Spatial distribution, niche ecology and conservation genetics of Degenia velebitica (Brassicaceae), a narrow endemic species of the north-western Dinaric Alps

The high-biodiversity phenomenon of the Balkan Peninsula is a result of the past and present topographic, climatic and geological conditions, as well as human impact. The Dinaric Alps, as a part of the Balkan Peninsula, harbour a high number of endemic species, some of them comprising a small number of populations, which are often endangered. We investigated spatial distribution, community composition, site ecology, genetic diversity and conservation of Degenia velebitica, a stenoendemic species of the north-western Dinaric Alps. Our results showed that D. velebitica is nowadays restricted to three localities with the area of occupancy of 48,560 m2, harbouring approximately 37,000 individuals. Degenia velebitica stands are differentiated into three well-characterized, floristically homogenous syntaxa, very distinct from the surrounding vegetation, suggesting their azonal occurrence and restriction to spatially highly fragmented microsites exposed to stormy winds. Spatial distances of populations, differences in D. velebitica community composition and site ecology are mirrored in genetic variation patterns of the populations, such as high-frequency down-weighted marker values in the north-western populations and high gene diversity in the south-eastern group of populations. The fact that we could not find a single D. velebitica individual at the locus classicus indicates the existence of the ever-growing fragmentation. The analyses of genetic structure using AFLP data recognized two main genetic groups of populations as evolutionary significant units that should be considered when planning protection measures. According to our IUCN Red List reassessment, D. velebitica should be treated as a critically endangered species that requires immediate conservation actions.