Nemoral species of Lepidoptera (Insecta) in Siberia: a novel view on their history and the timing of their range disjunctions

Abstract

Distributions in Siberia of nemorallepidopteran species, trophically or cenotically tied to broad-leaved (nemoral) forests or their phytocenotic derivates, display seven main types of range: Amphipalaearctic; Europe – West-Siberia – Far-East disjunctive; East-Europe – Altai – Far-East disjunctive; Altai – Far-East disjunctive; South-Siberia – Far-East; Transbaikalia – Far-East; Europe- Transuralia. An eastern origin can be traced for most of these species, with the exception of the last-mentioned type. According to palynological data, a continuous belt of broad-leaved forests was re-established during the Quaternary in North Eurasia at least twice: at the beginning of the Late Pleistocene and in the Middle Holocene. During the former the range of oak, as well as the fauna connected with it, was continuous through the Palaearctic. There is no reliable evidence for refuges of nemoral flora and fauna in Siberia during the last glaciation. We assume that the period since the Late Pleistocene (Kazantseva) Optimum (about 100,000-110,000 years) was sufficient for taxonomic divergence to species rank of western and eastern Palaearctic populations of Lepidoptera. During the Holocene climatic optimum the lepidopteran nemoral fauna could expand into a transpalaearctic distribution as a consequence of westward migration of eastern species due to an earlier optimum of broad-leaved forests in the eastern parts of Asia than in West Siberia and Eastern Europe. Disjunctive types of nemoral species range may have resulted from depletion of the forests with broad-leaved trees in Central Siberia during the Sub boreal period of the Holocene. Thus, they should not be dated to the late Pliocene - early Pleistocene, as was done earlier.