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SFS Annual Meeting

Monday, May 20, 2019
11:00 - 12:30

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11:00 - 11:15: / 251 DE HOW MUCH TOTAL VARIATION IN COMMUNITY COMPOSITION CAN WE REALLY ACCOUNT FOR? A CASE FOR FURTHER INVESTIGATION OF STOCHASTIC EFFECTS

5/20/2019  |   11:00 - 11:15   |  251 DE

HOW MUCH TOTAL VARIATION IN COMMUNITY COMPOSITION CAN WE REALLY ACCOUNT FOR? A CASE FOR FURTHER INVESTIGATION OF STOCHASTIC EFFECTS The relative importance of deterministic forces versus chance is one of the most important questions in ecology. Variance partitioning has been used to estimate the relative importance of species sorting (deterministic) versus dispersal limitations (chance) in determining the variation in the community composition among sites. Previous reviews indicate that both sorting and dispersal limitations explain part of the variation in community composition. We reviewed 186 variance-partitioning articles (55% freshwater studies, 43% terrestrial studies, 2% marine) to determine the total explained variation in community composition among sites, which is partitioned into sorting and dispersal limitations. The total explained variation averaged across all studies was 30.7% (± 19.2%) with 26.5% (± 18.4%) in freshwater environments. Since variance-partitioning accounts for so little variation in community composition, we conclude that any attempt to draw inferences on the relative importance of sorting versus dispersal limitations are futile. We refute the explanation that some unmeasured environmental factor(s) account for the remaining 73.5% of unexplained variation in community composition. We also summarize hypotheses on how stochastic effects on community assembly may comprise a substantial portion of unexplained variation in community composition.

Kevin Lamb (Primary Presenter/Author), Brigham Young University, kvieiralamb@gmail.com;


Russell Rader (Co-Presenter/Co-Author), Brigham Young University, russell_rader@byu.edu;


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11:15 - 11:30: / 251 DE STREAM CO-OCCURRENCE NETWORKS VARY IN COMPLEXITY AND STRUCTURE ALONG LATITUDINAL GRADIENTS

5/20/2019  |   11:15 - 11:30   |  251 DE

STREAM CO-OCCURRENCE NETWORKS VARY IN COMPLEXITY AND STRUCTURE ALONG LATITUDINAL GRADIENTS The Stress Gradient Hypothesis (SGH) predicts that communities have more negative interactions (e.g., competition) in benign environments, but more positive interactions (e.g., facilitation) in unfavorable conditions. Latitude represents a gradient of climate stress, allowing us to study the SGH at large scales. and The Dobzhansky-MacArthur Hypothesis (DMH) postulates that communities at high latitudes are governed by climate stress, whereas at low latitudes, they are controlled by competition. We tested these predictions for stream fish from the eastern US with a novel approach based on co-occurrence networks. We examined network topology, including number of positive and negative species interactions after controlling for environmental autocorrelation, dispersal and large-scale abiotic influences Contrary to SGH, we found that mid latitudes, but not low latitudes, contain the highest number of negative interactions, while low latitudes, but not high latitudes had the most positive interactions. Contrary to DMH, mid latitudes, but not low latitudes exhibited the most interactions. Our results indicate that species interactions in stream ecosystems have a more complex environmental underpinning and factors other than climate may have an important role in maintaining community structure.

William Budnick (Co-Presenter/Co-Author), University of Texas - Arlington, william.budnick@mavs.uta.edu;


Chad Larson (Co-Presenter/Co-Author), Washington State Department of Ecology, clar461@ecy.wa.gov;


Sophia Passy (Co-Presenter/Co-Author), University of Texas - Arlington, sophia.passy@uta.edu;


Joseph Mruzek (Primary Presenter/Author), University of Texas at Arlington, joseph.mruzek@mavs.uta.edu;


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11:30 - 11:45: / 251 DE UNRAVELLING THE IMPACTS OF DROUGHT, NUTRIENT ENRICHMENT AND RIPARIAN CANOPY REMOVAL ON STREAM ECOSYSTEMS –A MESOCOSM APPROACH

5/20/2019  |   11:30 - 11:45   |  251 DE

UNRAVELLING THE IMPACTS OF DROUGHT, NUTRIENT ENRICHMENT AND RIPARIAN CANOPY REMOVAL ON STREAM ECOSYSTEMS –A MESOCOSM APPROACH Agriculture and forestry degrade stream ecosystems by removing the riparian canopy and by intensifying nutrient runoff. In addition, catchment modification, hydropower and global warming are expected to alter the hydrological regime of boreal rivers, causing drought periods of varying duration and severity. While the individual impacts of these three stressors on stream ecosystems are well-addressed, their combined effects remain poorly understood. We assessed the individual and combined impacts of these stressors on the structure (invertebrates, diatoms, microbes) and functioning (algal production, organic matter decomposition) of stream ecosystems by experimentally manipulating nutrient enrichment, canopy removal and drought (pulse vs. press disturbance) in near-natural stream mesocosms. Drought predominantly altered the taxonomic composition of each group and the impact persisted even after a 3-week recovery period. The impacts of nutrients and canopy removal were weaker and taxa-specific. Drought suppressed algal productivity and the following recovery was aided by nutrients. Microbe- and invertebrate-mediated decomposition rates were amplified mainly by nutrients, with drought having additive positive effects on decomposition rates. Our study demonstrates that short-term drought has far-reaching impacts on stream biota and accelerates, together with nutrient enrichment, the key ecosystem processes of stream ecosystems.

Jussi Jyväsjärvi (Primary Presenter/Author), Ecology and Genetics Research Unit, University of Oulu, Finland, jussi.jyvasjarvi@oulu.fi;


Emma Göthe (Co-Presenter/Co-Author), County Administrative Board of Sweden, emma.gothe@lansstyrelsen.se;


Kaisa Lehosmaa (Co-Presenter/Co-Author), Ecology and Genetics Research Unit, University of Oulu, Finland, kaisa.lehosmaa@oulu.fi;


Anette Teittinen (Co-Presenter/Co-Author), Department of Geosciences and Geography, University of Helsinki, Finland , anette.teittinen@helsinki.fi;


Janne Soininen (Co-Presenter/Co-Author), Department of Geosciences and Geography, University of Helsinki, Finland , janne.soininen@helsinki.fi;


Ari Huusko (Co-Presenter/Co-Author), Natural Resources Institute Finland, ari.huusko@luke.fi;


Timo Muotka (Co-Presenter/Co-Author), Ecology and Genetics Research Unit, University of Oulu, Finland, timo.muotka@oulu.fi;


Brendan McKie (Co-Presenter/Co-Author), Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences, Uppsala, Sweden, brendan.mckie@slu.se;


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11:45 - 12:00: / 251 DE RELATIONSHIP BETWEEN BIODIVERSITY AND NUTRIENT CYCLING BY SUBTERRANEAN INVERTEBRATE COMMUNITIES IN THE EDWARDS AQUIFER, USA

5/20/2019  |   11:45 - 12:00   |  251 DE

RELATIONSHIP BETWEEN BIODIVERSITY AND NUTRIENT CYCLING BY SUBTERRANEAN INVERTEBRATE COMMUNITIES IN THE EDWARDS AQUIFER, USA Ecologists have long examined the relationship between ecosystem functioning and biodiversity. Subterranean aquatic ecosystems and their assemblages are unique and recycling of nutrients via excretion by invertebrates is virtually unknown. This study examined the relationship between biodiversity of subterranean aquatic organisms (stygobionts) and rates of stygobiont nutrient recycling in the Edwards Aquifer, Texas, USA. Taxon-specific nutrient excretion rates were measured and then linked to abundances at each site in order to calculate the contribution of each species to the overall community-wide nutrient excretion rate. Data were used in probabilistic numerical simulations to examine how community nutrient recycling (ecosystem functioning) was affected by loss of species from the community (loss of diversity). In general, declines in species richness led to declining rates of nutrient recycling. However, the shape of the response was dependent upon species identity and the order of species loss from the community. Large-bodied stygobiont species or species that comprised a substantial proportion of the community biomass had the largest effects on community recycling rates. These findings also highlight the trade-offs faced between species conservation priorities and preservation of ecosystem function.

Weston Nowlin (Primary Presenter/Author), Texas State University, wnowlin@txstate.edu;


Nathan Krupka (Co-Presenter/Co-Author), Texas State University, nathankrupka@gmail.com;


Benjamin Schwartz (Co-Presenter/Co-Author), Texas State University, bs37@txstate.edu;


Pete Diaz (Co-Presenter/Co-Author), US Fish and Wildlife Service, pete_diaz@fws.gov;


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12:00 - 12:15: / 251 DE AQUATIC MACROINVERTEBRATE COMMUNITY OF A WILD AND SCENIC RIVER IN THE SOUTHWESTERN UNITED STATES

5/20/2019  |   12:00 - 12:15   |  251 DE

AQUATIC MACROINVERTEBRATE COMMUNITY OF A WILD AND SCENIC RIVER IN THE SOUTHWESTERN UNITED STATES Our research presents the community structure and diversity for aquatic macroinvertebrates in the Wild and Scenic Verde River, Arizona. Our goal was to understand the relationships between aquatic macroinvertebrate communities and the three main habitats on the river: riffles, runs, and pools. Samples were collected in fall 2017 and spring 2018 from three reaches on the river. Three replicates taken from microhabitats (riffle-run-pool) per-reach. Results showed a diverse community with 106 taxa, 89 genera, and ~40% of the community belonging to Ephemeroptera, Plecoptera, and Trichoptera. Nonmetric multidimensional scaling analysis found distinct, low-stress, ordinations with high correlations between species occurrences and the three microhabitats. This work establishes baseline knowledge that will be used in the development of models to predict river health values under current and possible future flow scenarios. Our findings and the results of the model will inform managers in the development of policies allowing sustainable allocation of water to the river and the surrounding communities.

Justin Hockett (Co-Presenter/Co-Author), Oregon State University, hockettj@oregonstate.edu;


David Lytle (Co-Presenter/Co-Author), Oregon State University, lytleda@oregonstate.edu;


Eric Kortenhoeven (Primary Presenter/Author), Oregon State University, Kortenhe@oregonstate.edu;


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