title: Body size distributions signal a regime shift in a lake ecosystem.
abstract: Communities of organisms, from mammals to microorganisms, have discontinuous distributions of body size. This pattern of size structuring is a conservative trait of community organization and is a product of processes that occur at multiple spatial and temporal scales. In this study, we assessed whether body size patterns serve as an indicator of a threshold between alternative regimes. Over the past 7000 years, the biological communities of Foy Lake (Montana, USA) have undergone a major regime shift owing to climate change. We used a palaeoecological record of diatom communities to estimate diatom sizes, and then analysed the discontinuous distribution of organism sizes over time. We used Bayesian classification and regression tree models to determine that all time intervals exhibited aggregations of sizes separated by gaps in the distribution and found a significant change in diatom body size distributions approximately 150 years before the identified ecosystem regime shift. We suggest that discontinuity analysis is a useful addition to the suite of tools for the detection of early warning signals of regime shifts.
authors.affiliation: National Research Council, US Environmental Protection Agency, Cincinnati, OH 45268, USA Department of Earth and Atmospheric Sciences and School of Biological Sciences, University of Nebraska-Lincoln, Lincoln, NE 68588, USA spanbauer.trisha@epa.gov.
authors.forename: Trisha L
authors.identifier: 0000-0002-4014-4995
authors.initials: TL
authors.lastname: Spanbauer
authors.affiliation: US Geological Survey, Nebraska Cooperative Fish and Wildlife Research Unit, School of Natural Resources, University of Nebraska-Lincoln, Lincoln, NE 68583, USA.
authors.forename: Craig R
authors.initials: CR
authors.lastname: Allen
authors.affiliation: Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences, PO Box 7050 750 07, Uppsala, Sweden.
authors.forename: David G
authors.initials: DG
authors.lastname: Angeler
authors.affiliation: Office of Research and Development, National Risk Management Research Laboratory, US Environmental Protection Agency, Cincinnati, OH 45268, USA.
authors.forename: Tarsha
authors.initials: T
authors.lastname: Eason
authors.affiliation: Department of Earth and Atmospheric Sciences and School of Biological Sciences, University of Nebraska-Lincoln, Lincoln, NE 68588, USA.
authors.forename: Sherilyn C
authors.initials: SC
authors.lastname: Fritz
authors.affiliation: Office of Research and Development, National Risk Management Research Laboratory, US Environmental Protection Agency, Cincinnati, OH 45268, USA.
authors.forename: Ahjond S
authors.initials: AS
authors.lastname: Garmestani
authors.affiliation: Australian Research Council Centre of Excellence for Coral Reef Studies, James Cook University, Townsville, Queensland 4811, Australia Centre for Marine Socioecology, Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, Tasmania 7000, Australia.
authors.forename: Kirsty L
authors.initials: KL
authors.lastname: Nash
authors.affiliation: Department of Earth and Environmental Systems, Indiana State University, Terre Haute, IN 47809, USA.
authors.forename: Jeffery R
authors.identifier: 0000-0002-1313-0643
authors.initials: JR
authors.lastname: Stone
authors.affiliation: Great Lakes Environmental Research Laboratory, National Oceanic and Atmospheric Administration, Ann Arbor, MI 48108, USA.
authors.forename: Craig A
authors.initials: CA
authors.lastname: Stow
authors.affiliation: Nebraska Cooperative Fish and Wildlife Research Unit, School of Natural Resources, University of Nebraska-Lincoln, Lincoln, NE 68583, USA.
authors.forename: Shana M
authors.initials: SM
authors.lastname: Sundstrom
mesh_terms: D001499:Bayes Theorem; D049628:Body Size; D057231:Climate Change; D017377:Diatoms / Q000502:physiology*; D017753:Ecosystem; D060106:Lakes; D009009:Montana
keywords: body size; climate change; palaeoecology; regime shift; resilience; thresholds