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1. Herbivory enhances the effect of environmental variability on plant community composition and beta diversity

   https://doi.org/10.1111/jvs.12862  

   Brambila, Alejandro ; Chesnut, John W. ; Prugh, Laura R. ; Hallett, Lauren M. ; Ward, ed., David ( April 2020 , Journal of Vegetation Science)

   Understanding the factors that shape biodiversity over space and time is a central question in ecology. Spatiotemporal environmental variation in resource availability can favor different species, generating beta diversity patterns that increase overall diversity. A key question is the degree to which biotic processes—in particular herbivory—enhance or dampen the effect of environmental variation on resource availability at different scales.

   We tested this question in a semi‐arid California grassland, which is characterized by high rainfall variability. The system supports giant kangaroo rats (Dipodomys ingens), which form mounds that structure spatial variability in soil nutrient availability.

   From 2008 to 2017 we implemented a cattle herbivory exclusion experiment to test whether herbivory moderates the effect of spatial and inter‐annual resource variability on plant biomass and diversity both on and off mounds.

   Grazing reduced local diversity regardless of mound status or amount of precipitation. However, we found that plant productivity was higher on than off mounds, increased following high rainfall years, and that grazing increased these on‐ versus off‐mound differences in wet years—especially after a major drought. Correspondingly, grazing led to on‐mound communities that were more different from each other and from off‐mound communities.

   Taken together, our results suggest that herbivory generally enhances habitat heterogeneity across this arid landscape, but is resource context‐dependent with greater effects seen in wetter years.

    

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2. General destabilizing effects of eutrophication on grassland productivity at multiple spatial scales

   https://doi.org/10.1038/s41467-020-19252-4  

   Hautier, Yann ; Zhang, Pengfei ; Loreau, Michel ; Wilcox, Kevin R. ; Seabloom, Eric W. ; Borer, Elizabeth T. ; Byrnes, Jarrett E. ; Koerner, Sally E. ; Komatsu, Kimberly J. ; Lefcheck, Jonathan S. ; et al ( December 2020 , Nature Communications)

   null (Ed.)

   Abstract Eutrophication is a widespread environmental change that usually reduces the stabilizing effect of plant diversity on productivity in local communities. Whether this effect is scale dependent remains to be elucidated. Here, we determine the relationship between plant diversity and temporal stability of productivity for 243 plant communities from 42 grasslands across the globe and quantify the effect of chronic fertilization on these relationships. Unfertilized local communities with more plant species exhibit greater asynchronous dynamics among species in response to natural environmental fluctuations, resulting in greater local stability (alpha stability). Moreover, neighborhood communities that have greater spatial variation in plant species composition within sites (higher beta diversity) have greater spatial asynchrony of productivity among communities, resulting in greater stability at the larger scale (gamma stability). Importantly, fertilization consistently weakens the contribution of plant diversity to both of these stabilizing mechanisms, thus diminishing the positive effect of biodiversity on stability at differing spatial scales. Our findings suggest that preserving grassland functional stability requires conservation of plant diversity within and among ecological communities. 

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3. Invasion‐mediated mutualism disruption is evident across heterogeneous environmental conditions and varying invasion intensities

   https://doi.org/10.1111/ecog.06434  

   Roche, Morgan D. ; Pearse, Ian S. ; Sofaer, Helen R. ; Kivlin, Stephanie N. ; Spyreas, Greg ; Zaya, David N. ; Kalisz, Susan ( July 2023 , Ecography)

   The impact of a biological invasion on native communities is expected to be uneven across invaded landscapes due to differences in local abiotic conditions, invader abundance, and traits and composition of the native community. One way to improve predictive ability about the impact of an invasive species given variable conditions is to exploit known mechanisms driving invasive species' success. Invasive plants frequently exhibit allelopathic traits, which can be directly toxic to plants or indirectly impact them via disruption of root symbionts, including mycorrhizal fungi. The indirect mechanism – mutualism disruption – is predicted to impact plants that rely on mycorrhizas but not affect non‐mycorrhizal plant species. To assess whether invader‐driven mutualism disruption explains observed changes in native plant communities, we analyzed long‐term (1998–2018) plant cover data from forest plots across the state of Illinois. We evaluated native plant communities experiencing a range of abundance of invasive allelopathic garlic mustardAlliaria petiolataand varying environmental conditions. Consistent with the mutualism disruption hypothesis, we showed that as garlic mustard abundance increased over time in 0.25 m²sampling quadrats, the abundance of mycorrhizal plant species decreased, but non‐mycorrhizal plant species did not. Over space and time, garlic mustard abundance predicted plant abundances and diversity at the quadrat level, but this relationship was not present at a larger scale when quadrats were aggregated within sites. Garlic mustard's impact on the plant community was highly localized, yet it was as important as abiotic variables for predicting local plant diversity. We showed that garlic mustard abundance was a key predictor of patterns of plant diversity across invasion intensity and environmental heterogeneity in a way that is consistent with mutualism disruption. Our work indicates that the mutualism disruption hypothesis can provide generalizable predictions of the impacts of allelopathic invasive plants that are evident at a broad spatial scale.

    

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4. Centenary shipwrecks reveal the limits of artificial habitats in protecting regional reef fish diversity

   https://doi.org/10.1111/1365-2664.14053  

   Medeiros, Aline P. M. ; Ferreira, Beatrice P. ; Betancur‐R, Ricardo ; Cardoso, Aiara P. L. R. ; Matos, Marcello R. S. B. C. ; Santos, Bráulio A. ( October 2021 , Journal of Applied Ecology)

   The sinking of artificial structures has become increasingly common around the world, but whether the artificial structures favour or disfavour fish diversity remain under debate. Sinking may empty the nearby natural reefs locally and regionally by attracting their biota. Conversely, it may improve environmental conditions for species survival and reproduction, acting as source of diversity at the local and regional levels.

   We tested these contrasting hypotheses by assessing the taxonomic, functional and phylogenetic diversity of 12 fish communities in Northeast Brazil: four ageing (>100‐year‐old) shipwrecks and eight surrounding natural reefs at comparable depths and distances. We partitioned the gamma diversity of artificial and natural reef communities into independent alpha and beta components, accounted for species’ abundance and assessed whether beta patterns were mostly driven by spatial turnover or nestedness.

   We recorded 6,335 individuals distributed in 88 fish species and 38 families. While artificial and natural reefs shared 50 species (57%), 21 species (24%) were exclusive to the artificial reefs, suggesting that the nearby natural reefs—the most likely original source of these exclusive species—do not harbour them anymore. Alpha diversity of typical and dominant species did not significantly differ between the reef types, but alpha diversity of rare species was taxonomically, functionally and phylogenetically higher in artificial reefs, indicating positive effects of the structures at the local scale.

   By contrast, regional beta diversity was higher in natural reefs in terms of taxonomic and functional diversity, regardless of species abundance. Pairwise beta diversity indicated that turnover had a large effect on the compositional dissimilarity in both reef types, whereas nestedness was almost irrelevant in artificial reefs.

   Synthesis and applications. Artificial structures such as shipwrecks may promote the co‐occurrence of rare species, but they are unable to produce the beta diversity patterns that natural reefs do, even following many decades of colonization. Although artificial habitats host a significant portion of the regional reef fish diversity, they may have also contributed to the degradation of nearby natural reefs. We recommend the establishment of regulated diving spots, fishing grounds and no‐take areas as a strategy to conserve regional fish diversity.

    

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5. Plant communities in Chicago residential neighborhoods show distinct spatial patterns

   https://doi.org/10.1016/j.landurbplan.2022.104663  

   Minor, Emily ; Lopez, Bianca ; Smith, Alexis ; Johnson, Philip ( April 2023 , Landscape and Urban Planning)

   Residential yards and gardens can have surprisingly high plant diversity. However, we still do not understand all the factors that drive diversity in individual gardens, or how gardens scale up to create larger patterns of urban biodiversity. For example, social interactions between neighbors could affect whether they mimic each other’s yard design, affecting spatial turnover in plant communities. Further, socio-economic differences between neighborhoods might result in distinct plant assemblages across a city. In this paper, we used fieldwork, GIS, and spatial statistics to examine the variability in front yard vegetation—both cultivated and spontaneous plants—in 870 yards in Chicago, Illinois (USA). Our goals were to understand diversity and spatial patterning of plant communities in residential neighborhoods and how they vary with scale, considering alpha, beta, and gamma diversity. We addressed the following questions: (1) How do alpha, beta, and gamma diversity of cultivated and spontaneous plants vary between neighborhoods with different socioeconomic characteristics? (2) Within neighborhoods, do we see spatial autocorrelation in front-yard plant communities? If so, do those spatial patterns affect plant diversity at the neighborhood scale? We found diverse plant communities and distinct spatial patterns across Chicago. Richness and composition of both spontaneous and cultivated plants differed between neighborhoods, with some differences explained by socioeconomic factors such as education. Spontaneous and cultivated plants showed significant spatial autocorrelation, although that spatial autocorrelation generally did not influence neighborhood-scale diversity. Knowledge of these spatial patterns and their socioeconomic drivers could be exploited to increase adoption of environmentally-friendly yard management practices across a city. 

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