Genomic Consequences of Population Decline in the Endangered Florida Scrub-Jay

• Published in: Current biology Vol. 26; no. 21; pp. 2974 - 2979
• Main Authors: Chen, Nancy, Cosgrove, Elissa J., Bowman, Reed, Fitzpatrick, John W., Clark, Andrew G.
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 07.11.2016
• Subjects: Animals; conservation genomics; Endangered Species; Florida; Gene Flow; Genetic Fitness; Genome; habitat fragmentation; Inbreeding; inbreeding depression; Life History Traits; Phenotype; Population Dynamics; population genetics; Songbirds - genetics; gene flow; population genetics; inbreeding depression; conservation genomics; habitat fragmentation
• ISSN: 0960-9822; 1879-0445
• DOI: 10.1016/j.cub.2016.08.062

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. •Inbreeding levels are monitored over 19 years using pedigree and genomic data•Exhaustive sampling shows reduced immigration resulted in increased inbreeding•Inbreeding affects many life-history stages, from hatching success to adult fitness•Gene flow from small populations may be vital for conservation of large populations Chen et al. exhaustively sample a population for 19 years and use temporal genomic, demographic, and phenotypic data to show that reduced immigration into a demographically stable population has resulted in increased inbreeding and reduced fitness. Thus, it may be vital to preserve small and even inbred populations that facilitate gene flow.