A functional perspective for breeding and wintering waterbird communities: temporal trends in species and trait diversity

Abstract

Waterbird communities are prone to strong temporal changes both seasonally and annually, but little is known about how this affects their functional diversity and community assembly. Detecting temporal trends in taxonomic and functional diversity within (alpha diversity) and between (beta diversity) communities in breeding and wintering seasons could give insight into the ecological processes driving those trends. In this study, we investigated trends in wintering and breeding waterbirds within and between eleven wetlands in Mediterranean Spain, using a 28‐year time‐series up to 2017. We assessed the temporal trends in taxonomic and functional diversity measures, and compared observed functional diversity values with null expectations, in order to explore the mechanisms driving community assembly. We found increases over time in species richness and in the occupied functional space for both wintering and breeding communities, indicating that species with distinct functional roles were added in both seasons. However, the distribution of the abundances in the functional space was different for breeding and wintering communities. Dissimilarity of species and functional traits decreased among wetlands, suggesting that some of the same functional traits were added to the different wetlands, increasing regional homogenization through time. This is reflected in increases over time in mean body mass, diet plasticity and in the importance of fish in waterbird diets, plus declines in the dietary importance of invertebrates and in plasticity of feeding strata. Furthermore, species composition between wintering and breeding communities, but not trait composition, has become more similar through time. Our results highlight that annual changes, and especially seasonal changes, in the composition of waterbird communities have different effects on their functional diversity, and are influenced by opposing community assembly mechanisms.

Changes in functional composition and diversity of waterbirds: The roles of water level and submerged macrophytes

“…Furthermore, in permanent and large lakes such as our study lakes, environmental filtering is expected to be more prominent in community assembly as compared to smaller and temporary wetlands, where stochastic events and priority effect are expected to be major determinants of assembly (Daniel et al., 2019; Li et al., 2019). However, it should also be noted that there have been other studies reporting neutrally assembled waterbird communities (spring and autumn populations in Che et al., 2019; populations of temporary wetlands in Daniel et al., 2019; de Arruda Almeida et al., 2019) and functionally over‐dispersed waterbird communities (the eastern populations in Che et al., 2018; winter populations in Che et al., 2019). Overall, various factors including climate, wetland age, wetland size, season of the year, population densities, and trophic states of wetlands seem to be capable of influencing waterbird community assembly.…”

“…The simulated FD values were then combined with the observed values to calculate standardised effect sizes (SES) for each observation. Positive SES values indicate functional overdispersion and may point to limiting similarity being the dominant factor in community assembly, whereas negative SES values indicate functional clustering and may point to environmental filtering being the dominant force in community assembly (de Arruda Almeida, Sebastián‐González, dos Anjos, Green, & Botella, 2019). Standardised effect size values close to zero, by contrast, may indicate a neutrally assembled community or that the chosen functional traits are not important in community assembly (Mouchet, Villéger, Mason, & Mouillot, 2010).…”

“…may point to limiting similarity being the dominant factor in community assembly, whereas negative SES values indicate functional clustering and may point to environmental filtering being the dominant force in community assembly (de Arruda Almeida, Sebastián-González, dos Anjos,Green, & Botella, 2019).Standardised effect size values close to zero, by contrast, may indicate a neutrally assembled community or that the chosen functional traits are not important in community assembly…”

Effect of Flood Pulse on the Functional Diversity and Traits Composition of Birds With Different Degrees of Wetland Dependence in the Brazilian Pantanal

“…We also calculated functional dispersion (FDis), which is the average distance of individual species to the community centroid in a multidimensional characteristics space (Laliberte and Legendre 2010), which is high when niche complementarities increase. Increases in FDis mean that abundances of species with trait values further away from the centroid increased, indicating higher use of the margins of the functional space (Almeida et al 2019). Also, we calculated community-weighted means (CWM) for each trait of the community.…”

“…Although the number of studies approaching functional diversity measures has increased recently, the subject is considered poorly discussed for freshwater environments (Calaça and Grelle 2016). Some studies conducted in aquatic ecosystems demonstrate the strong relationship between functional traits and structural or seasonal environmental characteristics for vertebrates and invertebrates that depend on or are associated with wetlands (Almeida et al 2016;Cardoso et al 2017;Almeida et al 2018;Liu and Wang 2018;Almeida et al 2019;de Deus et al 2020b).…”