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1. Frugivoria: A trait database for birds and mammals exhibiting frugivory across contiguous Neotropical moist forests

   https://doi.org/10.1111/geb.13716  

   Gerstner, Beth E. ; Bills, Patrick ; Zarnetske, Phoebe L. ( June 2023 , Global Ecology and Biogeography)

   Biodiversity in many areas is rapidly declining because of global change. As such, there is an urgent need for new tools and strategies to help identify, monitor and conserve biodiversity hotspots. This is especially true for frugivores, species consuming fruit, because of their important role in seed dispersal and maintenance of forest structure and health. One way to identify these areas is by quantifying functional diversity, which measures the unique roles of species within a community and is valuable for conservation because of its relationship with ecosystem functioning. Unfortunately, the functional trait information required for these studies can be sparse for certain taxa and specific traits and difficult to harmonize across disparate data sources, especially in biodiversity hotspots. To help fill this need, we compiled Frugivoria, a trait database containing ecological, life‐history, morphological and geographical traits for mammals and birds exhibiting frugivory. Frugivoria encompasses species in contiguous moist montane forests and adjacent moist lowland forests of Central and South America—the latter specifically focusing on the Andean states. Compared with existing trait databases, Frugivoria harmonizes existing trait databases, adds new traits, extends traits originally only available for mammals to birds also and fills gaps in trait categories from other databases. Furthermore, we create a cross‐taxa subset of shared traits to aid in analysis of mammals and birds. In total, Frugivoria adds 8662 new trait values for mammals and 14,999 for birds and includes a total of 45,216 trait entries with only 11.37% being imputed. Frugivoria also contains an open workflow that harmonizes trait and taxonomic data from disparate sources and enables users to analyse traits in space. As such, this open‐access database, which aligns with FAIR data principles, fills a major knowledge gap, enabling more comprehensive trait‐based studies of species in this ecologically important region.

   Ecological, life‐history, morphological and geographical traits.

   Neotropical countries (Mexico, Guatemala, Costa Rica, Panama, El Salvador, Belize, Nicaragua, Ecuador, Colombia, Peru, Bolivia, Argentina, Venezuela and Chile) with contiguous montane regions.

   IUCN spatial data: obtained February 2023, spanning range maps collated from 1998 to 2022. IUCN species data: obtained June 2019–September 2022. Newly included traits: span 1924 to 2023.

   Classes Mammalia and Aves; 40,074 species‐level traits; 5142 imputed traits for 1733 species (mammals: 582; birds: 1147) and 16 sub‐species (mammals).

   .csv; R.

    

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2. Aggregated filter‐feeders govern the flux and stoichiometry of locally available energy and nutrients in rivers

   https://doi.org/10.1111/1365-2435.13778  

   Hopper, Garrett W. ; Chen, Shuo ; Sánchez González, Irene ; Bucholz, Jamie R. ; Lu, YueHan ; Atkinson, Carla L. ; Gonzalez, ed., Angélica ( March 2021 , Functional Ecology)

   Biogeochemical cycling has often been characterized by physical and microbial processes, yet animals can be essential mediators of energy and nutrients in ecosystems. Excretion by aggregated animals can be an important local source of inorganic nutrients in green food webs; however, whether animals are a source of dissolved energy that can support brown food webs is understudied.

   We tested whether animal aggregations are a substantial flux of bioavailable dissolved organic matter (DOM) by studying spatially stable, biogeochemical hotspots formed by filter‐feeding freshwater mussels. We used parallel‐factor analysis to quantify DOM fluorescent components composition of mussel excretion and expected digestive breakdown of particulate food sources would lead to excretion of labile DOM. Next, we combined measured excretion rates of DOM, ammonium (, N) and phosphorous (SRP; P) for 22 species with biomass estimates for 14 aggregations to quantify contributions of DOM, N and P to local availability. Because mussels occupy distinct stoichiometric niches, we anticipated that differences in species biomass and assemblage structure would elicit different flux and stoichiometries of aggregate excretion.

   Aggregate dissolved organic carbon (DOC) excretion was minor (1%–11%) compared to N (12%–2,860%) and P (1%–97%), yet generalities across assemblages emerged regarding organic matter transformation by mussels towards labile protein‐like compounds compared to abundant aromatic, humic compounds in ambient water.

   Aggregate excretion of labile DOM was a substantial pool of bioavailable energy, contributing 2%–114% of local labile DOM. Spatial differences in assemblage structure led to strong differences in aggregate flux and stoichiometry driven by biomass and stoichiometric trait expression of species with contrasting dominance patterns.

   Under the nutrient conditions of our study (high C:nutrient), biogeochemical hotspots associated with low‐trophic position animal biomass may indirectly control energy flow to the brown food web by shifting C:nutrient stoichiometry available to microbes or directly by increasing the flux of microbially available DOM. Collectively, our results highlight a potentially substantial flux of labile energy and nutrients to microbial communities through the transformation of ingested organic matter by aggregations of animals and emphasize that shared functional trait classification may not translate into shared ecological function.

   A freePlain Language Summarycan be found within the Supporting Information of this article.

    

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3. Emergent Hydrodynamics and Skimming Flow Over Mussel Covered Beds in Rivers

   https://doi.org/10.1029/2019WR026252  

   Sansom, B. J. ; Bennett, S. J. ; Atkinson, J. F. ; Vaughn, C. C. ( August 2020 , Water Resources Research)

   Freshwater mussels are dominant ecosystem engineers in many streams throughout North America, yet they remain among the world's most imperiled fauna. Extensive research has quantified the ecological role of mussels in aquatic habitats, but little is known about the interaction between mussels and their surrounding physical and hydrodynamic habitat. Here the physical interactions of mussels with near‐bed flow are investigated in an experimental channel using model mussels. The results show that (1) mussels disrupt the distributions and magnitudes of time‐averaged values of longitudinal flow velocity and Reynolds shear stress depending on mussel density, and (2) at densities of approximately 25 mussels m⁻²and greater, a hydrodynamic transition occurs where the maximum Reynolds shear stress is displaced from the bed to the height of the mussel canopy, near‐bed longitudinal flow velocity is reduced, and average turbulent shear stresses acting on the mussels are reduced by as much as 64%, thus markedly decreasing the dislodgement potential of the mussels by these stresses. These results provide strong empirical evidence for a positive density‐dependent effect related to flow‐organism interactions and their ecological success, such as enhancing river bed hydrodynamic habitat complexity or decreasing the turbulent shear stresses acting to dislodge mussels from the river bed. This information will improve the understanding of the long‐term persistence of mussel beds and help focus future conservation strategies.

    

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4. A test of the loose‐equilibrium concept with long‐lived organisms: Evaluating temporal change in freshwater mussel assemblages

   https://doi.org/10.1111/1365-2656.14046  

   Hopper, Garrett W. ; Miller, Edwin J. ; Haag, Wendell R. ; Vaughn, Caryn C. ; Hornbach, Daniel J. ; Jones, Jess W. ; Atkinson, Carla L. ( January 2024 , Journal of Animal Ecology)

   The loose‐equilibrium concept (LEC) predicts that ecological assemblages change transiently but return towards an earlier or average structure. The LEC framework can help determine whether assemblages vary within expected ranges or are permanently altered following environmental change.

   Long‐lived, slow‐growing animals typically respond slowly to environmental change, and their assemblage dynamics may respond over decades, which transcends most ecological studies. Unionid mussels are valuable for studying dynamics of long‐lived animals because they can live >50 years and occur in dense, species‐rich assemblages (mussel beds). Mussel beds can persist for decades, but disturbance can affect species differently, resulting in variable trajectories according to differences in species composition within and among rivers.

   We used long‐term data sets (10–40 years) from seven rivers in the eastern United States to evaluate the magnitude, pace and directionality of mussel assemblage change within the context of the LEC.

   Site trajectories varied within and among streams and showed patterns consistent with either the LEC or directional change. In streams that conformed to the LEC, rank abundance of dominant species remained stable over time, but directional change in other streams was driven by changes in the rank abundance and composition of dominant species.

   Characteristics of mussel assemblage change varied widely, ranging from those conforming to the LEC to those showing strong directional change. Conservation approaches that attempt to maintain or create a desired assemblage condition should acknowledge this wide range of possible assemblage trajectories and that the environmental factors that influence those changes remain poorly understood.

    

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5. Long-Term Monitoring Reveals Differential Responses of Mussel and Host Fish Communities in a Biodiversity Hotspot

   https://doi.org/10.3390/d13030122  

   Sanchez Gonzalez, Irene ; Hopper, Garrett W. ; Bucholz, Jamie ; Atkinson, Carla L. ( March 2021 , Diversity)

   null (Ed.)

   Biodiversity hotspots can serve as protected areas that aid in species conservation. Long-term monitoring of multiple taxonomic groups within biodiversity hotspots can offer insight into factors influencing their dynamics. Mussels (Bivalvia: Unionidae) and fish are highly diverse and imperiled groups of organisms with contrasting life histories that should influence their response to ecological factors associated with local and global change. Here we use historical and contemporary fish and mussel survey data to assess fish and mussel community changes over a 33 year period (1986–2019) and relationships between mussel abundance and their host fish abundance in Bogue Chitto Creek, a tributary of the Alabama River and a biodiversity hotspot. Mussel abundance declined by ~80% and community composition shifted, with eight species previously recorded not found in 2019, and a single individual of the endangered Pleurobema decisum. Fish abundances increased and life history strategies in the community appeared stable and there was no apparent relationship between mussel declines and abundance of host fish. Temporal variation in the proportion of life history traits composing mussel assemblages was also indicative of the disturbances specifically affecting the mussel community. However, changes and declines in mussel assemblages in Bogue Chitto Creek cannot be firmly attributed to any specific factor or events because of gaps in historical environmental and biological data. We believe that mobility differences contributed to differential responses of fish and mussel communities to stressors including habitat degradation, recent droughts and invasive species. Overall, our work indicates that monitoring biodiversity hotspots using hydrological measurements, standardized survey methods and monitoring invasive species abundance would better identify the effects of multiple and interactive stressors that impact disparate taxonomic groups in freshwater ecosystems. 

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