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1. Trait–environment relationships could alter the spatial and temporal characteristics of aquatic insect subsidies at the macrospatial scale

   https://doi.org/10.1111/ecog.05298  

   Kopp, Darin; Allen, Daniel (December 2020, Ecography)

   null (Ed.)

   Ecological flows across ecosystem boundaries are typically studied at spatial scales that limit our understanding of broad geographical patterns in ecosystem linkages. Aquatic insects that metamorphose into terrestrial adults are important resource subsidies for terrestrial ecosystems. Traits related to their development and dispersal should determine their availability to terrestrial consumers. Here, we synthesize geospatial, aquatic biomonitoring and biological traits data to quantify the relative importance of several environmental gradients on the potential spatial and temporal characteristics of aquatic insect subsidies across the contiguous United States. We found the trait composition of benthic macroinvertebrate communities varies among hydrologic regions and could affect how aquatic insects transport subsidies as adults. Further, several trait–environment relationships were underpinned by hydrology. Large bodied taxa that could disperse further from the stream were associated with hydrologically stable conditions. Alternatively, hydrologically variable conditions were associated with multivoltine taxa that could extend the duration of subsidies with periodic emergence events throughout the year. We also found that anthropogenic impacts decrease the frequency of individuals with adult flight but potentially extend the distance subsidies travel into the terrestrial ecosystem. Collectively, these results suggest that natural and anthropogenic gradients could affect aquatic insect subsidies by changing the trait composition of benthic macroinvertebrate communities. The conceptual framework and trait–environment relationships we present shows promise for understanding broad geographical patterns in linkages between ecosystems. 

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2. Enter the Mosaic: Aquatic‐Terrestrial Reciprocal Fluxes and Food Webs Are Dynamically Interdependent Across Space and Through Time

   https://doi.org/10.1111/fwb.70094  

   Brooks, Jeremy M; Baxter, Colden V; Warren, Dana R; MacNeill, Keeley L (September 2025, Freshwater Biology)

   ABSTRACT Decades‐old research describes dynamic interdependence among aquatic and terrestrial food webs, leading to calls for integrating cross‐ecosystem linkages with landscape ecology to evaluate dynamics of spatially‐subsidised food webs. Though development of meta‐community theory has suggested that such spatial dynamics may help sustain biodiversity, empirical data remain limited. In northern Yellowstone National Park, over a century of terrestrial wildlife dynamics, including the extirpation and subsequent reintroduction of wolves, have contributed to a habitat mosaic in which stream‐riparian ecosystems are dominated by either woody or herbaceous vegetation. In the context of this habitat mosaic, we addressed the overarching questions: (1) Are habitat mosaics associated with spatial and temporal variation in reciprocal fluxes and linked food webs and (2) how do biodiversity, organism traits and species interactions influence, and are they influenced by, that spatial and temporal variation?From 2019 to 2021, we intensively sampled eight headwater streams to characterise reciprocal fluxes of aquatic and terrestrial invertebrates and the patterns of potential responses by fish, birds, bats and spiders. We evaluated sites individually as well as how they contributed to a meta‐community.We found that local stream‐riparian ecosystems contributed to a mosaic in which reciprocal fluxes of invertebrates among local patches were asynchronous and tracked by both aquatic and terrestrial consumers in ways mediated by organism traits. Within sites, aquatic and terrestrial invertebrate fluxes were seasonally asynchronous with each other, but these patterns varied from site to site. Across the mosaic, comparisons of daily aquatic insect emergence varied from 25% to 167% among streams and did so variably throughout the year, revealing asynchronous dynamics created at the meta‐community scale. Daily inputs of terrestrial invertebrates were similarly asynchronous across the mosaic, varying from 14% to 170%. These asynchronies were positively correlated with invertebrate beta diversity and associated with varying riparian vegetation, stream temperature, and flow regimes. In turn, in situ consumers tracked the allochthonous invertebrate prey in ways that were mediated by site context (i.e., local habitat characteristics) and consumer traits (e.g., range, foraging strategy and breeding requirements).Based on these observations as an example, we infer there is not one way for food webs to be reciprocally and spatially linked, but multiple ways that can vary both across a spatial mosaic and through time. Our findings provide empirical evidence suggesting potential relationships between habitat complexity and the maintenance of biodiversity via aquatic‐terrestrial reciprocal fluxes and dynamic interdependence across mosaics. 

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3. Reduced complexity models for regional aquatic habitat suitability assessment

   https://doi.org/10.1111/1752-1688.13077  

   Goodrum, Gregory C.; Null, Sarah E. (November 2022, JAWRA Journal of the American Water Resources Association)

   Abstract Generalizable methods that identify suitable aquatic habitat across large river basins and regions are needed to inform resource management. Habitat suitability models intersect environmental variables to predict species occurrence, but are often data intensive and thus are typically developed at small spatial scales. This study estimated mean monthly aquatic habitat suitability throughout Utah (USA) for Bonneville Cutthroat Trout (Oncorhynchus clarkii utah) and Bluehead Sucker (Catostomus discobolus) with publicly available, geospatial datasets. We evaluated 15 habitat suitability models using unique combinations of percent of mean annual discharge, velocity, gradient, and stream temperature. Environmental variables were validated with observed conditions and species presence observations to verify habitat suitability estimates. Stream temperature, gradient, and discharge best predicted Bonneville Cutthroat Trout presence, and gradient and discharge best predicted Bluehead Sucker presence. Simple aquatic habitat suitability models outperformed models that used only streamflow to estimate habitat for both species, and are useful for conservation planning and water resources decision‐making. This modeling approach could enable resource managers to prioritize stream restoration across vast regions within their management domain, and is potentially compatible with water management modeling to improve ecological objectives in management models. 

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4. Lakeshore residential development as a driver of aquatic habitat and littoral fish communities: A cross‐system study

   https://doi.org/10.1002/eap.2896  

   Perales, K_Martin; Vander_Zanden, M_Jake (June 2023, Ecological Applications)

   Abstract Lakeshore riparian habitats have undergone intensive residential development in many parts of the world. Lakeshore residential development (LRD) is associated with aquatic habitat loss/alteration, including altered macrophyte communities and reduced coarse woody habitat. Yet habitat‐mediated and other generalized effects of LRD on lake biotic communities are not well understood. We used two approaches to examine the relationships among LRD, habitat, and fish community in a set of 57 northern Wisconsin lakes. First, we examined how LRD affected aquatic habitat using mixed linear effects models. Second, we evaluated how LRD affected fish abundance and community structure at both whole‐lake and site‐level spatial scales using generalized linear mixed‐effects models. We found that LRD did not have a significant relationship with the total abundance (all species combined) of fish at either scale. However, there were significant species‐specific responses to LRD at the whole‐lake scale. Species abundances varied across the LRD gradient, with bluegill (Lepomis macrochirus) and mimic shiners (Notropis volucellus) responding positively along the gradient and walleye (Sander vitreus) having the most negative response. We also quantified site‐level habitat associations for each fish species. We found that habitat associations did not inform a species' overall response to LRD, as illustrated by species with similar responses to LRD having vastly different habitat associations. Finally, even with the inclusion of littoral habitat information in models, LRD still had significant effects on species abundances, reflecting a role of LRD in shaping littoral fish communities independent of our measure of littoral habitat alteration. Our results indicated that LRD altered littoral fish communities at the whole‐lake scale through both habitat and non‐habitat‐mediated drivers. 

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5. Spatiotemporal patterns of emergence phenology reveal complex species‐specific responses to temperature in aquatic insects

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

   Finn, Debra S.; Johnson, Sherri L.; Gerth, William J.; Arismendi, Ivan; Li, Judith L.; Bates, ed., Amanda (January 2022, Diversity and Distributions)

   Abstract AimClimate change is broadly affecting phenology, but species‐specific phenological response to temperature is not well understood. In streams, insect emergence has important ecosystem‐level consequences because emergent adults link aquatic and terrestrial food webs. We quantified emergence timing and duration (within‐population synchronicity) of insects among streams along a spatiotemporal gradient of mean water temperature in a montane basin to assess the sensitivity of these phenological traits to heat accumulation from mid‐winter through spring emergence periods. LocationSix headwater streams in the Lookout Creek basin, H.J. Andrews Experimental Forest, Oregon, USA. MethodsWe collected emerging adults of four abundant insect species twice weekly throughout spring for 6 consecutive years. We fit Gaussian models to the empirical temporal distributions to characterize peak emergence timing (mean) and duration (days between 5th and 95th percentiles) for each species/stream/year combination. We then quantified relationships between degree‐day accumulation and phenological response. ResultsOnly one of the four species (a caddisfly) showed a simple response of earlier emergence timing in both warmer streams and years. One stonefly had lengthy emergence periods resulting in substantial phenological overlap between warmer and cooler streams/years. Interestingly, two species (a mayfly and a stonefly) responded strongly to temporal (interannual) temperature differences but minimally to spatial differences, indicating that emergence was nearly synchronous among streams, within years. These two species had among‐stream differences approaching 500 degree‐days from mid‐winter to peak emergence. Conversely, duration of emergence was more strongly associated with spatial than temporal differences, with longer duration in lower‐elevation (warmer) streams. Main conclusionsEmergence phenology has species‐specific responses to temperature likely driven by complex cues for diapause or quiescence periods during preceding life cycle stages. We hypothesize a trade‐off between complex phenological response that synchronizes emergence among heterogeneous sites and other traits such as adult longevity and dispersal capacity. 

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