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An experimental test of alternative population augmentation scenarios
Authors:John A Kronenberger  Jill C Gerberich  Sarah W Fitzpatrick  E Dale Broder  Lisa M Angeloni  W Chris Funk
Institution:1. Department of Biology, Colorado State University, Fort Collins, CO, U.S.A.;2. Graduate Degree Program in Ecology, Colorado State University, Fort Collins, CO, U.S.A.;3. Department of Molecular Biosciences, University of Texas, TX, U.S.A.;4. Kellogg Biological Station, Department of Integrative Biology, Michigan State University, Hickory Corners, MI, U.S.A.;5. Ecology, Evolutionary Biology, and Behavior Program, Michigan State University, East Lansing, MI, U.S.A.;6. Interdisciplinary Research Incubator for the Study of (in)Equality, University of Denver, Denver, CO, U.S.A.
Abstract:Human land use is fragmenting habitats worldwide and inhibiting dispersal among previously connected populations of organisms, often leading to inbreeding depression and reduced evolutionary potential in the face of rapid environmental change. To combat this augmentation of isolated populations with immigrants is sometimes used to facilitate demographic and genetic rescue. Augmentation with immigrants that are genetically and adaptively similar to the target population effectively increases population fitness, but if immigrants are very genetically or adaptively divergent, augmentation can lead to outbreeding depression. Despite well‐cited guidelines for the best practice selection of immigrant sources, often only highly divergent populations remain, and experimental tests of these riskier augmentation scenarios are essentially nonexistent. We conducted a mesocosm experiment with Trinidadian guppies (Poecilia reticulata) to test the multigenerational demographic and genetic effects of augmenting 2 target populations with 3 types of divergent immigrants. We found no evidence of demographic rescue, but we did observe genetic rescue in one population. Divergent immigrant treatments tended to maintain greater genetic diversity, abundance, and hybrid fitness than controls that received immigrants from the source used to seed the mesocosms. In the second population, divergent immigrants had a slightly negative effect in one treatment, and the benefits of augmentation were less apparent overall, likely because this population started with higher genetic diversity and a lower reproductive rate that limited genetic admixture. Our results add to a growing consensus that gene flow can increase population fitness even when immigrants are more highly divergent and may help reduce uncertainty about the use of augmentation in conservation.
Keywords:adaptive divergence  assisted migration  demographic rescue  genetic divergence  genetic rescue  Poecilia reticulata  supplementation  translocation  divergencia adaptativa  divergencia gené  tica  migració  n asistida  rescate demográ  fico  rescate gené  tico  reubicació  n  suplemento  Poecilia Reticulata                                                              (Poecilia reticulate)            
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