The first stygobiont species of Coleoptera from Portugal, with a molecular phylogeny of the Siettitia group of genera (Dytiscidae, Hydroporinae, Hydroporini, Siettitiina)

Iberoporus pluto sp. n., the first stygobiont beetle from Portugal (Dytiscidae, Hydroporinae), is described from a single female from the cave Soprador do Carvalho (Coimbra). The species is highly troglomorphic, depigmented, blind, and with elongated appendages not adapted for swimming. A molecular phylogeny based on a combination of three mitochondrial and two nuclear genes showed the new species to be sister to I. cermenius Castro & Delgado, 2001 from Cordoba (south of Spain), within the subtribe Siettitiina of the tribe Hydroporini. Both species are included in a Glade with Siettitia avenionensis Guignot, 1925 (south of France) and Rhitbrodytes agnus Foster, 1992 and R. aragaensis Fery & Baton, 1996 (north of Portugal), in turn sister to the rest of species of genus Rhithrodytes Bameul, 1989, in what is here considered the Siettitia group of genera. We resolve the paraphyly of Rhitbrodytes by transferring the two Portuguese species to lberoporus Castro & Delgado, 2001, I. again (Foster, 1992), comb. n. and I. argaensis (Fery & Bilton, 1996), comb. n.