The Eurasian steppe belt: Status quo, origin and evolutionary history

Abstract

We present a comprehensive review of the characteristics and structure of the Eurasian steppe and of its evolutionary history in space and time. During the last decades, tremendous advances in research methods in earth and palaeontological sciences have greatly increased knowledge on palaeoclimates and palaeoenvironments of the Cenozoic era. We discuss well-known facts against the background of the recent progress made in these fields and others related to our topics, and address open questions. In Part I (Status quo), we deal with steppe classification systems, human impact and present state of the Eurasian steppe. Here, we concentrate on prehistoric times when the first human cultures emerged, and on the last 100 to 200 years when drastic changes occurred and in many regions steppe nearly completely disappeared. In Part II (Origin and evolutionary history of the Eurasian steppe) we attend to the origin and evolution of grasses and grassland in general, and to the evolution and climate/landscape history of the Eurasian steppe belt in particular. Uplift of the Himalayan-Tibet Plateau, changes in land-sea distribution and global climate trends have been invoked as driving forces behind Cenozoic paleoclimate changes, but there is little consensus which one is the most important driver. We finally identify gaps/challenges in our knowledge about the evolutionary history of the Eurasian steppe and discuss research directions, which might help to unravel the florogenetic and steppe habitat dynamics from the beginning of steppe formation to the present time.

Comparative Phylogeography of Veronica spicata and V. longifolia (Plantaginaceae) Across Europe: Integrating Hybridization and Polyploidy in Phylogeography

“…Such a split between European and Central to East Asian populations has previously been found in Clausia (Franzke et al, 2004) with a split between groups found around 70 • East and further west along the Ural Mountains in Camelina microcarpa (ŽerdonerČalasan et al, 2019). This split along the Ural Mountains is in line with the division of periglacial steppes in two large ecosystems east and west of the Ural Mountains based on paleo-environmental reconstructions (Hurka et al, 2019). Considering the postulated East Asian origin of the subgenus (Kosachev et al, 2016), we hypothesize that V. longifolia originated in Eastern Asia and subsequently dispersed westward toward Europe and further differentiated there.…”

“…Hybridization due to secondary contacts is considered to be a common phenomenon following recolonization after retreat of Pleistocene glaciers (Hewitt, 2001). During these glaciations (glacial phases, in contrast to interglacials), communities of steppe vegetation and its ecological analogs (such as cold and dry periglacial steppes or similar dry grassland plant communities) were favored by predominantly continental climate in most part of Europe, thus possibly providing large and connected open habitats (Mai, 1995;Bezusko et al, 2011;Hurka et al, 2019); such habitats were most probably suitable for V. spicata and ensured its survival and dispersal during Pleistocene cycles. On the other hand, interglacial phases of the Pleistocene were normally warmer and more humid in most of Europe and thus promoted such habitats as riparian meadows and floodplain grasslands developing on fluvioglacial deposits, which were more favorable for survival and dispersal of V. longifolia.…”

A story from the Miocene: Clock‐dated phylogeny of Sisymbrium L. (Sisymbrieae, Brassicaceae)

“…DEC, DIVALIKE, and BAYAREALIKE biogeographic models with and without corresponding jumping parameter "+j" were tested using BioGeoBEARS v1.1.1 algorithm implemented in RASP through R (Matzke, 2013a(Matzke, , 2013b(Matzke, , 2014. Following the biogeographic division and evolutionary history of Eurasia and Africa (Hurka et al, 2019;Linder, 2014;Linder et al, 2012;Wesche et al, 2016) (Tables 1 and 2).…”

“…The southern East European Plain is part of a nowadays continuous Eurasian steppe belt, which is the vastest grassland region in the world with 8,000 km in length and up to 1,000 km in width. This ecoregion was under strong influence of glacial and interglacial cycles during the past five MYR, which continuously caused contractions, expansions, and latitudinal range shifts of the Eurasian steppe belt (Hurka et al, 2019). In contrast, the western and central regional subcenters of the Irano-Turanian region (Léonard, 1988) were not as strongly affected by the Quaternary glaciations as the Eurasian steppe belt.…”

To the bryophyte flora of communities of steppes and steppe scrubs in the Bashkir CIS-Urals (the Southern Urals region)

“…Steppes have a high economical and conservational value around the world and are recognized as vulnerable ecosystems dramatically degraded due to the human impact during the last centuries (Smelansky & Tishkov, 2012;Hurka et al, 2019). Steppes of the Bashkir Cis-Urals are no exception.…”