Q_ST < F_STAs a signature of canalization

Abstract

A key aim of evolutionary biology - inferring the action of natural selection on wild species - can be achieved by comparing neutral genetic differentiation between populations (F(ST)) with quantitative genetic variation (Q(ST)). Each of the three possible outcomes of comparisons of Q(ST) and F(ST) (Q(ST) > F(ST), Q(ST) = F(ST), Q(ST) < F(ST)) is associated with an inference (diversifying selection, genetic drift, uniform selection, respectively). However, published empirical and theoretical studies have focused on the Q(ST) > F(ST) outcome. We believe that this reflects the absence of a straightforward biological interpretation of the Q(ST) < F(ST) pattern. We here report recent evidence of this neglected evolutionary pattern, provide guidelines to its interpretation as either a canalization phenomenon or a consequence of uniform selection and discuss the significant importance this issue will have for the area of evolutionary biology.

Environmental versus Anthropogenic Effects on Population Adaptive Divergence in the Freshwater Snail Lymnaea stagnalis

“…Alternatively to the uniform selection hypothesis, the pattern exhibited by early traits would result from trait canalization, as a phylogenetically inherited characteristics [86]. Since the pattern was similar to that observed in Galba truncatula [77], the criterion of cross-species consistency (supporting the canalization hypothesis) may be met in basommatophorans, but this would need to be confirmed in other species.…”

“…Alternatively, apparent neutral evolution might result from a bias in Q ST estimation. Under genetic drift, dominance and epistasis bias Q ST estimates downward [84]–[86]. As Q ST is traditionally estimated without accounting for these non-additive sources of variation, and given the strong observed global F ST value, divergent selection might have been underestimated for fecundity.…”

Ecological genetics of range size variation in Boechera spp. (Brassicaceae)

“…Elevated F ST / Q ST indicates either poor responses to selection or strong responses to stabilizing selection (Whitlock 2008; Lamy et al. 2012). Interestingly, both rare species are locally abundant within their preferred habitat.…”

“…Quantitative genetic variation and, in particular, the ratio of quantitative to neutral molecular genetic structure (e.g., Q ST ‐ F ST comparisons) can shed light on patterns of historical adaptation (Whitlock 2008; Lamy et al. 2012). In the absence of dispersal limitation, the partitioning and extent of heritable genetic variation, plasticity, and molecular genetic structure (including gene flow) are thought to be the primary drivers of range limits (Angert and Schemske 2005; Pujol and Pannell 2008; Sexton et al.…”

Glacial History Affected Phenotypic Differentiation in the Alpine Plant, Campanula thyrsoides

“…It is important to note that unifying selection does not necessarily imply that stasis was selected for, but that differentiation is not as strong as expected from random drift [49]; in most traits, considerable differentiation within regions likely resulted from selection restricting, but not prohibiting, phenotypic change, which led to adaptations to the spatially and temporally heterogeneous Alpine landscape. In the light of the observed strong molecular drift during recolonisation ( i.e.…”