Author:
von Seth Johanna,van der Valk Tom,Lord Edana,Sigeman Hanna,Olsen Remi-André,Knapp Michael,Kardailsky Olga,Robertson Fiona,Hale Marie,Houston Dave,Kennedy Euan,Dalén Love,Norén Karin,Massaro Melanie,Robertson Bruce C.,Dussex Nicolas
Abstract
Abstract
Background
Understanding the micro-evolutionary response of populations to demographic declines is a major goal in evolutionary and conservation biology. In small populations, genetic drift can lead to an accumulation of deleterious mutations, which will increase the risk of extinction. However, demographic recovery can still occur after extreme declines, suggesting that natural selection may purge deleterious mutations, even in extremely small populations. The Chatham Island black robin (Petroica traversi) is arguably the most inbred bird species in the world. It avoided imminent extinction in the early 1980s and after a remarkable recovery from a single pair, a second population was established and the two extant populations have evolved in complete isolation since then. Here, we analysed 52 modern and historical genomes to examine the genomic consequences of this extreme bottleneck and the subsequent translocation.
Results
We found evidence for two-fold decline in heterozygosity and three- to four-fold increase in inbreeding in modern genomes. Moreover, there was partial support for temporal reduction in total load for detrimental variation. In contrast, compared to historical genomes, modern genomes showed a significantly higher realised load, reflecting the temporal increase in inbreeding. Furthermore, the translocation induced only small changes in the frequency of deleterious alleles, with the majority of detrimental variation being shared between the two populations.
Conclusion
Our results highlight the dynamics of mutational load in a species that recovered from the brink of extinction, and show rather limited temporal changes in mutational load. We hypothesise that ancestral purging may have been facilitated by population fragmentation and isolation on several islands for thousands of generations and may have already reduced much of the highly deleterious load well before human arrival and introduction of pests to the archipelago. The majority of fixed deleterious variation was shared between the modern populations, but translocation of individuals with low mutational load could possibly mitigate further fixation of high-frequency deleterious variation.
Funder
FORMAS
Brian Mason Scientific and Technical Trust
Mohamed bin Zayed Species Conservation Fund
Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung
Carl Tryggers Stiftelse för Vetenskaplig Forskning
Stockholm University
Publisher
Springer Science and Business Media LLC
Cited by
8 articles.
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