insects Review Distribution Patterns of Grasshoppers and Their Kin over the Eurasian Steppes Michael G. Sergeev 1,2 1 Department of General Biology and Ecology, Novosibirsk State University, 2, Pirogova Street, 630090 Novosibirsk, Russia; [email protected] 2 Laboratory of Invertebrate Ecology, Institute of Systematics and Ecology of Animals, Siberian Branch, Russian Academy of Sciences, 11, Frunze Street, 630091 Novosibirsk, Russia Simple Summary: The steppe zone is the huge area in temperate Eurasia where different grasslands form the main type of vegetation. The main part of this life zone has been transformed by human activity and used for crop cultivation (mainly wheat) and livestock. Regional and local transfor- mations and/or climate changes can result in some shifts in species and population distribution of Orthoptera. Over this area, the climatic conditions and the dominated grasslands are suitable for numerous grasshoppers and their relatives, especially the graminivorous ones. The general level of their diversity is usually high. Many species are very abundant and may become important pests. However, there are also many rare species. The main aims of this paper are to reveal general patterns of Orthoptera distribution in the Eurasian steppes, to evaluate long-term trends of changes in distribution of taxa and populations, and to estimate the potential for population changes relative to human activity and global warming trends. Abstract: The main aims of this paper are to reveal general patterns of Orthoptera distribution in the Eurasian steppes, to evaluate long-term trends of changes in distribution of taxa and populations, and to estimate the potential for population changes relative to human activity and global warming trends. The main publications concerning diversity and distribution of these insects over the steppes are analyzed. The fauna of the Eurasian steppes includes more than 440 species of Orthoptera. The general distribution of grasshoppers and their kin in the Eurasian steppes reflects their com- Citation: Sergeev, M.G. Distribution Patterns of Grasshoppers and Their mon associations with different grasslands. The species richness increases from the relatively cold Kin over the Eurasian Steppes. Insects forest-steppes to the semi-deserts with their warm summer. There are some endemic or subendemic 2021, 12, 77. https://doi.org/ taxa, including the tribe Onconotini (Tettigoniidae). The populations’ distribution of Orthoptera is 10.3390/insects12010077 also analyzed. The populations of native Orthoptera extend through all the herbaceous landscapes. Under these conditions, the interrelating of colonies of each species may result in great abundance. Received: 30 December 2020 The population distribution of three species locusts (Locusta migratoria, Calliptamus italicus, Dociostau- Accepted: 12 January 2021 rus maroccanus) is also discussed. Some notable changes of their populations’ distribution and Published: 15 January 2021 dynamics are characterized. The situation with rare Orthoptera is estimated. Retrospective and prospective of the steppe fauna of Orthoptera are discussed. Publisher’s Note: MDPI stays neu- tral with regard to jurisdictional clai- Keywords: Orthoptera; biological diversity; fauna; distribution; range; population; pest; rare species ms in published maps and institutio- nal affiliations. 1. Introduction Copyright: © 2021 by the author. Li- The steppe zone is the huge area in temperate Eurasia where different grasslands censee MDPI, Basel, Switzerland. form the main type of vegetation [1–4] (Figure1). The adjacent forest-steppes and semi- This article is an open access article deserts should be included in this area [5,6]. Average temperatures are relatively low distributed under the terms and con- (mean temperatures of the warmest month vary from 16 ◦C to 25 ◦C, the same for the ditions of the Creative Commons At- coldest month from −1 ◦C to −34 ◦C), and annual precipitation amounts are relatively tribution (CC BY) license (https:// low (for the temperate regions) and vary from 115 mm in the inner parts of Eurasia up to creativecommons.org/licenses/by/ 640 mm in the westernmost and the easternmost parts of the Eurasian steppes [3]. The main 4.0/). Insects 2021, 12, 77. https://doi.org/10.3390/insects12010077 https://www.mdpi.com/journal/insects Insects 2021, 12, x FOR PEER REVIEW 2 of 23 Insects 2021, 12, 77 2 of 23 mm in the westernmost and the easternmost parts of the Eurasian steppes [3]. The main part of this life zone has been transformed by human activity and used for crop cultivation part of this life zone has been transformed by human activity and used for crop cultivation (mainly wheat) and livestock. The steppes were commonly used as pasturelands for many (mainly wheat) and livestock. The steppes were commonly used as pasturelands for many centuries. However, the European steppes were gradually transformed to agriculture centuries. However, the European steppes were gradually transformed to agriculture fields fields several centuries ago. In the beginning of the 20th century, some territories were several centuries ago. In the beginning of the 20th century, some territories were also also ploughed in South Siberia. Later, in the middle of the last century, during the so- ploughed in South Siberia. Later, in the middle of the last century, during the so-called called Virgin Land campaign, huge steppe areas were ploughed, and many of the remain- Virgin Land campaign, huge steppe areas were ploughed, and many of the remaining areas ofing steppe areas haveof steppe become have overgrazed. become overgrazed. As a result, As many a result, habitats many of habitats grasshoppers of grasshoppers and their relativesand their have relatives been destroyedhave been or destroyed damaged. or Such damaged. regional Such and local regional transformations and local transfor- and/or climatemations changes and/or climate can result changes in some can shifts result in in species some andshifts population in species distribution.and population distri- bution. Figure 1. Distribution of the Eurasian steppes and their subregions. The boundaries of the steppe and the semi-desert life Figure 1. Distribution of the Eurasian steppes and their subregions. The boundaries of the steppe and the semi-desert zones based on [1–4] with some changes and simplification. Boundaries: green—general outline of the Eurasian steppes lifeincluding zones basedthe semi-deserts on [1–4] with and some excludin changesg the andmountain simplification. steppes of Boundaries:South-West and green—general Central Asia; outline yellow—boundary of the Eurasian be- steppestween the including dry steppes the semi-deserts and the semi-deserts and excluding; red—boundaries the mountain steppesbetween of western, South-West central, and Centraland eastern Asia; parts yellow—boundary of the steppes. between1—European the dry (western) steppes andparts the of semi-deserts;Scythian biogeographic red—boundaries subregion; between 1a—Pannonian western, central, Plain; and 2—Kazakhstan eastern parts Province of the steppes. of Sa- 1haran-Gobian—European (western) subregion; parts 3—West-Siberian of Scythian biogeographic parts of the Scythian subregion; subregion;1a—Pannonian 4—Mongolian-Siberian Plain; 2—Kazakhstan parts of Scythian Province sub- of Saharan-Gobianregion; 4a—insular subregion; parts of 3forest-steppes—West-Siberian and parts steppes of the of South Scythian Siberia; subregion; 5—Dongbei4—Mongolian-Siberian Province of Scythian parts subregion; of Scythian 6— subregion;Mongolian4a Province—insular of parts Saharan-Gobian of forest-steppes subregion. and steppes The basic of South map Siberia;is “A Two5—Dongbei Point Equidistant Province Projection of Scythian of subregion; Asia” (the 6control—Mongolian points Provinceare at 35° of N Saharan-Gobian 40° E and 35° N subregion. 140° E; the The reticle basic is map10 degrees is “A Twoin latitude Point Equidistantand longitude, Projection with the of central Asia” meridian at 90° E); the source image is a product of NASA’s Blue Marble Project public domain. (the control points are at 35◦ N 40◦ E and 35◦ N 140◦ E; the reticle is 10 degrees in latitude and longitude, with the central meridian at 90◦ E); the source image is a product of NASA’s Blue Marble Project public domain. From the zoogeographic point of view, the steppe zone almost coincides with the ScythianFrom (or the Euro-Siberian zoogeographic Steppe) point subregion of view, theof Palaearctic steppe zone erected almost mainly coincides on the with basis the of Scythianthe species (or distribution Euro-Siberian analysis Steppe) [7–11]. subregion Over this of Palaearcticarea, climatic erected conditions mainly and on dominated the basis ofgrasslands the species are distribution suitable for analysis numerous [7–11 grasshoppers]. Over this area, and climatictheir relatives, conditions especially and domi- the natedgraminivorous grasslands species. are suitable The general for numerous level of grasshopperstheir diversity and is usually their relatives, high [8–13]. especially Many the graminivorous species. The general level of their diversity is usually high [8–13]. Insects 2021, 12, 77 3 of 23 Many species are very abundant and may become important pests. However, there are also many rare species. Besides, numerous steppe or steppe-like habitats are distributed over the mountains of arid and semi-arid areas of temperate and subtropical Eurasia from South-East Europe to the Hengduan mountains. These mountains are characterized