Hidden on mountaintops: phylogeography and evolution of Parnassiana (Orthoptera: Tettigoniidae) in the sky-islands of the southern Balkans

Parnassiana is a micropterous, flightless genus of bush-crickets that inhabits the mountains of the southwestern Balkan Peninsula, displaying a sky-island distribution. It consists of 13 valid species and many populations with unknown taxonomic status. This study explores the phylogeography and evolution of Parnassiana by reconstructing its evolutionary relationships using multilocus DNA data (NAD2, COI and ITS), by estimating the divergence times of its lineages and relating them to significant geological and climatic events, and by delimiting the boundaries between Parnassiana taxa. Phylogenies are compared with morphological characters and bioacoustics data to inform species delimitation conclusions and evolutionary mechanisms. We conclude that the evolution of Parnassiana has been primarily shaped by tectonic and climatic events of the Pliocene (separation of Peloponnese from Central Greece, establishment of Mediterranean climate) and Early Pleistocene (warm and long interglacial periods), which led to allopatric speciation. Secondarily, the Middle and Late Pleistocene were characterized by dispersal, intra-species diversification, and possible gene exchange, adding complexity to the geographic pattern of the genus and causing discrepancies between the gene trees and phenotypic grouping. The evolutionary history of Parnassiana is reflected in its geographic distribution patterns, as isolated mountains host well-defined older lineages, while lineages from large massifs show a more uniform phenotype and complex phylogenetic relationships.