<i>Cardamine maritima</i> group (Brassicaceae) in the amphi‐Adriatic area: A hotspot of species diversity revealed by DNA sequences and morphological variation

Abstract

Abstract The western Balkans, characterized by high rates of endemism, are recognized as one of the most diverse and species‐rich areas of Europe. The present study focuses on diploid speciation in a poorly explored ancestral group of the genus Cardamine that is distributed in the amphi‐Adriatic territory. Morphological data and DNA sequences (plastid trnL intron and trnL ‐ trnF spacer, ITS of nrDNA, and single‐copy nuclear gene CHS ) were used to address taxonomic, phylogenetic and evolutionary questions. Recognition of several previously described, but recently not accepted narrow endemics is supported ( C . fialae , C . rupestris , C . serbica ). Cardamine maritima s.str. is segregated into three distinct entities, which were given species rank. A new taxonomic concept of the group is proposed, including identification key, synonymy, typifications, C . montenegrina sp. nov. and C . adriatica nom. nov. Chloroplast data indicate radiation of the ancestral lineage into a series of distinct endemic species; lack of resolution at internal nodes and incongruence with nuclear phylogenies suggest that this radiation occurred rapidly. Nuclear data indicate more recent hybridization events. It is assumed that glacial‐induced local‐scale and altitudinal migrations along the Balkan coastline and in adjacent massifs caused contacts between previously isolated populations, resulting in occasional interspecific gene‐flow. Trans‐Adriatic contacts and gene exchange are also suggested.