Neobidessodes Hendrich & Balke

HENDRICH, LARS, HAWLITSCHEK, OLIVER & BALKE, MICHAEL, 2009, The epigean Australasian species of Neobidessodes gen. n. diving beetles- a revision integrating morphology, cybertaxonomy, DNA taxonomy and phylogeny (Coleoptera: Dytiscidae, Bidessini), Zootaxa 2288 (1), pp. 1-41 : 7

Neobidessodes Hendrich & Balke gen.n.

( Figs 1–21 )

Type species. Bidessus denticulatus Sharp, 1882 by present designation.

Diagnosis. Neobidessodes Hendrich & Balke gen.n. is assigned to the Bidessini based on the bisegmented parameres of the aedeagus ( Figs 17 , 18 ) ( Biström 1988). It is a genus of small to medium sized Bidessini (2.3–4.2 mm), in Australia now represented by eight species and by one species in southern New Guinea.

Etymology. The name Neobidessodes is derived from the Greek word Neo [new] and Bidessodes , a valid genus name for a group of Neotropical predaceous water beetles. Its gender is masculine.

The new genus is well separated from all other Bidessini by the combination of the following combination of characters: 1) body elongate oval; 2) basal pronotal striae in some species absent or fine, in others sharply incised, oblique, not connected by a transverse groove; 3) elytra lacking basal striae and sutural striae; 4) epipleura lacking transverse carina; 5) head lacking cervical line and its foremargin not bordered; 6) prosternal process broad, distinctly excavated and marginated; 7) inner margin of both metacoxal wings strongly ridged; 8) hind margin of abdominal ventrites 3–5 without row of minor irregular dentate processes; 9) well-developed finger-like apical lobe on distal segment of paramere. All but two ( N. limestonensis and N. gutteridgei ) of the species studied have a more or less contrasting black/yellow surface. The ground pattern of these species includes various yellow or reddish spots ( Figs 1–12 ). The median lobes are simple and very elongate, in ventral view strongly tapered or rounded at tip.

The Neotropical genus Bidessodes can be separated from Australian Neobidessodes gen.n. by having 1) a non excavated and marginated prosternal process, and 2) a visible distinct row of minor irregular dentate processes on the hind margin of the abdominal ventrites 3–5.

Molecular systematics. Our phylogenetic analyses show ( Fig. 27 ) that Neobidessodes gen.n. is not part of the Allodessus / Limbodessus , the Uvarus / Gibbidessus / Kakadudessus or the Leiodytes / Clypeodytes clades. It is rather part of a separate lineage sister to the first two clades. The DNA sequence data from the mitochondrial cytochrome c oxidase 1 and 16S rRNA genes also show that Neobidessodes gen.n. does not belong to any of the known Oriental and Australasian Bidessini genera (the morphologically strongly deviating Borneodessus Balke, Hendrich, Mazzoldi & Biström, 2002 was not available for sequencing). Our data show that Australian Neobidessodes gen.n. are not closely related to South American Bidessodes and recognition of Neobidessodes gen.n. does not create paraphyly among other Australasian genera. This result is well supported in all analyses ( Fig. 27 ). Essentially the same tree topology was recovered with different analytical approaches (maximum likelihood, parsimony and Bayesian probabilities as implemented in MrBayes, Fig. 27 , node support values).

Remarks. The placement of the two stygobitic species in this genus was primarily based on evidence from cox1 and 16S sequence data ( Watts & Humphreys 2003) which suggested a relationship of the two species with N. bilita ( Watts, 1978) , N. mjobergi ( Zimmermann, 1922) and/or N. flavosignatus ( Zimmermann, 1922) . A subsequent, comprehensive analysis of Australian stygobitic Bidessini and their epigean relatives ( Leys et al. 2003) suggests a sister-group relation of the stygobitic and the epigean Neobidessodes (under the name Bidessodes at the time). There are no morphological characters that would negate their placement in Neobidessodes as currently defined. Our species level cox1 data analysis ( Fig. 28 ) confirms the sister-group relationship between stygobitic and epigean Neobidessodes .

Figures

FIGURE 27. Phylogram of the tree obtained using GARLI and cox1 and 16S data for Australasian Bidessini, Neotropical Bidessodes and outgroups. Node support, when above 50%: bold (GARLI bootstrap), italics (MrBayes posterior propablities>0.5, x100), normal font (TNT jackknife values). Note: “Clypeodytes migrator” will be transferred to Leiodytes in a forthcoming revision (Hendrich et al. in prep.).

FIGURE 28. Phylogram of the tree obtained using GARLI and with cox1 data for Neobidessodes alone. Node support, when above 50%: bold (GARLI bootstrap), normal font (TNT parsimony jackknife values). Abbreviations behind N. thoracicus sp.n.: “b.s” = black specimens; “l.f.” = “light form”.

FIGURES 1–4. Habitus of 1) N. denticulatus (WA, Pilbara, Millstream Chichester National Park, Fortescue River side branch); 2) N. denticulatus (NT, Kakadu N.P., Jim Jim District, Gungurul Lookout); 3) N. flavosignatus (WA, East Kimberley, Gibb Range, Gibb River Road, Russ Creek Crossing); 4) N. flavosignatus (NT, Manton Dam Recreation Area, 46 km S Darwin) (scale bar = 1 mm), (Photos: A. Riedel).

FIGURES 5–8. Habitus of 5) Neobidessodes samkrisi sp.n. (holotype, male); 6) N. grossus; 7) N. mjobergi; 8) Neobidessodes bilita (female) (scale bar = 1 mm) (Photos: A. Riedel).

FIGURES 9–12. 9) N. thoracicus sp.n. (paratype); 10) N. thoracicus sp.n. (paratype, “black specimen”); 11) N. thoracicus sp.n. (“light form”, WA, Kimberley Region, 50 km S Wyndham, Black Flag Creek); 12) N. thoracicus sp.n. (“light form”, NT, Kakadu N.P., Jim Jim District, Gungurul Lookout) (scale bar = 1 mm) (Photos: A. Riedel).

FIGURES 13–17. Median lobe of aedeagus in ventral (a) and lateral view (b), and right paramere in lateral view (c): 13) Neobidessodes thoracicus sp.n. (paratype); 14) N. thoracicus sp.n. (“light form”); 15) N. flavosignatus; 16) N. mjobergi and 17) N. samkrisi sp.n. (scale bar = 0.5 mm) (Photos: L. Hendrich).

FIGURES 18–20. Median lobe of aedeagus in ventral (a) and lateral view (b), and right paramere in lateral view (c): 18) Neobidessodes bilita; 19) N. denticulatus and 20) N. grossus (scale bar = 0.5 mm) (Photos: L. Hendrich).

FIGURES 21. Denticulate tip of elytra in Neobidessodes denticulatus (Photo: L. Hendrich).