A comparative analysis of mitochondrial and nuclear DNA sequences in blue butterflies of subgenus Polyommatus (s. str.) Latreille, 1804 (Lepidoptera: Lycaenidae: Polyommatus)

Abstract

A molecular phylogenetic analysis of the genus Polyommatus (s.str.) was carried out using two independent genetic markers, the mitochondrial cytochrome c oxidase I (COI) and the nuclear internal transcribed spacer 2 (ITS2). A 710bp section of COI (5’) and most of ITS2 (an aligned 638bp) was sequenced for 27 Polyommatus specimens belonging to 17 different taxa. The Bayesian method was applied to infer phylogenetic trees in the single gene and combined analyses. The resulting trees from the single gene analyses are congruent with each other although their resolution differs in parts of the tree. The combined analysis produced separate clusters for most species. Individuals belonging to Polyommatus icarus represent one such cluster in the tree. COI- and ITS2 sequences from different subspecies (P. icarus icarus, P. icarus fuchsia, P. icarus juno) turned out to be similar throughout its range, from the Iberian Peninsula to Transbaikalia. We can confirm that the sequences of P. andronicus are identical to P. icarus. Because both taxa occur in sympatry, we conclude that the former is a synonym to the latter: Polyommatus icarus (Rottemburg, 1775) = P. andronicus Coutsis et Ghavalas, 1995 syn. nov. P. ciloicus and P. icadius form separate clusters in the tree which confirms that both are separate species from P. icarus. P. icadius is recorded from Iran for the first time. The combined molecular phylogenetic analysis of mitochondrial and nuclear markers helped to clarify the taxonomy of the P. eros group. It confirmed earlier results obtained from COI sequences which showed that P. eroides and P. kamtshadalis are only subspecies of P. eros. ITS2 sequences of P. boisduvalii, P. erotides, P. menelaos and P. eroides orientalis are identical to P. eros. Therefore we suggest to rank these taxa as subspecies of P. eros: – Polyommatus eros boisduvalii (Herrich-Schäffer, 1844): «Lycaena Boisduvalii» [Herrich-Schäffer, 1844: 121]; «Lycaena Eros Var…Boisduvalii, HS.» [Krulikovsky, 1891: 223 (in Russian)]; «Polyommatus boisduvali (Herrich-Schäffer, 1844)» [Korshunov, 2002: 161, 385 (in Russian)]. – Polyommatus eros erotides (Staudinger, 1892) stat. rev.: «Lyc.[aena] Eros O. var. Erotides Stgr.» [Staudinger, 1892: 319]; « Polyommatus … eros… sbsp. erotides Stgr.» [Korshunov, 1972: 363 (in Russian)]. «Polyommatus erotides (Staudinger, 1892)» [Korshunov, 2002: 161, 385 (in Russian)]. – Polyommatus eros menelaos Brown, 1976 stat. nov.: «Polyommatus menelaos sp. nov.» [Brown, 1976: 82]. Because P. eros eroides is a subspecies of P. eros, the taxon «orientalis» also becomes a subspecies of P. eros: – Polyommatus eros orientalis comb. nov.: «Polyommatus eroides ssp. n. orientalis» [Krzywicki, 1983: 401]. P. forsteri from Iran is very similar to P. eros in morphology, but these taxa are markedly different in COIand ITS2 sequences. Therefore we suggest that P. forsteri is a distinct species. The taxa P. eros sichuanicus, P. erotides tartarus and P. tsvetajevi are very similar genetically but form a separate cluster from P. eros in the single gene and combined analyses. Therefore we suggest to combine P. eros sichuanicus, P. erotides tartarus and P. tsvetajevi into a distinct species. According to our research the valid species name for this taxon is Polyommatus amorata (Alpheraky, 1897) comb. nov., stat. nov., a taxon which was originally described as Lycaena Eros var. Amorata Alph. nova. Its type series is in the museum of the Zoological Institute in St. Petersburg. We designate the specimen with the following label as lectotype: “Sytschuan Mao-Djoov. 26 VIII” is written on the upperside and “Potanin 1893” on the underside of the label. The lectotypes of P. amorata and “P. eros sichuanicus” are very similar morphologically and these taxa appear to have identical areas of distribution. Therefore we propose the following synonymy: - Polyommatus amorata (Alpheraky, 1897) = P. eros sichuanicus Murayama, 1983 syn. nov. P. amorata contains two subspecies which appear to have some differences in sequences and wing patterns and are distributed in different areas: – Polyommatus amorata tartarus (Fruhstorfer, 1916) comb. nov.: «Lycaena tithonus tartarus subsp. nov.» [Fruhstorfer, 1916: 19]; «Polyommatus erotides tartarus (Fruhstorfer, 1916)» [Huang, 1999: 659]. – Polyommatus amorata tsvetajevi (Kurentzov, 1970) stat. nov.: «Lycaena tsvetajevi sp. n.» [Kurentzov 1970: 137 (in Russian)]; «Polyommatus tsvetaevi (Kurentzov, 1970)» [Korshunov, 2002: 161, 385 (in Russian)]. We conclude that the combined analysis of two independent mitochondrial and nuclear genetic markers enabled to resolve the taxonomy of a group of closely related species whose classification had been confused due to the shortage of available morphological characters.

Keywords

• Taxonomy of Polyommatus (s. str.)
• СOI and ITS2 genes