Strong divergences in regional distributions in Romania: recent ecological constraints in dragonflies (Odonata) versus ancient biogeographical patterns in butterflies (Lepidoptera: Rhopolocera)

.  1. While the biogeographical structuring of Europe as a whole is already relatively well understood, patterns at the more regional scale are still poorly explored. Especially the influence of differing ecological demands among species groups on regional distribution patterns is mostly unresolved. Therefore, we compare the distributions of strictly terrestrial butterflies with those of semi-aquatic dragonflies. 2. We analysed a regionalised distribution of the 196 butterfly and 68 dragonfly taxa of Romania with cluster analyses and principal component analyses, and worked out the different faunal regions and faunal elements for this country. 3. We obtained a clear regional structuring for the butterflies (e.g. Transylvanian Basin, Carpathians, SE Romania, W/SW Romania), but only a vertical structuring in the dragonflies from the Danube lowlands to the elevations of the Carpathians. 4. This structure implies a recent distribution trigger based on ecological and climatic constraints in dragonflies with water and energy availability being of high importance. 5. The more ancient biogeographical pattern in butterflies reflects the different biogeographical elements of Europe and the connections of the Carpathian regions to the Balkan Peninsula and the Eastern European steppes, with energy being of considerably higher importance for butterfly occurrences than water availability.