© Comparative Cytogenetics, 2010 . Vol. 4, No. 2, P. 123-131. ISSN 1993-0771 (Print), ISSN 1993-078X (Online) Boreonectes gen. n., a new genus for the Stictotarsus griseostriatus (De Geer) group of sibling species (Coleoptera: Dytiscidae), with additional karyosystematic data on the group R.B. Angus Department of Entomology, The Natural History Museum, Cromwell Road, London SW7 5BD, UK and School of Biological Sciences, Royal Holloway, University of London, Egham, Surrey TW20 0EX, UK. E-mail: [email protected] Abstract. A new genus, Boreonectes gen. n., is erected for the seven S. griseostriatus-group species as well as eight other American ones listed by Nilsson and Angus (1992) as comprising the Stictotarsus griseostriatus- group as DNA work by Ribera (2003) shows this arrangement to be untenable, and no other genus-group name has been found to be available. Chromosomal investigations have shown that B. griseostriatus (De Geer, 1774) occurs as far west as the Little St Bernard Pass in the Alps, with B. alpestris (Dutton et Angus, 2007) in the Italian Gran Paradiso National Park to the south of this. B. multilineatus (Falkenström, 1922) is recorded from the Pyrenees for the fi rst time, and B. ibericus (Dutton et Angus, 2007) is shown to be present in the Moyen Atlas of Morocco. Key words: Dytiscidae, Boreonectes, new genus, S. griseostriatus group, sibling species, chromosomes, distributions, Alps, Pyrenees, Morocco. INTRODUCTION as informal groupings as no synapomorphies The Generic Placement. One of the most were found for the S. griseostriatus group. unsatisfactory features of the Stictotarsus This arrangement at present stands, but has griseostriatus (De Geer, 1774) species-group never been popular with coleopterists (e.g. is its placement within the genus Stictotarsus Mazzoldi and Toledo, 1998). Then Ribera Zimmermann, 1919. Nilsson and Angus (1992), (2003) published a paper giving the results of in an attempt to sort out confusion concerning mitochondrial DNA analyses which rendered the classifi cation of the Dytiscid genera related Nilsson and Angus' arrangement untenable. to Deronectes Sharp, 1882, placed those species The Stictotarsus duodecimpustulatus group not in Deronectes, but with parameres lacking was shown to come out on phylograms near the apical hook, in Stictotarsus. They divided Nebrioporus Regimbart, 1906 and Scarodytes Stictotarsus into three species groups, the S. Gozis, 1914, while S. griseostriatus (sensu duodecimpustulatus (Fabricius, 1792) group lato), along with S. striatellus (LeConte, 1852) (true Stictotarsus) and the S. griseostriatus and (also in the S. griseostriatus group) and S. roffi S. roffi (Clark, 1862) groups. These were left came out between two sections of Oreodytes http://pensoftonline.net/compcytogen Comparative Cytogenetics doi: 10.3897/compcytogen.v4i2.46 124 R.B. Angus Seidlitz, 1887. Trichonectes otini Guignot, new genus may now be described. 1941, included in the S. griseostriatus group Boreonectes gen. n. Type species: Dytiscus by Nilsson and Angus, was shown to come out griseostriatus De Geer, 1774. Hydroporine basal to the Stictotarsus (duodecimpustulatus- beetles with the Deronectes group characters group) - Nebrioporus - Scarodytes clade, of the median keel of the metasternum not thus taking it right out of the S. griseostriatus touching the mesosternal fork and absence of group and rendering the generic name sucker-hairs on the fore and middle tarsi of the Trichonectes Guignot, 1941 unavailable for males. Parameres more or less similar, of the the S. griseostriatus group. Hydroporus pattern, without any apical hook or If the present unsatisfactory classifi cation other sclerotised apical section. Ventral surface of the S. griseostriatus group is to be of adults densely and fi nely punctate, without remedied, then at present there appear to be visible reticulation between the punctures. two alternative courses of action. One is to Elytra densely and fi nely punctured, without place the S. griseostriatus group (and probably reticulation between the punctures (except in also the S. roffi group) within an expanded Hydroporus panaminti Fall, 1923, q.v.), the Oreodytes. The other is to erect a new genus for primary series of larger punctures indistinct or the S. griseostriatus group of species. Neither very prominent, depending on species. Ventral course is without its pitfalls. Oreodytes is not surface of head behind the eyes shining, with regarded as one of the Deronectes group of superfi cial reticulation. Pronotum without genera (Deronectina), differing, among other distinct lateral grooves or depressions. Larvae ways, in having contact between the median with well-developed swimming-hairs on keel of the metasternum and the mesosternal the legs, these in most cases extending on fork, and sucker-hairs on the anterior and to the tarsi, including those of the anterior middle tarsi of the males. Such hairs are legs. Urogomphi of second and third instar widespread among Hydroporini but lacking larvae with numerous secondary setae on the in Deronectina (Nilsson and Angus, 1992). basal segment, this very long, 90% + of the To place the S. griseostriatus group within total length of the urogomphus in third instar Oreodytes would almost certainly simply larvae. result in a short-term change of name, to be Differential diagnosis. Median keel of altered later. metasternum not touching metasternal fork; The second course of action, to be adopted fore and mid tarsi of males without sucker- here, is to erect a new genus for the S. hairs; parameres of the Hydroporus pattern, griseostriatus group of species. The pitfalls without apical hook or other sclerotised apical here are fi rstly that the exact limits of the portion; ventral surface of head behind eyes new genus must remain to be established, and shining, with only superfi cial reticulation secondly that, assuming the DNA phylograms (closely punctate in Stictotarsus and the S. are correct, Oreodytes becomes a paraphyletic roffi group); ventral surface of body fi nely and genus. The limits of genera are always subject densely punctate, without visible reticulation to revision as more knowledge becomes between the punctures; urogomphi of second available, so that objection does not seem and third instar larvae with numerous overriding. As to Oreodytes, if more work is secondary setae (absent in Deronectes). needed to sort out its composition, that is a The etymology of the name is from the separate task awaiting further research. The Greek Boreas, the North, and Nectes, a Comparative Cytogenetics Comp. Cytogenet., 2010 4(2) Boreonectes gen. a new genus for the Stictotarsus griseostriatus group 125 Table 1. Material used for chromosomal analysis. Species Locality Number of specimens analysed B. griseostriatus (De Switzerland, Valais, Lake by the Illsee 1ƃ Geer) France, Col du Petit Saint-Bernard, pool at 2200 m 2 ƂƂ a.s.l., SW of la Baraque des Douaniers (Fig. 1). Italy, Colle del Piccolo San Bernardo, pools between 1ƃ, 2ƂƂ the French frontier and the NE edge of Lac Verney (Fig. 1). B. multilineatus France, Hautes-Pyrénées, Barèges, 2245 m. a.s.l. Pond 2ƃƃ, 3ƂƂ (Falkenström) south of the Lac d'Oncet. Leg. F. Bameul (Fig. 2). B. alpestris (Dutton et Italy, Piemonte, Gran Paradiso National Park. Colle del 7ƃƃ, 2ƂƂ Angus) Nivolet, roadside lake at ca 2500 m. a.s.l. (Fig. 1). B. ibericus (Dutton et Morocco, Moyen Atlas, Khenifra Province, roadside 2ƃƃ, 5ƂƂ Angus) pool ca 1 km N of Col du Zad, 2150 m a.s.l. (Fig. 2). swimmer. It refers to the mainly northern others, and the space between the punctures is distribution of Boreonectes griseostriatus. fi nely reticulate. Included species: Boreonectes may be The phylogram given by Ribera, 2003 expected to include most of the species listed on p 484 associates the S. roffi group with by Nilsson and Angus in the S. griseostriatus the griseostriatus group, though slightly group, with the proviso that as new information separate from it. These beetles were shown becomes available species may be excluded, as by Nilsson and Angus to have a somewhat has happened with Trichonectes otini. Based different morphology, with contact, apparently on Nilsson and Angus (1992), this gives the secondary, between the median keel of the following 15 species: The B. griseostriatus metasternum and the mesosternal fork, and the group – Dytiscus griseostriatus De Geer, ventral surface of the head, behind the eyes, Potamodytes multilineatus Falkenström, rugosely punctate, so for the moment it seems Potamonectes macedonicus Georgiev, 1959, better to exclude them from Boreonectes. Stictotarsus alpestris Dutton et Angus, 2007, The general appearance of the S. roffi group S. ibericus Dutton et Angus, 2007, S. inexpec- species is distinctly different from those tatus Dutton et Angus, 2007 and S. riberae included in Boreonectes. It should be noted Dutton et Angus, 2007 (seven species), plus that Boreonectes is an overwhelmingly Hydroporus aequinoctialis Clark, 1862, H. Nearctic genus, with only the griseostriatus coelamboides Fall, 1923, Deronectes dolerosus group extending into the Old World. Leech, 1945, Hydroporus expositus Fall, 1923, H. funereus Crotch, 1873, H. panaminti Fall, An ongoing programme of karyosystematic 1923, Deronectes spenceri Leech, 1945 and investigation of the Boreonectes griseostriatus Hydroporus striatellus LeConte, 1852. The group of sibling species (Dutton, Angus, 2007; inclusion of H. panaminti may be regarded as Angus, 2008 and Angus, 2010) is clarifying tentative because the elytral punctation of this the taxonomic status and distributions of the species, though fi ne, is more diffuse than in the various species involved. The investigations Comparative Comp. Cytogenet., 2010 4(2) Cytogenetics 126 R.B. Angus Fig. 1. Map showing the known distributions of B. griseostriatus-group species in the Alps and adjacent regions. a - B. griseostriatus. b - B. ibericus. c - B. inexpectatus. d - B. alpestris. e - B. multilineatus (Fig. 2). ! - new data, other data from Dutton, Angus (2007) and Angus (2010). reported here extend the known distributions Natural History Museum, London. of B. griseostriatus (De Geer, 1774) and B. alpestris (Dutton et Angus, 2007) in the Alps, RESULTS and record B.