title: Regularity underlies erratic population abundances in marine ecosystems.
abstract: The abundance of a species' population in an ecosystem is rarely stationary, often exhibiting large fluctuations over time. Using historical data on marine species, we show that the year-to-year fluctuations of population growth rate obey a well-defined double-exponential (Laplace) distribution. This striking regularity allows us to devise a stochastic model despite seemingly irregular variations in population abundances. The model identifies the effect of reduced growth at low population density as a key factor missed in current approaches of population variability analysis and without which extinction risks are severely underestimated. The model also allows us to separate the effect of demographic stochasticity and show that single-species growth rates are dominantly determined by stochasticity common to all species. This dominance-and the implications it has for interspecies correlations, including co-extinctions-emphasizes the need for ecosystem-level management approaches to reduce the extinction risk of the individual species themselves.
authors.affiliation: Department of Mathematics, Clarkson University, Potsdam, NY 13699, USA Department of Physics and Astronomy, Northwestern University, Evanston, IL 60208, USA.
authors.forename: Jie
authors.initials: J
authors.lastname: Sun
authors.affiliation: Center for Complex Network Research and Departments of Physics, Northeastern University, Boston, MA 02115, USA Channing Division of Network Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, USA Department of Physics and Astronomy, Northwestern University, Evanston, IL 60208, USA.
authors.forename: Sean P
authors.initials: SP
authors.lastname: Cornelius
authors.affiliation: School of Freshwater Sciences, University of Wisconsin, Milwaukee, WI 53204, USA.
authors.forename: John
authors.initials: J
authors.lastname: Janssen
authors.affiliation: Department of Civil and Environmental Engineering, Northwestern University, Evanston, IL 60208, USA.
authors.forename: Kimberly A
authors.initials: KA
authors.lastname: Gray
authors.affiliation: Department of Physics and Astronomy, Northwestern University, Evanston, IL 60208, USA Northwestern Institute on Complex Systems, Northwestern University, Evanston, IL 60208, USA motter@northwestern.edu.
authors.forename: Adilson E
authors.initials: AE
authors.lastname: Motter
mesh_terms: D000818:Animals; D059001:Aquatic Organisms / Q000502:physiology*; D017753:Ecosystem; D008954:Models, Biological; D011157:Population Dynamics
keywords: complex systems; growth rate statistics; nonlinear dynamics; population dynamics; stochastic processes; time series