Comparative niche modelling and early life cycle stage in related Aquilegia species

Speciation is a fundamental biological process of central interest in evolutionary biology. In recent years, taxon boundaries have been tested mostly through genetic and morphological data, whereas ecological and functional data are still little considered for taxonomic purposes. Columbines (Aquilegia, Ranunculaceae) are a model system in evolutionary biology, connecting the ecological interactions driving speciation with the genetic changes responsible for remodelling morphology. Nevertheless, the phylogenetic relationships inside this genus are poorly resolved. The aim of this study is to examine the role of adult ecological niche and regeneration by seeds in taxon delimitation by comparing adult plant ecology and seed morpho-functionality in closely related montane species of the genus Aquilegia. Ecological niche modelling (ENM), seed germination experiments and comparative seed morphometric analysis were performed in multiple population of closely related montane columbines. Ecological niche differentiation among species is relevant and consistent with phylogenetic relatedness. However, niche similarity tests indicate that all species exhibit some degree of niche conservatism. Seed germination results indicate the presence of seed dormancy in all investigated species and a moderate variability in germination responses to experimental conditions. Accordingly, seed morphology shows high overlap with moderate differentiation among species. Results of all three types of approaches are consistent, supporting that ecological/functional distances are in line with the phylogenetic relatedness. Nevertheless, a moderate degree of ecological and functional differentiation among species is detected. Overall, the integration of functional and ecological niche approaches is a novel and successful approach in understanding the role of selective pressures, genetic drift and/or trait conservatism in species divergence. Thus, this approach may provide meaningful information in phylogenetically unresolved systematic group and evaluating the strength of species delimitation.