Rhithrodytes argaensis BILTON & FERY, 1996

Fery, Hans, 2016, Notes on Rhithrodytes BAMEUL, 1989, with the description of R. minimus nov. sp. from Algeria (Coleoptera, Dytiscidae. Hydroporini, Siettitiina), Linzer biologische Beiträge 48 (1), pp. 431-450 : 442-443

Rhithrodytes argaensis BILTON & FERY, 1996 (new status)

Rhithrodytes agnus argaensis BILTON & FERY, 1996: 919 ; RIBERA et al. 1999: 60; RIBERA 2003: 477; FERY & FRESNEDA 2007: 138; ABELLÁN et al. 2013: 123 and Appendices (phylogeny).

Ty pe locality: " Portugal, Minho, NE Viana do Castelo, Serra de Arga, stream at 700 m ".

For the description of R. argaensis and comparison with Rhithrodytes agnus FOSTER, 1992 see BILTON & FERY (1996). The holotype is stored in the NMW. The habitus of this species is given in Fig. 16 , the male genitalia in Figs 29 and 33 ; see Figs 15 , 28 and 32 for R. agnus .

So far this taxon was treated as a subspecies of R. agnus . Because the type localities of the two subspecies are only about 10 km away from each other, the authors of the original description hesitated to assign specific rank to R. argaensis . On the other hand, they found that the two taxa are obviously incapable of dispersal by flight (BILTON & FERY 1996: 924). This is why the authors suspected that both subspecies might be given specific rank following (future) genetic investigations and wrote "... but it would appear that these represent taxa on their way to speciation." (BILTON & FERY 1996: 928).

Recently, such genetic investigations have been presented by ABELLÁN et al. (2013, appendices) and Ignacio Ribera (Barcelona, Spain) communicated privately that if both subspecies have "... enough morphological differences they can be upgraded to species... genetically they are very close, but well separated." In particular, the differences in the male genitalia are very distinct (see Figs 28 and 29 ), and thus the rank of argaensis is here elevated from subspecific to specific.

The data of the specimens used for the genetic studies in ABELLÁN et al. (2013) are: " 28.5.2006 (P) Viana do Castelo, ca. 6 km N Ponte de Lima , W Labruja, rest ponds of brook under bridge, UTM ca. NG 324311, H. Fery ; COI: HF931143 ; 16S: HF931362 " and " 9/v/2005 Serra de Arga , pools on summit, D.T. Bilton; COI: HF931183 , 16S: HF931405 " .

Figures

Figs 12-19: Habitus of: (12) Rhithrodytes minimus nov.sp.; (13) R. dorsoplagiatus; (14) R. numidicus; (15) R. argaensis; (16) R. agnus; (17) R. sexguttatus; (18) R. crux; (19) R. bimaculatus (scale bar 2.5 mm).

Figs 28-35: Male genitalia of: (28, 32) Rhithrodytes agnus; (29, 33) R. argaensis; (30, 34) R. crux; (31, 35) R. bimaculatus: Median lobe in ventral and lateral view and perpendicular view onto tip (28-31), left paramere (32-35).