Do large-scale associations in birds imply biotic interactions or environmental filtering?

Aim There has been a wide interest in the effect of biotic interactions on species' occurrences and abundances at large spatial scales, coupled with a vast development of the statistical methods to study them. Still, evidence for whether the effects of within-trophic-level biotic interactions (e.g. competition and heterospecific attraction) are discernible beyond local scales remains inconsistent. Here, we present a novel hypothesis-testing framework based on joint dynamic species distribution models and functional trait similarity to dissect between environmental filtering and biotic interactions. Location France and Finland. Taxon Birds. Methods We estimated species-to-species associations within a trophic level, independent of the main environmental variables (mean temperature and total precipitation) for common species at large spatial scale with joint dynamic species distribution (a multivariate spatiotemporal delta model) models. We created hypotheses based on species' functionality (morphological and/or diet dissimilarity) and habitat preferences about the sign and strength of the pairwise spatiotemporal associations to estimate the extent to which they result from biotic interactions (competition, heterospecific attraction) and/or environmental filtering. Results Spatiotemporal associations were mostly positive (80%), followed by random (15%), and only 5% were negative. Where detected, negative spatiotemporal associations in different communities were due to a few species. The relationship between spatiotemporal association and functional dissimilarity among species was negative, which fulfils the predictions of both environmental filtering and heterospecific attraction. Main conclusions We showed that processes leading to species aggregation (mixture between environmental filtering and heterospecific attraction) seem to dominate assembly rules, and we did not find evidence for competition. Altogether, our hypothesis-testing framework based on joint dynamic species distribution models and functional trait similarity is beneficial in ecological interpretation of species-to-species associations from data covering several decades and biogeographical regions.Peer reviewe

Global and regional ecological boundaries explain abrupt spatial discontinuities in avian frugivory interactions

Species interactions can propagate disturbances across space via direct and indirect effects, potentially connecting species at a global scale. However, ecological and biogeographic boundaries may mitigate this spread by demarcating the limits of ecological networks. We tested whether large-scale ecological boundaries (ecoregions and biomes) and human disturbance gradients increase dissimilarity among plant-frugivore networks, while accounting for background spatial and elevational gradients and differences in network sampling. We assessed network dissimilarity patterns over a broad spatial scale, using 196 quantitative avian frugivory networks (encompassing 1496 plant and 1004 bird species) distributed across 67 ecoregions, 11 biomes, and 6 continents. We show that dissimilarities in species and interaction composition, but not network structure, are greater across ecoregion and biome boundaries and along different levels of human disturbance. Our findings indicate that biogeographic boundaries delineate the world’s biodiversity of interactions and likely contribute to mitigating the propagation of disturbances at large spatial scales.The authors acknowledge the following funding: University of Canterbury Doctoral Scholarship (L.P.M.); The Marsden Fund grant UOC1705 (J.M.T., L.P.M.); The São Paulo Research Foundation - FAPESP 2014/01986-0 (M.G., C.E.), 2015/15172-7 and 2016/18355-8 (C.E.), 2004/00810-3 and 2008/10154-7 (C.I.D., M.G., M.A.P.); Earthwatch Institute and Conservation International for financial support (C.I.D., M.G., M.A.P.); Carlos Chagas Filho Foundation for Supporting Research in the Rio de Janeiro State – FAPERJ grant E-26/200.610/2022 (C.E.); Brazilian Research Council grants 540481/01-7 and 304742/2019-8 (M.A.P.) and 300970/2015-3 (M.G.); Rufford Small Grants for Nature Conservation No. 22426–1 (J.C.M., I.M.), No. 9163-1 (G.B.J.) and No. 11042-1 (MCM); Universidade Estadual de Santa Cruz (Propp-UESC; No. 00220.1100.1644/10-2018) (J.C.M., I.M.); Fundação de Amparo à Pesquisa do Estado da Bahia - FAPESB (No. 0525/2016) (J.C.M., I.M.); European Research Council under the European Union’s Horizon 2020 research and innovation program (grant 787638) and The Swiss National Science Foundation (grant 173342), both awarded to C. Graham (D.M.D.); ARC SRIEAS grant SR200100005 Securing Antarctica’s Environmental Future (D.M.D.); German Science Foundation—Deutsche Forschungsgemeinschaft PAK 825/1 and FOR 2730 (K.B.G., E.L.N., M.Q., V.S., M.S.), FOR 1246 (K.B.G., M.S., M.G.R.V.) and HE2041/20-1 (F.S., M.S.); Portuguese Foundation for Science and Technology - FCT/MCTES contract CEECIND/00135/2017 and grant UID/BIA/04004/2020 (S.T.) and contract CEECIND/02064/2017 (L.P.S.); National Scientific and Technical Research Council, PIP 592 (P.G.B.); Instituto Venezolano de Investigaciones Científicas - Project 898 (V.S.D.)

Potential of Airborne LiDAR Derived Vegetation Structure for the Prediction of Animal Species Richness at Mount Kilimanjaro

The monitoring of species and functional diversity is of increasing relevance for the development of strategies for the conservation and management of biodiversity. Therefore, reliable estimates of the performance of monitoring techniques across taxa become important. Using a unique dataset, this study investigates the potential of airborne LiDAR-derived variables characterizing vegetation structure as predictors for animal species richness at the southern slopes of Mount Kilimanjaro. To disentangle the structural LiDAR information from co-factors related to elevational vegetation zones, LiDAR-based models were compared to the predictive power of elevation models. 17 taxa and 4 feeding guilds were modeled and the standardized study design allowed for a comparison across the assemblages. Results show that most taxa (14) and feeding guilds (3) can be predicted best by elevation with normalized RMSE values but only for three of those taxa and two of those feeding guilds the difference to other models is significant. Generally, modeling performances between different models vary only slightly for each assemblage. For the remaining, structural information at most showed little additional contribution to the performance. In summary, LiDAR observations can be used for animal species prediction. However, the effort and cost of aerial surveys are not always in proportion with the prediction quality, especially when the species distribution follows zonal patterns, and elevation information yields similar results

Data from: Titmice are a better indicator of bird density in Northern European than in Western European forests

Population sizes of many birds are declining alarmingly and methods for estimating fluctuations in species' abundances at a large spatial scale are needed. The possibility to derive indicators from the tendency of specific species to co-occur with others has been overlooked. Here we tested whether the abundance of resident titmice can act as a general ecological indicator of forest bird density in European forests. Titmice species are easily identifiable and have a wide distribution, which makes them potentially useful ecological indicators. Migratory birds often use information on the density of resident birds, such as titmice, as a cue for habitat selection. Thus, the density of residents may potentially affect community dynamics. We examined spatio-temporal variation in titmouse abundance and total bird abundance, each measured as biomass, by using long-term citizen science data on breeding forest birds in Finland and France. We analyzed the variation in observed forest bird density (excluding titmice) in relation to titmouse abundance. In Finland, forest bird density linearly increased with titmouse abundance. In France, forest bird density non-linearly increased with titmouse abundance, the association weakening towards high titmouse abundance. We then analyzed whether the abundance (measured as biomass) of random species sets could predict forest bird density better than titmouse abundance. Random species sets outperformed titmice as an indicator of forest bird density only in 4.4% and 24.2% of the random draws, in Finland and France, respectively. Overall, the results suggest that titmice could act as an indicator of bird density in Northern European forest bird communities, encouraging the use of titmice observations by even less-experienced observers in citizen science monitoring of general forest bird density.Funding provided by: Kvantum-instituutti, Oulun YliopistoCrossref Funder Registry ID: http://dx.doi.org/10.13039/501100018871Award Number: Funding provided by: Koneen SäätiöCrossref Funder Registry ID: http://dx.doi.org/10.13039/501100005781Award Number: Funding provided by: Academy of FinlandCrossref Funder Registry ID: http://dx.doi.org/10.13039/501100002341Award Number: 275606Funding provided by: Academy of FinlandCrossref Funder Registry ID: http://dx.doi.org/10.13039/501100002341Award Number: 31483

Titmice are a better indicator of bird density in Northern European than in Western European forests

Abstract Population sizes of many birds are declining alarmingly and methods for estimating fluctuations in species’ abundances at a large spatial scale are needed. The possibility to derive indicators from the tendency of specific species to co-occur with others has been overlooked. Here, we tested whether the abundance of resident titmice can act as a general ecological indicator of forest bird density in European forests. Titmice species are easily identifiable and have a wide distribution, which makes them potentially useful ecological indicators. Migratory birds often use information on the density of resident birds, such as titmice, as a cue for habitat selection. Thus, the density of residents may potentially affect community dynamics. We examined spatio-temporal variation in titmouse abundance and total bird abundance, each measured as biomass, by using long-term citizen science data on breeding forest birds in Finland and France. We analyzed the variation in observed forest bird density (excluding titmice) in relation to titmouse abundance. In Finland, forest bird density linearly increased with titmouse abundance. In France, forest bird density nonlinearly increased with titmouse abundance, the association weakening toward high titmouse abundance. We then analyzed whether the abundance (measured as biomass) of random species sets could predict forest bird density better than titmouse abundance. Random species sets outperformed titmice as an indicator of forest bird density only in 4.4% and 24.2% of the random draws, in Finland and France, respectively. Overall, the results suggest that titmice could act as an indicator of bird density in Northern European forest bird communities, encouraging the use of titmice observations by even less-experienced observers in citizen science monitoring of general forest bird density

Do large-scale associations in birds imply biotic interactions or environmental filtering?

Abstract Aim: There has been a wide interest in the effect of biotic interactions on species’ occurrences and abundances at large spatial scales, coupled with a vast development of the statistical methods to study them. Still, evidence for whether the effects of within-trophic-level biotic interactions (e.g. competition and heterospecific attraction) are discernible beyond local scales remains inconsistent. Here, we present a novel hypothesis-testing framework based on joint dynamic species distribution models and functional trait similarity to dissect between environmental filtering and biotic interactions. Location: France and Finland. Taxon: Birds. Methods: We estimated species-to-species associations within a trophic level, independent of the main environmental variables (mean temperature and total precipitation) for common species at large spatial scale with joint dynamic species distribution (a multivariate spatiotemporal delta model) models. We created hypotheses based on species’ functionality (morphological and/or diet dissimilarity) and habitat preferences about the sign and strength of the pairwise spatiotemporal associations to estimate the extent to which they result from biotic interactions (competition, heterospecific attraction) and/or environmental filtering. Results: Spatiotemporal associations were mostly positive (80%), followed by random (15%), and only 5% were negative. Where detected, negative spatiotemporal associations in different communities were due to a few species. The relationship between spatiotemporal association and functional dissimilarity among species was negative, which fulfils the predictions of both environmental filtering and heterospecific attraction. Main conclusions: We showed that processes leading to species aggregation (mixture between environmental filtering and heterospecific attraction) seem to dominate assembly rules, and we did not find evidence for competition. Altogether, our hypothesis-testing framework based on joint dynamic species distribution models and functional trait similarity is beneficial in ecological interpretation of species-to-species associations from data covering several decades and biogeographical regions

Plant and animal functional diversity drive mutualistic network assembly across an elevational gradient

Species' functional traits set the blueprint for pair-wise interactions in ecological networks. Yet, it is unknown to what extent the functional diversity of plant and animal communities controls network assembly along environmental gradients in real-world ecosystems. Here we address this question with a unique dataset of mutualistic bird-fruit, bird-flower and insect-flower interaction networks and associated functional traits of 200 plant and 282 animal species sampled along broad climate and land-use gradients on Mt. Kilimanjaro. We show that plant functional diversity is mainly limited by precipitation, while animal functional diversity is primarily limited by temperature. Furthermore, shifts in plant and animal functional diversity along the elevational gradient control the niche breadth and partitioning of the respective other trophic level. These findings reveal that climatic constraints on the functional diversity of either plants or animals determine the relative importance of bottom-up and top-down control in plant-animal interaction networks

Plant and animal functional diversity drive mutualistic network assembly across an elevational gradient

Differential responses of plant and animal functional diversity to climatic variation could affect trait matching in mutualistic interactions. Here, Albrecht et al. show that network structure varies across an elevational gradient owing to bottom-up and top-down effects of functional diversity

Data and code: Global and regional ecological boundaries explain abrupt spatial discontinuities in avian frugivory interactions

Zip-file including the Data and Code necessary for reproducing the analyses from 'Global and regional ecological boundaries explain abrupt spatial discontinuities in avian frugivory interactions'. General Information regarding the data is included as a pdf file in the download.Species interactions can propagate disturbances across space via direct and indirect effects, potentially connecting species at a global scale. However, ecological and biogeographic boundaries may mitigate this spread by demarcating the limits of ecological networks. We tested whether large-scale ecological boundaries (ecoregions and biomes) and human disturbance gradients increase dissimilarity among plant-frugivore networks, while accounting for background spatial and elevational gradients and differences in network sampling. We assessed network dissimilarity patterns over a broad spatial scale, using 196 quantitative avian frugivory networks (encompassing 1,496 plant and 1,004 bird species) distributed across 67 ecoregions, 11 biomes, and 6 continents. We show that dissimilarities in species and interaction composition, but not network structure, are greater across ecoregion and biome boundaries and along different levels of human disturbance. Our findings indicate that biogeographic boundaries delineate the world’s biodiversity of interactions and likely contribute to mitigating the propagation of disturbances at large spatial scales.Funding: University of Canterbury Doctoral Scholarship; The Marsden Fund, Award: UOC1705; Earthwatch Institute and Conservation International for financial support; Carlos Chagas Filho Foundation for Supporting Research in the Rio de Janeiro State – FAPERJ , Award: E-26/200.610/2022 Universidade Estadual de Santa Cruz, Award: Propp-UESC No. 00220.1100.1644/10-2018; Fundação de Amparo à Pesquisa do Estado da Bahia, Award: 0525/2016; Horizon 2020, Award: 787638; Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung, Award: 173342 ARC SRIEAS, Award: SR200100005; National Scientific and Technical Research Council, Award: PIP 592; Instituto Venezolano de Investigaciones Científicas, Award: Project 898; Fundação de Amparo à Pesquisa do Estado de São Paulo, Award: 2014/01986-0; Fundação de Amparo à Pesquisa do Estado de São Paulo, Award: 2015/15172-7; Fundação de Amparo à Pesquisa do Estado de São Paulo, Award: 2016/18355-8; Fundação de Amparo à Pesquisa do Estado de São Paulo, Award: 2004/00810-3; Fundação de Amparo à Pesquisa do Estado de São Paulo, Award: 2008/10154-7; Brazilian Research Council, Award: 540481/01-7; Brazilian Research Council, Award: 304742/2019-8; Brazilian Research Council, Award: 300970/2015-3; Rufford Small Grants for Nature Conservation, Award: 22426–1; Rufford Small Grants for Nature Conservation, Award: 9163-1; Rufford Small Grants for Nature Conservation, Award: 11042-1; Deutsche Forschungsgemeinschaft, Award: PAK 825/1; Deutsche Forschungsgemeinschaft, Award: FOR 2730 Deutsche Forschungsgemeinschaft, Award: FOR 1246; Deutsche Forschungsgemeinschaft, Award: HE2041/20-1; Fundação para a Ciência e a Tecnologia, Award: CEECIND/00135/2017; Fundação para a Ciência e a Tecnologia, Award: UID/BIA/04004/2020; Fundação para a Ciência e a Tecnologia, Award: CEECIND/02064/2017Peer reviewe