Cryptic survival and an unexpected recovery of the long-tailed mayflyPalingenia longicauda(Olivier, 1791) (Ephemeroptera: Palingeniidae) in Southeastern Europe

Once widespread in the large European rivers, Palingenia longicauda underwent a drastic range contraction as a result of the intense pollution and hydromorphological interventions of the 19 th and 20 th centuries. For the last decades it was considered to be restricted only to the Tisa River and its tributaries, and to the Rába River, but new reports indicated its presence in the Danube River in Hungary, in the Danube Delta in Romania and Ukraine, and in the Prut River in the Republic of Moldova. The objective of this study is to analyze the phylogeographic pattern between the two main eco-regions (Pannon and Pontic) of the species distribution, based on the combined mitochondrial COI (472 bp) and 16S (464 bp) sequences generated for individuals collected in Romania and Ukraine, and from publicly available ones, representing the Tisa catchment populations. The presence of viable populations in the Danube Delta and on the Prut River in Romania is confirmed, and additional presence on the Mure□ and Bega rivers from Romania, and on the Styr and Horyn’ rivers in Northern Ukraine is shown. The phylogeographic results indicate that the presence of the analyzed populations are not the result of recent founding events from the Pannon region, confirming the survival and expansion of cryptic local lineages. The recent recovery of the species may be related to the improvement of water quality as a result of the implementation of the EU Water Framework Directive and the EU Floods Directive after 2000.