The evolutionary history of the Central Asian steppe-desert taxon Nitraria (Nitrariaceae) as revealed by integration of fossil pollen morphology and molecular data

Amber Woutersen (1) , Phillip E Jardine (2) , Daniele Silvestro (3, 4) , Raul Giovanni Bogotá-Angel (5) , Hong-Xiang Zhang (6) , Niels Meijer (7) , Johannes Bouchal (8) , Natasha Barbolini (9, 10) , Guillaum Dupont-Nivet (11, 12) , Andreas Koutsodendris (13) , Alexandre Antonelli (3, 14, 13) , Carina Hoorn (1)

1 IBED - Institute for Biodiversity and Ecosystem Dynamics
2 WWU - Westfälische Wilhelms-Universität Münster = University of Münster
3 UNIFR - Université de Fribourg = University of Fribourg
4 GU - University of Gothenburg
5 Universidad Distrital Francisco Jose de Caldas [Bogota]
6 Chinese Academy of Sciences [Xi’an]
7 Senckenberg Institute
8 University of Vienna [Vienna]
9 Stockholm University
10 UiB - University of Bergen
11 GR - Géosciences Rennes
12 University of Potsdam = Universität Potsdam
13 Universität Heidelberg [Heidelberg] = Heidelberg University
14 Departement of Computer of Science University of Oxford

The transition from a greenhouse to an icehouse world at the Eocene-Oligocene Transition (EOT) coincided with a large decrease of pollen from the steppe-adapted genus Nitraria. This genus, now common along the Mediterranean coast, Asia and Australia, has a proposed coastal origin and a geographically widespread fossil record. Here we investigated the evolution, taxonomic diversity and morphological disparity of Nitraria throughout the Cenozoic by integrating extant taxa and fossil palynological morphotypes into a unified phylogenetic framework based on both DNA sequences and pollen morphological data. We present the oldest fossil pollen grain of Nitraria, at least 53 Myr old. This fossil was found in Central Asian deposits, providing new evidence for its origin in this area. We found that the EOT is an evolutionary bottleneck for Nitraria, coinciding with retreat of the proto-Paratethys Sea, a major global cooling event and a turnover in Central Asian steppe vegetation. We infer the crown age of modern Nitraria spp. to be significantly younger (Miocene) than previously estimated (Palaeocene). The diversity trajectory

Keywords: desert -Eurasian steppe -light microscopy -phylogeny -SEM -Tibetan Plateau

Domains: Paleontology; Stratigraphy

Amber Woutersen, Phillip E Jardine, Daniele Silvestro, Raul Giovanni Bogotá-Angel, Hong-Xiang Zhang, et al.. The evolutionary history of the Central Asian steppe-desert taxon Nitraria (Nitrariaceae) as revealed by integration of fossil pollen morphology and molecular data. Botanical Journal of the Linnean Society, In press, pp.boac050. ⟨10.1093/botlinnean/boac050/7066909⟩. ⟨insu-04047103⟩