Plebejus idas reshetnikovi, Churkin & Yakovlev, 2024

Churkin, Sergei V. & Yakovlev, Roman V., 2024, New data about Plebejus idas (Linnaeus, 1761) (Lepidoptera, Lycaenidae) from Russia, with the description of the new subspecies, Ecologica Montenegrina 73, pp. 106-115 : 111-115

4. Plebejus idas reshetnikovi ssp. nov.

https://zoobank.org/ urn:lsid:zoobank.org:act:5F28FEE7-87AE-42E4-9C60-B6618B3EFD52

Figures 1 (upperside) − 2 (underside): 5−8.

Holotype: male, Russia, East Sayan, Burjatia, Oka r. valley , 20 km SW Khuzhyr v., Zham-Bolot spring, 1500−1600m, 2.07.2023 S. Churkin leg.

Paratypes: 62 males, 30 females, same data, S. Churkin leg. ; 60 males, 12 females, same data, V. Tuzov leg. ; 17 males, 24 females, Russia, East Sayan, Burjatia, Oka r. valley , 15 km NW Orlik v., 1300 m, 3.07.2023, S. Churkin leg. ; 20 males, 7 females, same data, K. Kolesnichenko leg.

Description

Holotype FW length 15 mm, male paratypes 14−16.2 mm, female paratypes 14−16.5 mm.

Antennae, palpi, body coloration and hairs seem to have no taxonomically valuable characters. Male

Wings (FW and HW) upperside violet-blue with slight light-blue tint, without expressed shine. Marginal stripe quite narrow 1-2 mm, usually with slightly blurred inner border. Veins darkened. Fringe white with small dark inner inserts. FW sometimes with developed discal spot.

Underside color steel-grey, dark, with medium-sized spots with non-contrasting rings around, discal spot medium sized.

FW underside with reduced pattern, often completely absent on costal half, orange segments of spots hardly noticeable. Postdiscal series often shifted to wing margin, straight, wing outside this series clarified.

HW underside with thin bluish coating reaching basal series of spots (as in all neighboring taxa). Size of discal series spots normal. Submarginal spots: orange segments thin, no single band, outer and inner black segments flat, thin, metallic scales normally developed, clearly noticeable in several submarginal spots (even in darkened forms).

Female

Similar to females of subsolanus , underside lighter than that of male, 65% of females without any pattern on upperside, unicolorous brown, the remaining ones with developed pale-orange or yellowish submarginal spots, series of spots not complete.

Orange-yellow spots on FW underside developed and clearly visible, unlike in males. HW underside pattern developed like that of males, but orange spots larger, sometimes forming single orange band. Metallic scales well developed.

Variability. Highly developed, as in most related taxa. Size is dependent on food plant (see below) and biotope, however, it is not completely determined by these factors. Dark forms of males (darkened portion from one third to most of wing) amount to no more than 5%−7% from the population, but occur regularly, lightened forms also amount to about 5%. It is important to note that sharply darkened forms, as a rule, are melanistic – they have a sharply darkened underside and slightly enlarged spots (see the underside of dark specimen on the Figs 1−2 : 7). And on the contrary, light forms usually have a lightened underside and reduced spots.

On FW underside postdiscal series can be sharply curved and/or moved far away from wing edge, on HW underside rare reduced metallic scales.

Diagnosis. Despite the variability, it is clearly different from the neighboring subspecies, being close to subsolanus . From ssp. obukhovi (photo – see Churkin et Zhdanko 2003, pl. III−IV: 13−16, 23, 24), inhabiting the Tunkin valley, it is different by the bright upperside, the steel but not dark-grey-brown color of the underside (the sharply expressed melanists of the new subspecies in their color resemble obukhovi), the normally developed metallic scales, the clarified postdiscal band, often contrasting, the spots color, as a rule, exactly orange.

In Tunkin butterflies the upperside is almost completely dark, the metallic scales are reduced, the colorful spots on the underside have yellow tint, and are better developed, which is most noticeable on the FW underside, the postdiscal area has no significant lightening, the wing is almost unicolorous.

From subsolanus the new subspecies differs by the dark underside (color steel instead of light-grey), at the same time, the marginal stripe is almost twice more narrow (though these are exclusions which are much darker on the underside than the typical form), the submarginal pattern is reduced (especially on FW), the orange segments on the HW underside are narrow, upperside distinctively bluish (not simply violet).

Bionomics. Within the Oka valley – almost eurytopic, a background species. There are two basic biotopes: wet grassland along rivers and rooks, where it develops on Vicia oracca L. ( Fabaceae ) and dry feet of cliffs and mountain slopes, where the foot plant is Gueldenstaedtia verna (Georgi) Boriss. (Fabaeceae). The presence of another food plant cannot be ruled out – the females were observed in abundance even where the two plants mentioned above were not present, but we could not track the oviposition in this case.

The dry grassland populations are apparently, but only statistically, smaller than the wet grassland populations and have narrower wings (see the note about the relationship between the butterfly size and the width of wing) and somewhat more often darkened on the upperside. However, both life forms represent the same species and it is not possible to separate the micropopulations according to any characteristics.

Doesn’t go upper to mountains as well as into clearings in the forest.

Distribution. Obviously, endemic of the isolated Oka valley, bounded on all sides by mountains: from the south by Tunkinsky Goltsy (a wide swampy pass at least 2000 meters above sea level), from the north – by the Kropotkin range with average altitudes of almost 3000 meters, from the east – by the Belskie Goltsy range (peaks over 2700 meters) and from the west – a huge plateau with an average height of 2000 meters.

The only opportunity for gene exchange at this time is the narrow sides of the Oka river in the gorge between Belskie Goltsy and Kropotkin ranges (the river flows in the taiga zone, where there are no suitable biotopes).

Etymology. The new subspecies is named after Sergei Pavlovich Reshetnikov (Kirov), well-known Russian butterfly collector who did a lot for the study of the Baikal region.

Discussion

The return of taxa kenteana and cleobis (with the type point in Northern Transbaikalia) resolves almost all problems that arose after the publication of the complex revision. The similarity of cleobis with the group tancrei (the generally accepted opinion in the first half of the 20th century) is explained, the persistent desire of many entomologists to move this taxon to the east or change its status becomes clear, the extreme variability of “ subsolanus ” in its previous, expanded interpretation, disappears.

A coherent and more logical system is being built, within which new hypotheses can be put forward and tested.

The range of the present subsolanus must border the habitat of P. idas , close to the nominate European subspecies (whose range extends at least to Novosibirsk). The result of contact between taxa of two completely different groups will be the key to understanding the status of the entire Siberian-Far Eastern group of taxa.

It is important to note that the undoubted relationship of cleobis with the group tancrei provides direct evidence of the existence of a direct route of gene exchange between the Lower Amur and Northern Transbaikalia – one can assume an expansion (and more than one!) of the Amur fauna to the north and northwest as the climate warmed.

There is no doubt that the blue and violet subspecies (the group subsolanus and the group tancrei ) belong to one species, since in each taxon there are transitional forms that are similar to the neighboring ones. Ssp. khramovi is an example of the two groups mutual hybridization. However, the revision of the gigantic Siberian territory is not completed, and within the Baikal region two specific questions require answers:

1) status of the populations inhabiting the upper Lena river basin (see above about the material from Kachug);

2) status of the populations inhabiting the shores of Lake Baikal; and here, separately, the question about the population from the Barguzin river valley. It should be noted that they constitute a separate entity, which may require a separate name. The lack of material and its hybridity do not allow us to come to an unambiguous solution. To resolve the situation, we first need serial material from the southern coast of Lake Baikal and the northern macroslope of Khamar-Daban, as well as from the eastern part of the Tunkinsky Goltsy range (for example, Arshan village).

The subspecies from the Oka Valley allows for a new interpretation of the existing scattered darkened specimens from various other parts of the Eastern Sayan.

Acknowledgments

Many thanks to V. Tuzov, K. Kolesnichenko (Moscow) and N. Rubin ( Grodno ) for the advices and help during the work. Separate gratitude to A. Kryukov (Kirov) for valuable material and information. We are grateful to Anna Ustjuzhanina (Tomsk, Russia) for language improvements .

References

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Churkin, S.V., Zhdanko, A.B. (2003) A review of the Plebejus idas - subsolanus complex of the Asian part of Russia and Mongolia with the descriptions of new taxa (Lepidoptera, Lycaenidae). Helios, 4, 3–74, 5 figs., cpls. I-II (1–32), III-IV (1–36).

Churkin, S.V., Yakovlev, R.V. & Lvovsky, A.L. (2022) Lectotypes of Erebia kefersteinii (Eversmann, 1851), Clossiana selenis (Eversmann, 1837), Melitaea arcesia Bremer, 1861 and holotype of Melitaea baikalensis Bremer, 1861 (Lepidoptera: Nymphalidae). Ecologica Montenegrina, 55, 17−25.

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Figures

Figure 1. Adult specimens of Plebejus, upper side: 1 – Plebejus idas subsolanus, male, Russia, Siberia, Irkutsk reg., Nizhneudinsk, B. Uk r., 1.07.1999, S. Koleshichenko leg. 2 – Plebejus idas subsolanus, male, Russia, Siberia, Irkutsk reg., Ol’khon distr., Kosaya Step’, 10.07.2003, S. Koleshichenko leg. 3 – Plebejus idas subsolanus, male, Russia, Siberia, Irkutsk reg., 10 km E Kultuk v., 27.06.2003, S. Churkin leg. 4 – Plebejus idas subsolanus, female, same data as 1. 5 – Plebejus idas reshetnikovi ssp. nova, holotype, male, Russia, East Sayan, Burjatia, Oka r. valley, 20 km SW Khuzhyr v., Zham-Bolot spring, 1500 -1600m, 2.07.2023 S.Churkin leg. 6 – Plebejus idas reshetnikovi ssp. nova, paratype, male, same data as 5. 7 – Plebejus idas reshetnikovi ssp. nova, paratype, male, same data as 5. 8 – Plebejus idas reshetnikovi ssp. nova, paratype, female, same data as 5. 9 – Plebejus idas cleobis, male, North Baikal reg., Verkhnyaya Angara r., Novyi Uoyan vic., 5−7.07.2006, A. Kryukov leg. 10 – Plebejus idas cleobis, male, same data as 9. 11 – Plebejus idas cleobis, male, same data as 9. 12 – Plebejus idas cleobis, female, same data as 9. 13 – Plebejus idas cleobis, female, same data as 9 (dark form). 14 – Plebejus idas ternejana, male, Russia, Far East, Komsomolsk-on-Amur, 13.07.2005. 15 – Plebejus idas reshetnikovi ssp. nova, paratype, female (dark form), same data as 5. 16 – Plebejus idas ssp.?- male, Russia, Siberia, Irkutsk reg., Lena r., 8 km NNW Kachug v., 24.06.2023, S. Churkin leg.

Figure 2. Adult specimens of Plebejus, under side: 1 – Plebejus idas subsolanus, male, Russia, Siberia, Irkutsk reg., Nizhneudinsk, B. Uk r., 1.07.1999, S. Koleshichenko leg. 2 – Plebejus idas subsolanus, male, Russia, Siberia, Irkutsk reg., Ol’khon distr., Kosaya Step’, 10.07.2003, S. Koleshichenko leg. 3 – Plebejus idas subsolanus, male, Russia, Siberia, Irkutsk reg., 10 km E Kultuk v., 27.06.2003, S. Churkin leg. 4 – Plebejus idas subsolanus, female, same data as 1. 5 – Plebejus idas reshetnikovi ssp. nova, holotype, male, Russia, East Sayan, Burjatia, Oka r. valley, 20 km SW Khuzhyr v., Zham-Bolot spring, 1500−1600 m, 2.07.2023, S. Churkin leg. 6 – Plebejus idas reshetnikovi ssp. nova, paratype, male, same data as 5. 7 – Plebejus idas reshetnikovi ssp. nova, paratype, male, same data as 5. 8 – Plebejus idas reshetnikovi ssp. nova, paratype, female, same data as 5. 9 – Plebejus idas cleobis, male, North Baikal reg., Verkhnyaya Angara r., Novyi Uoyan vic., 5−7.07.2006, A. Kryukov leg. 10 – Plebejus idas cleobis, male, same data as 9. 11 – Plebejus idas cleobis, male, same data as 9. 12 – Plebejus idas cleobis, female, same data as 9. 13 – Plebejus idas cleobis, female, same data as 9 (dark form). 14 – Plebejus idas ternejana, male, Russia, Far East, Komsomolsk-on-Amur, 13.07.2005. 15 – Plebejus idas reshetnikovi ssp. nova, paratype, female (dark form), same data as 5. 16 – Plebejus idas ssp.?- male, Russia, Siberia, Irkutsk reg., Lena r., 8 km NNW Kachug v., 24.06.2023, S. Churkin leg.