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1. Weak but consistent abundance–occupancy relationships across taxa, space and time

   https://doi.org/10.1111/geb.13472  

   Ten_Caten, Cleber; Holian, Lauren; Dallas, Tad (March 2022, Global Ecology and Biogeography)

   Abstract AimAbundance–occupancy relationships posit that more locally abundant species occupy more sites than less abundant species. Although widely supported, the occurrence and detection of abundance–occupancy relationships is sensitive to sampling and detection processes. Data from large‐scale standardized sampling efforts are key to address abundance–occupancy relationships. We aimed to use such a dataset to evaluate the occurrence of abundance–occupancy relationships across different spatial grains and over time for aquatic and terrestrial taxa. LocationUSA. Time period2014–2019. Major taxa studiedBirds, mammals, beetles, ticks, fishes, macroinvertebrates and zooplankton. MethodsSpecies abundance and occupancy data were obtained from the National Ecological Observatory Network (NEON). Species mean abundance and occupancy (fraction of sampled locations that were occupied) were estimated for three different spatial grains (i.e., plot, site and domain) for all years sampled. Linear models were used to explore the consistency of interspecific abundance–occupancy relationships. The slope coefficients of these models were related to temporal and spatial variables and to species richness while controlling for taxa in a linear mixed‐effects model (LMM) framework. ResultsWe found evidence for positive abundance–occupancy relationships across the three spatial grains and over time for all taxa we studied. However, our linear models had low explanatory power, suggesting that relationships, although general, were weak. Abundance–occupancy relationships were slightly stronger at the smallest spatial grain than at the largest spatial grain, but showed no detectable change over time for any taxa. Finally, species richness was not associated with the strength of these relationships. Main conclusionsTogether, our results suggest that positive interspecific abundance–occupancy relationships are fairly general but are not capable of explaining substantial variation in spatial patterns of abundance, and that other factors, such as species traits and niche, are also likely to influence these relationships. 

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2. Evolutionary history and environmental variability structure contemporary tropical vertebrate communities

   https://doi.org/10.1111/geb.13829  

   Hsieh, Chia; Gorczynski, Daniel; Bitariho, Robert; Espinosa, Santiago; Johnson, Steig; Lima, Marcela Guimarães Moreira; Rovero, Francesco; Salvador, Julia; Santos, Fernanda; Sheil, Douglas; et al (March 2024, Global Ecology and Biogeography)

   Abstract AimTropical regions harbour over half of the world's mammals and birds, but how their communities have assembled over evolutionary timescales remains unclear. To compare eco‐evolutionary assembly processes between tropical mammals and birds, we tested how hypotheses concerning niche conservatism, environmental stability, environmental heterogeneity and time‐for‐speciation relate to tropical vertebrate community phylogenetic and functional structure. LocationTropical rainforests worldwide. Time periodPresent. Major taxa studiedGround‐dwelling and ground‐visiting mammals and birds. MethodsWe used in situ observations of species identified from systematic camera trap sampling as realized communities from 15 protected tropical rainforests in four tropical regions worldwide. We quantified standardized phylogenetic and functional structure for each community and estimated the multi‐trait phylogenetic signal (PS) in ecological strategies for the four regional species pools of mammals and birds. Using linear regression models, we test three non‐mutually exclusive hypotheses by comparing the relative importance of colonization time, palaeo‐environmental changes in temperature and land cover since 3.3 Mya, contemporary seasonality in temperature and productivity and environmental heterogeneity for predicting community phylogenetic and functional structure. ResultsPhylogenetic and functional structure showed non‐significant yet varying tendencies towards clustering or dispersion in all communities. Mammals had stronger multi‐trait PS in ecological strategies than birds (mean PS: mammal = 0.62, bird = 0.43). Distinct dominant processes were identified for mammal and bird communities. For mammals, colonization time and elevation range significantly predicted phylogenetic clustering and functional dispersion tendencies respectively. For birds, elevation range and contemporary temperature seasonality significantly predicted phylogenetic and functional clustering tendencies, respectively, while habitat diversity significantly predicted functional dispersion tendencies. Main conclusionsOur results reveal different eco‐evolutionary assembly processes structuring contemporary tropical mammal and bird communities over evolutionary timescales that have shaped tropical diversity. Our study identified marked differences among taxonomic groups in the relative importance of historical colonization and sensitivity to environmental change. 

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3. Regional species gains outpace losses across North American continental shelf regions

   https://doi.org/10.1111/geb.13681  

   Kitchel, Zoë J.; Pinsky, Malin L. (April 2023, Global Ecology and Biogeography)

   Abstract AimAlthough species richness globally is likely to be declining, patterns in diversity at the regional scale depend on species gains within new habitats and species losses from previously inhabited areas. Our understanding of the processes associated with gains or losses remains poor, including whether these events exhibit immediate or delayed responses to environmental change. LocationThe study focuses on nine temperate marine ecosystems in North America. Time periodThe study period varies by region, but overall encompasses observations from 1970 to 2014. Major taxa studiedWe identified regional gains and losses for 577 marine fish and invertebrate species. MethodsFrom a total of 166,213 sampling events from bottom trawls across North America that informed 17,997 independent observations of species gains and losses, we built generalized linear mixed effects models to test whether lagged temperature can explain instances of gains and losses of marine fishes and invertebrates in North American continental shelf habitats. ResultsWe found that gains were less likely in years with high seasonality, consistent with seasonal extremes as a strong constraint on species occurrence. Losses were also negatively associated with high seasonality, but the response was delayed by 3 years. Main conclusionsEnvironmental conditions play a role in species occupancy across diverse temperate marine ecosystems. Immediate gains paired with delayed losses can drive transient increases in species richness during times of environmental change. Identifying the dynamics behind regional species gains and losses is an important step towards prediction of biodiversity changes across ecosystems. 

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4. Diversity–stability relationships across organism groups and ecosystem types become decoupled across spatial scales

   https://doi.org/10.1002/ecy.4136  

   Wisnoski, Nathan I.; Andrade, Riley; Castorani, Max C. N.; Catano, Christopher P.; Compagnoni, Aldo; Lamy, Thomas; Lany, Nina K.; Marazzi, Luca; Record, Sydne; Smith, Annie C.; et al (July 2023, Ecology)

   Abstract The relationship between biodiversity and stability, or its inverse, temporal variability, is multidimensional and complex. Temporal variability in aggregate properties, like total biomass or abundance, is typically lower in communities with higher species diversity (i.e., the diversity–stability relationship [DSR]). At broader spatial extents, regional‐scale aggregate variability is also lower with higher regional diversity (in plant systems) and with lower spatial synchrony. However, focusing exclusively on aggregate properties of communities may overlook potentially destabilizing compositional shifts. It is not yet clear how diversity is related to different components of variability across spatial scales, nor whether regional DSRs emerge across a broad range of organisms and ecosystem types. To test these questions, we compiled a large collection of long‐term metacommunity data spanning a wide range of taxonomic groups (e.g., birds, fish, plants, invertebrates) and ecosystem types (e.g., deserts, forests, oceans). We applied a newly developed quantitative framework for jointly analyzing aggregate and compositional variability across scales. We quantified DSRs for composition and aggregate variability in local communities and metacommunities. At the local scale, more diverse communities were less variable, but this effect was stronger for aggregate than compositional properties. We found no stabilizing effect of γ‐diversity on metacommunity variability, but β‐diversity played a strong role in reducing compositional spatial synchrony, which reduced regional variability. Spatial synchrony differed among taxa, suggesting differences in stabilization by spatial processes. However, metacommunity variability was more strongly driven by local variability than by spatial synchrony. Across a broader range of taxa, our results suggest that high γ‐diversity does not consistently stabilize aggregate properties at regional scales without sufficient spatial β‐diversity to reduce spatial synchrony. 

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5. Area, environmental heterogeneity, scale and the conservation of alpine diversity

   https://doi.org/10.1111/jbi.14573  

   Malanson, George P.; Testolin, Riccardo; Pansing, Elizabeth R.; Jiménez‐Alfaro, Borja (February 2023, Journal of Biogeography)

   Abstract AimArea and environmental heterogeneity together explain most patterns of species diversity but disentangling their relative importance has been difficult. Here, we empirically examined this relationship and parsed their relative importance, and that of the heterogeneity—effective area trade‐off, at different spatial scales and in different spatial representations in simulations. LocationAlpine grasslands of 23 mountain ranges of southern and central Europe. TaxonVascular plants. MethodsWe developed metrics of climatic and edaphic heterogeneity, using principal components analyses and the shoelace algorithm, and added elevation range. We applied commonality analysis to partition the unique and shared explanation of the observed vascular plant species richness among selected metrics. A simulation was developed to separate the relative importance of area and heterogeneity at different extents and representations of spatial nestedness, and the heterogeneity—effective area trade‐off was evaluated by altering spatial discreteness. ResultsThe explanation of the observed regional richness was shared by area and heterogeneity. The simulation revealed that heterogeneity was consistently more important, but less so among smaller areas. This qualitative pattern was maintained regardless of whether and how nestedness was represented. The heterogeneity–effective area trade‐off occurred in a few simulations of more discrete habitats. Main ConclusionsScale dependence may account for discrepancies among past empirical studies wherein environmental heterogeneity has usually outweighed area in the explanation of species richness; and it is not affected by nestedness. The potential heterogeneity–effective area trade‐off may be limited to locations where the environmental heterogeneity is quite discrete or if the added environment is beyond the niches of any species in the potential pool. The significant importance of area per se in small territories indicates that microrefugia, even with an unlikely full range of heterogeneity, will suffer local extinctions in the face of climate change. 

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