Seasonal patterns of ecological uniqueness of anuran metacommunities along different ecoregions in Western Brazil

Omernik's Ecoregion Framework: a Legacy for Understanding Regional Patterns in Attainable Resource Quality

An initial and comprehensive map of ecological regions across the conterminous United States was provided by Omernik in 1987. Because that paper was the most-cited published by the Annals of the American Association of Geographers, we sought to assess and quantify its contribution to science. To do so, we conducted a scientometric analysis to address the following main questions: 1) What are the temporal and spatial citation trends? We expected that Omernik's paper would still be employed 36 years after its publication, and mostly in the United States of America. 2) For what types of environments and organisms has it been applied? Based on its generality, we expected that it had been applied to both terrestrial and aquatic ecosystems. 3) What are the main applications of Omernik's article? We predicted that it would mostly be used for describing and delineating study sites and management areas, as well as for selecting regional reference sites. The number of citations presented a positive temporal increase, indicating its continued applicability. Most papers dealt with aquatic environments, mainly in streams carried out predominantly in the United States of America, as was one of its earliest applications. The usefulness of ecoregions for assessing and managing biotic and abiotic patterns and distributions were the main topics addressed by scientists. Ecoregions have offered a general framework for developing regional expectations and rational regional management policies across large areas, as was their original intent. In addition, ecoregion maps were used for communicating patterns-or the lack of them-to interested scientists, citizens, and decision-makers. That comprehensiveness of Omernik's ecoregion approach has led to its widespread applicability and continued usefulness to a diverse set of scientific and management disciplines.

Contrasting elevational patterns and underlying drivers of stream bacteria and fungi at the regional scale on the Tibetan Plateau

Elevational gradients are the focus of development and evaluation of general theories on biodiversity. However, elevational studies of microorganisms and the underlying mechanisms remain understudied, especially at regional scales. Here, we examined stream bacterial and fungal communities along an elevational gradient of 990-4,600 m with a geographic distance up to 500 km in the southeastern Tibetan Plateau and further analyzed their elevational patterns and drivers of three biodiversity indicators, including species richness, ecological uniqueness and community composition. Bacteria and fungi showed distinct elevational trends in species richness and consistently decreasing patterns in their ecological uniqueness. The distance-decay relationships were concordant for the two microbial groups, while fungi showed higher dissimilarity and a lower turnover rate. Interestingly, bacterial and fungal compositions substantially differed between the elevations below and above 3,000 m. Climate predictors, such as the mean annual temperature and precipitation seasonality, had greater effects than local environment drivers. Notably, fungal diversity was mainly influenced by climate, while bacterial diversity was explained by the shared contributions of climate and local factors. Collectively, these findings revealed the elevational patterns of stream microbial biodiversity across mountains on a large spatial scale and highlight their underlying response mechanisms to environmental predictors.

Differences in prey availability across space and time lead to interaction rewiring and reshape a predator-prey metaweb

Space and time promote variation in network structure by affecting the likelihood of potential interactions. However, little is known about the relative roles of ecological and biogeographical processes in determining how species interactions vary across space and time. Here, we study the spatiotemporal variation in predator-prey interaction networks formed by anurans and arthropods and test for the effects of prey availability in determining interaction patterns, information that is often absent and limits the understanding of the determinants of network structure. We found that network dissimilarity between ecoregions and seasons was high and primarily driven by interaction rewiring. Interaction rewiring drove variation across seasons and ecoregions and species turnover was positively related to geographical distance. Using a null model approach to disentangle the effect of prey availability on the spatial and temporal variation we show that differences in prey availability were important in determining the variation in network structure between seasons and among areas. Our study reveals that fluctuations in prey abundance, along with limited dispersal abilities of anurans and their prey, may be responsible for the spatial patterns that emerged in our predator-prey metaweb. These findings contribute to our understanding of the assembly rules that maintain biotic processes in metacommunities and highlight the importance of prey availability to the structure of these systems.