Search

Recent studies suggest that differences in species composition across habitat types lead to increased multifunctionality on the regional scale. However, data about species turnover—and especially complementarity in the functional composition—across neighbouring habitat types from natural communities are rare. We studied frog communities in lowland rainforest in Malaysian Borneo and compared the species composition and functional-trait composition of different habitat types (alluvial forest, limestone forest, kerangas). Forest types differed strongly in their species composition and, to a lesser extent, in their functional-trait composition. We also compared functional-trait combinations of frogs directly across the forest types and identified six clusters of functionally similar species: three were found in all forest types, the others were absent from at least one forest type. The complementarity in species and functional-trait composition between the forest resulted in high regional gamma diversity, and most of this regional functional diversity was unique to individual forest types. Moreover, the strict separation in species composition suggests that even functionally similar frog species from different forest types cannot easily replace each other in case of local extinctions. The maintenance of ecological functions fulfilled by frogs on the landscape scale therefore requires the conservation of all forest-specific frog communities.

In ecological networks, neutral predictions suggest that species’ interaction frequencies are proportional to their relative abundances. Deviations from neutral predictions thus correspond to interaction preferences (when positive) or avoidances (when negative), driven by nonneutral (e.g., niche-based) processes. Exotic species interact with many partners with which they have not coevolved, and it remains unclear whether this systematically influences the strength of neutral processes on interactions, and how these interaction-level differences scale up to entire networks. To fill this gap, we compared interactions between plants and frugivorous birds at nine forest sites in New Zealand varying in the relative abundance and composition of native and exotic species, with independently sampled data on bird and plant abundances from the same sites. We tested if the strength and direction of interaction preferences differed between native and exotic species. We further evaluated whether the performance of neutral predictions at the site level was predicted by the proportion of exotic interactions in each network from both bird and plant perspectives, and the species composition in each site. We found that interactions involving native plants deviated more strongly from neutral predictions than did interactions involving exotics. This “pickiness” of native plants could be detrimental in a context of global biotic homogenization where they could be increasingly exposed to novel interactions with neutrally interacting mutualists. However, the realization of only a subset of interactions in different sites compensated for the neutrality of interactions involving exotics, so that neutral predictions for whole networks did not change systematically with the proportion of exotic species or species composition. Therefore, the neutral and niche processes that underpin individual interactions may not scale up to entire networks. This shows that seemingly simplistic neutral assumptions entail complex processes and can provide valuable understanding of community assembly or invasion dynamics., JMT is funded by the Bioprotection Centre. ID was funded by the FPI Program-European Social Fund BES2012-052863 and the Mobility Grant EEBB-I-14-08279 within the MinECo/FEDER projects CGL2015-68963-C2-2-R, and PRI-AIBNZ2011-0863 granted to DG. ID is funded by the Alexander von Humboldt Foundation. DBS was funded by a Marsden Fast-Start Grant and a Rutherford Discovery Fellowship (11-UOC-1101 and RDF-13-UOC-003), administered by the Royal Society of New Zealand Te Apārangi.

AimRecent studies increasingly use statistical methods to infer biotic interactions from co-occurrence information at a large spatial scale. However, disentangling biotic interactions from other factors that can affect co-occurrence patterns at the macroscale is a major challenge.ApproachFindingsWe present a set of questions that analysts and reviewers should ask to avoid erroneously attributing species association patterns to biotic interactions. Our questions relate to the appropriateness of data and models, the causality behind a correlative signal, and the problems associated with static data from dynamic systems. We summarize caveats reported by macroecological studies of biotic interactions and examine whether conclusions on the presence of biotic interactions are supported by the modelling approaches used.Irrespective of the method used, studies that set out to test for biotic interactions find statistical associations in species' co-occurrences. Yet, when compared with our list of questions, few purported interpretations of such associations as biotic interactions hold up to scrutiny. This does not dismiss the presence or importance of biotic interactions, but it highlights the risk of too lenient interpretation of the data. Combining model results with information from experiments and functional traits that are relevant for the biotic interaction of interest might strengthen conclusions.Main conclusionsMoving from species- to community-level models, including biotic interactions among species, is of great importance for process-based understanding and forecasting ecological responses. We hope that our questions will help to improve these models and facilitate the interpretation of their results. In essence, we conclude that ecologists have to recognize that a species association pattern in joint species distribution models will be driven not only by real biotic interactions, but also by shared habitat preferences, common migration history, phylogenetic history and shared response to missing environmental drivers, which specifically need to be discussed and, if possible, integrated into models.

AIM: Positive relationships in compositional similarity between consumer and resource assemblages are widely known in free‐living taxa, but less is known about parasites and their hosts. We investigated whether congruent patterns of assemblage similarity across diverse taxa of hosts and parasites exist at a continental scale and quantified the relative importance of host assemblages and environmental variables in shaping these relationships. LOCATION: European freshwaters. MAJOR TAXA STUDIED: The hosts were fishes, birds and mammals. The parasites were monogeneans, trematodes and copepods. METHODS: We extracted distribution data from the Limnofauna Europaea for three aquatic parasite taxa and for three vertebrate taxa functioning as their definitive hosts across 25 biogeographical regions in Europe. First, we investigated β‐diversity congruence patterns between parasite and host assemblages, corrected for the distance between regions using partial Mantel tests. Second, we assessed the relative importance of host assemblages and environmental variables in shaping parasite β‐diversity patterns using generalized dissimilarity models (GDMs). RESULTS: Spatial community dissimilarities of regional parasite assemblages were positively correlated with those of their respective host assemblages in all five parasite–host groups studied. The GDMs highlighted the equal importance of both host assemblages and environmental variables in shaping parasite assemblages. However, the direct effect of host assemblages was relatively small compared with the effect of environmental factors mediated by host assemblages. Climatic parameters (precipitation and temperature) contributed most to the variance explained by environmental variables. MAIN CONCLUSIONS: Our analyses indicate that spatially congruent patterns of assemblage similarity exist between parasites and their hosts at a continental scale. They also suggest that this congruence is driven not only by host assemblages but also by environmental (climatic) variables, either directly or indirectly via their effects on host assemblages. Thus, environmental variables are important for mapping, forecasting and management of parasites at a geographical scale.

Niche and neutral processes jointly influence species interactions. Predictions of interactions based on these processes assume that they operate similarly across all species. However, species characteristics could systematically create differences in the strength of niche or neutral processes for each interspecific interaction. We used national-level records of plant–frugivore interactions, species traits, biogeographic status (native vs. exotic), phylogenies and species range sizes to test the hypothesis that the strength of niche processes in species interactions changes in predictable ways depending on trophic generalism and biogeographic status of the interacting species. The strength of niche processes (measured as trait matching) decreased when the generalism of the interacting partners increased. Furthermore, the slope of this negative relationship between trait matching and generalism of the interacting partners was steeper (more negative) for interactions between exotic species than those between native species. These results remained significant after accounting for the potential effects of neutral processes (estimated by species range size). These observed changes in the strength of niche processes in generating species interactions, after accounting for effects of neutral processes, could improve predictions of ecological networks from species trait data. Specifically, due to their shorter co-evolutionary history, exotic species tend to interact with native species even when lower trait matching occurs than in interactions among native species. Likewise, interactions between generalist bird species and generalist plant species should be expected to occur despite low trait matching between species, whereas interactions between specialist species involve higher trait matching. Fil: Peralta, Guadalupe. University of Canterbury; Nueva Zelanda Fil: Perry, George L.W.. University of Auckland; Nueva Zelanda Fil: Vazquez, Diego P.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Investigaciones de las Zonas Áridas. Provincia de Mendoza. Instituto Argentino de Investigaciones de las Zonas Áridas. Universidad Nacional de Cuyo. Instituto Argentino de Investigaciones de las Zonas Áridas; Argentina Fil: Dehling, D. Matthias. University of Canterbury; Nueva Zelanda Fil: Tylianakis, Jason M.. University of Canterbury; Nueva Zelanda

The species composition of local communities varies in space, and its similarity generally decreases with increasing geographic distance between communities, a phenomenon known as distance decay of similarity. It is, however, not known how changes in local species composition affect ecological processes, that is, whether they lead to differences in the local composition of species' functional roles. We studied eight seed-dispersal networks along the South American Andes and compared them with regard to their species composition and their composition of functional roles. We tested (1) if changes in bird species composition lead to changes in the composition of bird functional roles, and (2) if the similarity in species composition and functional-role composition decreased with increasing geographic distance between the networks. We also used cluster analysis to (3) identify bird species with similar roles across all networks based on the similarity in the plants they consume, (i) considering only the species identity of the plants and (ii) considering the functional traits of the plants. Despite strong changes in species composition, the networks along the Andes showed similar composition of functional roles. (1) Changes in species composition generally did not lead to changes in the composition of functional roles. (2) Similarity in species composition, but not functional-role composition, decreased with increasing geographic distance between the networks. (3) The cluster analysis considering the functional traits of plants identified bird species with similar functional roles across all networks. The similarity in functional roles despite the high species turnover suggests that the ecological process of seed dispersal is organized similarly along the Andes, with similar functional roles fulfilled locally by different sets of species. The high species turnover, relative to functional turnover, also indicates that a large number of bird species are needed to maintain the seed-dispersal process along the Andes. Fil: Dehling, D. Matthias. University of Canterbury; Nueva Zelanda Fil: Peralta, Guadalupe. University of Canterbury; Nueva Zelanda Fil: Bender, Irene Maria Antoinetta. Universidad Nacional de Tucumán. Instituto de Ecología Regional. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Ecología Regional; Argentina Fil: Blendinger, Pedro Gerardo. Universidad Nacional de Tucumán. Instituto de Ecología Regional. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Ecología Regional; Argentina Fil: Böhning Gaese, Katrin. Goethe Universitat Frankfurt; Alemania Fil: Muñoz, Marcia C.. Universidad de la Salle; Colombia Fil: Neuschulz, Eike Lena. Senckenberg Biodiversität Und Klima Forschungszentrum; Alemania Fil: Quitián, Marta. Senckenberg Biodiversität Und Klima Forschungszentrum; Alemania Fil: Saavedra, Francisco. Universidad Mayor de San Andrés; Bolivia Fil: Santillán, Vinicio. Senckenberg Biodiversität Und Klima Forschungszentrum; Alemania Fil: Schleuning, Matthias. Senckenberg Biodiversität Und Klima Forschungszentrum; Alemania Fil: Stouffer, Daniel B.. University of Canterbury; Nueva Zelanda

Many different concepts have been used to describe species' roles in food webs (i.e., the ways in which species participate in their communities as consumers and resources). As each concept focuses on a different aspect of food-web structure, it can be difficult to relate these concepts to each other and to other aspects of ecology. Here we use the Eltonian niche as an overarching framework, within which we summarize several commonly-used role concepts (degree, trophic level, motif roles, and centrality). We focus mainly on the topological versions of these concepts but, where dynamical versions of a role concept exist, we acknowledge these as well. Our aim is to highlight areas of overlap and ambiguity between different role concepts and to describe how these roles can be used to group species according to different strategies (i.e., equivalence and functional roles). The existence of “gray areas” between role concepts make it essential for authors to carefully consider both which role concept(s) are most appropriate for the analyses they wish to conduct and what aspect of species' niches (if any) they wish to address. The ecological meaning of differences between species' roles can change dramatically depending on which role concept(s) are used.

[Aim] Biogeographical comparisons of interaction networks help to elucidate differences in ecological communities and ecosystem functioning at large scales. Neotropical ecosystems have higher diversity and a different composition of frugivores and fleshy-fruited plants compared with Afrotropical systems, but a lack of intercontinental comparisons limits understanding of (a) whether plant–frugivore networks are structured in a similar manner, and (b) whether the same species traits define the roles of animals across continents., [Location] Afrotropics and Neotropics., [Time period] 1977-2015., [Taxa] Fleshy-fruited plants and frugivorous vertebrates., [Methods] We compiled a dataset comprising 17 Afrotropical and 48 Neotropical weighted seed-dispersal networks quantifying frugivory interactions between 1,091 fleshy-fruited plant and 665 animal species, comprising in total 8,251 interaction links between plants and animals. In addition, we compiled information on the body mass of animals and their degree of frugivory. We compared four standard network-level metrics related to interaction diversity and specialization, accounting for differences related to sampling effort and network location. Furthermore, we tested whether animal traits (body mass, degree of frugivory) differed between continents, whether these traits were related to the network roles of species and whether these relationships varied between continents., [Results] We found significant structural differences in networks between continents. Overall, Neotropical networks were less nested and more specialized than Afrotropical networks. At the species level, a higher body mass and degree of frugivory were associated with an increasing diversity of plant partners. Specialization of frugivores increased with the degree of frugivory, but only in the Neotropics., [Main conclusions] Our findings show that Afrotropical networks have a greater overlap in plant partners among vertebrate frugivores than the more diverse networks in the Neotropics that are characterized by a greater niche partitioning. Hence, the loss of frugivore species could have stronger impacts on ecosystem functioning in the more specialized Neotropical communities compared with the more generalized Afrotropical communities., We thank Beth A. Kaplin and Norbert J. Cordeiro for their guidance and support for P.J.D., who received a travel grant by The Center for Tropical Studies and Conservation (CTEC). L.C. and I.G. were supported by the Robert Bosch Foundation. D.M.D. (DE 2754/1‐1), F.S. (HE 3041/20‐1), M.Q., V.S., E.L.N. (Research Unit 823‐825), and K.B.G., M.S. and M.G.R.V. (FOR 1246) thank the German Research Foundation (DFG) for funding. F.A.F.J. acknowledges funding by a CAPES scholarship, N.F. and D.G.S. by the Robert Bosch Foundation, M.G., C.E., A.P. and M.A.P. by Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP 2010/52315‐7; 2015/15172‐7; 2016/18355‐8) and Conselho Nacional de Desenvolvimento Científico (CNPq), M.C.M. by Doctoral Fellowships from COLCIENCIAS and Rufford, M.S.S. by Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) and FONCyT (PICT2013‐2759 and PICT2016‐0608), P.G.B. by CONICET (PIP 2014‐592) and FONCyT (PICT 2013‐1280), R.A.R. by a Doctoral Fellowship from CONICET, R.H. and S.T. (IF/00441/2013) and M.C. (SFRH/BD/96050/2013) by Fundação para a Ciência e Tecnologia, Portugal, and A.T. (CGL2013‐44386‐P) and D.G. (CGL2015‐68963‐C2‐2‐R) by the Spanish government. T.

SummarySpecies-rich tropical communities are expected to be more specialized than their temperate counterparts [1–3]. Several studies have reported increasing biotic specialization toward the tropics [4–7], whereas others have not found latitudinal trends once accounting for sampling bias [8, 9] or differences in plant diversity [10, 11]. Thus, the direction of the latitudinal specialization gradient remains contentious. With an unprecedented global data set, we investigated how biotic specialization between plants and animal pollinators or seed dispersers is associated with latitude, past and contemporary climate, and plant diversity. We show that in contrast to expectation, biotic specialization of mutualistic networks is significantly lower at tropical than at temperate latitudes. Specialization was more closely related to contemporary climate than to past climate stability, suggesting that current conditions have a stronger effect on biotic specialization than historical community stability. Biotic specialization decreased with increasing local and regional plant diversity. This suggests that high specialization of mutualistic interactions is a response of pollinators and seed dispersers to low plant diversity. This could explain why the latitudinal specialization gradient is reversed relative to the latitudinal diversity gradient. Low mutualistic network specialization in the tropics suggests higher tolerance against extinctions in tropical than in temperate communities.

Interactions between resource and consumer species are organized in ecological networks. Species interactions in these networks are influenced by the functional traits of the interacting partners, but the generality of trait-based interaction rules and the relationship between functional traits and a species’ specialization on specific interaction partners are not yet understood. Here we combine data on eight interaction networks between fleshy-fruited plants and frugivorous birds sampled across the tropical and subtropical Andean range. We test which combinations of morphological plant and animal traits determine trait matching between resource and consumer species in these networks. In addition, we test which of the morphological traits influence functional specialization of plant and bird species. In a meta-analysis across network-specific fourth-corner analyses, we found that plant–animal trait pairs related to size matching (fruit size–beak size) and avian foraging behavior (plant height–wing shape and crop mass–body mass) were positively related in these networks. The degree of functional specialization on specific interaction partners was positively related to crop mass in plants and to the pointedness of the wing in birds. Our findings show that morphological trait matching between fleshy-fruited plants and frugivorous birds is a general phenomenon in plant–frugivore networks across the Andes and that specific plant and bird traits can be used to approximate the degree of functional specialization. These insights into the generality of interaction rules are the base for predictions of species interactions in ecological networks, for instance in novel communities in the future, and can be applied to identify plant and animal species that fulfill specialized functional roles in ecological communities. Fil: Bender, Irene Maria Antoinetta. Universidad Nacional de Tucumán. Instituto de Ecología Regional. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Ecología Regional; Argentina. Martin-Luther-Universität Halle-Wittenberg; Alemania. Senckenberg Biodiversität und Klima Forschungszentrum; Alemania. Universitätsbund Halle – Jena – Leipzig. German Centre for Integrative Biodiversity Research; Alemania Fil: Kissling, W. Daniel. University of Amsterdam; Países Bajos Fil: Blendinger, Pedro Gerardo. Universidad Nacional de Tucumán. Instituto de Ecología Regional. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Ecología Regional; Argentina Fil: Böhning Gaese, Katrin. Senckenberg Biodiversität und Klima Forschungszentrum; Alemania. Universitätsbund Halle – Jena – Leipzig. German Centre for Integrative Biodiversity Research; Alemania. Goethe Universitat Frankfurt; Alemania Fil: Hensen, Isabell. Martin-Luther-Universität Halle-Wittenberg; Alemania. Universitätsbund Halle – Jena – Leipzig. German Centre for Integrative Biodiversity Research; Alemania Fil: Kühn, Ingolf. Universitätsbund Halle – Jena – Leipzig. German Centre for Integrative Biodiversity Research; Alemania. Martin-Luther-Universität Halle-Wittenberg; Alemania. Helmholtz-Zentrum für Umweltforschung; Alemania Fil: Muñoz, Marcia C.. Senckenberg Biodiversität und Klima Forschungszentrum; Alemania. Goethe Universitat Frankfurt; Alemania Fil: Neuschulz, Eike Lena. Senckenberg Biodiversität und Klima Forschungszentrum; Alemania Fil: Nowak, Larissa. Goethe Universitat Frankfurt; Alemania. Senckenberg Biodiversität und Klima Forschungszentrum; Alemania Fil: Quitián, Marta. Goethe Universitat Frankfurt; Alemania. Senckenberg Biodiversität und Klima Forschungszentrum; Alemania Fil: Saavedra, Francisco. Universidad Mayor de San Andrés; Bolivia Fil: Santillán, Vinicio. Goethe Universitat Frankfurt; Alemania. Senckenberg Biodiversität und Klima Forschungszentrum; Alemania Fil: Töpfer, Till. Zoologisches Forschungsmuseum Alexander Koenig; Alemania Fil: Wiegand, Thorsten. Universitätsbund Halle – Jena – Leipzig. German Centre for Integrative Biodiversity Research; Alemania. Helmholtz-Zentrum für Umweltforschung; Alemania Fil: Dehling, Matthias. University of Canterbury; Nueva Zelanda. Senckenberg Biodiversität und Klima Forschungszentrum; Alemania Fil: Schleuning, Matthias. Senckenberg Biodiversität und Klima Forschungszentrum; Alemania

1. Interactions between resource and consumer species result in complex ecological networks. The overall structure of these networks is often stable in space and time, but little is known about the temporal stability of the functional roles of consumer species in these networks.2. We used a trait‐based approach to investigate whether consumers (frugivorous birds) show similar degrees of functional specialisation on resources (plants) in ecological networks across seasons. We additionally tested whether closely related bird species have similar degrees of functional specialisation and whether birds that are functionally specialised on specific resource types within a season are flexible in switching to other resource types in other seasons.3. We analysed four seasonal replicates of two species‐rich plant–frugivore networks from the tropical Andes. To quantify fruit preferences of frugivorous birds, we projected their interactions with plants into a multidimensional plant trait space. To measure functional specialisation of birds, we calculated a species’ functional niche breadth (the extent of seasonal plant trait space utilised by a particular bird) and functional originality (the extent to which a bird species’ fruit preference functionally differs from those of other species in a seasonal network). We additionally calculated functional flexibility, i.e. the ability of bird species to change their fruit preference across seasons in response to variation in plant resources.4. Functional specialisation of bird species varied more among species than across seasons, and phylogenetically similar bird species showed similar degrees of functional niche breadth (phylogenetic signal λ = 0·81) and functional originality (λ = 0·89). Additionally, we found that birds with high functional flexibility across seasons had narrow functional niche breadth and high functional originality per season, suggesting that birds that are seasonally specialised on particular resources are most flexible in switching to other fruit resources across seasons.5. The high flexibility of functionally specialised bird species to switch seasonally to other resources challenges the view that consumer species rely on functionally similar resources throughout the year. This flexibility of consumer species may be an important, but widely neglected mechanism that could potentially stabilise consumer–resource networks in response to human disturbance and environmental change.