Comparing species richness, functional diversity and functional composition of waterbird communities along environmental gradients in the neotropics

RESEARCH ARTICLE Comparing species richness, functional diversity and functional composition of waterbird communities along environmental gradients in the neotropics Bia de Arruda Almeida1*, Andy J. Green2, Esther Sebastián-González3, Luiz dos Anjos4 a1111111111 a1111111111 a1111111111 a1111111111 a1111111111 1 Programa de Pós-Graduação e Ecologia de Ambientes Aquáticos Continentais, Universidade Estadual de Maringá, Maringá, Paraná, Brazil, 2 Department of Wetland Ecology, Doñana Biological Station, EBD-CSIC, Sevilla, Spain, 3 Departamento de Biologı́a Aplicada, Universidad Miguel Hernández, Elche, Alicante, Spain, 4 Departamento de Biologia Animal e Vegetal, Centro de Ciências Biológicas, Universidade Estadual de Londrina, Londrina, Paraná, Brazil * Abstract OPEN ACCESS Citation: Arruda Almeida Bd, Green AJ, SebastiánGonzález E, dos Anjos L (2018) Comparing species richness, functional diversity and functional composition of waterbird communities along environmental gradients in the neotropics. PLoS ONE 13(7): e0200959. https://doi.org/10.1371/ journal.pone.0200959 Editor: Willem F. de Boer, Wageningen Universiteit, NETHERLANDS Received: March 8, 2018 Accepted: July 4, 2018 Published: July 20, 2018 Copyright: © 2018 Arruda Almeida et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Data Availability Statement: Community and environmental data are available from 10.6084/m9. figshare.5962837. Funding: Field work has been funded by the Proex program of the Coordination for the Improvement of Higher Education Personnel (CAPES-Brazil). B. A. A. received grant PDSE/88881.133362/2016-01 from the Brazilian Coordination for the Improvement of Higher Education Personnel (CAPES). E. S. received a fellowship IJCI-2015- Waterbirds have a major functional role in wetlands, and understanding how functional traits of waterbirds depend on environmental characteristics can facilitate management of ecosystems and their services. We investigate how the waterbird community in a Neotropical river-floodplain system responds to environmental gradients, identifying how they affect waterbird species richness, functional diversity (measured as functional dispersion) and functional composition (specific functional traits). We sampled 22 lakes in the Upper Paraná floodplain system in southern Brazil, and modelled avian functional diversity and species richness as a function of environmental variables. Then we used a unified RLQ and fourthcorner analysis to evaluate environment-trait relationships. Waterbird species richness and functional diversity varied according to different environmental variables. Lake area and diversity of aquatic vegetation were associated with avian species richness, while relative abundance of grass and emergent macrophytes and mean and variation of depth were related to functional diversity. Furthermore, changes in functional diversity seemed to be mainly driven by presence of species that depend on perches for foraging (e.g. kingfishers, cormorants, and kites), whose presence was mainly associated with deep water and emergent macrophytes. Nevertheless, changes in functional diversity and functional composition did not depend on exactly the same set of environmental variables, suggesting that trait combinations (e.g. below surface feeders who feed on fish), not only specific traits, are important drivers of the variation in functional diversity between lakes. Given the observed differences in responses of species richness and functional diversity, both these diversity metrics should be used as complementary tools in ecosystem management. Furthermore, our results show that functional diversity and composition are partially coupled, suggesting that although functional diversity is influenced by the environmental filtering of particular traits, it also reflects other ecological mechanisms (e.g. competitive interactions among species). PLOS ONE | https://doi.org/10.1371/journal.pone.0200959 July 20, 2018 1 / 18 Waterbird functional traits and environmental gradients 24947 from the Ministerio de Economı́a, Industria y Competitividad of Spain. Competing interests: We have read the journal’s policy and the authors of this manuscript have the following competing interests: AJG is an Academic Editor at PlosOne. We would also like to state that this does not alter our adherence to PLOS ONE policies on sharing data and materials. Introduction Wetlands provide key ecosystem services such as fishery maintenance, water quality improvement, nutrient fixation, carbon management, and flood prevention [1]. The maintenance of these globally important services depends on physical and chemical processes, but also on biological processes sustained by different groups of organisms within aquatic ecosystems [2]. Waterbirds have a major functional role in aquatic ecosystems, and may have profound effects e.g. through predation [3], herbivory [4], bioturbation [5], guanotrophication [6] and as dispersal vectors [7]. The ways in which waterbirds use resources in wetlands influence their roles in the ecosystem [8]. However, we know little about how the use of resources by the community varies according to particular characteristics of wetlands. Understanding how waterbird functional traits depend on wetland characteristics is important if we are to maintain functions performed by waterbirds, and consequently ecosystem services. Functional traits are any morphological, physiological or phenological characteristics measurable at the individual level [9], which are linked to ways in which organisms interact with the ecosystem. There are many previous studies of wetland features associated with the habitat use [10] or species richness [11,12] of waterbirds, or with the distribution of particular species [13]. However, taxonomic measures of diversity such as species richness do not account for the diversity of functional traits in the community. For this reason, taxonomic and functional measures of diversity may vary independently, according to different variables. So far, few studies have addressed the effect of environmental variables on the functional traits and functional diversity of waterbird communities [14–16]. There are two different approaches to evaluating community functional structure in an ecosystem. One focuses on the functional diversity of the community, represented by a diversity index that quantifies the distribution of the functional traits of a group of organisms within an ecosystem [17].The other approach focuses on functional composition, and considers individual changes in each of the traits displayed by the species in the community [18]. In this study, we use both approaches to enable a more complete view of how environmental characteristics of floodplain lakes a (...truncated)