Phylogeny and biogeography of the Pleistocene Holarctic steppe and semi-desert goosefoot plant Krascheninnikovia ceratoides

Anna Seidl,Ernesto Pérez-Collazos,Karin Tremetsberger,Mark Carine,Pilar Catalán,Karl-Georg Bernhardt

doi:10.1016/j.flora.2019.151504

Abstract

Krascheninnikovia ceratoides (Chenopodiaceae) is a steppe and semi-desert plant with two subspecies, K. ceratoides subsp. ceratoides, which is widespread in Eurasia, and K. ceratoides subsp. lanata, which grows in western and central North America. A few disjunct populations of K. ceratoides subsp. ceratoides are found in Anatolia, Europe and North Africa to the west of its otherwise continuous Eurasian distribution. To understand the evolutionary history of this characteristic steppe and semi-desert plant, we analysed its phylogeny and biogeography. We sequenced several loci including ITS, ETS and the chloroplast intergenic spacer regions atpB-rbcL, rpl32-trnL and trnL-trnF to establish a time-calibrated phylogeny and reconstruct intraspecific relationships. Furthermore, we identified the ploidy level of individuals. While diploid, tetraploid and hexaploid individuals have been reported in the literature, we were only able to find diploids and tetraploids. The diploids were found in the east of Mongolia, Kazakhstan, Kyrgyzstan, Russia and the USA. The tetraploids were located in the west of Mongolia, Kazakhstan, Tajikistan, Russia, and Europe. Populations were uniformly di- or tetraploid. Our results indicate that the species may have spread from the area of Mongolia, northern China and Middle Asia (i.e., the Altai Mountains region) in two opposite directions – on the one hand, diploids migrated to the east, to eastern Asia and North America, and on the other hand diploids and tetraploids migrated to the west, to western Asia and Europe. Fossil-calibrated gene trees were used to estimate the age of the species. Diversification within the species is probably of Pleistocene age. Our dated analysis indicates that the first split among extant lineages of the species took place in the Early Pleistocene (Gelasian). The spread of the main lineages is likely related to major phases of steppe and semi-desert expansions during glacial periods of the Pleistocene.

Highlights

The goosefoot genus Krascheninnikovia Gueldenst. (Chenopodiaceae) is represented by a single species, Krascheninnikovia ceratoides (L.) Gueldenst., that inhabits shortgrass steppes, desert steppes and semi-deserts of the Holarctic temperate region with extensions into the subtropical region throughout the Northern Hemisphere (Heklau and Röser, 2008; Heklau and von Wehrden, 2011; Pfadenhauer and Klötzli, 2014)
Our results indicate that the species may have spread from the area of Mongolia, northern China and Middle Asia in two opposite directions – on the one hand, diploids migrated to the east, to eastern Asia and North America, and on the other hand diploids and tetraploids migrated to the west, to western Asia and Europe
Only one study had focused on the phylogenetic relationships, morphological variation and taxonomy within Krascheninnikovia, but no attempt to estimate the timing of the origin of the genus was performed (Heklau and Röser, 2008)

Summary

Introduction

The goosefoot genus Krascheninnikovia Gueldenst. (Chenopodiaceae) is represented by a single species, Krascheninnikovia ceratoides (L.) Gueldenst., that inhabits shortgrass steppes, desert steppes and semi-deserts of the Holarctic temperate region with extensions into the subtropical region throughout the Northern Hemisphere (Heklau and Röser, 2008; Heklau and von Wehrden, 2011; Pfadenhauer and Klötzli, 2014). (Chenopodiaceae) is represented by a single species, Krascheninnikovia ceratoides (L.) Gueldenst., that inhabits shortgrass steppes, desert steppes and semi-deserts of the Holarctic temperate region with extensions into the subtropical region throughout the Northern Hemisphere (Heklau and Röser, 2008; Heklau and von Wehrden, 2011; Pfadenhauer and Klötzli, 2014). Ceratoides has a broad and continuous distribution in Asia from Mongolia and Inner Mongolia (China) in the east to the southern Volga and Don region (Russia) in the west (Fig. 1). To the south, it reaches the Himalayas and Iran.

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