Hydraena Kugelann, 1794

PERKINS, PHILIP D., 2014, A revision of the water beetle genus Hydraena Kugelann for southern Africa (Coleoptera: Hydraenidae), Zootaxa 3758 (1), pp. 1-92 : 6

Hydraena Kugelann, 1794

Hydraena Kugelann, 1794: 578 (type species Hydraena riparia Kugelann 1794: 579 ).

The speciose, cosmopolitan genus Hydraena is well defined by the following autapomorphic morphological characteristics: 1) presence of a labral-mandibular interlocking device (Perkins 1989), 2) mentum with an acute median projection anteriorly (Perkins 1989), 3) various complex sensilla ( Perkins 1997), and 4) specialized features of the exocrine secretion delivery system ( Perkins 1997). There is general agreement among current workers that Hydraena is monophyletic, based on these morphological characters (for example, Jäch et al. 2000).

In a recently published landmark paper ( Trizzino et al. 2013) the phylogeny of Hydraena was reconstructed using 212 species plus several outgroups and approximately 4 kb of sequence data from two nuclear (SSU and LSU) and four mitochondrial genes (cox1, rrnL, trnL and nad1). The study found strong support for the monophyly of Hydraena and many of the clades that have been recognized on the basis of morphological data. The following clades were considered by Trizzino et al. (2013) as subgenera: Phothydraena Kuwert , Spanglerina Perkins , Holcohydraena Kuwert , Hydraenopsis Janssens and Hydraena s.str. The placement of three species groups, two Neotropical ( H. multispina group, H. paeminosa group) and one South African/Madagascan ( H. monikae group), was found to be uncertain, and they were considered incertae sedis within Hydraena .

The study by Trizzino et al. included four southern African species of Hydraena . Two of the species, H. accurata and H. cooperi were found to be members of the subgenus Hydraenopsis . Two other species that were sequenced, represented by one specimen each, were H. monikae and H. sp.; these were determined to be in the same, subgenerically uncertain, clade (= H. monikae group). The second species (" H. sp.") is a member of H. duodecimata .

Based on morphological similarity, five species are herein placed in the Monikae Group. The 24 other species are quite similar in basic morphology to H. accurata and H. cooperi , and are consequently placed in the subgenus Hydraenopsis . More DNA sequence studies are needed to corroborate these placements.