Polygenic adaptation: From sweeps to subtle frequency shifts.
PLoS Genet
; 15(3): e1008035, 2019 03.
Article
en En
| MEDLINE
| ID: mdl-30893299
ABSTRACT
Evolutionary theory has produced two conflicting paradigms for the adaptation of a polygenic trait. While population genetics views adaptation as a sequence of selective sweeps at single loci underlying the trait, quantitative genetics posits a collective response, where phenotypic adaptation results from subtle allele frequency shifts at many loci. Yet, a synthesis of these views is largely missing and the population genetic factors that favor each scenario are not well understood. Here, we study the architecture of adaptation of a binary polygenic trait (such as resistance) with negative epistasis among the loci of its basis. The genetic structure of this trait allows for a full range of potential architectures of adaptation, ranging from sweeps to small frequency shifts. By combining computer simulations and a newly devised analytical framework based on Yule branching processes, we gain a detailed understanding of the adaptation dynamics for this trait. Our key analytical result is an expression for the joint distribution of mutant alleles at the end of the adaptive phase. This distribution characterizes the polygenic pattern of adaptation at the underlying genotype when phenotypic adaptation has been accomplished. We find that a single compound parameter, the population-scaled background mutation rate Θbg, explains the main differences among these patterns. For a focal locus, Θbg measures the mutation rate at all redundant loci in its genetic background that offer alternative ways for adaptation. For adaptation starting from mutation-selection-drift balance, we observe different patterns in three parameter regions. Adaptation proceeds by sweeps for small Θbg â² 0.1, while small polygenic allele frequency shifts require large Θbg â³ 100. In the large intermediate regime, we observe a heterogeneous pattern of partial sweeps at several interacting loci.
Texto completo:
1
Colección:
01-internacional
Base de datos:
MEDLINE
Asunto principal:
Selección Genética
/
Adaptación Fisiológica
/
Herencia Multifactorial
Tipo de estudio:
Prognostic_studies
Idioma:
En
Revista:
PLoS Genet
Asunto de la revista:
GENETICA
Año:
2019
Tipo del documento:
Article
País de afiliación:
Austria