A trapped evolutionary lineage? Evidence of ecological speciation in Salvia

Natural hybridization can facilitate gene flow between closely related taxa, but may also lead to genetic assimilation of one parental species from the other, causing the loss of the first. Assessing whether this is a realistic risk requires understanding how ecological differentiation and reproductive barriers interact. Salvia pratensis and the narrow endemic S. saccardiana are evolutionarily closely related species that may occur in sympatry, with the first growing mainly on limestone, and the second on dolomitic soil. The two also differ in flower size, a characteristic considered as a reliable diagnostic trait. A previous study, however, reported few individuals with intermediate-sized flowers, hypothesized to result either from environmental effects associated with growing on an unhabitual soil or from interspecific hybridization. In the study linked to this dataset, other than evaluating the role of soil type (calcareous vs. dolomitic) in shaping vegetative and floral traits, we tested: (i) whether reproductive barriers between the two effectively maintain isolation, and (ii) whether interspecific crosses generate hybrids.