SFS Annual Meeting

6/06/2024  |   13:30 - 13:45   |  Independence Ballroom D

USING TRAIT-BASED MODELS TO TEST FOOD WEB THEORY AT A CONTINENTAL SCALE Food webs are powerful tools for biodiversity assessment, yet most food web studies span limited spatial and temporal scales. While modeling has produced a rich literature of food web theory, these ideas are seldom tested empirically. Here, we capitalize on a large, multi-trophic dataset from the U.S. National Ecological Observatory Network (NEON) to generate trait-based, heuristic food webs using a text-mined database (AQUA-TRACE: AQUAtic Traits for RApid Construction of Ecological networks) and a previously published pipeline. Using NEON biodiversity observations from both morphological and environmental DNA (eDNA) metabarcoding samples, we constructed heuristic food webs for NEON streams, across several seasons and years, and extracted their network properties to explore how they vary through space and time, as well as what environmental drivers influenced this variation. We also examined how network properties changed when using morphological compared to eDNA metabarcoding data. Finally, we tested several hypotheses predicted from food web theory that have not been tested across large spatial and temporal scales: 1) food webs with higher maximum trophic position are more stable temporally, 2) omnivory stabilizes food webs, 3) as food web complexity increases, food web stability increases, and 4) trophic coherence increases food web stability. Testing these hypotheses provides important insights into how real food webs function over space and time and helps to reconcile different ecological predictions that have arisen from food web theory.

Zacchaeus Compson (Primary Presenter/Author), University of North Texas, zacchaeus.compson@unt.edu;

Morgan Bucher (Co-Presenter/Co-Author), University of North Texas, MorganBucher@my.unt.edu;

Medha Gollapudi (Co-Presenter/Co-Author), University of North Texas, MedhaGollapudi@my.unt.edu;

Madison Peters (Co-Presenter/Co-Author), Western Washington University, mpeters0825@gmail.com;

Roxanne MacKinnon (Co-Presenter/Co-Author), University of New Brunswick, roxanne@acapsj.org;

Tim Poirier (Co-Presenter/Co-Author), University of New Brunswick, tim.poirier@unb.ca;

Kaley Cave (Co-Presenter/Co-Author), University of North Texas, KaleyCave@my.unt.edu;

James Junker (Co-Presenter/Co-Author), University of North Texas, james.junker1@gmail.com;

Ethan Phillips (Co-Presenter/Co-Author), University of North Texas, EthanPhillips@my.unt.edu;

Winston Ihemeremadu (Co-Presenter/Co-Author), University of North Texas, WinstonIhemeremadu@my.unt.edu;

Megan Malish (Co-Presenter/Co-Author), University of Oklahoma, megan.malish@ou.edu;

Stephen Cook (Co-Presenter/Co-Author), University of Oklahoma, stephen.cook.c@gmail.com;

Thomas Neeson (Co-Presenter/Co-Author), University of Oklahoma, neeson@ou.edu;

Daniel Allen (Co-Presenter/Co-Author), Penn State, daniel.c.allen@psu.edu;

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6/06/2024  |   13:45 - 14:00   |  Independence Ballroom D

ASYMMETRIC COMPETITION AMONG STREAM FISHES: DO FOOD WEB PATHWAYS AFFECT COMPETITIVE OUTCOMES? Limiting resources are often unevenly distributed among competing consumers, as larger, more aggressive, fast growing, early emerging, or rapidly reproducing species disproportionately exploit food or habitat. In such cases, asymmetric competition can occur, resulting in stronger negative effects for some species and comparatively weaker effects for others. We hypothesize that the accessibility of food web pathways influences asymmetric competition among stream fishes. To test this hypothesis, we studied the interactions of invasive Brown trout (Salmo trutta) with native Rio Grande sucker (Catostomus plebeius) and Rio Grande chub (Gila pandora) in mountain streams of New Mexico, USA. Our study found that the accessibility of food web pathways drives asymmetric competition in mountain stream fishes, as native chub and sucker grew at slower rates than invasive trout across all observed body sizes. Our conclusion is evidenced by (1) strong diet overlap driven by benthic macroinvertebrates that (2) were important in fueling the growth of native fishes but were also (3) disproportionately exploited by trout. Trout, chub, and sucker competed for small benthic prey, trout could also incorporate other sources of food whereas chub and sucker had fewer options. Our work demonstrates that such food web pathways help explain differences in growth and production between invasive and native fishes. Our findings show that tracking energy flows through the different food web pathways provides a useful and intuitive means of describing the important sources of food that fuel growth and production and sheds light on the processes that drive asymmetric competition.

Owen George (Primary Presenter/Author), Texas Tech University, owgeorge@ttu.edu;

Scott Collins (Co-Presenter/Co-Author), Texas Tech University, Scott.Collins@ttu.edu;

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6/06/2024  |   14:00 - 14:15   |  Independence Ballroom D

Diet plasticity in a regulated Great Plains river fish assemblage Diet plasticity within and among fish species is a proposed mechanism that allows fish to adapt to variable environmental conditions over space and time, and might be particularly important in rivers with regulated discharge and sediment releases. High diet plasticity is advantageous in rapidly shifting conditions and when food availability and accessibility is unpredictable. Conversely, low diet plasticity ensures regular and dependable nutrition for fish when food is abundant and predictable. We compared fish diets across sites, seasons, and species to understand the trophic relationships between fishes and the environmental variability in a regulated Great Plains river. We evaluated the stomach contents of over 1,000 small-bodied fishes across 8 species, sampled in spring, summer, and fall 2023. Using diet to characterize species feeding preferences, we used a multivariate technique (RLQ analysis) to identify if spatial (sample site) and temporal (hydrologic conditions and season) variables influenced diets and fish community structure. Despite considerable variation in diet among species, there was no significant association between feeding preferences and the spatial or temporal variables based on a fourth-corner analysis (P = 0.95). Although this result suggests partitioning of food resources is relatively stable across a range of environmental conditions in the Kansas River, 2023 was a drought year with stable, low flows most of the year. Thus, these trends might be an artifact of low environmental variability when species interactions and resource partitioning was high.

Logan Rowley (Primary Presenter/Author), Kansas State University, lrowley@ksu.edu;

Keith Gido (Co-Presenter/Co-Author), Kansas State University, kgido@ksu.edu;

Darixa Hernandez Abrams (Co-Presenter/Co-Author), US Army Corps of Engineers, darixa.hernandez@uga.edu;

Aubrey Harris (Co-Presenter/Co-Author), US Army Crops of Engineers, Aubrey.E.Harris@usace.army.mil;

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6/06/2024  |   14:15 - 14:30   |  Independence Ballroom D

SPATIAL AND INTERSPECIFIC VARIATION IN THE FEEDING HABITS OF FOUR NATIVE PRAIRIE STREAM FISHES Environmental variation is known to influence the quality, quantity, and availability of autochthonous and allochthonous food resources for stream consumers. We assessed the effects of stream discharge, turbidity, and conductivity gradients on the feeding habits of an understudied group of prairie fishes including plains minnow (Hybognathus placitus), prairie chub (Macrhybopsis australis), Red River shiner (Notropis bairdi), and Red River pupfish (Cyprinodon rubrofluviatilis) using integrated stable isotope analysis (d13C, d15N) and gut content analysis. Stream discharge (0.08 – 22.48 m3 s-1) and turbidity (4.99 – 755 FTU) increased significantly from westernmost to easternmost sites, whereas conductivity (36,563 – 1,314 µS cm-1) decreased. Carbon d13C values of Red River pupfish differed significantly from d13C values of plains minnow, prairie chub, and Red River shiner (p < 0.05) which may suggest that Red River pupfish acquire basal energy from a different source of primary production. Interspecific d15N values indicated that prairie chub and Red River shiner were significantly higher trophic level consumers compared to plains minnow and Red River pupfish (p < 0.05). These results were supported by gut content analyses, which revealed that prairie chub and Red River shiner consumed a higher proportion of macroinvertebrates, whereas plains minnow and Red River pupfish consumed higher proportions of diatoms and sediment. Characterization of food-web structure along environmental gradients may provide baseline data from which to compare how species may be affected by ongoing stream regulation, stream fragmentation, and secondarily altered salinity.

Wade Wilson (Primary Presenter/Author), Texas Cooperative Fish and Wildlife Research Unit, Texas Tech University, wadewils@ttu.edu;

Jane Rogosch (Co-Presenter/Co-Author), U.S. Geological Survey, Texas Cooperative Fish and Wildlife Research Unit/Texas Tech University, jrogosch@ttu.edu;

Scott Collins (Co-Presenter/Co-Author), Texas Tech University, Scott.Collins@ttu.edu;

Bart Durham (Co-Presenter/Co-Author), Lubbock Christian University, bart.durham@lcu.edu;

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6/06/2024  |   14:30 - 14:45   |  Independence Ballroom D

ON THE ANALYSIS OF ISOTOPE TRACER ADDITION EXPERIMENTS Understanding how nutrients flow through food webs is central to ecosystem ecology. Tracer addition experiments are powerful tools to reconstruct nutrient flows by adding an isotopically enriched element into an ecosystem and tracking its fate through time. Historically, the design and analysis of tracer studies have varied widely, ranging from descriptive studies to modeling approaches of varying complexity. Increasingly, isotope tracer data are being used to compare ecosystems and analyze experimental manipulations. This calls for a formal statistical framework for analyzing such experiments that calculates the errors associated with the model fit, accounts for the interdependence of compartments, and handles the uncertainty in the diet of consumers. I will present a method based on Bayesian hidden Markov models and implemented in R as package ‘isotracer’. I will illustrate it with the analysis of 15N tracer additions in two Trinidadian streams in which light was experimentally manipulated. Through this case study, I will illustrate how to estimate N fluxes between ecosystem compartments, turnover rates of N within those compartments, and the associated uncertainty. We also show how the method can be used to compare alternative models of food web structure, calculate the error around derived parameters, and make statistical comparisons between sites or treatments.

Andrés López-Sepulcre (Primary Presenter/Author), Cornell University, al2365@cornell.edu;

Matthieu Bruneaux (Co-Presenter/Co-Author), University of Jyväskylä, matthieu.d.bruneaux@jyu.fi;

Sarah Collins (Co-Presenter/Co-Author), University of Wyoming, sarah.collins@uwyo.edu;

Rana El-Sabaawi (Co-Presenter/Co-Author), University of Victoria, rana@uvic.ca;

Alexander Flecker (Co-Presenter/Co-Author), Cornell University, Ithaca, NY, USA, asf3@cornell.edu;

Steven Thomas (Co-Presenter/Co-Author), University of Alabama, sathomas16@ua.edu;

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6/06/2024  |   14:45 - 15:00   |  Independence Ballroom D

Salty Scrapers? Unpacking benthic macroinvertebrate declines in the central Appalachian coalfield through trait-based secondary production approaches Mountaintop removal mining practices in central Appalachia have directly altered headwater streams through elevated ions (e.g. calcium, sulfate) that increase specific conductance (SC). Up to 98% loss of Ephemeroptera production, that are often scrapers, has been documented in the region. While significant declines are documented among mayflies, Plecoptera, Trichoptera and Diptera show increases in density and biomass despite the loss of sensitive taxa. Though the mechanisms behind these salt-induced shifts remain debated and largely untested in field experiments, food quality and quantity might be limiting for scrapers but not for other shredding taxa. We are investigating how certain functional feeding groups could be selected for in freshwater salinization by measuring macroinvertebrate secondary production through routine sampling at 9 streams across southwestern Virginia and West Virginia, with SC ranges from 25-1242 µS/cm. We expect that scraper secondary production will decline with increasing salinity as a function of periphyton response to rising ion concentrations, whereas allochthonous inputs will be less influenced and lead to shredder compensation. Therefore, secondary production will remain the same across a salinity gradient, but shredders will contribute disproportionately to biomass as SC rises. Recording size class and biomass throughout the year, at different salinity levels, will guide us in exploring how individual taxa sensitivities and traits influence cohort production dynamics. Secondary production of headwater streams can have downstream impacts for biological and physical processes, so unpacking the functionality of community energetics can reveal important drivers of taxon decline in these salinized, mining-influenced headwater streams.

Kelley Sinning (Primary Presenter/Author), Virginia Tech, kelley.sinning@gmail.com;

Stephen Schoenholtz (Co-Presenter/Co-Author), Virginia Tech, schoenhs@vt.edu;

Teresa Brown (Co-Presenter/Co-Author), University of Virginia's College at Wise, tlb9fd@uvawise.edu;

Erin Hotchkiss (Co-Presenter/Co-Author), Virginia Polytechnic Institute and State University (Virginia Tech), ehotchkiss@vt.edu;

Daniel McLaughlin (Co-Presenter/Co-Author), Virginia Tech, mclaugd@vt.edu;

Caleigh Meehan (Co-Presenter/Co-Author), Virginia Tech, cemeehan@vt.edu;

Gregory Pond (Co-Presenter/Co-Author), USEPA, Region 3, Laboratory Services and Applied Science Division, pond.greg@epa.gov;

Lisa Tabor (Co-Presenter/Co-Author), Virginia Tech, lmt@vt.edu;

Carl Zipper (Co-Presenter/Co-Author), Virginia Tech, czip@vt.edu;

Sally Entrekin (Co-Presenter/Co-Author), Virginia Tech, sallye@vt.edu;

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