Analyzing community-weighted trait means across environmental gradients: should phylogeny stay or should it go?

Direct development in Atlantic Forest anurans: What can environmental and biotic influences explain about its evolution and occurrence?

Different environmental and biological factors can originate and support different alternative life histories in different taxonomic groups. Likewise, these factors are important for the processes that assemble and structure communities. Amphibians, besides being highly susceptible to environmental conditions, have various reproductive strategies, such as the direct development of individuals. Several hypotheses have been raised about possible selective pressures related to the emergence of direct development in anurans, as well as the relationship between environmental characteristics and the occurrence of these species. Such investigations, however, have mainly focused on specific clades and/or regions. Here, we use structural equation modelling to investigate the relationships between different abiotic (temperature, precipitation, humidity, and terrain slope) and biotic (phylogenetic composition and functional diversity) factors and the proportion of species with direct development in 766 anuran communities of the Atlantic Forest, a biome with a vast diversity of anuran species and high environmental complexity. Anuran communities with higher proportions of direct developing species were found to be mainly influenced by low potential evapotranspiration, low temperature seasonality, and high functional diversity. Phylogenetic composition and terrain slope were also found to be important in determining the occurrence of these species in Atlantic Forest communities. These results show the importance of these factors in the structuring of these communities and provide important contributions to the knowledge of direct development in anurans.

Vapour pressure deficit modulates hydraulic function and structure of tropical rainforests under nonlimiting soil water supply

Atmospheric conditions are expected to become warmer and drier in the future, but little is known about how evaporative demand influences forest structure and function independently from soil moisture availability, and how fast-response variables (such as canopy water potential and stomatal conductance) may mediate longer-term changes in forest structure and function in response to climate change. We used two tropical rainforest sites with different temperatures and vapour pressure deficits (VPD), but nonlimiting soil water supply, to assess the impact of evaporative demand on ecophysiological function and forest structure. Common species between sites allowed us to test the extent to which species composition, relative abundance and intraspecific variability contributed to site-level differences. The highest VPD site had lower midday canopy water potentials, canopy conductance (gc ), annual transpiration, forest stature, and biomass, while the transpiration rate was less sensitive to changes in VPD; it also had different height-diameter allometry (accounting for 51% of the difference in biomass between sites) and higher plot-level wood density. Our findings suggest that increases in VPD, even in the absence of soil water limitation, influence fast-response variables, such as canopy water potentials and gc , potentially leading to longer-term changes in forest stature resulting in reductions in biomass.

Site-specific ecological effect assessment at community level for polymetallic contaminated soil

Current ecological risk assessment (ERA) is based more on book-keeping than on science especially for terrestrial ecosystems due to the lack of relevance to real field. Accordingly, site-specific ecological effect assessment is critical for ERA, especially at high tiers. This study developed procedures to assess ecological effect at community level based on field data. As a case study, we assessed ecological effect of polymetallic contamination in soil in the surrounding of an abandoned mining and smelting site in Hunan, China. Firstly, Zn was identified as the dominant contaminant in soil and slope gradient (SG) and pH as environmental impact factors using distance-based redundancy analysis(db-RDA). Secondly, sensitive endpoints were screened using correlation analysis between Zn and parameters of plant community composition and functional traits. Thirdly, exposure-effect curves between Zn and screened endpoints were developed by taking SG and pH as covariates using Bayesian kernel machine regression analysis (BKMR), based on which half-effect concentrations (EC₅₀s) and 10 %-effect concentrations (EC₁₀s) of soil Zn for each endpoint were calculated. Finally, site-specific hazardous concentrations (HC₅₀s) of Zn were estimated. It was revealed site-specific EC₅₀s and EC₁₀s for soil Zn ranged 80.5-201 mg kg^-1 and 342-893 mgkg^-1, respectively, and HC₅₀s based on EC₁₀s and EC₅₀s ranged 104-110 mg kg^-1 and 595-612 mg kg^-1, respectively, which are more specific and inclusive than those obtained based on crop and vegetable seed germination and seedling growth toxicity experiments.

The hidden side of diversity: Effects of imperfect detection on multiple dimensions of biodiversity

Studies on ecological communities often address patterns of species distribution and abundance, but few consider uncertainty in counts of both species and individuals when computing diversity measures.We evaluated the extent to which imperfect detection may influence patterns of taxonomic, functional, and phylogenetic diversity in ecological communities.We estimated the true abundance of fruit-feeding butterflies sampled in canopy and understory strata in a subtropical forest. We compared the diversity values calculated by observed and estimated abundance data through the hidden diversity framework. This framework evaluates the deviation of observed diversity when compared with diversities derived from estimated true abundances and whether such deviation represents a bias or a noise in the observed diversity pattern.The hidden diversity values differed between strata for all diversity measures, except for functional richness. The taxonomic measure was the only one where we observed an inversion of the most diverse stratum when imperfect detection was included. Regarding phylogenetic and functional measures, the strata showed distinct responses to imperfect detection, despite the tendency to overestimate observed diversity. While the understory showed noise for the phylogenetic measure, since the observed pattern was maintained, the canopy had biased diversity for the functional metric. This bias occurred since no significant differences were found between strata for observed diversity, but rather for estimated diversity, with the canopy being more clustered.We demonstrate that ignore imperfect detection may lead to unrealistic estimates of diversity and hence to erroneous interpretations of patterns and processes that structure biological communities. For fruit-feeding butterflies, according to their phylogenetic position or functional traits, the undetected individuals triggered different responses in the relationship of the diversity measures to the environmental factor. This highlights the importance to evaluate and include the uncertainty in species detectability before calculating biodiversity measures to describe communities.

A multifaceted approach to analyzing taxonomic, functional, and phylogenetic β diversity

Ecological literature offers a myriad of methods for quantifying β diversity. One such method is determining BD_total (BD), which, unlike other methods, can be decomposed into meaningful components that indicate how unique a sampling unit is regarding its composition (local contribution) and how unique a species is regarding its occurrence in the community (species contribution). Despite this advantage, the original formulation of the BD metric only assesses taxonomic variation and neglects other important dimensions of biodiversity. We expanded the original formulation of BD to capture variation in the functional and phylogenetic dimensions of community data by computing two new metrics-BD_Fun and BD_Phy -as well as their respective components that represent the local and species contribution. We tested the statistical performance of these new metrics for capturing variation in functional and phylogenetic composition through simulated communities and illustrated the potential use of these new metrics by analyzing β diversity of stream fish communities. Our results demonstrated that BD_Phy and BD_Fun have acceptable type I error and great power to detect the effect of deep evolutionary relationships and attributes mediating patterns of β diversity. The empirical example illustrated how BD_Phy and BD_Fun reveal complementary aspects of β diversity relative to the original BD metric. These new metrics can be used to identify local communities that are of conservation importance because they represent unique functional, phylogenetic, and taxonomic compositions. We conclude that BD_Phy and BD_Fun are important tools for providing complementary information in the investigation of the structure of biological communities.

Plant functional traits regulate soil bacterial diversity across temperate deserts

Despite the known influence of plant diversity on soil microbial diversity, the potential role of plant functional traits in regulating soil bacterial diversity remains largely unclear. There is a lack of strong empirical evidence for the relative effects of plant diversity and functional traits on soil bacterial diversity across large-scale deserts. Here, we simultaneously explore the internal links among plant diversity, functional traits and soil bacterial diversity across 90 temperate deserts habitat of China, after accounting for confounding abiotic and spatial factors. The results showed that soil bacterial alpha and beta diversities were mainly determined by abiotic and spatial factors, follow by plant factors. However, plant diversity and functional traits played diverse roles in shaping soil bacterial alpha and beta diversities. Plant diversity exerted a substantial influence on soil bacterial beta diversity, but not on alpha diversity. In contrast, plant functional traits still directly influenced soil bacterial alpha and beta diversity, after accounting for other confounding key drivers. More precisely, plant functional traits surpass plant diversity in affecting soil bacterial alpha diversity. These results provide robust evidence that plant functional traits can effectively regulate soil bacterial diversity across temperate deserts. Taken together, we highlight the importance and irreplaceability of plant functional traits in predicting soil biodiversity under current and future global environmental changes.