Molecular phylogeny, taxonomy and biogeography of the "haenydra" lineage (coleoptera, hydraenidae, genus hydraena)

The water beetle family Hydraenidae includes more than 1500 species worldwide, currently divided into four subfamilies: Hydraeninae, Ochthebiinae, Prosthetopinae and Orchymontinae. The majority of species are adapted for marginal life in the microscopic, mainly freshwater, aquatic world, feedeing dyatoms algae, even if details about the ecology of these beetles are poorly known. Most Hydraenidae species usually live in a layer of nearly stationary waters, where they adhere to the submerged stones within the fastest regions of cold, clean and fastflowing perennial streams. Hydraena Kugelann represents the largest genus within the water beetle family Hydraenidae, and in particular within Hydraeninae, with about 850 species widely distributed all over the world and several hundreds not yet described. In a recent cladistic analysis, based on morphological characters, Hydraena s.l. was split in two subgenera: Hydraenopsis Janssens (Gondwanian) and Hydraena s.str. (Laurasian). Moreover, within Hydraena s.str, some derived and well-supported monophyletic clades were recognised, and defined as “lineages”. Among them, the "Haenydra" Rey lineage, previously considered by many authors as a valid genus/subgenus, includes about 90 species distributed esclusively in western Palaearctic, from Portugal to Iran, but absent in North Africa. According mainly to male genitalia features, "Haenydra" species could be divided into several species groups and complexes. The first objective of the present project was to completely re–examinate morphology (analyzing the diagnostic characters in a cladistic standpoint), taxonomy, ecology, biogeography and conservation of the whole lineage. Furthermore, the second aim of the present work was to investigate the molecular phylogeny of the "Haenydra" lineage using both mitochondrial (COI, 16S rDNA, NAD1, tRNALeu) and nuclear (18S rDNA, 28S rDNA) markers, in order to clarify the evolutionary relationships among the different species groups and complexes, and to confirm the phylogenetic position of the "Haenydra" lineage within the large genus Hydraena s.l. In fact, although the monophyly of "Haenydra" is generally accepted, hydraenid specialists have been often discordant about the phylogenetic position of the lineage within Hydraena, sometimes considering it a basal taxon, sometimes a derived lineage. Moreover, molecular clocks were used to investigate the natural history of Hydraena s.str., and particularly of "Haenydra". Preliminarly results well supported the monophyly and the derived phylogenetic position of the “Haenydra” lineage, that was split in two major monophyletic clades: the H. gracilis and the H. dentipes clades (that split ca. 7.5 MYA), each one including several sub-clades, often corresponding to previously morphologically defined species groups/complexes