Independent evolution toward larger body size in the distinctive Faroe Island mice.

Ricardo Wilches,William H Beluch,Yingguang Frank Chan,Ellen Mcconnell,Diethard Tautz,M Rockman

doi:10.1093/g3journal/jkaa051

Abstract

Most phenotypic traits in nature involve the collective action of many genes. Traits that evolve repeatedly are particularly useful for understanding how selection may act on changing trait values. In mice, large body size has evolved repeatedly on islands and under artificial selection in the laboratory. Identifying the loci and genes involved in this process may shed light on the evolution of complex, polygenic traits. Here, we have mapped the genetic basis of body size variation by making a genetic cross between mice from the Faroe Islands, which are among the largest and most distinctive natural populations of mice in the world, and a laboratory mouse strain selected for small body size, SM/J. Using this F2 intercross of 841 animals, we have identified 111 loci controlling various aspects of body size, weight and growth hormone levels. By comparing against other studies, including the use of a joint meta-analysis, we found that the loci involved in the evolution of large size in the Faroese mice were largely independent from those of a different island population or other laboratory strains. We hypothesize that colonization bottleneck, historical hybridization, or the redundancy between multiple loci have resulted in the Faroese mice achieving an outwardly similar phenotype through a distinct evolutionary path.

Highlights

In this sense, represent an outstanding opportunity to study parallel evolution: the house mouse is exceedingly successful in colonizing diverse habitats, including numerous remote islands, many at high latitudes
These resources present a unique opportunity to study the genetic basis of evolutionary change in nature, and to make connections to results obtained among laboratory strains
Following a generation of breeding under common conditions, we set up crosses with the small SM/J strain to determine firstly the genetic basis of body weight and length variation using a quantitative trait locus (QTL) mapping approach, and to assess the extent of QTL sharing with other examples of body weight evolution, principally by a combined QTL meta-analysis using previously published QTL studies involving the SM/J strain, mostly against the large LG/J line (Cheverud, 1996; Stylianou et al, 2006; Parker et al, 2011)

Summary

Introduction

In this sense, represent an outstanding opportunity to study parallel evolution: the house mouse is exceedingly successful in colonizing diverse habitats, including numerous remote islands, many at high latitudes Following colonization, they have often evolved to large body size (Foster, 1964; Lomolino, 1985). For genes controlling body-weight, we have previously detected evidence of selective sweeps in the Faroese mice at two loci found to be repeated involved among laboratory mice selected for body weight changes (Chan et al, 2012) This makes the Faroese mice a compelling example of island gigantism for a large-scale genetic mapping study. The MYK mice were significantly larger and heavier than SM/J mice between weeks 8 to 13 of age

Methods

Findings

Conclusion