Seasonal dynamics of waterbird assembly mechanisms revealed by patterns in phylogenetic and functional diversity in a subtropical wetland

The diversity of resident passerine bird in the East Yunnan-Kweichow Plateau is closely related to plant species richness, vertical altitude difference and habitat area

East Yunnan-Kweichow Plateau is rich in biodiversity in China. Complex geographical and climatic conditions and rich bird resources made this area an ideal system for studying the spatial distribution mechanism and influencing factors of birds, which were still unknown. Bird community data from 37 sites in this region were collected, including 505 bird species and 164 species of resident passerine bird, were extracted for analysis. The taxonomic diversity, phylogenetic diversity, functional diversity (FD), and community structure index were calculated. Ordinary least square (OLS), spatial autoregressive models (SAR), and structural equation model (SEM) were used to explore the relationship between bird diversity index and environmental factors which were used to describe the habitat conditions of birds. Results indicated that species richness (SR), phylogenetic diversity (PD), and FD have similar distribution patterns and are mainly affected by vascular plant species richness, habitat area, and vertical altitude difference. The phylogenetic and functional structure of bird community changed in both longitude and latitude direction, and the phylogenetic structure of community was dispersed in the west and clustered in the east, significantly related to habitat area, and vertical altitude difference, the functional structure was dispersed in all sites, significantly related to average annual precipitation. The community in the west and south of the East Yunnan-Kweichow Plateau is mainly driven by interspecific competitive, while the process in the east and north is mainly driven by environmental filtration. Distribution pattern of bird diversity was caused by the comprehensive action of various habitat factors which were mainly related to food availability and habitat heterogeneity. For maintaining the living space of birds, the protection of urban parks, wetland parks, campuses, and other urban green spaces is as important as national and provincial nature reserves. Revealing the construction mechanism and main influencing factors of bird communities in different areas is conducive to targeted protection work.

Intra- and interannual dynamics of grassland community phylogenetic structure are influenced by meteorological conditions before the growing season

The impact of global climate change on ecosystem structure has attracted much attention from researchers. However, how climate change and meteorological conditions influence community phylogenetic structure remains poorly understood. In this research, we quantified the responses of grassland communities' phylogenetic structure to long- and short-term meteorological conditions in Inner Mongolia, China. The net relatedness index (NRI) was used to characterize phylogenetic structure, and the relationship between the NRI and climate data was analyzed to understand the dynamics of community phylogenetic structure and its relationship with extreme meteorological events. Furthermore, multiple linear regression and structural equation models (SEMs) were used to quantify the relative contributions of meteorological factors before and during the current growing season to short-term changes in community phylogenetic structure. In addition, we evaluated the effect of long-term meteorological factors on yearly NRI anomalies with classification and regression trees (CARTs). We found that 1) the degree of phylogenetic clustering of the community is relatively low in the peak growing season, when habitat filtering is relatively weak and competition is fiercer. 2) Extreme meteorological conditions (i.e., drought and cold) may change community phylogenetic structure and indirectly reduce the degree of phylogenetic clustering by reducing the proportion of dominant perennial grasses. 3) Meteorological conditions before the growing season rather than during the current growing season explain more variation in the NRI and interannual NRI anomalies. Our results may provide useful information for understanding grassland community species assembly and how climate change affects biodiversity.

Effects of Meteorological Factors on Waterbird Functional Diversity and Community Composition in Liaohe Estuary, China

Functional trait diversity represents ecological differences among species, and the structure of waterbird communities is an important aspect of biodiversity. To understand the effect of meteorological changes on the waterbird functional diversity and provide suggestions for management and conservation, we selected a study area (726 km²) in Liaohe Estuary, located in northeast China. We explored the trends of the waterbird functional diversity changes in response to meteorological factors using fourth corner analysis. Our study demonstrated that temperature was a key factor that impacted waterbird functional diversity in spring, while precipitation had a greater impact in autumn. The population size of goose and duck was positively associated with temperature and negatively with precipitation, while that of the waders (Charadriiformes) showed opposite association trends. Herbivores and species nesting on the bare ground exhibited responses to meteorological factors similar to those of geese and ducks, while benthivores and waterbirds nesting under grass/shrubs exhibited trends similar to those of waterbirds. Waterbirds with smaller bodies, shorter feathers, and lower reproductive rates preferred higher temperatures and less precipitation than other waterbirds. In addition, we observed seasonal variations in waterbird functional diversity. In spring, we should pay attention to waders, herbivores, and waterbirds nesting on the bare ground when the temperature is low. In autumn, waders, benthivores, and omnivores need more attention under extreme precipitation. As the global climate warms in this study area, waterbird functional diversity is expected to decline, and community composition would become simpler, with overlapping niches. Biodiversity management should involve protecting intertidal habitats, supporting benthic macrofaunal communities, preparing bare breeding fields for waterbirds favoring high temperatures to meet their requirements for population increase, and preventing the population decline of geese and ducks, herbivores, and species nesting under grass/shrubs. The findings of our study can aid in developing accurate guidelines for waterbird biodiversity management and conservation.

Long-term trends in the phylogenetic and functional diversity of Anatidae in South China coastal wetlands

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 yr 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 1950s to 2010s, 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.

How fish traits and functional diversity respond to environmental changes and species invasion in the largest river in Southeastern China

Background

Freshwater fish populations are facing multiple stressors, including climate change, species invasion, and anthropogenic interference. Temporal studies of fish functional diversity and community assembly rules based on trait-environment relationships provide insights into fish community structure in riverine ecosystems.

Methods

Fish samples were collected in 2015 in the Min River, the largest freshwater riverine system in Southeastern China. Fish functional diversity was compared with the background investigation in 1979. Changes in functional richness, functional evenness, functional divergence, and functional beta diversity were analyzed. Relationships between functional diversity and environmental factors were modeled by random forest regression. Correlations between fish functional traits and environmental factors were detected by fourth-corner combined with RLQ analysis.

Results

Functional richness was significantly reduced in 2015 compared with 1979. Functional beta diversity in 2015 was significantly higher than that in 1979, with functional nestedness being the driving component. Reduction of functional richness and domination of functional nestedness is associated with species loss. Trait convergence was the dominant mechanism driving the temporal changes of functional diversity. Precipitation, temperature, species invasion, and human population were the most significant factors driving fish functional diversity. Higher precipitation, higher temperature, and presence of invasive species were significantly associated with higher swimming factor and higher relative eye diameter, while the opposite environmental conditions were significantly associated with higher pectoral fin length and eurytopic water flow preference.

Conclusions

Environmental filtering is the dominant temporal assembly mechanism shaping fish community structure. This work contributes to the understanding of temporal freshwater fish community assembly and the associations between fish functional structure and local environmental conditions, which will be informative for future freshwater fish conservation.

The Effects of Multi-Scale Climate Variability on Biodiversity Patterns of Chinese Evergreen Broad-Leaved Woody Plants: Growth Form Matters

Large-scale patterns of species diversity are thought to be linked to contemporary climate variability and Quaternary glacial–interglacial climate change. For plants, growth forms integrate traits related to competition or migration capacity, which determine their abilities to deal with the climate variability they face. Evergreen broad-leaved woody plants (EBWPs) are major components of numerous biomes in the subtropical and tropical regions. Hence, incorporating phylogenetic (temporal) and biogeographic (spatial) approaches, we assessed the relative importance of short- and long-term climate variability for biodiversity patterns of different growth forms (i.e., tree, shrub, liana, and bamboo) in EBWPs. We used a dated phylogeny and the distribution records for 6,265 EBWP species which are naturally occurred in China, and computed the corrected weighted endemism, standardized phylogenetic diversity and net relatedness index for the four growth forms, respectively. Ordinary least squares linear regressions, spatial error simultaneous autoregressive models, partial regression and hierarchical variation partitioning were employed to estimate the explanatory power of contemporary climate variability and climate-change velocity from the Last Glacial Maximum to the present. Our results showed that short- and long-term climate variability play complementary role in the biogeographic patterns of Chinese EBWPs. The former had larger effects, but the legacy effects of past climate changes were also remarkable. There were also differences in the effects of historical and current climate among the four growth forms, which support growth forms as a critical plant trait in predicting vegetation response to climate change. Compared to the glacial-interglacial climate fluctuation, seasonality as a unique feature of mid-latitude monsoon climate played a dominant role in the diversification and distribution of EBWP species at the macroscale. The results indicated that the relative importance of climate variability at different temporal scales may relate to distinct mechanisms. To understand effects of future climate change on species distribution more thoroughly, climate conditions in different time scales should be incorporated.