title: Genomic Consequences of Population Decline in the Endangered Florida Scrub-Jay.
abstract: Understanding the population genetic consequences of declining population size is important for conserving the many species worldwide facing severe decline [1]. Thorough empirical studies on the impacts of population reduction at a genome-wide scale in the wild are scarce because they demand huge field and laboratory investments [1, 2]. Previous studies have demonstrated the importance of gene flow in introducing genetic variation to small populations [3], but few have documented both genetic and fitness consequences of decreased immigration through time in a natural population [4-6]. Here we assess temporal variation in gene flow, inbreeding, and fitness using longitudinal genomic, demographic, and phenotypic data from a long-studied population of federally Threatened Florida scrub-jays (Aphelocoma coerulescens). We exhaustively sampled and genotyped the study population over two decades, providing one of the most detailed longitudinal investigations of genetics in a wild animal population to date. Immigrants were less heterozygous than residents but still introduced genetic variation into our study population. Owing to regional population declines, immigration into the study population declined from 1995-2013, resulting in increased levels of inbreeding and reduced fitness via inbreeding depression, even as the population remained demographically stable. Our results show that, contrary to conventional wisdom, small peripheral populations that already have undergone a genetic bottleneck may play a vital role in preserving genetic diversity of larger and seemingly stable populations. These findings underscore the importance of investing in the persistence of small populations and maintaining population connectivity in conservation of fragmented species.
authors.affiliation: Center for Population Biology and Department of Evolution and Ecology, University of California, Davis, Davis, CA 95616, USA; Cornell Lab of Ornithology, Cornell University, Ithaca, NY 14850, USA. Electronic address: nanchen@ucdavis.edu.
authors.forename: Nancy
authors.initials: N
authors.lastname: Chen
authors.affiliation: Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, USA.
authors.forename: Elissa J
authors.initials: EJ
authors.lastname: Cosgrove
authors.affiliation: Archbold Biological Station, Venus, FL 33960, USA.
authors.forename: Reed
authors.initials: R
authors.lastname: Bowman
authors.affiliation: Cornell Lab of Ornithology, Cornell University, Ithaca, NY 14850, USA; Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, NY 14853, USA.
authors.forename: John W
authors.initials: JW
authors.lastname: Fitzpatrick
authors.affiliation: Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, USA; Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, NY 14853, USA.
authors.forename: Andrew G
authors.initials: AG
authors.lastname: Clark
mesh_terms: D000818:Animals; D056727:Endangered Species; D005431:Florida; D051456:Gene Flow; D056084:Genetic Fitness; D016678:Genome; D007178:Inbreeding; D000071421:Life History Traits; D010641:Phenotype; D011157:Population Dynamics; D020308:Songbirds / Q000235:genetics*
keywords: conservation genomics; gene flow; habitat fragmentation; inbreeding depression; population genetics