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A paleontological deposit near San Clemente de Térapa represents one of the very few Rancholabrean North American Land Mammal Age sites within Sonora, Mexico. During that time, grasslands were common, and the climate included cooler and drier summers and wetter winters than currently experienced in northern Mexico. Here, we demonstrate restructuring in the mammalian community associated with environmental change over the past 40,000 years at Térapa. The fossil community has a similar number of carnivores and herbivores whereas the modern community consists mostly of carnivores. There was also a 97% decrease in mean body size (from 289 kg to 9 kg) because of the loss of megafauna. We further provide an updated review of ungulates and carnivores, recognizing two distinct morphotypes of Equus, including E. scotti and a slighter species; as well as Platygonus compressus; Camelops hesternus; Canis dirus; and Lynx rufus; and the first regional records of Palaeolama mirifica, Procyon lotor, and Smilodon cf. S. fatalis. The Térapa mammals presented here provide a more comprehensive understanding of the faunal community restructuring that occurred in northern Mexico from the late Pleistocene to present day, indicating further potential biodiversity loss with continued warming and drying of the region.

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Yes / The mechanisms regulating community composition and local dominance of trees in species-rich forests are poorly resolved, but the importance of interactions with soil microbes is increasingly acknowledged. Here, we show that tree seedlings that interact via root-associated fungal hyphae with soils beneath neighbouring adult trees grow faster and have greater survival than seedlings that are isolated from external fungal mycelia, but these effects are observed for species possessing ectomycorrhizas (ECM) and not arbuscular mycorrhizal (AM) fungi. Moreover, survival of naturally-regenerating AM seedlings over ten years is negatively related to the density of surrounding conspecific plants, while survival of ECM tree seedlings displays positive density dependence over this interval, and AM seedling roots contain greater abundance of pathogenic fungi than roots of ECM seedlings. Our findings show that neighbourhood interactions mediated by beneficial and pathogenic soil fungi regulate plant demography and community structure in hyperdiverse forests. / This research was funded by the National Key Research and Development Program of China (Project No. 2017YFA0605100) and the National Natural Science Foundation of China (NSFC 31770466 to X.L. and 31870403 to M.L.), and partly supported by awards from the UK Natural Environment Research Council (NERC NE/M004848/1 and NE/R004986/1). D.J. is also supported by the N8 AgriFood programme.

<p><a>Natural enemy ecology strives to integrate the fields of disease ecology and community ecology to forge a broader understanding of how pathogens and predators structure communities. To advance this field, we need a greater emphasis on: 1) quantifying pathogen-mediated effects on community structure and comparing these effects to those observed with predators and 2) determining the interactive effects of combined natural enemies on communities. I conducted a mesocosm experiment designed to assess the individual and combined effects of predators (dragonfly larvae and adult water bugs) and a pathogen (ranavirus) on a larval amphibian community. Additionally, I conducted laboratory experiments to assess whether ranavirus exposure increases the vulnerability of tadpoles to predation. In my laboratory experiments, I found that virus exposure increased predation rates with dragonflies, but not water bugs. For tadpoles in the dragonfly treatments, the probability of survival for virus-exposed tadpoles was 66-77% lower compared to unexposed tadpoles. This data suggests that predators may selectively remove infected individuals from the population, which can enhance the magnitude of the healthy herds effect. I found that the risk level of the predators largely explained effects on the community. For instance, high-risk dragonflies reduce overall survival to 30% whereas low-risk water bugs only reduced survival to 67%. Additionally, I found that virus reduce survival to 62%, which was comparable to effect of the low-risk predator. Interestingly, all three natural enemies influenced community structure (i.e. species relative abundance) in unique ways. These results demonstrate that pathogens can have effects similar to predators on communities, and that natural enemy identity is important when considering impacts on community structure. When predators were combined with the virus, I found that mortality was relatively unchanged from the predator-only treatments suggesting less than additive effects of combined natural enemies. This result was driven by the healthy herds effect; the presence of dragonflies reduced overall infection prevalence in the community to 7% compared to 30% in the virus-only treatment. This effect was observed in the water bug treatments, to a lesser degree, suggesting that predator risk or efficiency contributes the magnitude of the effect. Collectively, my work demonstrates the importance of examining the individual and combined effects of natural enemies on ecological communities.</a></p>

<p dir="ltr">Succession is a foundational idea in ecology and serves as way to study ecological community assembly. Here, we test the three alternative mechanisms for succession: (I) facilitation, where species arrival order is not random and can be categorized as falling into distinct stages of succession such as early and late species; (ii) tolerance, where species arrival is random, but species interactions that promote coexistence or exclusion determine the community structure through time, and; (iii) inhibition, where species arrival is once again random, but species hold space until they die, and only then can there be a change in species composition through colonization of gaps. To do this, we used a 70-year time series of succession in an oak-hickory forest system in northwest Indiana called the Ross Biological Reserve. Every ten years tree species identity and abundance were measured beginning in 1951. Non-metric multidimensional scaling (NMDS) revealed distinct periods of community assembly that we categorized as distinct early, mid, and late successional communities. We used an index of species co-occurrence (the checkerboard score) and found that early successional communities were largely random, while mid and late successional communities were characterized by nonrandom co-occurrence of species. Alpha and gamma richness increased, and species turnover rate also increased. Specific species relative abundance showed typical patterns of species abundance when classified by their successional status. We conclude that facilitation was the predominant mechanism at the landscape scale, while tolerance was more of a driver on a smaller local scale. We found no evidence of inhibition. Succession at the scale we have documented is difficult to study, because of the long times required to document change. More successional studies of this nature will benefit the field of community assembly and ecology as a whole.</p>

<p dir="ltr">Using historic acoustic bat data collected by the Indiana Department of Natural Resources, we constructed Bayesian occupancy models to gain insights into bat communities and populations across Indiana. Through use of informative prior distributions, we addressed two important considerations for bat conservation with our occupancy models: 1) exploring a compensatory community dynamic causing the expansion of evening bat (<i>Nycticeius humeralis</i>) populations in Indiana following the establishment of white-nose syndrome (WNS), and 2) estimating a percent decline of summertime hoary bat (<i>Lasiurus cinereus</i>) populations in Indiana due to wind energy development. We found evidence for a potential compensatory community dynamic in the evening bat system, in which losses of the Indiana bat (<i>Myotis sodalis</i>) and the little brown bat (<i>Myotis lucifugus</i>) due to WNS may be resulting in new realized niche space for evening bats, thereby contributing to a compensatory community dynamic. In our hoary bat system, we found evidence of a regional summertime decline of 8.9% annually since 2012. These findings have important conservation implications considering imperiled nature and conservation priorities for bats in North America. </p>

The western Amazon is known to be one of the most biologically diverse regions in the world, yet information about the spatial distribution of that biodiversity and the processes governing its distribution remains scarce. An improved understanding of those biogeographic patterns and processes can inform conservation and development planning in areas where anthropogenic landscape change is ongoing. Spatial components of biodiversity are known to be influenced by historical and present-day physical and human geographic processes. There is evidence that major Amazonian rivers form the boundaries of biological regions, at least for birds. Other factors that may influence bird species composition include the dispersal limitations of individual species, forest plant species composition and structure, topography, forest fragmentation, and hunting. Sites where bird species composition was measured in this study represented mature, upland forest on both sides of the Amazon River, and a range of non-flooded forest types, as indicated by soil and plant surveys. Bird species compositional variation was closely correlated with variation in plant species composition, human disturbance associated with forest fragmentation, and position north or south of the Amazon River. The strongest differences were between opposite sides of the river, even though local environments, including plant composition, were not different on the two sides. This strongly suggests that historical biogeographic factors, rather than present-day environmental gradients, are responsible for bioregional boundaries at Amazonian rivers. The difference between plant and bird distributions at this scale underscores the pressing need to re-evaluate general notions of bioregional complexity and pattern in the Amazon basin. Locally, the influence of habitat fragmentation on animal communities, including reduced species richness, was confirmed. The influence of local floristic variation is of particular importance due to its ubiquity across western Amazonia. Thus, understanding the distributions of soils and vegetation is critical for explaining Amazonian animal diversity. The use of these factors to model bird community heterogeneity contradicts assumptions that the processes shaping Amazonian animal community diversity are too complex to measure efficiently, and their use contributes a new understanding of the dimensions of that diversity. / text