Estimators for QST and coalescence times.

Timothy D Weaver

doi:10.1002/ece3.2522

Abstract

Comparisons of QST to FST can provide insights into the evolutionary processes that lead to differentiation, or lack thereof, among the phenotypes of different groups (e.g., populations, species), and these comparisons have been performed on a variety of taxa, including humans. Here, I show that for neutrally evolving (i.e., by genetic drift, mutation, and gene flow alone) quantitative characters, the two commonly used QST estimators have somewhat different interpretations in terms of coalescence times, particularly when the number of groups that have been sampled is small. A similar situation occurs for FST estimators. Consequently, when observations come from only a small number of groups, which is not an unusual situation, it is important to match estimators appropriately when comparing QST to FST.

Highlights

An important goal of evolutionary studies is to understand the processes that lead to differentiation, or lack thereof, among the phenotypes of different groups
We would like to know: did genetic drift or diversifying natural selection produce the between-group differences? Or, in the case of limited differentiation, did stabilizing selection keep the phenotypes similar? One way to approach these questions is to compare the degree of genetic differentiation for phenotypes of interest, QST, with the degree of genetic differentiation for presumably neutral DNA markers, FST (Prout & Barker, 1993; Relethford, 1994; Rogers & Harpending, 1983; Spitze, 1993)
If the character is evolving neutrally and its genetic basis is a large number of loci that contribute and additively to the value of the measurement, SH,W and SH,B can be expressed in terms of coalescence times as

Summary

Introduction

An important goal of evolutionary studies is to understand the processes that lead to differentiation, or lack thereof, among the phenotypes of different groups (e.g., populations, species). I show that for neutrally evolving (i.e., by genetic drift, mutation, and gene flow alone) characters, Q PBS and have somewhat different interpretations in terms of coalescence times. 3 | EXPRESSING QST ESTIM ATO R S I N TERMS OF COALESCENCE TIMES

Results

Conclusion