title: Unexpected positive and negative effects of continuing inbreeding in one of the world's most inbred wild animals.
abstract: Inbreeding depression, the reduced fitness of offspring of related individuals, is a central theme in evolutionary biology. Inbreeding effects are influenced by the genetic makeup of a population, which is driven by any history of genetic bottlenecks and genetic drift. The Chatham Island black robin represents a case of extreme inbreeding following two severe population bottlenecks. We tested whether inbreeding measured by a 20-year pedigree predicted variation in fitness among individuals, despite the high mean level of inbreeding and low genetic diversity in this species. We found that paternal and maternal inbreeding reduced fledgling survival and individual inbreeding reduced juvenile survival, indicating that inbreeding depression affects even this highly inbred population. Close inbreeding also reduced survival for fledglings with less-inbred mothers, but unexpectedly improved survival for fledglings with highly inbred mothers. This counterintuitive interaction could not be explained by various potentially confounding variables. We propose a genetic mechanism, whereby a highly inbred chick with a highly inbred parent inherits a "proven" genotype and thus experiences a fitness advantage, which could explain the interaction. The positive and negative effects we found emphasize that continuing inbreeding can have important effects on individual fitness, even in populations that are already highly inbred.
authors.affiliation: Allan Wilson Centre for Molecular Ecology and Evolution, Department of Zoology, University of Otago, Dunedin, New Zealand. Emily.L.Weiser@gmail.com.|Division of Biology, Kansas State University, Manhattan, Kansas. Emily.L.Weiser@gmail.com.
authors.forename: Emily L
authors.initials: EL
authors.lastname: Weiser
authors.affiliation: Allan Wilson Centre for Molecular Ecology and Evolution, Department of Zoology, University of Otago, Dunedin, New Zealand.|Faculty of Veterinary Science, The University of Sydney, Sydney, Australia.|San Diego Zoo Global, San Diego, California.
authors.forename: Catherine E
authors.initials: CE
authors.lastname: Grueber
authors.affiliation: Science and Policy, Department of Conservation, Christchurch, New Zealand.
authors.forename: Euan S
authors.initials: ES
authors.lastname: Kennedy
authors.affiliation: Allan Wilson Centre for Molecular Ecology and Evolution, Department of Zoology, University of Otago, Dunedin, New Zealand.
authors.forename: Ian G
authors.initials: IG
authors.lastname: Jamieson
mesh_terms: D000818:Animals; D003247:Conservation of Natural Resources; D005260:Female; D056084:Genetic Fitness; D007178:Inbreeding; D008136:Longevity; D008297:Male; D009520:New Zealand; D012098:Reproduction; D020308:Songbirds / Q000235:genetics / Q000502:physiology*
keywords: Fecundity; fitness; inbreeding depression; outbreeding depression; purging; small populations