title: Abiotic and biotic interactions determine whether increased colonization is beneficial or detrimental to metapopulation management.
abstract: Increasing the colonization rate of metapopulations can improve persistence, but can also increase exposure to threats. To make good decisions, managers must understand whether increased colonization is beneficial or detrimental to metapopulation persistence. While a number of studies have examined interactions between metapopulations, colonization, and threats, they have assumed that threat dynamics respond linearly to changes in colonization. Here, we determined when to increase colonization while explicitly accounting for non-linear dependencies between a metapopulation and its threats. We developed patch occupancy metapopulation models for species susceptible to abiotic, generalist, and specialist threats and modeled the total derivative of the equilibrium proportion of patches occupied by each metapopulation with respect to the colonization rate. By using the total derivative, we developed a rule for determining when to increase metapopulation colonization. This rule was applied to a simulated metapopulation where the dynamics of each threat responded to increased colonization following a power function. Before modifying colonization, we show that managers must understand: (1) whether a metapopulation is susceptible to a threat; (2) the type of threat acting on a metapopulation; (3) which component of threat dynamics might depend on colonization, and; (4) the likely response of a threat-dependent variable to changes in colonization. The sensitivity of management decisions to these interactions increases uncertainty in conservation planning decisions.
authors.affiliation: Australian Research Council Centre of Excellence for Environmental Decisions, School of BioSciences, University of Melbourne, Vic, 3010, Australia. Electronic address: darren_southwell@hotmail.com.
authors.forename: Darren M
authors.initials: DM
authors.lastname: Southwell
authors.affiliation: Australian Research Council Centre of Excellence for Environmental Decisions, School of Geography, Planning and Environmental Management, University of Queensland, St Lucia, Queensland, 4072, Australia. Electronic address: j.rhodes@uq.edu.au.
authors.forename: Jonathan R
authors.initials: JR
authors.lastname: Rhodes
authors.affiliation: Australian Research Council Centre of Excellence for Environmental Decisions, School of Biological Sciences, University of Queensland, St Lucia, Queensland, 4072, Australia; CSIRO Ecosystem Sciences, Ecosciences Precinct, 41 Boggo Rd, Dutton Park, Brisbane, Queensland, 4102, Australia. Electronic address: e.mcdonaldmadden@uq.edu.au.
authors.forename: Eve
authors.initials: E
authors.lastname: McDonald-Madden
authors.affiliation: CSIRO Ecosystem Sciences, Ecosciences Precinct, 41 Boggo Rd, Dutton Park, Brisbane, Queensland, 4102, Australia. Electronic address: sam.nicol@csiro.au.
authors.forename: Sam
authors.initials: S
authors.lastname: Nicol
authors.affiliation: Australian Research Council Centre of Excellence for Environmental Decisions, School of Mathematics and Physics, University of Queensland, St Lucia, Queensland, 4072, Australia. Electronic address: katehelmstedt@gmail.com.
authors.forename: Kate J
authors.initials: KJ
authors.lastname: Helmstedt
authors.affiliation: Australian Research Council Centre of Excellence for Environmental Decisions, School of BioSciences, University of Melbourne, Vic, 3010, Australia. Electronic address: mamcca@unimelb.edu.au.
authors.forename: Michael A
authors.initials: MA
authors.lastname: McCarthy
mesh_terms: D017753:Ecosystem; D008954:Models, Biological; D011157:Population Dynamics; D035501:Uncertainty
keywords: Abiotic threats; Colonization; Epidemiology; Host–pathogen; Metapopulation; Predator–prey