Synthesis reveals approximately balanced biotic differentiation and homogenization

This work was supported by the German Research Foundation (FZT 118, to S.A.B., T.E., A.S., R.v.K., W.-B.X., and J.M.C.) and ERC GA 101044975 and the Leverhulme Centre for Anthropocene Biodiversity (to M.D.). This work was also supported by the German Research Foundation (DFG) project “Establishment of the National Research Data Infrastructure (NFDI)” in the consortium NFDI4Biodiversity (project number 442032008) (to T.E.), European Union Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement no. 894644 (to I.S.M.), USDA Hatch grant MAFES #1011538 and NSF EPSCOR Track II grant #2019470 (to B.M.), and NSF Track II grant #2019470 (to N.J.G.).It is commonly thought that the biodiversity crisis includes widespread declines in the spatial variation of species composition, called biotic homogenization. Using a typology relating homogenization and differentiation to local and regional diversity changes, we synthesize patterns across 461 metacommunities surveyed for 10 to 91 years, and 64 species checklists (13 to 500+ years). Across all datasets, we found that no change was the most common outcome, but with many instances of homogenization and differentiation. A weak homogenizing trend of a 0.3% increase in species shared among communities/year on average was driven by increased numbers of widespread (high occupancy) species and strongly associated with checklist data that have longer durations and large spatial scales. At smaller spatial and temporal scales, we show that homogenization and differentiation can be driven by changes in the number and spatial distributions of both rare and common species. The multiscale perspective introduced here can help identify scale-dependent drivers underpinning biotic differentiation and homogenization.Peer reviewe

Supplementary information files for Regional occupancy increases for widespread species but decreases for narrowly distributed species in metacommunity time series

Supplementary files for article Regional occupancy increases for widespread species but decreases for narrowly distributed species in metacommunity time series   While human activities are known to elicit rapid turnover in species composition through time, the properties of the species that increase or decrease their spatial occupancy underlying this turnover are less clear. Here, we used an extensive dataset of 238 metacommunity time series of multiple taxa spread across the globe to evaluate whether species that are more widespread (large-ranged species) differed in how they changed their site occupancy over the10-90 years the metacommunities were monitored relative to species that are more narrowly distributed (small-ranged species). We found that on average, large-ranged species tended to increase in occupancy through time, whereas small-ranged species tended to decrease. These relationships were stronger in marine than in terrestrial and freshwater realms. However, in terrestrial regions, the directional changes in occupancy were less extreme in protected areas. Our findings provide evidence for systematic decreases in occupancy of small-ranged species, and that habitat protection could mitigate these losses in the face of environmental change.</p

Local biodiversity change reflects interactions among changing abundance, evenness, and richness

Biodiversity metrics often integrate data on the presence and abundance of multiple species. Yet our understanding of covariation between changes to the numbers of individuals, the evenness of species relative abundances, and the total number of species remains limited. Using individual-based rarefaction curves, we show how expected positive relationships among changes in abundance, evenness and richness arise, and how they can break down. We then examined interdependencies between changes in abundance, evenness and richness in more than 1100 assemblages sampled either through time or across space. As predicted, richness changes were greatest when abundance and evenness changed in the same direction, and countervailing changes in abundance and evenness acted to constrain the magnitude of changes in species richness. Site-to-site differences in abundance, evenness, and richness were often decoupled, and pairwise relationships between these components across assemblages were weak. In contrast, changes in species richness and relative abundance were strongly correlated for assemblages varying through time. Temporal changes in local biodiversity showed greater inertia and stronger relationships between the component changes when compared to site-to-site variation. Overall, local variation in assemblage diversity was rarely due to repeated passive samples from an approximately static species abundance distribution. Instead, changing species relative abundances often dominated local variation in diversity. Moreover, how changing relative abundances combined with changes to total abundance frequently determined the magnitude of richness changes. Embracing the interdependencies between changing abundance, evenness and richness can provide new information to better understand biodiversity change in the Anthropocene

Diversity is maintained by seasonal variation in species abundance

Background Some of the most marked temporal fluctuations in species abundances are linked to seasons. In theory, multi-species assemblages can persist if species use shared resources at different times, thereby minimizing inter-specific competition. However, there is scant empirical evidence supporting these predictions and, to our knowledge, seasonal variation has never been explored in the context of fluctuation-mediated coexistence. Results Using an exceptionally well-documented estuarine fish assemblage, sampled monthly for over 30 years, we show that temporal shifts in species abundances underpin species coexistence. Species fall into distinct seasonal groups, within which spatial resource use is more heterogeneous than would be expected by chance at those times when competition for food is most intense. We also detect seasonal variation in the richness and evenness of the community, again linked to shifts in resource availability. Conclusion These results reveal that spatio-temporal shifts in community composition minimize competitive interactions and help stabilize total abundance.Publisher PDFPeer reviewe

Pal Application To the Study of Sorption Mechanism in Polymers - Capillary Effects

The positron annihilation lifetime technique can be applied to the study of the sorption mechanism in polymers in a quite unique way. In our previous experiments it had been shown that τ$\text{}_{3}$ and I$\text{}_{3}$ of polymers show a V-shaped dependence as a function of the contact with vapors. The decreasing part of the V-shaped dependence had been attributed to the Langmuir-type sorption, and the increasing part to delayed occurrence of the Henry-type sorption. But since there was some doubt that a capillary effect, i.e. the vapor to be sorbed is deposited in between the polymer membranes, might be involved in the increasing part, we performed a careful experiment to avoid the capillary effect. We have performed further experiments in a careful condition to avoid the capillary effect, and have observed the same V-shape as before. Thus our interpretation of the V-shaped dependence has been established. Furthermore, in another example it is shown a case where the capillary effect is observed. This latter case is an example how positron annihilation lifetime can distinguish the real sorption and false sorption (capillary effect)

Optimization of excimer-forming two-probe nucleic acid hybridization method with pyrene as a fluorophore.

A previously presented homogeneous assay method, named the excimer-forming two-probe nucleic acid hybridization (ETPH) method, is based on specific excimer formation between two pyrenes attached at the neighboring terminals of two sequential probe oligonucleotides complementary to a single target. In this study, we investigated assay conditions and optimal molecular design of probes for intense excimer emission using a pyrenemethyliodoacetamide-introduced 16mer probe, a pyrene butanoic acid-introduced 16merprobe and a target 32mer. The length of the linker between the pyrene residue and the terminal sugar moiety remarkably influenced the quantum efficiency of excimer emission; the pair of linker arms of these two probes was optimal. The quantum efficiency was also dependent upon the concentrations of dimethylformamide and NaCl added to the assay solution. Spectroscopic measurements and T m analysis showed that an optimal configuration of the two pyrene residues for intense excimer emission might be affected by pyrene-pyrene interaction, pyrene-duplex interaction (intercalation/stacking) and solvent conditions as a whole. We then demonstrated the practicality of the ETPH method with the optimal hybridization conditions thus attained by determining that the concentration of 16S rRNA in extracts from Vibrio mimicus ATCC 33655 cells in exponential growth phase is 18 500 16S rRNA molecules/cell on average

Corrigendum

Sakai T, Kohzaki K, Watanabe A, Tsuneoka H, Shimadzu M. Use of DNA microarray analysis in diagnosis of bacterial and fungal endophthalmitis. Clin Ophthalmol. 2012;6:321&amp;ndash;326. The following sentence on page 322 was incorrect in the published paper:&amp;quot;This study was performed in accordance with the Helsinki Declaration of 1975 (1983 revision) and the institutional review boards of Jikei University.&amp;quot;The correct sentence should read:&amp;quot;This study was performed in accordance with the Helsinki Declaration of 1975 (1983 revision).&amp;quot;Read the original articl