Morphological variation, genetic diversity and genome size of critically endangered Haberlea (Gesneriaceae) populations in Bulgaria do not support the recognition of two different species

Haberlea is one of the few Gesneriaceae genera that has entered Europe. It is a highly endangered genus and red-listed in Bulgaria. Two species, H. rhodopensis and H. ferdinandi-coburgii, have been described to occur in Bulgaria, but this has never been addressed systematically. Here, we used molecular ISSR markers, morphological and nuclear DNA content to investigate the taxonomic and genetic status of Haberlea in Bulgaria. We found low levels of genetic diversity but significant genetic differentiation among the 12 investigated populations, with a strong separation between Balkan Mountain populations in the north and Rhodope Mountain populations in the south. However, the multivariate morphological analyses did not support such a division. The population from near Lovech, the type locality of the putative species H. ferdinandi-coburgii, did not differ in ploidy level from H. rhodopensis and did not form a separate entity in neither of the analyses and the existence of this species is therefore not supported.