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1. Trait sensitivities to seagrass fragmentation across spatial scales shape benthic community structure

   https://doi.org/10.1111/1365-2656.13067  

   Yeager, Lauren A.; Geyer, Julie K.; Fodrie, Fredrick Joel; Rueda, ed., Marta (August 2019, Journal of Animal Ecology)

   Abstract The structure of local ecological communities is thought to be determined by a series of hierarchical abiotic and biotic filters which select for or against species based on their traits. Many human impacts, like fragmentation, serve to alter environmental conditions across a range of spatial scales and may impact trait–environment interactions.We examined the effects of environmental variation associated with habitat fragmentation of seagrass habitat measured from microhabitat to landscape scales in controlling the taxonomic and trait‐based community structure of benthic fauna.We measured patterns in species abundance and biomass of seagrass epifauna and infauna sampled using sediment cores from 86 sites (across 21 meadows) in Back Sound, North Carolina, USA. We related local faunal community structure to environmental variation measured at three spatial scales (microhabitat, patch and landscape). Additionally, we tested the value of species traits in predicting species‐specific responses to habitat fragmentation across scales.While univariate measures of faunal communities (i.e. total density, biomass and species richness) were positively related to microhabitat‐scale seagrass biomass only, overall community structure was predicted by environmental variation at the microhabitat, patch (i.e. patch size) and landscape (i.e. number of patches, landscape seagrass area) scales. Furthermore, fourth‐corner analysis revealed that species traits explained as much variation in organismal densities as species identity. For example, species with planktonic‐dispersing larvae and deposit‐feeding trophic modes were more abundant in contiguous, high seagrass cover landscapes while suspension feeders favoured more fragmented landscapes.We present quantitative evidence supporting hierarchal models of community assembly which predict that interactions between species traits and environmental variation across scales ultimately drive local community composition. Variable responses of individual traits to multiple environmental variables suggest that community assembly processes that act on species via traits related to dispersal, mobility and trophic mode will be altered under habitat fragmentation. Additionally, with increasing global temperatures, the tropical seagrassHalodule wrightiiis predicted to replace the temperateZostera marinaas the dominate seagrass in our study region, therefore potentially favouring species with planktonic‐dispersing larva and weakening the strength of environmental control on community assembly. 

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2. Resistance of rocky intertidal communities to oceanic climate fluctuations

   https://doi.org/10.1371/journal.pone.0297697  

   Gravem, Sarah A; Poirson, Brittany N; Robinson, Jonathan W; Menge, Bruce A (May 2024, PLOS ONE)

   Paiva, Vitor_Hugo Rodrigues (Ed.)

   A powerful way to predict how ecological communities will respond to future climate change is to test how they have responded to the climate of the past. We used climate oscillations including the Pacific Decadal Oscillation (PDO), North Pacific Gyre Oscillation, and El Niño Southern Oscillation (ENSO) and variation in upwelling, air temperature, and sea temperatures to test the sensitivity of nearshore rocky intertidal communities to climate variability. Prior research shows that multiple ecological processes of key taxa (growth, recruitment, and physiology) were sensitive to environmental variation during this time frame. We also investigated the effect of the concurrent sea star wasting disease outbreak in 2013–2014. We surveyed nearly 150 taxa from 11 rocky intertidal sites in Oregon and northern California annually for up to 14-years (2006–2020) to test if community structure (i.e., the abundance of functional groups) and diversity were sensitive to past environmental variation. We found little to no evidence that these communities were sensitive to annual variation in any of the environmental measures, and that each metric was associated with < 8.6% of yearly variation in community structure. Only the years elapsed since the outbreak of sea star wasting disease had a substantial effect on community structure, but in the mid-zone only where spatially dominant mussels are a main prey of the keystone predator sea star,Pisaster ochraceus. We conclude that the established sensitivity of multiple ecological processes to annual fluctuations in climate has not yet scaled up to influence community structure. Hence, the rocky intertidal system along this coastline appears resistant to the range of oceanic climate fluctuations that occurred during the study. However, given ongoing intensification of climate change and increasing frequencies of extreme events, future responses to climate change seem likely. 

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3. Topography and disturbance influence trait‐based composition and productivity of adjacent habitats in a coastal system

   https://doi.org/10.1002/ecs2.3139  

   Brown, Joseph K.; Zinnert, Julie C. (May 2020, Ecosphere)

   Abstract Coastal systems experience frequent disturbance and multiple environmental stressors over short spatial and temporal scales. Investigating functional traits in coastal systems has the potential to inform how variation in disturbance frequency and environmental variables influence differences in trait‐based community composition and ecosystem function. Our goals were to (1) quantify trait‐based communities on two barrier islands divergent in topography and long‐term disturbance response and (2) determine relationships between community trait‐based composition and ecosystem productivity. We hypothesized that locations documented with high disturbance would have habitats with similar environmental conditions and trait‐based communities, with the opposite relationship in low‐disturbance locations. Furthermore, we expected higher productivity and lower site‐to‐site variation with low disturbance. Functional traits, biomass, and environmental metrics (soil salinity, elevation, and distance to shoreline) were collected and analyzed for two habitat types (dune and swale) on two Virginia barrier islands. Our results show that trait‐based community composition differed among habitat types and was related to disturbance. Habitats exhibited more similarity on the high‐disturbance island in both trait‐based composition and environmental variables. Conversely, the low‐disturbance island habitats were more dissimilar. We found the habitat with the lowest disturbance had the highest ecosystem productivity and had trait‐based communities indicative of highly competitive environments, while the high‐disturbance trait‐based communities were influenced by traits that indicate rapid recovery and growth. Site‐to‐site variation was similar in all dune habitats but differed among inter‐island swale habitats that varied in disturbance. These results highlight the importance of incorporating trait‐based analyses when approaching questions about community structure and ecosystem productivity in disturbance‐mediated habitats, such as coastal systems. 

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4. Shifting taxonomic and functional community composition of rivers under land use change

   https://doi.org/10.1002/ecy.4155  

   Chen, Kai; Midway, Stephen R.; Peoples, Brandon K.; Wang, Beixin; Olden, Julian D. (September 2023, Ecology)

   Abstract Land use intensification has led to conspicuous changes in plant and animal communities across the world. Shifts in trait‐based functional composition have recently been hypothesized to manifest at lower levels of environmental change when compared to species‐based taxonomic composition; however, little is known about the commonalities in these responses across taxonomic groups and geographic regions. We investigated this hypothesis by testing for taxonomic and geographic similarities in the composition of riverine fish and insect communities across gradients of land use in major hydrological regions of the conterminous United States. We analyzed an extensive data set representing 556 species and 33 functional trait modalities from 8023 fish communities and 1434 taxa and 50 trait modalities from 5197 aquatic insect communities. Our results demonstrate abrupt threshold changes in both taxonomic and functional community composition due to land use conversion. Functional composition consistently demonstrated lower land use threshold responses compared to taxonomic composition for both fish (urbanp = 0.069; agriculturep = 0.029) and insect (urbanp = 0.095; agriculturep = 0.043) communities according to gradient forest models. We found significantly lower thresholds for urban versus agricultural land use for fishes (taxonomic and functionalp < 0.001) and insects (taxonomicp = 0.001; functionalp = 0.033). We further revealed that threshold responses in functional composition were more geographically consistent than for taxonomic composition to both urban and agricultural land use change. Traits contributing the most to overall functional composition change differed along urban and agricultural land gradients and conformed to predicted ecological mechanisms underpinning community change. This study points to reliable early‐warning thresholds that accurately forecast compositional shifts in riverine communities to land use conversion, and highlight the importance of considering trait‐based indicators of community change to inform large‐scale land use management strategies and policies. 

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5. Large-herbivore nemabiomes: patterns of parasite diversity and sharing

   https://doi.org/10.1098/rspb.2021.2702  

   Titcomb, Georgia C.; Pansu, Johan; Hutchinson, Matthew C.; Tombak, Kaia J.; Hansen, Christina B.; Baker, Christopher C.; Kartzinel, Tyler R.; Young, Hillary S.; Pringle, Robert M. (May 2022, Proceedings of the Royal Society B: Biological Sciences)

   Amidst global shifts in the distribution and abundance of wildlife and livestock, we have only a rudimentary understanding of ungulate parasite communities and parasite-sharing patterns. We used qPCR and DNA metabarcoding of fecal samples to characterize gastrointestinal nematode (Strongylida) community composition and sharing among 17 sympatric species of wild and domestic large mammalian herbivore in central Kenya. We tested a suite of hypothesis-driven predictions about the role of host traits and phylogenetic relatedness in describing parasite infections. Host species identity explained 27–53% of individual variation in parasite prevalence, richness, community composition and phylogenetic diversity. Host and parasite phylogenies were congruent, host gut morphology predicted parasite community composition and prevalence, and hosts with low evolutionary distinctiveness were centrally positioned in the parasite-sharing network. We found no evidence that host body size, social-group size or feeding height were correlated with parasite composition. Our results highlight the interwoven evolutionary and ecological histories of large herbivores and their gastrointestinal nematodes and suggest that host identity, phylogeny and gut architecture—a phylogenetically conserved trait related to parasite habitat—are the overriding influences on parasite communities. These findings have implications for wildlife management and conservation as wild herbivores are increasingly replaced by livestock. 

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