Evolutionary origins and species delineation of the two Pyrenean endemics Campanula jaubertiana and C. andorrana (Campanulaceae): evidence for transverse alpine speciation

Species diversity may be underestimated even in well-explored mountain regions due to the lack of in-depth research in taxonomically intricate groups. Filling such knowledge gap is necessary to optimize conservation management, specially for species occurring in vulnerable ecosystems such as Southern European mountains. Campanula sect. Heterophylla is a complex group with a high proportion of endemic taxa in European mountain ranges, and whose species delineation is often controversial due to extensive morphological variation. We investigated the phylogenetic relationships and evolutionary entity of its taxa occurring in the Pyrenees, with a special focus on the Pyrenean endemic C. jaubertiana (which is sometimes included as a subspecies of or merged with C. cochleariifolia); and C. andorrana, a taxon allegedly endemic to Andorra (Eastern Pyrenees) and of uncertain taxonomic value. We obtained chloroplast genome and nuclear ribosomal DNA sequences, including several individuals of the three focus taxa, and conducted morphometric analyses. Phylogenetic analyses show that C. jaubertiana sensu lato (s. l.; i.e. including C. andorrana) constitutes a clearly distinct lineage that is not even closely related to C. cochleariifolia; consistent differences in floral morphology were detected between them. Our results support two main evolutionary lineages within C. jaubertiana s. l., one corresponding to populations in Central Pyrenees, and another one in Eastern Pyrenees plus Catalan Pre-Pyrenees. Given the degree of genetic and morphological differentiation, we propose the species rank for each lineage (C. jaubertiana and C. andorrana, respectively) and provide a taxonomic treatment. These two Pyrenean endemics likely diverged through transverse allopatric speciation.