The History and Origin on the Nemoral Fauna of Lepidoptera
* Siberian Zoological Museum, Institute of Systematics and Ecology of Animals SD RAS
** Institute of Cytology and Genetics SD RAS
Formation of particular species assemblies of Lepidoptera is tightly linked with formation of a corresponding plant communities. This is as well true for the nemoral fauna inhabiting broad-leaved forest (hardwood). As nemoral we consider those species of Lepidoptera which either are trophically connected to broad-leaved trees, for instance, elms, oaks (Nordmannia w-album, species of the genus Favonius), or exhibit ragnes the main parts of which reside within the zone of broad-leaved forests and which do not extend from zone of plant communities being closest derivates of such forests (species of the genus Apatura, Limenitis camilla, etc... Such species are mostly pertained to the western or south-eastern moderately warm regions of Palaearctic. Sometimes they occur both in the West and East to form so-called amphipalaearctic ranges. To this type or region similar is a range type, firstly revealed by us, with a disjunction between the south-eatsrn West Siberia (including Altai) and the main Far-Eastern part (such as in Limenitis helmanni, Limenitis sydyi and Acronicta major). All these disjunctions seem to be of not so ancient an origin, most probably they should be dated to have taken place in the Holocene, since isolated populations of these species diverged to a subspeces rank only. It should be taken into account that most of the recent Lepidoptera species formed in Pleistocene, no recent species of macrolepidoptera being known so far from the Plyocene and earlier.
Several glaciation/interglaciation cycles passed during the Pleistocene. During glaciations the nemoral fauna following the broad-leaved forests retrived to the refugia situated in South Japan and Korea, on the Caucasus, maybe in South Pre-Uralia. During interglaciations a contiguous belt of broad-leaved forests was severl times restored. In the Upper Pleistocene the most warm was the Kazantseva (Mikulino, or Riss-Wurm) Interglaciation when the forests with participation of elm, linden, and oak extended in Siberia as north as to the Podkamennaya Tunguska River, and the oak, as we firstly deduced from different palaeopalinological sources [Belova, 1985; Arkhipov, Volkova, 1994 and others), last time enjoied a contiguous transeurasian range. Broad-leaved trees, e.g. elm, were also recoreded from the Karginskii (Middle Valdai) Interval. During the climatic optimum of the Holocene (the Atlantic time) the belt of forests with participation of broad-leaved tree species (elm, linden) was also contiguous in Siberia and reached at least the Angara River lower flow. At this time the oak occured in the southern West Siberai and then, after a disjunction, east of the Tunkin Hollow throughout the southern Transbaikalia and NE Mongolia to the Okhot coast. Noteworthr that the optimum of the broad-leaved forests in the East took place earlier than in the West: in the Boreal / Atlantic time in the southern Far East, in the Atlantic time in the southern East Siberia, and in the Atlantic / Subboreal time in the southern West Siberia. The latest oak pollen is recorded in West Siberia downstream of Tobolsk and dated 900 years ago
The most probable recent analog of the forests with broad-leaved trees of the climatic optimum of the Holocene is the southern taiga forests of the East Transbaikalia, where grow three species of Ulmus and the Mongolian oak and which have a lepidoptera fauna noticeably enriched with nemoral species (Sinoprinceps xuthus, Aporia hippia, Neozephyrus japonicus, Favonius taxila, F. cognatus, Nordmannia w-album, Niphanda fusca, three species of Apatura, Neptis tshetverikovi, Kirinia epimenides, Melanargia halimede, Actias gnoma, Neodaruma tamanukii etc.). In West Siberia the reminders of nemoral communities persist at Tyumen and Tobolsk where still grow elm and linden and such characteristic nemoral species of Lepidoptera are present as, for instance Parnassius mnemosyne, Apatura iris. Another interesting region is NE and W Altai aith the adjacent regions where such species of East-Asiatic origin are present isolatedly as Limenitis helmanni, L. sydyi, Eversmannia exornata, Acronicta major etc. A number of South Siberian/Far Eastern species with contiguous ranges can also be regarded as nemoral, such as Parnassius stubbendorffii, Damora sagana, Nordmannia prunoides, Ahlbergia frivaldszkyi , etc.
By their trophic connections all the above-mentioned species are either polyhagous, or feed on poplar and willows, honey-suckles, Rosaceae, some herbs or are monophagous on the genus Ulmus. Tha is, except for the latter case, these species feed not on the broad-leaved trees and are nemoral only in a climatic respect. The mentioned plants are widely distributed well over the territory of South Siberia, except for Ulmus (which also had a contiguous distribition in the climatic optimum of the Holocene)
Notewirthy that among species with disjunctive ranges there is no one being strict monophagous on the oak. The only species connected with this tree and exhibiting an amphipalaearctic range is a Tortricid Strophedra nitidana, but it on some conditions can feed on the birch. One can suppose that Lepidoptera feeding on the oak managed to diverge to close but different species such as Spatalia argentina and S. doerriesi, Catocala sponsa and C. dula, some Microlepidoptera. Most probably in these cases isolation arised much earlier than in the cases of amphipalaearctic species. Above we noted that the last time a contiguous oak belt in Palaearctic was restored in the Kazantseva Interglaciation of the Pleistocene, about 130-100 thousand years ago. Most probably, an isolation of 100 thousand years appeared to be sufficient for divergency to reach a level, at least in Lepidoptera. As a consequence of isolation since the last degradation of a contiguous belt of the forests with elm and linden in the climatic Optimum of the Holocene, that is no more than 6-7 for thousand years, only different subsecies were able to evolve.
Most of the Siberian nemoral species of Lepidoptera seem to be of an East-Asiatic origin. It Most probably, during the climatic optimum of the Holocene a considerable westward migration of East-Asiatic nemoral species took place. Due to a relative shortness of this time only some species managed to reach the Atlantic (Nordmannia w-album, species of the genus Apatura, Limenitis camilla etc.). Later on they formed amphipalaearctic ranges. Some species reached East Europe (Eversmannia exornata), others penetrated only to the southern West Siberia (Parnassius stubbendorffii, Limenitis helmanni, L. sydyi, Damora sagana, Acronicta major). Most of the species of all these groups, including amphipalaearcts, have their closest relatives just in East Asia.The opposite migration of nemoral species from Europe to the East can not be traced among Macrolepidoptera. Only south-taiga species, not nemoral ones (such as Lemonia dumi), managed to extend their range eastwards. Characteristic species of the European broad-leaved forests occur west to Ural or the closest Transuralia (Parnassius mnemosyne, Pararge aegeria, Epicallia villica etc.), some through the steppen zone extend to West Altai (Iphiclides podalirius, Mellicta aurelia). Absence of far eastwards migrations during the climatic optimumm of the Holocene most probably can be explained by the fact that the optimum of broad-leaved forests took place earlier in the eastern part of Eurasia. In the late Atlantic/early Subboreal time European nemoral species quite could inhabit the southern Wesr Siberia as well, however, they disappeared after depletion of the broad-leaved forests, only some of them being retained in the extreme SW territories of the region (Coenonympha leander, C. arcania, Epicallia villica).
The authors express their sincere gratitude to Drs. V.S. Volkova and M. G. Sergeev for valuable consultations and the help with literature, to Drs. E.A. Belyaev, O.G. Berezina, D.V. Logunov for discussing of the matter of the work.
Arkhipov, S.A., Volkova, V.S. [Geological History, Landscapes and Climates of the Pleistocene of West Siberia] - Novosibirsk: NITs OIGTM SO RAN, 1994. - 105 p. - (Proceedings of OIGTM SO RAN. - Issue 823). [in Russian]
Belova, V.A. [Vegetation and Climate of the Late Cenosoic of the southern East Siberia] - Novosibirsk: Nauka, Siberian Division. 1985. - 158 p.