Grinnellian Niche Research Articles

The Relationship between Grinnellian and Eltonian Niche Characteristics and Passerine Distribution across a Latitudinal Gradient

The degree to which Grinnellian and Eltonian niche characteristics influence species distribution may depend on latitude. Tropical regions are environmentally stable and resource-rich, whereas temperate regions are comparatively less environmentally stable (e.g., environmental filtering). Moreover, phylogenetic niche conservatism could influence distributions by inhibiting the ability for species to colonize environmentally different locations. Herein, we examine relationships between niche characteristics, passerine distributions, and phylogenetic niche conservatism across the latitudinal gradient. We used environmental and climatic variables to characterize Grinnellian niches and diets to characterize Eltonian niches. We conducted variation partitioning with retained components from ordination methods to evaluate the degree of association of Grinnellian and Eltonian niche characteristics with passerine distribution across latitudes. We examined the relationship between phylogenetic signal and niche characteristics with a phylogenetic regression. Passerine distributions were more related to environmental gradients than resources across latitudes. While niche conservatism was prevalent in Eltonian niche characteristics, phylogeny was related to Grinnellian niche characteristics in only 46% of biomes. There was no latitudinal gradient in phylogenetic niche conservatism or the degree to which Eltonian and Grinnellian niche characteristics relate to passerine distribution. Niche conservatism, albeit weak, was present for Grinnellian niche characteristics, thus potentially influencing the expansion of passerine distributions into the northern hemisphere.

Connection between ecological niche changes and population trends in the Eurasian Skylark (Alauda arvensis) breeding in lowland and mountain areas of Southern Europe

Population responses to environmental changes can often vary geographically and between environments, potentially as a consequence of differing niche dynamics. The Eurasian Skylark Alauda arvensis is an open‐habitat passerine bird that is declining throughout Europe, mainly due to agricultural intensification. We compared population trends (1992–2021) of the species across three sub‐regions of northern Italy characterized by different environmental conditions and human pressures: the Alpine sub‐region (less anthropized mountains), the Plain (strongly anthropized and intensively cultivated) and the Oltrepò (extensively cultivated hills), with changes in the realized Grinnellian niches over three decades. In each sub‐region, niche comparisons did not show divergence over the study. However, we found an overall reduction in niche occupancy over time. In the Alpine sub‐region, a reduction in niche occupancy in hayfields and pastures was not associated with population decline; indeed, we found an increasing population (+164%), probably because high availability of natural grasslands counteracted niche contraction. Conversely, in the Plain and Oltrepò sub‐regions, the observed population declines (−99% and −36%, respectively) are associated with a general reduction of niche occupancy in arable lands that represented the core of the niche in these ranges. In the Plain, the lack of alternative suitable habitats might have limited any opportunity for the species to colonize new environments. Conversely, in the Oltrepò, the less severe population decline is combined with increased niche occupancy in hayfields and pastures at higher elevations. The joint application of population trend analysis and niche modelling as well as the decomposition of population changes across different environmental contexts can contribute to a better understanding of ecological processes affecting population dynamics, supporting policy‐makers to implement targeted conservation strategies.

An environmental habitat gradient and within-habitat segregation enable co-existence of ecologically similar bird species.

Niche theory predicts that ecologically similar species can coexist through multidimensional niche partitioning. However, owing to the challenges of accounting for both abiotic and biotic processes in ecological niche modelling, the underlying mechanisms that facilitate coexistence of competing species are poorly understood. In this study, we evaluated potential mechanisms underlying the coexistence of ecologically similar bird species in a biodiversity-rich transboundary montane forest in east-central Africa by computing niche overlap indices along an environmental elevation gradient, diet, forest strata, activity patterns and within-habitat segregation across horizontal space. We found strong support for abiotic environmental habitat niche partitioning, with 55% of species pairs having separate elevation niches. For the remaining species pairs that exhibited similar elevation niches, we found that within-habitat segregation across horizontal space and to a lesser extent vertical forest strata provided the most likely mechanisms of species coexistence. Coexistence of ecologically similar species within a highly diverse montane forest was determined primarily by abiotic factors (e.g. environmental elevation gradient) that characterize the Grinnellian niche and secondarily by biotic factors (e.g. vertical and horizontal segregation within habitats) that describe the Eltonian niche. Thus, partitioning across multiple levels of spatial organization is a key mechanism of coexistence in diverse communities.

Conservation at the nexus of niches: Multidimensional niche modeling to improve management of Prairie Chub

AbstractObjectiveA central challenge in applied ecology is understanding how organisms are spatially and temporally distributed and how management might be tailored to maintain or restore species distributions. The niche concept is central to understanding species distributions, but the diversity of niche definitions requires that multiple dimensions be considered. For example, the Grinnellian niche concept focuses on environmental conditions that allow species to persist, the Eltonian niche concept stresses the influence of biotic interactions, and the fundamental niche concept considers both abiotic and biotic environmental features to define spaces that organisms could occupy.MethodsWe combined abiotic (A), biotic (B), and movement (M) information (collectively, BAM model) to map the multidimensional niche of Prairie Chub Macrhybopsis australis, a regionally endemic freshwater fish currently under review for listing under the Endangered Species Act. We estimated A using remotely sensed environmental riverscape variables, B using the spatial distribution of a hybridization zone between Prairie Chub and Shoal Chub M. hyostoma, and M using data from a mark–recapture study.ResultThe BAM model estimated the spatial extent of multiple niches, including the Grinnellian (A; extent = 944 km of river), Eltonian (B; 2974 km), and fundamental niche (overlap of A + B; 645 km) niches. When A, B, and M components were combined, the estimated extent of the Prairie Chub niche was 645 km.ConclusionOur work shows that the realized, multidimensional niche of Prairie Chub includes medium to large rivers with high habitat connectivity in the upper–middle Red River basin upstream of the distribution of Shoal Chub. The current Prairie Chub distribution could be maintained by preventing further habitat fragmentation and maintaining the environmental gradient separating Prairie Chub from Shoal Chub. Expansion of the species distribution may be possible through restoration of longitudinal fluvial connectivity.

Uncovering the Grinnellian niche space of the cryptic species complex Gammarus roeselii.

The discovery of cryptic species complexes within morphologically established species comes with challenges in the classification and handling of these species. We hardly know to what extent species within a species complex differ ecologically. Such knowledge is essential to assess the vulnerability of individual genetic lineages in the face of global change. The abiotic conditions, i.e., the Grinnellian niche that a genetic lineage colonizes, provides insights into how diverse the ecological requirements of each evolutionary lineage are within a species complex. We sampled the cryptic species complex of the amphipod Gammarus roeselii from Central Germany to Greece and identified genetic lineages based on cytochrome c oxidase subunit I (COI) barcoding. At the same time, we recorded various abiotic parameters and local pollution parameters using a series of in vitro assays to then characterize the Grinnellian niches of the morphospecies (i.e., Gammarus roeselii sensu lato) as well as each genetic lineage. Local pollution can be a significant factor explaining current and future distributions in times of increasing production and release of chemicals into surface waters. We identified five spatially structured genetic lineages in our dataset that differed to varying degrees in their Grinnellian niche. In some cases, the niches were very similar despite the geographical separation of lineages, supporting the hypothesis of niche conservatism while being allopatrically separated. In other cases, we found a small niche that was clearly different from those of other genetic lineages. The variable niches and overlaps of different dimensions make the G. roeselii species complex a promising model system to further study ecological, phenotypic and functional differentiation within this species complex. In general, our results show that the Grinnellian niches of genetically distinct molecular operational taxonomic units (MOTUs) within a cryptic species complex can differ significantly between each other, calling for closer inspection of cryptic species in a conservational and biodiversity context.

A dynamic theory of the area of distribution

AbstractAimsThe aim of this study is to propose and analyse a general, dynamic, process‐oriented theory of the area of distribution.LocationMexico, Southern United States and the Caribbean.TaxonPierid butterflies.MethodsThe area of distribution is modelled by combining (by multiplication) three matrices: one matrix represents movements, another niche tolerances and a third, biotic interactions. Results are derived from general properties of this product and from simulation of a cellular automaton defined in terms of the matrix operations. Everything is implemented practically in an R package.ResultsResults are obtained by simulation and mathematical analysis. We show that the mid‐domain effect is a direct consequence of dispersal; that to include movements to Ecological Niche Modelling significantly affect results, but cannot be done without choosing an ancestral area of distribution. We discuss ways of estimating such ancestral areas. We show that, in our approach, movements and niche effects are mixed in ways almost impossible to disentangle, and show this is a consequence of the singularity of a matrix. We introduce a tool (the Connectivity‐Suitability‐Dispersal plot) to extend the results of simple niche modelling to understand the effects of dispersal.Main conclusionsThe conceptually straightforward scheme we present for the area of distribution integrates, in a mathematically sound and computationally feasible way, several key ideas in biogeography: the geographic and environmental matrix, the Grinnellian niche, dispersal capacity and the ancestral area of origin of groups of species. We show that although full simulations are indispensable to obtain the dynamics of an area of distribution, interesting results can be derived simply by analysing the matrices representing the dynamics.

More time for aliens? Performance shifts lead to increased activity time budgets propelling invasion success

In the Grinnellian niche concept, the realized niche and potential distribution is characterized as an interplay among the fundamental niche, biotic interactions and geographic accessibility. Climate is one of the main drivers for this concept and is essential to predict a taxon’s distribution. Mechanistic approaches can be useful tools, which use fitness-related aspects like locomotor performance and critical thermal limits to predict the potential distribution of an organism. These mechanistic approaches allow the inclusion key ecological processes like local adaptation and can account for thermal performance traits of different life-history stages. The African Clawed Frog, Xenopus laevis, is a highly invasive species occurring on five continents. The French population is of special interest due to an ongoing expansion for 40 years and a broad base of knowledge. We hypothesize that (1) the French population exhibits increased activity time in the invasive European range that could be devoted to fitness-relevant activity and (2) tadpoles may have less activity time available than adult frogs from the same range. We investigate how thermal performance traits translate into activity time budgets and how local adaptation and differences in the thermal responses of life-history stages may boost the European Xenopus invasion. We use a mechanistic approach based on generalized additive mixed models, where thermal performance curves were used to predict the hours of activity and to compare the potential activity time budgets for two life-history stages of native and invasive populations. Our results show that adult French frogs have more activity time available in Europe compared to South African frogs, which might be an advantage in searching for prey or escaping from predators. However, French tadpoles do not have more activity time in Europe compared to the native South African populations suggesting that tadpoles do not suffer the same strong selective pressure as adult frogs.

New Evidence on the Linkage of Population Trends and Species Traits to Long-Term Niche Changes

Despite the assessment of long-term niche dynamics could provide crucial information for investigating species responses to environmental changes, it is a poorly investigated topic in ecology. Here, we present a case study of multi-species niche analysis for 71 common breeding birds in Northern Italy, exploring long-term niche changes from 1992 to 2017 and their relationship with both population trends and species traits. We (i) quantified the realized Grinnellian niche in the environmental space, (ii) compared variations in niche breadth and centroid, (iii) tested niche divergence and conservatism through equivalency and similarity tests, (iv) calculated niche temporal overlap, expansion and unfilling indices, and (v) investigated their association with both population changes and species traits. Results supported niche divergence (equivalency test) for 32% of species, although two-thirds were not supported by the similarity test. We detected a general tendency to adjust the niche centroids towards warmer thermal conditions. Increasing populations were positively correlated with niche expansion, while negatively correlated with niche overlap, albeit at the limit of the significance threshold. We found moderate evidence for a non-random association between niche changes and species traits, especially for body size, clutch size, number of broods per year, inhabited landscape type, and migration strategy. We encourage studies correlating long-term population trends and niche changes with species traits’ information and a specific focus on cause-effect relationship at both the single and multiple-species level.

Reflections of Grinnellian and Eltonian niches on the distribution of phyllostomid bats in the Atlantic Forest

AbstractAimEcological niches are complex and result from interactions with biotic and abiotic environments across the entire geographic range of species. One recent distinction is between Grinnellian niche characteristics that reflect influences at large spatial scales such as climate and Eltonian niche characteristics that reflect influences at the local level such as distribution of resources and their allocation among species. Aims of this research were to estimate Grinnellian and Eltonian niche characteristics of phyllostomid bats distributed throughout the Atlantic Forest, examine degree of phylogenetic non‐independence of distribution and niche characteristics, and estimate the relative contribution of niche characteristics to distribution across this large Neotropical region.LocationThe Atlantic Forest.TaxonPhyllostomid bats.MethodsCanonical correlation analysis was used to characterize the association between Grinnellian and Eltonian niche characteristics. Phylogenetic non‐independence of distribution and niche characteristics was estimated with phylogenetic eigenvector regression. Variation partitioning was used to distinguish relative contributions of Grinnellian and Eltonian niche characteristics to the distribution of bats.ResultsGrinnellian and Eltonian niche characteristics were strongly and significantly associated. Phylogenetic signal was weak for Grinnellian and strong for Eltonian niche characteristics. Both suites accounted for significant unique variation in the distribution of phyllostomid bats in the Atlantic Forest. Grinnellian niche characteristics accounted for more than five times the variation in distribution than Eltonian characteristics.Main ConclusionsDistinct Grinnellian and Eltonian perspectives on the niche provide valuable insights into the distribution of species. The degree to which these two different sets of characteristics account for distribution is likely scale dependent with Grinnellian characteristics more important at geographic spatial scales and Eltonian characteristics more important at local spatial scales. Grinnellian and Eltonian niches are important corollaries of α‐ and β‐ niches and their associated traits and similarities and differences in the two distinct concepts should be better explored across different taxa and geographic domains.

Temperature affects both the Grinnellian and Eltonian dimensions of ecological niches – A tale of two Arctic wolf spiders

To better understand the consequences of global warming for species and their distribution, we need studies quantifying how environmental change affects communities and interaction networks. Where studies to date have mainly focused on climatic effects on species distribution (the Grinnellian dimension of the niche), recent research has emphasised how the environment shapes ecological interactions among species (the Eltonian dimension).Here, we explore both dimensions in a system consisting of two wolf spider species – Pardosa palustris and Pirata piraticus – and their prey. Drawing on a natural experiment consisting of differential geothermal heating of soil, we describe the effects of temperature on the abundance of each species and on its interactions with its prey (using metabarcoding of gut contents). The two spider species differed substantially in their Grinnellian niche, with a peak in the abundance of P. palustris around 10 °C and in P. piraticus around 22 °C. While P. piraticus consumed more prey taxa on average than did P. palustris, both predators maintained their diet breadth and taxon richness of consumed prey across the temperature gradient. This indicates that effects of temperature on metabolic demands did not alter the dietary specialisation of the two predators. Nevertheless, we did also detect effects of temperature on the Eltonian niche, with significant changes in the prey community consumed by the two spider species across the temperature gradient, and a greater turnover of prey taxa in their diet with increasing soil temperature. Importantly, this suggests that the Eltonian niche of species may be conditional on the environment, and that prey use by generalist predators may thus be modified by climate change.

Interspecific and interpopulation variation in individual diet specialization: Do environmental factors have a role?

Individual diet specialization (IS) has important community- and population-level implications and its ecological drivers are actively investigated. Here, to test the hypothesis that local environmental conditions may influence IS in wild populations, we analyzed the stomach contents of 395 individuals from eight populations of five allopatric species of European cave salamanders (genus Hydromantes). We assessed whether their degree of individual diet specialization (1) scaled positively with the respective niche widths, in agreement with Van Valen's niche variation hypothesis (NVH), and (2) could be predicted by satellite-derived climatic and vegetation characteristics of the sites where the populations live. Consistent with the NVH, the degree of individual diet specialization increased with the populations' total niche width. Furthermore, two variables describing local nonarboreal vegetation cover and habitat heterogeneity successfully predicted the variation in individual specialization across the eight populations. Climatic factors had a generally low predictive power, with individual specialization in low- and high-elevation populations showing contrasting patterns of co-variation with air temperature in the warmest quarter of the year. However, independently from elevation, specialization peaked under conditions of high nonarboreal vegetation cover and high precipitation regimes. We discussed the results against two mutually nonexclusive scenarios hypothesizing different mechanisms linking environmental factors to salamanders' trophic strategy at an individual and population level. We concluded that satellite-derived climatic and vegetation variables to date generally adopted to model Grinnellian niches might also be useful in predicting spatial variations in dietary habits of populations, that is, their Eltonian niches.

Species geographical co‐occurrence and the effect of Grinnellian and Eltonian niche partitioning: The case of a Neotropical felid assemblage

AbstractUnderstanding local coexistence and broad‐scale species co‐occurrence patterns are central questions in ecology and macroecology. Niche theory relates both spatial scales by considering the resources (Eltonian niche) and conditions (Grinnellian niche) used by species and allow us to assess the contribution of these factors for species co‐occurrence. Indeed, combining local field data on diet preferences and climatic variables across species distributions can help us to evaluate their co‐occurrence while jointly considering resources and conditions on niche partitioning. Here, using information drawn from literature, we evaluated the relationship between geographic, climatic (Grinnellian) and trophic (Eltonian) niche dimensions among five highly sympatric felid species in favoring species co‐occurrence at broad spatial scales across the Neotropical region. We obtain potential geographic distributions of species through ecological niche models. Then, we calculated the pairwise species overlaps for each niche dimension and tested for a relationship between each pair of dimensions using Mantel and partial Mantel tests. We found a positive and significant relationship between geographic co‐occurrence and climatic overlap. This relationship remained after controlling for trophic overlap. Geographic and trophic overlap, as well as climatic and trophic overlap, did not show significant relationships. We conclude that the high degree of geographic co‐occurrence among our studied felid species is favored by climate and that their high degree of trophic overlap is not limiting their co‐occurrence pattern.

Interconnectedness of the Grinnellian and Eltonian Niche in Regional and Local Plant-Pollinator Communities.

Understanding the causes and consequences of coexistence and thus biodiversity is one of the most fundamental endeavors of ecology, which has been addressed by studying species’ requirements and impacts – conceptualized as their Grinnellian and Eltonian niches. However, different niche types have been mostly studied in isolation and thus potential covariation between them remains unknown. Here we quantified the realized Grinnellian niche (environmental requirements), the fundamental (morphological phenotype) and realized Eltonian niche (role in networks) of plant and pollinator taxa at a local and regional scale to investigate the interconnectedness of these niche types. We found a strong and scale-independent co-variation of niche types suggesting that taxa specialized in environmental factors are also specialized in their position in trait spaces and their role in bipartite networks. The integration of niche types thus will help to detect the true causes for species distributions, interaction networks, as well as the taxonomic and functional diversity of communities.

A Grinnellian Niche Perspective on Species-Area Relationships.

In this work, Grinnellian niche theory (a body of theory about geographic distributions of species in terms of noninteracting niche variables) is used to demonstrate that species-area relationships emerge with both size of environmental space and size of geographic area. As environmental space increases, more species' fundamental niches are included, thus increasing the number of species capable of living in the corresponding region. This idea is made operational by proposing a size measure for multidimensional environmental space and approximating fundamental niches with minimum volume ellipsoids. This framework allows estimating a presence-absence matrix based on the distribution of fundamental niches in environmental space, from which many biodiversity measures can be calculated, such as beta diversity. I establish that Whittaker's equation for beta diversity is equivalent to MacArthur's formula relating species numbers and niche breadth; this latter equation provides a mechanism for the species-niche space relationship. I illustrate the theoretical results via exploration of niches of the terrestrial mammals of North America (north of Panama). Each world region has a unique structure of its environmental space, and the position of fundamental niches in niche space is different for different clades; therefore, species-area relationships depend on the clades involved and the region of focus, mostly as a function of MacArthur's niche beta diversity. Analyzing species-area relationships from the perspective of niche position in environmental space is novel, shifting emphasis from demographic processes to historical, geographic, and climatic factors; moreover, the Grinnellian approach is based on available data and is computationally feasible.

The relative influence of abiotic and biotic factors on suitable habitat of Old World fruit bats under current and future climate scenarios

There is growing evidence that biotic factors such as predator-prey interactions play significant roles in driving species distribution across large spatial scales. The relative influence of abiotic and biotic factors on species distribution, however, may change under climate change. We investigated the relative influence of abiotic and biotic variables on the potential current and future distributions of three fruit bat species, Epomophorus angolensis (Gray, 1870), E. wahlbergi (Sundevall, 1846) and Rousettus aegyptiacus (E. Geoffroy St.-Hilaire, 1810), in southern Africa. We tested three hypotheses, namely that bat species’ distribution is primarily driven by (1) productivity; (2) physiological tolerance to climate; and (3) biotic interactions, specifically fig distribution. We adopted an ensemble niche modelling approach to project the suitable habitat of fruit bat species for current and future climate scenarios, and assessed variable importance in the models using a randomised variable shuffle procedure. We predicted that both biotic and abiotic factors influence suitable habitat of fruit bats, the relative influence of factors on habitat suitability of bat species are taxon specific, and the relative influence of abiotic and biotic factors will change from current to future climate scenarios. Abiotic variables associated with productivity were the primary determinants of habitat suitability for E. wahlbergi and E. angolensis under both current and future conditions. By contrast, suitable habitat of R. aegyptiacus was primarily mediated by temperature under current climatic conditions yet by freestanding fig distribution under both moderate and extreme future climate change scenarios. Freestanding fig distribution was also the most significant factor of habitat suitability for E. angolensis under the extreme future climate change scenario. Our results were congruent with our predictions and suggest that biotic variables play important roles in determining habitat suitability of species at relatively large spatial scales, contrary to the conventional assumptions of the Grinnellian niche.

What is the shape of the fundamental Grinnellian niche?

Since it was defined by Hutchinson, in 1957, the fundamental niche has been assumed, implicitly or explicitly, to have some convex shape. This assumption requires some critical analysis. In this work, we examine the special case of Grinnellian niches (those composed by sets of points of non-interactive variables in multidimensional spaces). We show that annual species in seasonal environments are likely to have very non-convex shapes, and be composed not of sets of points, but of sets of trajectories. We also examine under what circumstances trajectories may be approximated using sets of points. It appears to be the case that the breadth of requirements at each stage in the life history is a key parameter. We conclude by comparing the situation with perennial species.

Stable isotopes reveal limited Eltonian niche conservatism across carnivore populations

Abstract Niche conservatism—the retention of ecological traits across space and time—is an emerging topic of interest because it can predict responses to global change. The conservation of Grinnellian niche characteristics, like species‐habitat associations, has received widespread attention, but the conservation of Eltonian traits such as consumer–resource interactions remains poorly understood. The inability to quantify Eltonian niches through space and time has historically limited the assessment of Eltonian niche conservatism and the dynamics of foraging across populations. Consequently, the relative influence of endogenous factors like phylogeny versus exogenous features like environmental context has rarely been addressed. We tested Eltonian niche conservatism using a paired design to compare foraging among four populations of American martens Martes americana and Pacific martens Martes caurina, morphologically and ecologically similar sister taxa that are allopatrically distributed throughout western North America. We developed a three‐stage isotopic framework and then quantified dietary niche overlap between the sister species and paired island‐mainland sites to assess the relative influence of endogenous (i.e., species) versus exogenous (i.e., environment) factors on Eltonian niches. First, we calculated pairwise dietary overlap in scaled δ‐space using standard ellipses. We then estimated proportional diets (“p‐space”) for individuals using isotopic mixing models and developed a novel utilization distribution overlap approach to quantify proportional dietary overlap. Lastly, we estimated population‐level proportional diets and quantified the differential use of functional prey groups across sites. We detected no pairwise overlap of dietary niches in δ‐space, and distributions of individual diets in p‐space revealed little overlap in core diets across populations. All pairwise comparisons of individuals revealed significant differences in diet, and population‐level comparisons detected contrasting use of functional prey groups. We developed a multi‐faceted isotopic framework to quantify Eltonian niches and found limited evidence of Eltonian niche conservatism across carnivore populations. Our findings are consistent with the growing recognition of dietary plasticity in consumers and suggest that consumer–resource dynamics are largely driven by exogenous environmental factors like land cover and community composition. These results illustrate the context‐dependent nature of foraging and indicate consumer functionality can be dynamic. A plain language summary is available for this article.

Bringing the Eltonian niche into functional diversity

Studies of functional diversity (FD) have gained immense interest because they promise a more mechanistic understanding of the relationship between diversity and ecosystem functioning. However, the concept of FD is currently not used to its full potential because of several biases and shortcomings. For instance, while the analysis of traits related to species’ Grinnellian niches, i.e. traits influencing species’ fitness under different environmental conditions, is well‐advanced, there is a lack of studies on the functional diversity related to species’ Eltonian niches, i.e. species’ functional roles in ecological processes and their effects on other species, a discrepancy known as theEltonian Shortfall. Most importantly, the current indirect approach of measuring FD via species traits restricts analyses to species with similar traits, usually a taxon. Consequently, FD is generally measured for only one taxon but across different ecological processes, when it would ideally be measured for one ecological process but across all taxa that contribute to that process. These discrepancies hinder advances of our understanding of the relationship between diversity and ecosystem functions and services. We introduce a new approach to measuring functional diversity that is designed to overcome these shortcomings by bridging research on networks, species niches, and functional traits. Instead of characterizing functional rolesindirectlyvia species’ traits, we propose to characterize functional rolesdirectlyvia the traits of species’ resources and interaction partners in a given ecological process. Critically, this shift in perspective for the first time allows comparisons of the functional roles of all taxa that participate in an ecological process regardless of their own morphology. We illustrate our new approach with a study on functional roles of frugivores in seed‐dispersal systems. Our approach is an important addition to existing approaches to studying FD, and it facilitates new studies in a vastly unexplored field of functional diversity research.

Climate complexity in the migratory cycle of Ammodramus bairdii.

One way to understand the ecology of bird migration is to analyze how birds use their ecological niche during their annual cycle. Ammodramus bairdii is a grassland specialist sparrow that breeds in southern Canada and the northern U.S.A. and winters in the Chihuahuan Desert. A continuous and alarming decrease of its populations has been observed over the last 50 years, and studying its seasonal distribution and associated climatic niches could help improve strategies for its conservation. We analyzed the temporal use of its Grinnellian niche (GN) -set of environmental conditions under which a species can establish and persist; in this case the climatic attributes-. We modeled the GN for the reproductive and winter seasons and projected them onto each other (inter-prediction), and also onto transient migratory periods. To measure niche breadth and their overlap, minimum convex polygons (MCP) were calculated for the climatic space. The niches of each of the two seasons were tested for similarity using the PCA axes of climatic variables. The geographic areas with optimal, suboptimal and marginal conditions were identified, based on the distance to the centroid of the GN. The models for each season revealed no geographic inter-prediction among them, with the exception of winter to migratory seasons. The niche breadth of the winter was greater than that of the reproductive season, with an overlap of 22.47% and 45.18%, respectively. The similarity analyses showed a value of zero between seasons. The climate conditions for the records during the migratory months corresponded with suboptimal and marginal conditions of the sparrow’s winter niche. These results suggest that A. bairdii uses different climate conditions within ecological niches of each season during its migratory cycle.

The potential invasiveness of an aquatic macrophyte reflects founder effects from native niche

Biological invasions are important drivers of biodiversity loss. Hence, predicting invasion risks considering the invasion history of a species might help drive meaningful conservation strategies. We investigated the niche dynamics occurring during the invasion of Hydrilla verticillata in North and South America. Because of founder effects, we hypothesised that occupied invaded area niches across North and South American are a subset of the occupied niche in the native range. Moreover, according to the invasion history, we expected that the South American niche is more similar to the North American one than the native niche. We built ecological niche models to predict the potential distribution of hydrilla from native and invaded occurrence records, as well as analysing niche overlap, equivalency, and similarity between the native and two invaded areas. Although the models predicted spatially congruent suitable sites, the ones based on native occurrence records predicted larger geographical ranges for hydrilla across South America than those based on the records of its North American invasions. The environmental conditions the species occupied in both invaded areas are modestly overlapped with the native area (Schoener’s D < 0.6), with native and South American niches showing the highest overlap and significant equivalency. Contrary to our prediction, the invaded North and South American niches presented the smallest niche overlap. Our findings suggest that founder effects triggered deep shifts in hydrilla’s occupation abilities across invaded areas, but do not support successive invasion events. Hydrilla’s Grinnellian niche was maintained throughout the invaded areas, and its potential invasion across South America is massive, regardless of its origin.