant functional groups that are not well adapted to disturbance.
We present a meta‐analysis of plant responses to fertilization experiments conducted in lowland, species‐rich, tropical forests. We also update a key result and present the first species‐level analyses of tree growth rates for a 15‐yr factorial nitrogen (N), phosphorus (P), and potassium (K) experiment conducted in central Panama. The update concerns community‐level tree growth rates, which responded significantly to the addition of N and K together after 10 yr of fertilization but not after 15 yr. Our experimental soils are infertile for the region, and species whose regional distributions are strongly associated with low soil P availability dominate the local tree flora. Under these circumstances, we expect muted responses to fertilization, and we predicted species associated with low‐P soils would respond most slowly. The data did not support this prediction, species‐level tree growth responses to P addition were unrelated to species‐level soil P associations. The meta‐analysis demonstrated that nutrient limitation is widespread in lowland tropical forests and evaluated two directional hypotheses concerning plant responses to N addition and to P addition. The meta‐analysis supported the hypothesis that tree (or biomass) growth rate responses to fertilization are weaker in old growth forests and stronger in secondary forests, where rapid biomass accumulation provides a nutrient sink. The meta‐analysis found no support for the long‐standing hypothesis that plant responses are stronger for P addition and weaker for N addition. We do not advocate discarding the latter hypothesis. There are only 14 fertilization experiments from lowland, species‐rich, tropical forests, 13 of the 14 experiments added nutrients for five or fewer years, and responses vary widely among experiments. Potential fertilization responses should be muted when the species present are well adapted to nutrient‐poor soils, as is the case in our experiment, and when pest pressure increases with fertilization, as it does in our experiment. The statistical power and especially the duration of fertilization experiments conducted in old growth, tropical forests might be insufficient to detect the slow, modest growth responses that are to be expected.
Environmental change is accelerating in the 21st century, but how multiple drivers may interact to alter forest resilience remains uncertain. In forests affected by large high‐severity disturbances, tree regeneration is a resilience linchpin that shapes successional trajectories for decades. We modeled stands of two widespread western U.S. conifers, Douglas‐fir ( Pseudotsuga menziesii var. glauca ), and lodgepole pine ( Pinus contorta var. latifolia) , in Yellowstone National Park (Wyoming, USA ) to ask (1) What combinations of distance to seed source, fire return interval, and warming‐drying conditions cause postfire tree‐regeneration failure? (2) If postfire tree regeneration was successful, how does early tree density differ under future climate relative to historical climate? We conducted a stand‐level (1 ha) factorial simulation experiment using the individual‐based forest process model iL and to identify combinations of fire return interval (11–100 yr), distance to seed source (50–1,000 m), and climate (historical, mid‐21st century, late‐21st century) where trees failed to regenerate by 30‐yr postfire. If regeneration was successful, we compared stand densities between climate periods. Simulated postfire regeneration were surprisingly resilient to changing climate and fire drivers. Douglas‐fir regeneration failed more frequently (55%) than lodgepole pine (28% and 16% for non‐serotinous and serotinous stands, respectively). Distance to seed source was an important driver of regeneration failure for Douglas‐fir and non‐serotinous lodgepole pine; regeneration never failed when stands were 50 m from a seed source and nearly always failed when stands were 1 km away. Regeneration of serotinous lodgepole pine only failed when fire return intervals were ≤20 yr and stands were far (1 km) from a seed source. Warming climate increased regeneration success for Douglas‐fir but did not affect lodgepole pine. If regeneration was successful, postfire density varied with climate. Douglas‐fir and serotinous lodgepole pine regeneration density both increased under 21st‐century climate but in response to different climate variables (growing season length vs. cold limitation). Results suggest that, given a warmer future with larger and more frequent fires, a greater number of stands that fail to regenerate after fires combined with increasing density in stands where regeneration is successful could produce a more coarse‐grained forest landscape.
N ‐mixture models provide an appealing alternative to mark–recapture models, in that they allow for estimation of detection probability and population size from count data, without requiring that individual animals be identified. There is, however, a cost to using the N ‐mixture models: inference is very sensitive to the model's assumptions. We consider the effects of three violations of assumptions that might reasonably be expected in practice: double counting, unmodeled variation in population size over time, and unmodeled variation in detection probability over time. These three examples show that small violations of assumptions can lead to large biases in estimation. The violations of assumptions we consider are not only small qualitatively, but are also small in the sense that they are unlikely to be detected using goodness‐of‐fit tests. In cases where reliable estimates of population size are needed, we encourage investigators to allocate resources to acquiring additional data, such as recaptures of marked individuals, for estimation of detection probabilities.
Ecologically dominant species often define ecosystem states, but as human disturbances intensify, their subordinate counterparts increasingly displace them. We consider the duality of disturbance by examining how environmental drivers can simultaneously act as a stressor to dominant species and as a resource to subordinates. Using a model ecosystem, we demonstrate that CO 2 ‐driven interactions between species can account for such reversals in dominance; i.e., the displacement of dominants (kelp forests) by subordinates (turf algae). We established that CO 2 enrichment had a direct positive effect on productivity of turfs, but a negligible effect on kelp. CO 2 enrichment further suppressed the abundance and feeding rate of the primary grazer of turfs (sea urchins), but had an opposite effect on the minor grazer (gastropods). Thus, boosted production of subordinate producers, exacerbated by a net reduction in its consumption by primary grazers, accounts for community change (i.e., turf displacing kelp). Ecosystem collapse, therefore, is more likely when resource enrichment alters competitive dominance of producers, and consumers fail to compensate. By recognizing such duality in the responses of interacting species to disturbance, which may stabilize or exacerbate change, we can begin to understand how intensifying human disturbances determine whether or not ecosystems undergo phase shifts.
Dispersal is a key ecological process that influences the dynamics of spatially and socially structured populations and consists of three stages—emigration, transience, and settlement—and each stage is influenced by different social, individual, and environmental factors. Despite our appreciation of the complexity of the process, we lack a firm empirical understanding of the mechanisms underlying the different stages. Here, using data from 65 GPS ‐collared dispersing female coalitions of the cooperatively breeding meerkat ( Suricata suricatta ), we present a comprehensive analysis of the effects of population density, mate availability, dispersing coalition size, and individual factors on each of the three stages of dispersal in a wild population. We expected a positive effect of density on dispersal due to increased kin competition at high densities. We further anticipated positive effects of mate availability, coalition size, and body condition on dispersal success. We observed increasing daily emigration and settlement probabilities at high population densities. In addition, we found that emigration and settlement probabilities also increased at low densities and were lowest at medium densities. Daily emigration and settlement probabilities increased with increasing female coalition size and in the presence of unrelated males. Furthermore, the time individuals spent in the transient stage increased with population density, whereas coalition size and presence of unrelated males decreased dispersal distance. The observed nonlinear relationship between dispersal and population density is likely due to limited benefits of cooperation at low population densities and increased kin competition at high densities. Our study provides empirical validation for the theoretical predictions that population density is an important factor driving the evolution of delayed dispersal and philopatry in cooperative breeders.
More than 200 years ago, Alexander von Humboldt reported that tropical plant species richness decreased with increasing elevation and decreasing temperature. Surprisingly, coordinated patterns in plant, bacterial, and fungal diversity on tropical mountains have not yet been observed, despite the central role of soil microorganisms in terrestrial biogeochemistry and ecology. We studied an Andean transect traversing 3.5 km in elevation to test whether the species diversity and composition of tropical forest plants, soil bacteria, and fungi follow similar biogeographical patterns with shared environmental drivers. We found coordinated changes with elevation in all three groups: species richness declined as elevation increased, and the compositional dissimilarity among communities increased with increased separation in elevation, although changes in plant diversity were larger than in bacteria and fungi. Temperature was the dominant driver of these diversity gradients, with weak influences of edaphic properties, including soil pH . The gradients in microbial diversity were strongly correlated with the activities of enzymes involved in organic matter cycling, and were accompanied by a transition in microbial traits towards slower‐growing, oligotrophic taxa at higher elevations. We provide the first evidence of coordinated temperature‐driven patterns in the diversity and distribution of three major biotic groups in tropical ecosystems: soil bacteria, fungi, and plants. These findings suggest that interrelated and fundamental patterns of plant and microbial communities with shared environmental drivers occur across landscape scales. These patterns are revealed where soil pH is relatively constant, and have implications for tropical forest communities under future climate change.
In 2015–2016, record temperatures triggered a pan‐tropical episode of coral bleaching. In the southern hemisphere summer of March–April 2016, we used aerial surveys to measure the level of bleaching on 1,156 individual reefs throughout the 2,300 km length of the Great Barrier Reef, the world's largest coral reef system. The accuracy of the aerial scores was ground‐truthed with detailed underwater surveys of bleaching at 260 sites (104 reefs), allowing us to compare aerial and underwater bleaching data with satellite‐derived temperatures and with associated model predictions of bleaching. The severity of bleaching on individual reefs in 2016 was tightly correlated with the level of local heat exposure: the southernmost region of the Great Barrier Reef escaped with only minor bleaching because summer temperatures there were close to average. Gradients in nutrients and turbidity from inshore to offshore across the Great Barrier Reef had minimal effect on the severity of bleaching. Similarly, bleaching was equally severe on reefs that are open or closed to fishing, once the level of satellite‐derived heat exposure was accounted for. The level of post‐bleaching mortality, measured underwater after 7–8 months, was tightly correlated with the aerial scores measured at the peak of bleaching. Similarly, reefs with a high aerial bleaching score also experienced major shifts in species composition due to extensive mortality of heat‐sensitive species. Reefs with low bleaching scores did not change in composition, and some showed minor increases in coral cover. Two earlier mass bleaching events occurred on the Great Barrier Reef in 1998 and 2002, that were less severe than 2016. In 2016, 60% of corals affected) was four times higher in 2016. The geographic footprint of each of the three events is distinctive, and matches satellite‐derived sea surface temperature patterns. Our aerial surveys indicate that past exposure to bleaching in 1998 and 2002 did not lessen the severity of bleaching in 2016. This data set of aerial bleaching scores provides a historical baseline for comparison with future bleaching events. No copyright restrictions apply to the use of this data set other than citing this publication.
Plant functional traits provide information about adaptations to climate and environmental conditions, and can be used to explore the existence of alternative plant strategies within ecosystems. Trait data are also increasingly being used to provide parameter estimates for vegetation models. Here we present a new database of plant functional traits from China. Most global climate and vegetation types can be found in China, and thus the database is relevant for global modeling. The China Plant Trait Database contains information on morphometric, physical, chemical, and photosynthetic traits from 122 sites spanning the range from boreal to tropical, and from deserts and steppes through woodlands and forests, including montane vegetation. Data collection at each site was based either on sampling the dominant species or on a stratified sampling of each ecosystem layer. The database contains information on 1,215 unique species, though many species have been sampled at multiple sites. The original field identifications have been taxonomically standardized to the Flora of China. Similarly, derived photosynthetic traits, such as electron‐transport and carboxylation capacities, were calculated using a standardized method. To facilitate trait–environment analyses, the database also contains detailed climate and vegetation information for each site. The data set is released under a Creative Commons BY license. When using the data set, we kindly request that you cite this article, recognizing the hard work that went into collecting the data and the authors' willingness to make it publicly available.
Eutrophication has become one of the most widespread anthropogenic forces impacting freshwater biological diversity. One potentially important mechanism driving biodiversity changes in response to eutrophication is the alteration of seasonal patterns of succession, particularly among species with short, synchronous, life cycles. We tested the hypothesis that eutrophication reduces seasonally driven variation in species assemblages by focusing on an understudied aspect of biodiversity: temporal beta diversity (β t ). We estimated the effect of eutrophication on β t by sampling benthic macroinvertebrate assemblages bimonthly for two years across 35 streams spanning a steep gradient of total phosphorus (P) and benthic algal biomass (as chlorophyll a [chl a ]). Two widely used metrics of β diversity both declined sharply in response to increasing P and chl a , regardless of covariates. The most parsimonious explanatory model for β t included an interaction between P and macroinvertebrate biomass, which revealed that β t was lower when macroinvertebrate biomass was relatively high. Macroinvertebrate biomass explained a greater amount of deviance in β t at lower to moderate concentrations of P, providing additional explanatory power where P concentration alone was unable to fully explain declines in β t . Chl a explained similar amounts of deviance in β t in comparison to the best P model, but only when temperature variability, which was positively related to β t , also was included in the model. Declines in β t suggest that nutrient enrichment decreases the competitive advantage that specialists gain by occupying particular temporal niches, which leads to assemblages dominated by generalists that exhibit little seasonal turnover. The collapse of seasonal variation in assemblage composition we observed in our study suggests that treating dynamic communities as static assemblages is a simplification that may fail to detect the full impact of anthropogenic stressors. Our results show that eutrophication leads to more temporally homogenous communities and therefore degrades a fundamental facet of biodiversity.
Occupancy–abundance ( OA ) relationships are a foundational ecological phenomenon and field of study, and occupancy models are increasingly used to track population trends and understand ecological interactions. However, these two fields of ecological inquiry remain largely isolated, despite growing appreciation of the importance of integration. For example, using occupancy models to infer trends in abundance is predicated on positive OA relationships. Many occupancy studies collect data that violate geographical closure assumptions due to the choice of sampling scales and application to mobile organisms, which may change how occupancy and abundance are related. Little research, however, has explored how different occupancy sampling designs affect OA relationships. We develop a conceptual framework for understanding how sampling scales affect the definition of occupancy for mobile organisms, which drives OA relationships. We explore how spatial and temporal sampling scales, and the choice of sampling unit (areal vs. point sampling), affect OA relationships. We develop predictions using simulations, and test them using empirical occupancy data from remote cameras on 11 medium‐large mammals. Surprisingly, our simulations demonstrate that when using point sampling, OA relationships are unaffected by spatial sampling grain (i.e., cell size). In contrast, when using areal sampling (e.g., species atlas data), OA relationships are affected by spatial grain. Furthermore, OA relationships are also affected by temporal sampling scales, where the curvature of the OA relationship increases with temporal sampling duration. Our empirical results support these predictions, showing that at any given abundance, the spatial grain of point sampling does not affect occupancy estimates, but longer surveys do increase occupancy estimates. For rare species (low occupancy), estimates of occupancy will quickly increase with longer surveys, even while abundance remains constant. Our results also clearly demonstrate that occupancy for mobile species without geographical closure is not true occupancy. The independence of occupancy estimates from spatial sampling grain depends on the sampling unit. Point‐sampling surveys can, however, provide unbiased estimates of occupancy for multiple species simultaneously, irrespective of home‐range size. The use of occupancy for trend monitoring needs to explicitly articulate how the chosen sampling scales define occupancy and affect the occupancy–abundance relationship.