Biological Flora of Central Europe: Chondrilla chondrilloides (Ard.) H. Karst

Chondrilla chondrilloides (Asteraceae) is a rare and endangered early-successional plant species endemic to the Eastern European Alps. Its distribution is restricted to near-natural braided rivers and to alluvial fans. The species was common along Alpine gravel rivers, but has declined markedly due to river regulation and degradation in the 19th and 20th century, while some recent restoration projects benefit the plant. Its population declines were caused by habitat fragmentation and destruction as a consequence of extensive hydro-engineering. This paper summarises the published material on taxonomy, morphology, habitat requirements and distribution of the species. The review is complemented by own research data and a phylogenetic assessment of extant and extinct populations within the infrageneric context. A summary on location, size and structure of the remaining populations in the north-eastern and south-eastern Alps is combined with data on seed germination and the habitat niche of the species, with a particular focus on differences between northern and southern populations. Chondrilla chondrilloides forms meta-populations on consolidated gravel bars and older terraces, with extinction and recolonisation due to floodplain dynamics; small populations quickly recover from few founder individuals. Populations in the southern parts of the species’ range are larger with bigger plants and more reproduction, while germination is very high in all populations. Thus, C. chondrilloides has characteristics that allow it to respond rapidly to degradation and restoration of its habitats along gravel rivers in the Eastern Alps.