A meta-analysis of the effects of plant traits and geographical scale on the magnitude of adaptive differentiation as measured by the difference between QST and FST

The impact of directional selection on specific trait types in plant species, and how a species’ life history mediates this response to selection remains understudied. Discovering such interactions is however crucial for understanding the interplay between ecological and genetic processes underlying local adaptation in plants, and to evaluate a species’ evolutionary potential with respect to changing environments. Furthermore, it remains unclear whether the degree of adaptive differentiation generally increases with the geographical distance between plant populations. Here, we present a weighted mixed model based meta-analysis aimed at unraveling the potential interactions between plant trait types, life history characteristics and Q_ST–F_ST comparisons, and assessing the effect of geographical scale on population differentiation. Based on 51 studies we found that Q_ST values exceeded their corresponding F_ST values in 71.74 % out of 401 cases. Furthermore, different trait types were found to be differently susceptible to natural selection and the magnitude of Q_ST–F_ST comparisons was mediated by a plant species’ life span. These findings may be closely related to the genetic architectures of trait types and life histories, with the proportion of large-effect genes likely shaping the response to natural selection. Q_ST–F_ST values also increased with increasing distance between populations, pinpointing the combined effects of environmental differentiation and isolation by distance on the magnitude of population divergence. Finally, our model showed an inverse relationship between F_ST and Q_ST–F_ST values, presumably resulting from isolation by distance, the exchange of advantageous alleles, or genetic correlations among traits.