Species loss has attracted much attention among scientists for more than half a century. However, we have little information on the trends in phylogenetic and functional changes behind the species loss although this information is always asynchronous and important for conservation and management. We measured community trends in Anatidae (ducks and geese) for the last 50 years to quantify trends in phylogenetic and functional diversity patterns coinciding with taxonomic historical dynamics. We used one-way ANOVAs to test if there was a significant historical trend in communities of Anatidae. We characterized taxonomic, phylogenetic and functional diversity of communities. For taxonomic diversity, we used species richness (SR). For phylogenetic diversity, we calculated the standardized effect size of mean pairwise distances (ses.MPD) and the standard effect size of mean nearest taxon distances (ses.MNTD) in communities. For functional diversity, we calculated functional richness (FRic), functional evenness (FEve), functional divergence (FDiv) and the community-level weighted means (CWM) of trait values for diet, foraging stratum and body mass, separately. From the 1950’s to 2010’s, species richness declined without significant trends. The ses.MNTD of Anatidae communities showed no clear trends. However, ses.MPD of Anatidae communities declined dramatically during this period. For functional diversity, functional evenness of diet, foraging stratum, body mass and functional dispersion of diet, foraging stratum did not increase or decline significantly. However, functional evenness of all traits, functional richness and functional dispersion of body mass showed declined trends. The basic phylogenetic diversity and species body mass of Anatidae communities declined significantly because of a declining trend in the relative independent branch of geese. This makes it more challenging for implement community recovery in the future. More attention in conservation biology should consider taxonomic diversity and asynchrony in phylogenetic and functional diversity.

Anatidae species assemblages were obtained from monographs, literature, databases and expert surveys. Dataset of the 1950’s was extracted from Bird Distribution Catalogue in China I. Non-Passeriformes (Zheng 1955), with the dataset of the 1960’s extracted from Guan et al. (1963), datasets of the 1970’s was extracted from Bird Distribution List of China (Zheng 1975), datasets of the 1980’s was extracted from Deng et al. (1989), datasets from the 2000’s was extracted from China Bird Report (http://www.birdreport.cn/) and datasets from the 2010’s was extracted from our expert surveys.

We downloaded 2,000 phylogenetic trees of the complete Anatidae species pool in our study from BirdTree (http://birdtree.org), the recently published phylogeny of the world's bird species, using the source of the “Ericson All Species” (Rubolini et al. 2015). We then calculated a maximum clade credibility tree with a 50% posterior probability limit by using the “TreeAnnotator” in the BEAST 2 software package (Bouckaert et al. 2014). Subsequent analyses of phylogenetic diversity were based on this annotated tree.

We quantified three functional traits for birds that are commonly used to define functional diversity within the bird communities, categorical variables diet, foraging stratum and continuous variable body mass, which has shown to be functionally important (Wilman et al. 2014). We extracted those metrics from the Elton Traits database 1.0 (Wilman et al. 2014). Diet was classified into four categories, and each category was ranked based on percentage used for each species: (1) invertebrates, (2) vertebrates and fish and carrion, (3) plant and seeds and (4) omnivore.

Datasets from books (1950s and 1970s) included species but not abundance.