Corresponding author: Evgeniy Zinovyev (
Academic editor: Hans Turin
The distribution of beetles at the end of the Middle Pleninglacial (=terminal Quaternary) was examined based on sub-fossil material from the Ural Mountains and Western Siberia, Russia. All relevant localities of fossil insects have similar radiocarbon dates, ranging between 33,000 and 22,000 C14 years ago. Being situated across the vast territory from the southern Ural Mountains in the South to the middle Yamal Peninsula in the North, they allow latitudinal changes in beetle assemblages of that time to be traced. These beetles lived simultaneously with mammals of the so-called “mammoth fauna” with mammoth, bison, and wooly rhinoceros, the often co-occurring mega-mammalian bones at some of the sites being evidence of this. The beetle assemblages found between 59° and 57°N appear to be the most interesting. Their bulk is referred to as a “mixed” type, one which includes a characteristic combination of arcto-boreal, boreal, steppe and polyzonal species showing no analogues among recent insect complexes. These peculiar faunas seem to have represented a particular zonal type, which disappeared since the end of the Last Glaciation to arrive here with the extinction of the mammoth biota. In contrast, on the sites lying north of 60°N, the beetle communities were similar to modern sub-arctic and arctic faunas, yet with the participation of some sub-boreal steppe components, such as
One of the main tasks of any zoological investigation is the study of the influence of environmental factors on the structure of communities, including changes in insect faunas. These changes may be estimated from modern faunas. But it is necessary to study such factors, which could define the specific structure of insect communities in the past.
With respect to research on palaeo-entomological processes, it is extremely difficult to estimate the character of external influences on the structure of communities, because there are no real opportunities to inspect them directly. It is only possible to make reconstructions, which are based on the analysis of sub-fossil insect assemblages found in Quaternary strata. The term “sub-fossil” means, that insect remains are presented in these layers by isolated chitin fragments not yet fossilized. Present ecological requirements of these species can be extrapolated to the period of the past investigated; the conclusions of which can be compared with results of palaeo-botanical analysis and studies of mega and small mammals. The comparison of these conclusions allows a reconstruction to be made of palaeoenvironmental conditions prevailing in the given territory in the analyzed period of the past.
The aim of this study is to try to explain peculiarities of the insect faunas in relation with the paleoenvironmental conditions of the terminal phase of the Late Pleistocene and estimate the factors possibly determining the composition of insect species in the past, including the influence of the large herbivorous mammals.
To this end, I took some synchronous sites situated in the vast territory from the Jamal peninsula in the North up to vicinities of Ekaterinburg city in the South. Radiocarbon dating confirmed the synchrony of these sites. The period of investigations covers the end of the Late Pleistocene including terminal phase of Middle Pleninglacial period and the beginning of the Late Pleninglacial or Late Glacial Maximum (LGM). Chronologically this time corresponds to the end of Maritime Isotope Stage (MIS) 3 and the beginning of MIS 2; 33,000–22,000 years Before Present (BP). This period is considered by geologists as the most severe time of the Late Pleistocene and characterized by a cooler-than-present climate which fluctuated heavily on time scales of a few thousand years (
The work is based on sub-fossil material obtained from 13 sites scattered over the large territory of the Ural Mountains and West Siberia (
Geographical location of the study sites in the Ural Mountains and Western Siberia. Numbers of sites:
Chronological position of the study sites dated by the end of the Middle Pleninglacial period and associated with the “mammoth fauna”
Sites where sub-fossil insect faunas were found | Coordinates | Radiocarbon data, years before present (yr. BP). The abbreviation of organization and laboratory number of this data are given in parenthesis | ||||
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1. | Syoyakha-Mutnaya (V.I.Nazarov, unpublished data) | 72°25' | 66°48' | 30,700±1100 (UPI-716) | ||
2. | 430 km of Ob | 64°25' | 70°50' | 24,000±1500 (IPAE-63) | ||
3. | Aganskiy uval-1290/2 | 61°22' | 76°45' | 23,300±575 (IPAE-95) | ||
4. | Mega-2172 | 60°56' | 72°20' | 33,100±2300 (IOAN 132) | ||
60°56' | 72°20' | 26,285±590 (SOAN 982) | ||||
5. | Lokosovo | 60°40' | 71°32' | 22,930±650 (SOAN 956) | ||
6. | Kul’egan-2247 Point I | 60°25' | 75°50' | 21,815±225 (SOAN-6837) | ||
7. | Kul’egan -2247 Point II | 60°25' | 75°50' | 26,730±250 (LOIA-8663) | ||
8. | Skorodum | 57°47' | 70°58' | 26,500±550 (SOAN 4538) | ||
9. | Andriyshino | 57°41' | 66°08' | approximately 30,000 C14 yr. BP | ||
10. | Nizhnyaya Tavda | 57°41' | 66°12' | 27,400±335 (SOAN 4534) | ||
57°41' | 66°12' | 24,820±750 (SOAN 4535) | ||||
11. | Mal’kovo | 56°25' | 66°10' | 31,800±350 (GIN-5338) | ||
12. | Nikitino | 57°34' | 63°17' | 24,480±550 (SOAN 4537) | ||
57°34' | 63°17' | 28,460±800 (SOAN 4536) | ||||
13. | Shurala | Plant detritus | 57°28' | 60°15' | 27,600±150 (Ki-15505) | |
Mammalian bone | 57°28' | 60°15' | 36,700±250 (Ki-15512) |
All studied insect faunas occurred in the interval between 33,000 and 22,000 C14 yr. BP (
According to the classification by
Only faunas of the arctic type were found at the sites lying north of 61°N latitude (sites 1–3 in
1. Dominance or sub-dominance of arctic species –
2. Dominance or sub-dominance of sub-arctic species of the sub-genus
3. Single occurrences of sub-boreal steppe species –
Entomo-complexes referred to as “arctic” allow the reconstruction of severe environmental conditions similar to the modern arctic tundra, characterized by a cold climate with temperatures of July +12°C, January -27°C, the distribution of open landscapes and the absence of wood.
Between 61° and 59°N, the fossil beetle faunas of the sub-arctic type are similar to the recent communities of the south tundra and forest tundra (sites 4–7 in
1. Presence of arctic species –
2. Dominance of sub-arctic species presented by the sub-genus
3. Occurrence of sub-boreal steppe species –
4. Presence of single xylophagous beetles associated with larch or spruce, the weevil
Insect assemblages referred to as belonging to the “sub-arctic” type, are similar to modern insect faunas from the southern part of the contemporary Sub-arctic. Presumably, reconstructed landscapes look like modern south tundra or forest tundra with the presence of single trees, such as larch or spruce. The thermal regime is probably characterized by several temperatures: July +13° – +14°C, January -25° – -26°C. These reconstructions are confirmed by palaeo-botanical data.
The faunas from sites situated south of 59°N are of a “mixed” type characterized by species combinations not presently found together; insect complexes of the majority of these localities resemble each other, with main features:
1. Dominance or sub-dominance of weevils
2. Presence of arctic and sub-arctic species –
3. Presence of sub-boreal steppe and sub-alpine insects –
4. Occurrence of some halophylous beetles –
5. Occurrence of xylophagous beetles (e.g., the bark beetle
These faunas have no analogues among modern insect complexes, and may be classified as indicative of tundra steppe, although their species composition differs from that known from relict tundra steppe communities found today in Eastern Siberia and described by
Species of beetles found in the study sites associated with the “mammoth fauna”
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At first, these faunas suggest cooler than present climatic conditions, which is confirmed by the occurrence of sub-arctic species (
As evidence of the lack of dense forest, is an absence of such typically boreal beetles as
At the same time, the presence of halophylous species, such as ground beetles of the genus
It may be assumed that such faunas inhabited open communities which can be defined as “cool grasslands” with a presence of rarefied forests or of single trees and local soil salinity. Similar conclusions have been drawn from palaeo-botanical data obtained at the same sites: they show a dominance of herbal vegetation with an abundance of cereals, wormwoods and chenopodiaceous plants.
The occurrence of some boreal faunas in single sites (Niznyaya Tavda, C14 27,400 ± 335 yr. BP) do not contradict the overall distribution of open landscapes, and show the presence of isolated patches of forest vegetation, like in modern forest steppes.
Therefore, entomological data show that at the time of the terminal phase of Middle Pleninglacial the following types of landscapes were distributed in the territories of the Ural Mountains and West Siberia: the northern part of the region north of 61°N was dominated by open landscapes similar to modern tundra, between 64 and 62°N - similar to forest tundra and between 59 and 57°N – non-analogue landscapes, which may be defined as “open grasslands” or savannas with a presence of rarefied forests.
The main influence on the natural ecosystems came from palaeo-environmental factors. The Middle Weichselian Interstadial was characterized by a continental and a cooler-than-present climate with low winter temperatures and a wide distribution of permafrost; the resulting development of large ice sheets caused a strong drying effect. Decreasing sea levels provided the opening of sea shelves and the connection between Europe and the British Isles, and the Beringian Bridge between Siberia and Alaska. Cold and dry climatic conditions reconstructed for main territories of Europe, even for the Mediterranean region (
It is necessary to define which factors might prevent the distribution of woods in the period of the Late Pleistocene studied. The main environmental factor is climate as a combination of thermal regime, precipitation, insulation, etc. At present I can suggest that severe climatic conditions similar to the palaeo-environment of the terminal phase end of the Middle Pleninglacial in the Central part of North Eurasia between 59° and 57°N are presented in the inner parts of Central and East Siberia. However, the modern conditions of cool and continental climate cannot avert the present distribution of woodland vegetation in this area. I suggest that not only climatic factor prevented of the distribution of woods in the central part of northern Eurasia between 59° and 57°N. Apart from climate, other factors might influence Pleistocene ecosystems; these factors may have impeded reforestation and stimulate the distribution of open landscapes.
The influence of mammoths and other large herbivorous mammals representing the “mammoth fauna” is probably large. It is known that vast areas of the continent were occupied by mammals belonging to the mammoth complex at that time (
Firstly, in many sites fossil insects were found along with mammoth remains (
Secondly, in the majority of sites fragments of dung beetles of the genus
According to the literature, mammoths and other mega mammals such as woolly rhinoceros (
Mammoths and other mammals were indicators of certain communities, and preserved specific ecosystems (
1. Destruction of undergrowth and feeding impeded reforestation and might preserve herbal communities.
2. The hooves of mammoths destroyed the moss turf; as a result, moss cover disappeared in the territories of modern taiga and tundra zones, being replaced by mezo- and xerophylous herbal vegetation.
That is, mammoths and other mega mammals could rarefy forests and promote the distribution of zoogenic herbal vegetation consisting of cereals (
Consequently, Pleistocene forests were rare, and meadow and steppe plants were significant in the Siberian ecosystems.
I therefore suggest that the species composition of insects was affected by two important factors:
1. Cool and dry climate which caused low winter temperatures and a wide distribution of permafrost.
2. Pasture of large herbivorous mammals (mammoth and accompanying species) which caused the formation of «pasture» savannas with an abundance of herbal vegetation and rare forests.
Firstly, cool and dry climate may cause a southward advance of arctic and sub-arctic species (
Secondly, the pasture of mammoths and other mega mammals may cause the distribution of grasslands with a dominance of cereals and an abundance of weevils of the genus
A combination of these factors may have caused the distribution of several landscapes.
In the central and northern parts of the region north of 59°N, the cold climate and corresponding mammoth pasture formed communities similar to modern tundra and forest tundra. South of 59°N and up to 57°N, specific landscapes and according insect faunas were formed. These conclusions do not contradict literature data on the palaeo-geography of that period (
It may be assumed, that ground beetles of the species
At the beginning of the Holocene (10,000 yr. BP) in the Northern Hemisphere significant climatic changes took place, modifying all natural communities, and the final degradation of “mammoth faunas” took place. The largest mammals, mammoth (
The subsequent Early Holocene warming and humidification of climate, the extinction of mammoths and its consequent failing of the “pasture load” caused the reforestation and water logging of vast territories, the formation of the boreal belt, the transformation of the flora and fauna, and the wide distribution of conifer forests.
Therefore, climatic changes and the extinction of the large mammals happening between the Pleistocene and Holocene caused the disappearance of the “mixed” or non-analogue insect faunas. However, the insect species did not die out, but only changed the location of their ranges. At that time the “mixed” insect faunas disintegrated into groups of single species, shifting their ranges northwards (
The “mixed” or non-analogue faunas of the central part of North Eurasia were compared with synchronous insect faunas as described for East Siberia (
Sub-fossil insect assemblages from Northeastern Siberia may reflect the existence of tundra steppe landscapes which have no analogue among modern ecosystems (
Insect faunas at the end of the Middle Pleninglacial in Western Europe (
It is possible that these faunas, belonging to the “mixed” type, were distributed mainly in the Central part of North Eurasia (including West Siberia and the Ural Mountains) during the Late Pleistocene (MIS 4-MIS 2). So, similar faunas were found in the Gornova site, situated in the South Ural Mountains, near Ufa city (data given by F.G.Bidashko (Kazakhstan)). These assemblages are characterized by abundance of remains of the genus
1. Sub-fossil insect assemblages allow us to reconstruct several elements of the natural zonality which existed in the central part of Northern Eurasia during the terminal phase of the Middle Pleninglacial (MIS 3). In the northern and central parts of the region north of 59°N, the cold climate and the corresponding mammoth pasture formed communities similar to modern tundra and forest tundra. In the southern part of the study area between 57° and 59°N, specific landscapes and corresponding insect faunas formed, known as “mammoth savannas”.
2. Insect faunas of a “mixed” type of the Ural Mountains and West Siberia differ from East Siberian sub-fossil insect assemblages found in synchronous layers with the presence of numerous fragments of weevils
3. The species composition of insect complexes was determined not only by climate, but by pasture pressure of mammoths and other herbivorous mammals as well. A pasture load occurred in all territories of the Ural Mountains and West Siberia, but is defined differently in different parts of the study area. In the central and northern parts of the region north of 59°N, a combination of these factors formed communities similar to modern tundra and forest tundra in accordance to the southward advance of arctic and sub-arctic insect complexes relative to contemporary faunas. In those territories lying during the terminal phase of MIS 3 between 59° and 57°N insect faunas existed without any analogues among modern insect complexes and included sub-arctic, sub-boreal steppe species, halophilic insects and weevils of the genus
The author thanks his colleagues at the Laboratory of Historical Ecology of IPAE – Dr. P. Kosintsev, Dr. A. Borodin, Dr. E. Kuzmina for discussions during the preparation of this article, Dr. A. Borodin, Dr. P. Kosintsev, Dr. V. Stefanovsky, Mr. S. Zykov - for their help with collecting fossil data, Mrs. O. Korona and Mrs. S. Trofimova for providing palaeo-botanical data, Dr. P. Kositsev and Mr. N. Erokhin – for their help in obtaining radiocarbon data. Special thanks to Dr Tijs van Kolfschoten (Leiden Univ., the Netherlands) and Hans Turin for improving and reviewing this manuscript. This work was supported by the Russian Foundation for Basic Research (project 10–04-96102-r_Ural_a).