Linking divergent selection on vegetative traits to environmental variation and phenotypic diversification in the...

Divergent selection is a key in the ecological theory of adaptive radiation. Most evidence on its causes and consequences relies on studies of pairs of populations or closely related taxa. However, adaptive radiation involves multiple taxa adapted to different environmental factors. We propose an operational definition of divergent selection to explore the continuum between divergent and convergent selection in multiple populations and taxa, and its links with environmental variation and phenotypic and taxonomic differentiation. We apply this approach to explore phenotypic differentiation of vegetative traits between 15 populations of four taxa of Iberian columbines (Gen. Aquilegia). Differences in soil rockiness impose divergent selection on inflorescence height and the number of flowers per inflorescence, likely affecting the processes of phenotypic and, in the case of inflorescence height, taxonomic diversification between taxa. Elevational variation imposes divergent selection on the number of leaves; however, the current pattern of divergent selection on this trait seems related to ecotypic differentiation within taxa but not to their taxonomic diversification.