Jeferson Vizentin-Bugoni

Opposed latitudinal patterns of network‐derived and dietary specialization in avian plant‐frugivore interaction systems

Latitudinal patterns of biodiversity have been studied for centuries, but it is only during the last decades that species interaction networks have been used to examine the proposed latitudinal gradient of biotic specialization. These studies have given idiosyncratic results, which may either be because of genuine biological differences between systems, different concepts and scales used to quantify biotic specialization or because the methodological approaches used to compare interaction networks were inappropriate. Here we carefully examine the latitudinal specialization gradient using a global dataset of avian plant-frugivore assemblages and interaction networks. In particular, we test whether network-derived specialization patterns differ from patterns based on assemblage-level information on avian dietary preferences on specific food types. We found that network-derived measures of specialization (complementary specialization H2’ and , modularity Q) increased with latitude, i.e. frugivorous birds divide the niche of fruiting plants most finely at high latitudes where they also formed more modular interaction networks than at tropical latitudes. However, the strength and significance of the relationship between specialization metrics and latitude was influenced by the methodological approach. On the other hand, assemblage-level information on avian specialization on fruit diet (i.e. the proportion of obligate frugivorous bird species feeding exclusively on fruit diet) revealed an opposed latitudinal pattern as more bird species were specialized on fruit diet in tropical than in temperate assemblages. This difference in the latitudinal specialization gradient reflects that obligate frugivores require a high diversity of fruit plants, as observed in tropical systems, and fulfil more generalized roles in plant-frugivore networks than bird species feeding on different food types. Future research should focus on revealing the underlying ecological, historical and evolutionary mechanisms shaping these patterns. Our results highlight the necessity of comparing different scales of biotic specialization for a better understanding of geographical patterns of specialization in resource-consumer interactions. . This article is protected by copyright. All rights reserved.

Plant-hummingbird interactions and temporal nectar availability in a restinga from Brazil

Hummingbirds are the most important and specialized group of pollinating birds in the Neotropics and their interactions with plants are key components to many communities. In the present study we identified the assemblage of plants visited by hummingbirds and investigated the temporal availability of floral resources in an area of restinga, sandy plain coastal vegetation associated with the Atlantic forest, in Southeastern Brazil. We recorded flower and nectar features, flowering phenology and interactions between plants and hummingbirds and estimated the amount of calories produced per hectare from June 2005 to August 2006. Ten plant species were visited by two hummingbirds, Amazilia fimbriata and Eupetomena macroura. Resource availability was highly variable among plant species and over time. Nectar volume and concentration per flower were similar to other Neotropical hummingbird-visited plant assemblages. The estimated nectar resource availability between months varied from 0.85 to 5.97 Kcal per hectare/day, demanding an area between one and 6.8 ha to support a single hummingbird. Our study reports an unusual tropical setting where almost all interactions between hummingbirds and plants were performed by a single hummingbird species, A. fimbriata. Hence, the variable nectar availability is probably influencing hummingbird movements, its foraging area, and consequently plant pollination.

Abundance drives generalisation in hummingbird-plant pollination networks

Abstract Abundant pollinators are often more generalised than rare pollinators. This could be because abundance drives generalisation: neutral effects suggest that more abundant species will be more generalised simply because they have more chance encounters with potential interaction partners. On the other hand, generalisation could drive abundance, as generalised species could have a competitive advantage over specialists, being able to exploit a wider range of resources and gain a more balanced nutrient intake. Determining the direction of the abundance-generalisation relationship is therefore a ‘chicken-and-egg’ dilemma. Here we determine the direction of the relationship between abundance and generalisation in plant-hummingbird pollination networks sampled from a variety of locations across the Americas. For the first time we resolve the direction of the abundance-generalisation relationship using independent data on animal abundance. We find evidence that hummingbird pollinators are generalised because they are abundant, and little evidence that hummingbirds are abundant because they are generalised. Additionally, a null model analysis suggests this pattern is due to neutral processes: most patterns of species-level abundance and generalisation were well explained by a null model that assumed interaction neutrality. These results suggest that neutral processes play a key role in driving broad patterns of generalisation in animal pollinators across large spatial scales. Declarations Funding – BIS is supported by the Natural Environment Research Council as part of the Cambridge Earth System Science NERC DTP [NE/L002507/1]. JVB was funded by CERL - Engineer Research and Development Center. PKM was funded by the Sao Paulo Research Foundation (FAPESP grant #2015/21457-4). PAC was funded by the David Lack studentship from the British Ornithologists’ Union and Wolfson College, University of Oxford. CL was funded by the ESDEPED-UAT grant. MAM acknowledges the Consejo Nacional para Investigaciones Cientificas y Tecnologicas (Costa Rica), German Academic Exchange Service and the research funding program ‘LOEWE-Landes-Offensive zur Entwicklung Wissenschaftlicho konomischer Exzellenz’ of Hesse’s Ministry of Higher Education, Research, and the Arts (Germany). ROP was funded by CONACyT (project 258364). MAR was supported by the State of Sao Paulo Research Foundation (FAPESP) within the BIOTA/FAPESP, The Biodiversity Institute Program (www.biota.org.br) and the ‘Parcelas Permanentes’ project, as well as by Coordenacao de Pessoal de Nivel Superior (CAPES), Fundo de Apoio ao Ensino e a Pesquisa (FAEP)/Funcamp/Unicamp and The Nature Conservancy (TNC) of Brazil. LCR was supported by CNPq and Capes. MS was funded by CNPq (grant #302781/2016-1). AMMG is supported through a Marie Sklodowska-Curie Individual Fellowship (H2020-MSCA-IF-2016-704409). LVD was supported by the Natural Environment Research Council (grants NE/K015419/1 and NE/N014472/1). AMMG, JS, CR and BD thank the Danish National Research Foundation for its support of the Center for Macroecology, Evolution and Climate (grant no. DNRF96). WJS is funded by Arcadia.Abundant pollinators are often more generalised than rare pollinators. This could be because abundance drives generalisation: neutral effects suggest that more abundant species will be more generalised simply because they have more chance encounters with potential partners. On the other hand, generalisation could drive abundance, as generalised species could have a competitive advantage over specialists, being able to exploit a wider range of resources and gain a more balanced nutrient intake. Determining the direction of the abundance-generalisation relationship is therefore a chicken-and-egg dilemma. Here we determine the direction of the relationship between abundance and generalisation in hummingbird-plant pollination networks sampled from a variety of locations across the Americas. We find evidence that hummingbirds are generalised because they are abundant, and little evidence that hummingbirds are abundant because they are generalised. Additionally, a null model analysis suggests this pattern is due to neutral processes: most patterns of species-level abundance and generalisation were well explained by a null model that assumed interaction neutrality. These results suggest that neutral processes play a key role in driving broad patterns of generalisation in hummingbird pollinators. Declarations Funding – BIS is supported by the Natural Environment Research Council as part of the Cambridge Earth System Science NERC DTP [NE/L002507/1]. JVB was funded by CERL - Engineer Research and Development Center. PKM was funded by the São Paulo Research Foundation (FAPESP grant #2015/21457-4). PAC was funded by the David Lack studentship from the British Ornithologists’ Union and Wolfson College, University of Oxford. CL was funded by the ESDEPED-UAT grant. MAM acknowledges the Consejo Nacional para Investigaciones Científicas y Tecnológicas (Costa Rica), German Academic Exchange Service and the research funding program ‘LOEWE-Landes-Offensive zur Entwicklung Wissenschaftlichö konomischer Exzellenz’ of Hesse’s Ministry of Higher Education, Research, and the Arts (Germany). ROP was funded by CONACyT (project 258364). LCR was supported by CNPq and Capes. MS was funded by CNPq (grant #302781/2016-1). AMMG is supported through a Marie Skłodowska-Curie Individual Fellowship (H2020-MSCA-IF-2016-704409). LVD was supported by the Natural Environment Research Council (grants NE/K015419/1 and NE/N014472/1). AMMG, CR and BD thank the Danish National Research Foundation for its support of the Center for Macroecology, Evolution and Climate (grant no. DNRF96). WJS is funded by Arcadia.