title: Divergence in sink contributions to population persistence.
abstract: Population sinks present unique conservation challenges. The loss of individuals in sinks can compromise persistence; but conversely, sinks can improve viability by improving connectivity and facilitating the recolonization of vacant sources. To assess the contribution of sinks to regional population persistence of declining populations, we simulated source-sink dynamics for 3 very different endangered species: Black-capped Vireos (Vireo atricapilla) at Fort Hood, Texas, Ord's kangaroo rats (Dipodomys ordii) in Alberta, and Northern Spotted Owls (Strix occidentalis caurina) in the northwestern United States. We used empirical data from these case studies to parameterize spatially explicit individual-based models. We then used the models to quantify population abundance and persistence with and without long-term sinks. The contributions of sink habitats varied widely. Sinks were detrimental, particularly when they functioned as strong sinks with few emigrants in declining populations (e.g., Alberta's Ord's kangaroo rat) and benign in robust populations (e.g., Black-capped Vireos) when Brown-headed Cowbird (Molothrus ater) parasitism was controlled. Sinks, including ecological traps, were also crucial in delaying declines when there were few sources (e.g., in Black-capped Vireo populations with no Cowbird control). Sink contributions were also nuanced. For example, sinks that supported large, variable populations were subject to greater extinction risk (e.g., Northern Spotted Owls). In each of our case studies, new context-dependent sinks emerged, underscoring the dynamic nature of sources and sinks and the need for frequent re-assessment. Our results imply that management actions based on assumptions that sink habitats are generally harmful or helpful risk undermining conservation efforts for declining populations.
authors.affiliation: School of Environmental and Forest Sciences, University of Washington, P.O. Box 352100, Seattle, WA, 98195-2100, U.S.A.
authors.forename: Julie A
authors.initials: JA
authors.lastname: Heinrichs
authors.affiliation: School of Environmental and Forest Sciences, University of Washington, P.O. Box 352100, Seattle, WA, 98195-2100, U.S.A.
authors.forename: Joshua J
authors.initials: JJ
authors.lastname: Lawler
authors.affiliation: Western Ecology Division, U.S. EPA, 200 SW 35th Street, Corvallis, OR, 97333, U.S.A.
authors.forename: Nathan H
authors.initials: NH
authors.lastname: Schumaker
authors.affiliation: School of Environmental and Forest Sciences, University of Washington, P.O. Box 352100, Seattle, WA, 98195-2100, U.S.A.
authors.forename: Chad B
authors.initials: CB
authors.lastname: Wilsey
authors.affiliation: Department of Geography, University of Calgary, 2500 University Drive NW, Calgary, Alberta, T2N 1N4, Canada.
authors.forename: Darren J
authors.initials: DJ
authors.lastname: Bender
mesh_terms: D000416:Alberta; D000818:Animals; D003247:Conservation of Natural Resources; D004173:Dipodomys / Q000502:physiology*; D017753:Ecosystem; D056727:Endangered Species; D005260:Female; D008297:Male; D008954:Models, Biological; D015205:Northwestern United States; D011157:Population Dynamics; D020308:Songbirds / Q000502:physiology*; D020305:Strigiformes / Q000502:physiology*; D013781:Texas
keywords: Dipodomys ordii; Strix occidentalis caurina; Vireo atricapilla; contribuciones de vertedero; dinámicas de fuente-vertedero; ecological traps; modelo espacialmente explícito basado en individuos; persistencia poblacional; population persistence; sink contributions; source-sink dynamics; spatially explicit individual-based model; trampas ecológicas