Identifying the genes underlying quantitative traits: a rationale for the QTN programme.
The goal of identifying the genes or even nucleotides underlying quantitative and adaptive traits has been characterized as the 'QTN programme' and has recently come under severe criticism. Part of the reason for this criticism is that much of the QTN programme has asserted that finding the genes and nucleotides for adaptive and quantitative traits is a fundamental goal, without explaining why it is such a hallowed goal. Here we outline motivations for the QTN programme that offer general insight, regardless of whether QTNs are of large or small effect, and that aid our understanding of the mechanistic dynamics of adaptive evolution. We focus on five areas: (i) vertical integration of insight across different levels of biological organization, (ii) genetic parallelism and the role of pleiotropy in shaping evolutionary dynamics, (iii) understanding the forces maintaining genetic variation in populations, (iv) distinguishing between adaptation from standing variation and new mutation, and (v) the role of genomic architecture in facilitating adaptation. We argue that rather than abandoning the QTN programme, we should refocus our efforts on topics where molecular data will be the most effective for testing hypotheses about phenotypic evolution.
Department of Ecology & Evolutionary Biology, University of Toronto, Toronto, ON, Canada M5S 3B2.
Young Wha
YW
Lee
Billie A
BA
Gould
John R
JR
Stinchcombe
Adaptation; QTL; QTN; ecological genomics; ecologically important traits; genetic variation; phenotypic evolution; population genomics; quantitative genetics; vertical integration.