Elgiva connexa, Steyskal, 1954

Vikhrev, Nikita E. & Yanbulat, Maria O., 2021, Notes on genus Elgiva Meigen, 1838 (Diptera, Sciomyzidae), Amurian Zoological Journal XIII (2), pp. 257-264 : 263

E. connexa Steyskal, 1954

E. divisa connexa Steyskal, 1954 stat. nov. CANADA: Alberta: Banff , (51.18 ° N 115.58 ° W), C. Garrett, 25 May 1922, 1♂ (paratype Hydroneura connexa, Steyskal No 6050);

Ontario, Moose Factory (51.26 ° N 80.60 ° W), B.J. LeBoux, 10 June 1949, 1♀ (paratype Hydroneura connexa, Steyskal No 6050) ; Manitoba, Fort Churchill (58.76 ° N 94.14 ° W), J.G. Chillcott, 3 June 1952, 1♀ (all ZIN) .

USA, Colorado, Platte Canyon near Idlewild (presently Winter Park 39.89 ° N 105.76 ° W), J.M. Aldrich, 10 June 1927, 1♂, 1♀ (paratype Hydroneura connexa, Steyskal, No 51609 USNM) ( ZIN) .

REMARKS. Steyskal 1954: fig. 7 showed swellings on the tip of the male abdomen. It is not clear if we should regard these swellings as a genitalic or a non-genitalic character.

E. elegans Orth et Knutson, 1987

REMARKS. Two specimens from Platte Canyon listed here under E. connexa and were included in the type series E. connexa (by Steyskal 1954: 62). However, Orth, Knutson (1987: 836) listed them as E. elegans . The male from Platte Canyon has the swellings on the tip of the abdomen and should be identified as E. connexa according to the key offered by Orth, Knutson (1987). In our opinion, genital differential characters of this species are the most doubtful.

E. pacnowesa Orth et Knutson, 1987

REMARKS. Surstyli with robust lobes. No material examined.

Why the population of E. divisa is a single species in its homeland, i.e. in Palaearctic, despite the presence of mountain exclaves, but gave a complex of species when spread to the Nearctic? The reason is that different approaches are used to recognise species in the Palaearctic and Nearctic. The Palaearctic E. solicita and E. divisa are similar but they differ by a set of correlated characters both non-genitalic and genitalic; differences in male genitalia are unmistakable; females also can be identified. The species of the Nearctic E. divisa complex differ by a single genital character which is not convincing; females are undistinguishable.

There is an opinion that differences (even very small ones) in the structure of male genitalia are a more reliable argument for separating species than non-genitalic characters. However, we do not see confirmation of this either in the literature or in our own observations. In groups that are characterized by distinct sexual dimorphism (some Muscidae , for example, Hydrotaea ), males are often easily distinguished by non-genitalic characters but have similar genitalia, the reverse situation is much rarer.

For taxa described as species of the Nearctic E. divisa complex it is unknown if they are reproductively isolated from each other or not. It is unknown for the vast majority of organisms. However, it is known, for example, that Neanderthals and humans did not lose the ability to interbreed, despite more than half a million years of isolation and significant morphological differences accumulated during this time ( Reich 2018).

We believe that the taxonomy of Sciomyzidae has an obvious trend towards oversplitting, and this trend causes more harm than benefit ( Vikhrev, Yanbulat 2019). In our opinion, Occam’s presumption “entities should not be multiplied without necessity” is the best approach until otherwise is clearly indicated.

Without examination of the Nearctic material we cannot offer to synonymise, for example, E. elegans . However, we share Rozkosny’s (1987) opinion that E. connexa is “very closely related if not identical” to E. divisa and we decrease its taxonomic rank to subspecies: E. divisa connexa Steyskal, 1954 . Thus, American specimens may be identified either as E. divisa (any female, for example) or as E. d. divisa or E. d. connexa if necessary and possible.