Tightening the loose equilibrium concept: New seasonal insights with benthic insect data from National Ecological Observatory Network streams
17 affiliations
- 1School of Life Sciences & Sustainability, Virginia Commonwealth University, Richmond, Virgina, United States of America
- 2National Ecological Observatory Network, Battelle, Boulder, Colorado, United States of America
- 3Department of Biological Sciences, Wayne State University, Detroit, Michigan, United States of America
- 4Odum School of Ecology, University of Georgia, Athens, Georgia, United States of America
- 5Institute of Environment, Florida International University, Miami, Florida, United States of America
- 6Padre Associates, Bakersfield, California, United States of America
- 7Department of Civil, Environmental & Architectural Engineering, University of Kansas, Lawrence, Kansas, United States of America
- 8Department of Biological Sciences, Florida International University, Miami, Florida, United States of America
- 9Missouri Department of Natural Resources, Jefferson City, Missouri, United States of America
- 10Land Resources and Environmental Sciences, Montana State University, Bozeman, Montana, United States of America
- 11Department of Biology, Georgia Southern University, Statesboro, Georgia, United States of America
- 12Department of Natural Resources & Environmental Science, University of Nevada at Reno, Reno, Nevada, United States of America
- 13Environmental Science, Policy & Management, University of California at Berkeley, Berkeley, California, United States of America
- 14Virginia Department of Wildlife Resources, Henrico, Virginia, United States of America
- 15City of Omaha Environmental Quality Control Division, Omaha, Nebraska, United States of America
- 16Eurofins, Albuquerque, New Mexico, United States of America
- 17Department of Geology and Environmental Science, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America
Abstract
The loose equilibrium (LE) hypothesis predicts that biotic assemblages will exhibit modest change from year-to-year but will not follow directed trajectories away from a stable baseline over longer periods of time. Using 8 years (2016–2023) of data from 21 National Ecological Observatory Network streams, we test the LE hypothesis for benthic insect assemblages. We also expand the traditional LE method, which focuses on a single sampling season, by using multi-season data to determine whether LE is influenced by seasonal change. Results indicate that most benthic insect assemblages may be in a state of LE. Seventeen of the 21 assemblages exhibited random, non-directional change among sampling events, consistent with the LE hypothesis. However, directional movement away from a baseline condition was detected for two insect assemblages, while directional movement from the baseline, followed by a return toward the baseline was detected for the remaining two assemblages. Supplementary taxonomic, feeding behavior, and environmental data suggest that the four instances of directional change may be responses to recent disturbances or altered physicochemical habitat. Distinct seasonal clusters (spring, summer, fall) of insects are also detected for 13 of the 21 assemblages. Among the 13 clustered assemblages, 11 have at least one significantly small cluster that reflects minimal interannual change within the respective season. We conclude by explaining how strong seasonality may support LE. Specifically, we hypothesize that seasonally distinct, yet predictable environments promote inter-seasonal consistency in assemblage structure, thereby constraining opportunities for insect assemblages to shift far from the baseline condition. This work adds to the broader field of equilibrium theory in ecology and may help anticipate future changes in benthic assemblage structure. Author summary: Assemblages of living organisms are never truly static. They all change through time, though change is often gradual and centered about a stable baseline. To characterize this dynamic, ecologists have developed a theory of ‘loose equilibrium’ (LE). LE predicts that biotic assemblages will exhibit modest change over short time intervals but will not follow continuous or directed trajectories away from a stable baseline over longer intervals. This study is a novel test of LE for freshwater insect assemblages. It begins with an 8-year record of seasonal insect samples from 21 streams in the National Ecological Observatory Network. Using this robust dataset in combination with multivariate analyses and Monte Carlo tests, we find that insect assemblages in 81% of the study streams are likely to be in a state of LE. We also show that seasonal clustering, defined by distinct spring, summer, and fall subsets of insects, is a common feature of the study streams. Finally, we hypothesize that seasonally variable, yet predictable environments may help maintain LE by creating a template that promotes intraseasonal consistency in assemblage structure while constraining change among seasons.
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BibTeX
@article{mcgarvey2026tightening,
title = {{Tightening the loose equilibrium concept: New seasonal insights with benthic insect data from National Ecological Observatory Network streams}},
author = {Daniel J. McGarvey and Stephanie M. Parker and Héctor J. Esparra-Escalera and Natalia Vargas-López and Lauren K. Emer and Jonathan R. Juarez and Victoria Secondine and Liz D. Ortiz Muñoz and Viviana Bravo Ortiz and Alexis R. Reifsteck and Jordyn Solliday and Reginald K. Turner and Deandre Presswood and Patina K. Mendez and Makayla DeVivo and Rodrigo Meza Gonzalez and Hope K. Romero and Jason Aguirre and Breanna Ondich},
journal = {PLOS Ecosystems},
year = {2026},
month = oct,
doi = {10.1371/journal.pesy.0000037},
url = {https://doi.org/10.1371/journal.pesy.0000037},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Tightening the loose equilibrium concept: New seasonal insights with benthic insect data from National Ecological Observatory Network streams
AU - Daniel J. McGarvey
AU - Stephanie M. Parker
AU - Héctor J. Esparra-Escalera
AU - Natalia Vargas-López
AU - Lauren K. Emer
AU - Jonathan R. Juarez
AU - Victoria Secondine
AU - Liz D. Ortiz Muñoz
AU - Viviana Bravo Ortiz
AU - Alexis R. Reifsteck
AU - Jordyn Solliday
AU - Reginald K. Turner
AU - Deandre Presswood
AU - Patina K. Mendez
AU - Makayla DeVivo
AU - Rodrigo Meza Gonzalez
AU - Hope K. Romero
AU - Jason Aguirre
AU - Breanna Ondich
PY - 2026
DA - 2026/10/12
JO - PLOS Ecosystems
DO - 10.1371/journal.pesy.0000037
UR - https://doi.org/10.1371/journal.pesy.0000037
AB - The loose equilibrium (LE) hypothesis predicts that biotic assemblages will exhibit modest change from year-to-year but will not follow directed trajectories away from a stable baseline over longer periods of time. Using 8 years (2016–2023) of data from 21 National Ecological Observatory Network streams, we test the LE hypothesis for benthic insect assemblages. We also expand the traditional LE method, which focuses on a single sampling season, by using multi-season data to determine whether LE is influenced by seasonal change. Results indicate that most benthic insect assemblages may be in a state of LE. Seventeen of the 21 assemblages exhibited random, non-directional change among sampling events, consistent with the LE hypothesis. However, directional movement away from a baseline condition was detected for two insect assemblages, while directional movement from the baseline, followed by a return toward the baseline was detected for the remaining two assemblages. Supplementary taxonomic, feeding behavior, and environmental data suggest that the four instances of directional change may be responses to recent disturbances or altered physicochemical habitat. Distinct seasonal clusters (spring, summer, fall) of insects are also detected for 13 of the 21 assemblages. Among the 13 clustered assemblages, 11 have at least one significantly small cluster that reflects minimal interannual change within the respective season. We conclude by explaining how strong seasonality may support LE. Specifically, we hypothesize that seasonally distinct, yet predictable environments promote inter-seasonal consistency in assemblage structure, thereby constraining opportunities for insect assemblages to shift far from the baseline condition. This work adds to the broader field of equilibrium theory in ecology and may help anticipate future changes in benthic assemblage structure. Author summary: Assemblages of living organisms are never truly static. They all change through time, though change is often gradual and centered about a stable baseline. To characterize this dynamic, ecologists have developed a theory of ‘loose equilibrium’ (LE). LE predicts that biotic assemblages will exhibit modest change over short time intervals but will not follow continuous or directed trajectories away from a stable baseline over longer intervals. This study is a novel test of LE for freshwater insect assemblages. It begins with an 8-year record of seasonal insect samples from 21 streams in the National Ecological Observatory Network. Using this robust dataset in combination with multivariate analyses and Monte Carlo tests, we find that insect assemblages in 81% of the study streams are likely to be in a state of LE. We also show that seasonal clustering, defined by distinct spring, summer, and fall subsets of insects, is a common feature of the study streams. Finally, we hypothesize that seasonally variable, yet predictable environments may help maintain LE by creating a template that promotes intraseasonal consistency in assemblage structure while constraining change among seasons.
SN - 3070-8141
ER -