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1. Longevity, Not Stream Flow, Explains Variation in Freshwater Mussel Growth Rates Across Four Rivers

   https://doi.org/10.1111/fwb.14373  

   Brunetz, Ian_A; Lopez, Jonathan_W; Hopper, Garrett_W; González, Irene_Sánchez; Atkinson, Carla_L (December 2024, Freshwater Biology)

   ABSTRACT Freshwater mussels (Bivalvia: Unionida) are among the most imperilled freshwater taxa. Yet, there is a lack of basic life history information for mussels, including data on their growth and longevity. These data help inform conservation efforts, as they can indicate whether species or populations may be vulnerable to decline and inform which species may be best adapted to certain habitats. We aimed to quantify growth and longevity in five mussel species from four river systems in the southeastern United States and test whether growth was related to stream flow. We also interpreted our findings in the context of life history theory.To model mussel growth and longevity, we cut radial thick sections from the shells of mussels and used high‐resolution photography to image the shells. We identified annual growth rings (annuli) and used von Bertalanffy growth models to estimate growth rate (K) and maximum age (A_max) across 13 mussel populations. We then used biochronological methods to remove age‐related variation in annual growth in each shell. We tested whether annual growth was correlated with stream flow using discharge‐based statistics.We found substantial variation inKandA_maxamong species and among populations of the same species.Kwas negatively related toA_max. We did not find consistent correlations between annual growth and stream flow.Our estimates ofKandA_maxalign with previous studies on closely related species and populations. They also match the eco‐evolutionary prediction that growth rate and longevity are negatively related. Life history theory predicts that short‐lived species with higher growth rates should be better adapted to environments with cyclical disturbance regimes, whereas longer‐lived species with low growth rates should be better adapted to stable environments. The lack of correlation between annual growth and stream flow suggests that mussel growth may be limited by other factors in our study system.While some species seem to have relatively narrow ranges for growth and longevity, other species show wide variation among populations. This highlights the need for species‐ and population‐specific conservation efforts. Fundamental life history information can be integrated with other species traits to predict how freshwater taxa may respond to ecological threats. 

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2. 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)

   Abstract 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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3. Introduction into natural environments shifts the gut microbiome of captivity-raised filter-feeding bivalves

   https://doi.org/10.1093/ismeco/ycae125  

   Vaughn, Stephanie_N; Hopper, Garrett_W; González, Irene_Sánchez; Bucholz, Jamie_R; Garrick, Ryan_C; Lozier, Jeffrey_D; Johnson, Paul_D; Atkinson, Carla_L; Jackson, Colin_R (October 2024, ISME Communications)

   Abstract The gut microbiome is influenced by host species and the environment, but how the environment influences the microbiome of animals introduced into a new ecosystem has rarely been investigated. Freshwater mussels are aquatic fauna, with some threatened or endangered species propagated in hatcheries and introduced into natural systems as part of conservation efforts. The effects of the environment on the freshwater mussel gut microbiome were assessed for two hatchery-propagated species (Lampsilis ovata, Lampsilis ornata) introduced into rivers within their natural range. Mussels were placed in rivers for 8 weeks, after which one subset was collected, another subset remained in that river, and a third subset was reciprocally transplanted to another river in the same river basin for a further 8 weeks. Gut microbiome composition and diversity were characterized for all mussels. After the initial 8 weeks, mussels showed increased gut bacterial species richness and distinct community composition compared to hatchery mussels, but gut microbiome diversity then decreased for mussels that remained in the same river for all 16 weeks. The gut bacterial community of mussels transplanted between rivers shifted to resemble that of mussels placed initially into the recipient river and that remained there for the whole study. All mussels showed high proportions of Firmicutes in their gut microbiome after 8 weeks, suggesting an essential role of this phylum in the gut of Lampsilis species. These findings show that the mussel gut microbiome shifts in response to new environments and provide insights into conservation strategies that involve species reintroductions. 

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4. Characterizing the Gut Microbial Communities of Native and Invasive Freshwater Bivalves after Long-Term Sample Preservation

   https://doi.org/10.3390/microorganisms11102489  

   Vaughn, Stephanie N; Atkinson, Carla L; Johnson, Paul D; Jackson, Colin R (October 2023, Microorganisms)

   Freshwater mussels are important indicators of the overall health of their environment but have suffered declines that have been attributed to factors such as habitat degradation, a loss of fish hosts, climate change, and excessive nutrient inputs. The loss of mussel biodiversity can negatively impact freshwater ecosystems such that understanding the mussel’s gut microbiome has been identified as a priority topic for developing conservation strategies. In this study, we determine whether ethanol-stored specimens of freshwater mussels can yield representative information about their gut microbiomes such that changes in the microbiome through time could potentially be determined from museum mussel collections. A short-term preservation experiment using the invasive clam Corbicula fluminea was used to validate the use of ethanol as a method for storing the bivalve microbiome, and the gut microbiomes of nine native mussel species that had been preserved in ethanol for between 2 and 9 years were assessed. We show that ethanol preservation is a valid storage method for bivalve specimens in terms of maintaining an effective sequencing depth and the richness of their gut bacterial assemblages and provide further insight into the gut microbiomes of the invasive clam C. fluminea and nine species of native mussels. From this, we identify a “core” genus of bacteria (Romboutsia) that is potentially common to all freshwater bivalve species studied. These findings support the potential use of ethanol-preserved museum specimens to examine patterns in the gut microbiomes of freshwater mussels over long periods. 

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5. 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)

   Abstract MotivationBiodiversity 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. Main Types of Variable ContainedEcological, life‐history, morphological and geographical traits. Spatial Location and GrainNeotropical countries (Mexico, Guatemala, Costa Rica, Panama, El Salvador, Belize, Nicaragua, Ecuador, Colombia, Peru, Bolivia, Argentina, Venezuela and Chile) with contiguous montane regions. Time Period and GrainIUCN 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. Major Taxa and Level of MeasurementClasses Mammalia and Aves; 40,074 species‐level traits; 5142 imputed traits for 1733 species (mammals: 582; birds: 1147) and 16 sub‐species (mammals). Software Format.csv; R. 

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