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1. The hidden legacy of megafaunal extinction: Loss of functional diversity and resilience over the Late Quaternary at Hall’s Cave

   https://doi.org/10.1111/geb.13428  

   Hedberg, Carson P. ; Lyons, S. Kathleen ; Smith, Felisa A. ; Schrodt, ed., Franziska ( November 2021 , Global Ecology and Biogeography)

   Functional traits mediate the interactions of species among themselves and with their environment, providing a link between diversity and ecosystem function. Crucially, the loss of biodiversity can jeopardize the functionality of ecosystems. Much focus is on predicting the impacts of current and future species loss; however, modern ecosystems have undergone biodiversity decline throughout the Late Quaternary, starting with the Pleistocene megafaunal extinctions. Thus, the fossil record offers the opportunity to investigate the long‐term legacy of biodiversity erosion and how this is affecting modern ecosystems in a cumulative manner. We aimed to investigate changes in functional diversity and redundancy of a local mammal community at Hall’s Cave, a site with a continuous record from 21,000 years ago to the present. Additionally, we included several common introduced species in the modern community to test whether they restore some lost ecological function.

   Central Texas.

   Late Pleistocene to Present.

   Mammals.

   We used eight functional traits (mass, diet, arboreality, cursoriality, soil disturbance, group size, activity period and migration habit), which, collectively, describe the ecological role of a species and its influence on ecosystem processes, to construct a multidimensional functional space. The functional richness, range and distribution of the Hall’s Cave community and the degree of functional redundancy were characterized statistically over time.

   We found that declines in functional diversity were greater than expected given the decrease in species richness, implying that lost taxa contributed higher than average distinct ecological function. Functional distances between the remaining species increased through time, leading to reduced functional redundancy in younger communities. However, recently introduced taxa increased functional diversity to levels similar to those in the Holocene and partly restored the functional space occupied by Late Pleistocene fauna.

   Our local‐scale analysis demonstrates how prolonged biodiversity erosion not only leads to functionally depauperate communities, but, crucially, lowers ecological resilience to future disturbance.

    

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2. Functional consequences of animal community changes in managed grasslands: An application of the CAFE approach

   https://doi.org/10.1002/ecy.4192  

   Hogan, Katharine F. E. ; Jones, Holly P. ; Savage, Kirstie ; Burke, Angela M. ; Guiden, Peter W. ; Hosler, Sheryl C. ; Rowland‐Schaefer, Erin ; Barber, Nicholas A. ( November 2023 , Ecology)

   In the midst of an ongoing biodiversity crisis, much research has focused on species losses and their impacts on ecosystem functioning. The functional consequences (ecosystem response) of shifts in communities are shaped not only by changes in species richness, but also by compositional shifts that result from species losses and gains. Species differ in their contribution to ecosystem functioning, so species identity underlies the consequences of species losses and gains on ecosystem functions. Such research is critical to better predict the impact of disturbances on communities and ecosystems. We used the “Community Assembly and the Functioning of Ecosystems” (CAFE) approach, a modification of the Price equation to understand the functional consequences and relative effects of richness and composition changes in small nonvolant mammal and dung beetle communities as a result of two common disturbances in North American prairie restorations, prescribed fire and the reintroduction of large grazing mammals. Previous research in this system has shown dung beetles are critically important decomposers, while small mammals modulate much energy in prairie food webs. We found that dung beetle communities were more responsive to bison reintroduction and prescribed fires than small nonvolant mammals. Dung beetle richness increased after bison reintroduction, with higher dung beetle community biomass resulting from changes in remaining species (context‐dependent component) rather than species turnover (richness components); prescribed fire caused a minor increase in dung beetle biomass for the same reason. For small mammals, bison reintroduction reduced energy transfer through the loss of species, while prescribed fire had little impact on either small mammal richness or energy transfer. The CAFE approach demonstrates how bison reintroduction controls small nonvolant mammal communities by increasing prairie food web complexity, and increases dung beetle populations with possible benefits for soil health through dung mineralization and soil bioturbation. Prescribed fires, however, have little effect on small mammals and dung beetles, suggesting a resilience to fire. These findings illustrate the key role of re‐establishing historical disturbance regimes when restoring endangered prairie ecosystems and their ecological function.

    

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3. Different components of biodiversity mediate two ecosystem functions derived from naturally assembled filter‐feeder communities

   https://doi.org/10.1111/oik.09699  

   Hopper, Garrett W. ; González, Irene Sánchez ; Bucholz, Jamie R. ; Lozier, Jeffrey D. ; Atkinson, Carla L. ( June 2023 , Oikos)

   Positive biodiversity–ecosystem functioning (BEF) relationships observed in experiments can be challenging to identify in natural communities. Freshwater animal communities are disproportionately harmed by global change that results in accelerated species loss. Understanding how animal-mediated ecosystems functions may change as a result of global change can help determine whether biodiversity or species-specific conservation will be effective at maintaining function. Unionid mussels represent half of imperiled species in freshwater ecosystems globally and perform important ecological functions such as water filtration and nutrient recycling. We explored BEF relationships for 22 naturally assembled mussel aggregations spanning three river basins. We used the Price equation to partition the contributions of species richness, composition, and context dependent interactions to two functions of interests: spatially-explicit standing-stock biomass (indirect proxy for function) and species-specific nitrogen (N) excretion rates (direct measure of N recycling). Random and non-random species loss each reduced biomass and N recycling. Many rare species with low contributions to biomass contributed to standing-stock biomass in all basins. Widespread species had variable function across sites, such that context dependent effects (CDEs) outweighed richness effects on standing-stock biomass in two basins, and were similar to richness effects in the third. Richness effects outweighed CDEs for N recycling. Thus, many species contributed a low proportion to overall N-recycling; a product we attribute to the high evenness and functional effect trait diversity associated with these communities. The loss of low-functioning species reduced the function of persisting species. This novel result using observational data adds evidence that positive species interactions, such as interspecific facilitation, may be a mechanism by which biodiversity enhances ecosystem functions. Our work stresses the importance of evaluating species-specific contributions to functions in diverse systems, such as nutrient cycling when maintaining specific animal-mediated functions is a management goal because indirect proxies may not completely characterize BEF relationships. 

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4. Foredune‐forming grass and plant diversity show contrasting responses along the southeastern United States coast after hurricane disturbance

   https://doi.org/10.1111/jvs.13230  

   De Battisti, Davide ; Angelini, Christine ; Joyce, Matthew ; Crotty, Sinead ; Fairchild, Tom P. ; Fischman, Hallie S. ; Griffin, John N. ( January 2024 , Journal of Vegetation Science)

   Latitudinal gradients in plant communities are well studied, yet how these fundamental ecological patterns influence ecosystem recovery after extreme weather events remains largely unknown. In coastal foredunes, we investigated how the cover of a key dune‐building grass (Uniola paniculata), vegetation diversity and vegetation cover vary along a short latitudinal gradient during recovery from hurricane disturbance.

   Southeastern USA.

   We surveyed 24 sites, from central Florida to north Georgia (>400 km), four times over 18 months. General linear mixed‐effect models were used to unravel patterns of vegetation responses across latitude.

   Vegetation properties showed countervailing patterns across the latitudinal gradient. While vegetation richness, functional diversity and total cover generally declined,Uniolacover increased with increasing latitude. Further, the latitude–richness relationship strengthened while the latitude–functional diversity relationship was invariant with increasing time since the hurricane disturbance. Meanwhile, the latitude–Uniolaassociation was seasonally dependent and strongest in the summer. Latitude also influenced diversity–cover relationships: vegetation cover was positively related to species richness at lower latitudes, while it was positively associated with functional diversity only at northern sites. We found no relationship between species richness or functional diversity and increases in cover between time steps; however, recruitment of new species and functional groups was associated with increases in vegetation cover between time steps at northern sites.

   Our study highlights the temporal dynamism and contrasting patterns along latitudinal gradients exhibited by key engineering species and overall plant diversity in foredunes — a crucial line of coastal protection — exposed to hurricane disturbances. These results suggest a need for greater integration of latitudinal and diversity effects into our understanding of coastal dune resilience. They also highlight the potential benefits of enhancing dune plant biodiversity, particularly in areas where the dune‐building grasses that are classically employed in restoration (e.g.,Uniola) are unfavoured, to accelerate the re‐establishment of well‐vegetated dunes.

    

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5. Quantifying cryptic function loss during community disassembly

   https://doi.org/10.1111/1365-2664.13507  

   Terui, Akira ; Finlay, Jacques C. ; Hansen, Amy T. ; Kozarek, Jessica L. ; Januchowski‐Hartley, ed., Stephanie ( October 2019 , Journal of Applied Ecology)

   Emerging theory suggests that the ecosystem‐level consequences of anthropogenic pressures depend on how species will be disassembled from ecological communities (i.e. the disassembly rule). Species loss, however, is not the sole ecological cause of ecosystem function loss: behaviours underpinning ecosystem function can also be disrupted by anthropogenic pressures without detectable declines of component species (‘cryptic function loss’).

   Here, we introduce a novel framework that integrates behavioural responses into community disassembly metrics. We applied this framework to freshwater mussel communities (order Unionida) of the midwestern United States, in which intensive agricultural land use threatens stream biota. We combined a field experiment, meta‐analysis and watershed‐scale population dataset to assess how excessive sediment concentrations, one of the leading drivers of freshwater biodiversity loss, influence community‐level water clearance rates of freshwater mussels via behavioural (changes in mass‐specific clearance rate) and population (changes in population density) responses.

   Our study provided three key insights. First, freshwater mussels exhibited high behavioural sensitivity to increased total suspended solids (TSS) across species (i.e. reduced water clearance rate), whereas population responses were highly species‐specific. Second, the behavioural response to increased TSS causes substantial cryptic function loss under stressful conditions: simulated water clearance rates when behavioural response is included can be less than half that of mussel communities with no behavioural response. Finally, simulations revealed that mussel communities are likely to show rapid but consistent rates of ecosystem function loss irrespective of disassembly rules. The similar rates of function loss are due to the uniform behavioural response to TSS that masks the linkage between population sensitivity of a species and its contribution to ecosystem function.

   Synthesis and applications. Our findings suggest that ignoring behavioural processes may cause non‐negligible underestimation of ecosystem function loss during community disassembly, potentially leading to overly optimistic assessments of ecosystem resilience. Furthermore, unlike species declines or local extinctions, behaviour response tied to function loss may occur concurrently with increasing anthropogenic pressures. Therefore, managers should acknowledge the risk of immediate function loss after human‐induced environmental changes.

    

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