Genetic load and extinction in peripheral populations: The roles of migration, drift and demographic stochasticity

Sachdeva H, Olusanya OO, Barton NH. 2022. Genetic load and extinction in peripheral populations: The roles of migration, drift and demographic stochasticity. Philosophical Transactions of the Royal Society B. 377(1846), 20210010.

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Journal Article | Published | English
Abstract
We analyse how migration from a large mainland influences genetic load and population numbers on an island, in a scenario where fitness-affecting variants are unconditionally deleterious, and where numbers decline with increasing load. Our analysis shows that migration can have qualitatively different effects, depending on the total mutation target and fitness effects of deleterious variants. In particular, we find that populations exhibit a genetic Allee effect across a wide range of parameter combinations, when variants are partially recessive, cycling between low-load (large-population) and high-load (sink) states. Increased migration reduces load in the sink state (by increasing heterozygosity) but further inflates load in the large-population state (by hindering purging). We identify various critical parameter thresholds at which one or other stable state collapses, and discuss how these thresholds are influenced by the genetic versus demographic effects of migration. Our analysis is based on a ‘semi-deterministic’ analysis, which accounts for genetic drift but neglects demographic stochasticity. We also compare against simulations which account for both demographic stochasticity and drift. Our results clarify the importance of gene flow as a key determinant of extinction risk in peripheral populations, even in the absence of ecological gradients. This article is part of the theme issue ‘Species’ ranges in the face of changing environments (part I)’.
Publishing Year
Date Published
2022-01-24
Journal Title
Philosophical Transactions of the Royal Society B
Acknowledgement
This research was partly funded by the Austrian Science Fund (FWF) (grant no. P-32896B).
Volume
377
Issue
1846
Article Number
20210010
ISSN
eISSN
IST-REx-ID

Cite this

Sachdeva H, Olusanya OO, Barton NH. Genetic load and extinction in peripheral populations: The roles of migration, drift and demographic stochasticity. Philosophical Transactions of the Royal Society B. 2022;377(1846). doi:10.1098/rstb.2021.0010
Sachdeva, H., Olusanya, O. O., & Barton, N. H. (2022). Genetic load and extinction in peripheral populations: The roles of migration, drift and demographic stochasticity. Philosophical Transactions of the Royal Society B. The Royal Society. https://doi.org/10.1098/rstb.2021.0010
Sachdeva, Himani, Oluwafunmilola O Olusanya, and Nicholas H Barton. “Genetic Load and Extinction in Peripheral Populations: The Roles of Migration, Drift and Demographic Stochasticity.” Philosophical Transactions of the Royal Society B. The Royal Society, 2022. https://doi.org/10.1098/rstb.2021.0010.
H. Sachdeva, O. O. Olusanya, and N. H. Barton, “Genetic load and extinction in peripheral populations: The roles of migration, drift and demographic stochasticity,” Philosophical Transactions of the Royal Society B, vol. 377, no. 1846. The Royal Society, 2022.
Sachdeva H, Olusanya OO, Barton NH. 2022. Genetic load and extinction in peripheral populations: The roles of migration, drift and demographic stochasticity. Philosophical Transactions of the Royal Society B. 377(1846), 20210010.
Sachdeva, Himani, et al. “Genetic Load and Extinction in Peripheral Populations: The Roles of Migration, Drift and Demographic Stochasticity.” Philosophical Transactions of the Royal Society B, vol. 377, no. 1846, 20210010, The Royal Society, 2022, doi:10.1098/rstb.2021.0010.
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