A review of cross-backed grasshoppers of the genus Dociostaurus Fieber (Orthoptera: Acrididae) from the western Mediterranean: insights from phylogenetic analyses and DNA-based species delimitation

Phylogenetic analyses and species delimitation methods are powerful tools for understanding patterns of species diversity. Given the current biodiversity crisis, such approaches are invaluable for urgent assessment and delimitation of truthful species, particularly of endangered and morphologically cryptic taxa from vulnerable areas submitted to strong climate change and progressive human intervention such as the Mediterranean region. In this study, we applied two DNA-based species delimitation methods and performed a Bayesian phylogenetic reconstruction using three mitochondrial gene fragments (12S, 16S and COI) to solve several taxonomic uncertainties among species of cross-backed grasshoppers (genus DociostaurusFieber) from the western Mediterranean. Phylogenetic analyses demonstrate the polyphyletic character of subgenera Dociostaurus, KazakiaBey-Bienko and StauronotulusTarbinsky and, thus, the necessity of revising the currently accepted taxonomic subgenera within the genus Dociostaurus. We propose the split of closely related taxa with allopatric distributions such as D.(S.)kraussi and D. (S.)crassiusculus, considering the later a distinct species limited to the Iberian Peninsula and excluding the name crassiusculus from other forms of D.(S.)kraussi from East Europe and Asia. Estimates of divergence times indicate that diversification of Dociostaurus probably happened during the Miocene-Pliocene (3-7Ma), and the split of the studied pairs of sister taxa took place during the middle and late Pleistocene (1-2Ma). This study highlights the need for more molecular studies on the genus and their different species for a better understanding of their evolution, genetic variation and population dynamics in order to prioritize strategies for their adequate conservation and management.