Authors |
Woutersen, A., P. E. Jardine, R. G. Bogota-Angel, H. X. Zhang, D. Silvestro, A. Antonelli, E. Gogna, R. H. J. Erkens, W. D. Gosling, G. Dupont-Nivet and C. Hoorn |
Abstract |
Nitraria is a halophytic taxon (i.e., adapted to saline environments) that belongs to the plant family Nitrariaceae and is distributed from the Mediterranean, across Asia into the south-eastern tip of Australia. This taxon is thought to have originated in Asia during the Paleogene (66-23 Ma), alongside the proto-Paratethys epicontinental sea. The evolutionary history of Nitraria might hold important clues on the links between climatic and biotic evolution but limited taxonomic documentation of this taxon has thus far hindered this line of research. Here we investigate if the pollen morphology and the chemical composition of the pollen wall are informative of the evolutionary history of Nitraria and could explain if origination along the proto-Paratethys and dispersal to the Tibetan Plateau was simultaneous or a secondary process. To answer these questions, we applied a novel approach consisting of a combination of Fourier Transform Infrared spectroscopy (FTIR), to determine the chemical composition of the pollen wall, and pollen morphological analyses using Light Microscopy (LM) and Scanning Electron Microscopy (SEM). We analysed our data using ordinations (principal components analysis and non-metric multidimensional scaling), and directly mapped it on the Nitrariaceae phylogeny to produce a phylomorphospace and a phylochemospace. Our LM, SEM and FTIR analyses show clear morphological and chemical differences between the sister groups Peganum and Nitraria. Differences in the morphological and chemical characteristics of highland species (Nitraria schoberi, N. sphaerocarpa, N. sibirica and N. tangutorum) and lowland species (Nitraria billardierei and N. retusa) are very subtle, with phylogenetic history appearing to be a more important control on Nitraria pollen than local environmental conditions. Our approach shows a compelling consistency between the chemical and morphological characteristics of the eight studied Nitrariaceae species, and these traits are in agreement with the phylogenetic tree. Taken together, this demonstrates how novel methods for studying fossil pollen can facilitate the evolutionary investigation of living and extinct taxa, and the environments they represent. |
Author Address |
[Woutersen, Amber; Giovanni Bogota-Angel, Raul; Gosling, William D.; Hoorn, Carina] Univ Amsterdam, IBED, Amsterdam, Netherlands. [Jardine, Phillip E.; Dupont-Nivet, Guillaume] Univ Potsdam, Inst Earth & Environm Sci, Potsdam, Germany. [Jardine, Phillip E.] Univ Munster, Inst Geol & Palaeontol, Munster, Germany. [Giovanni Bogota-Angel, Raul] Univ Dist Francisco Jose de Caldas, Fac Medio Ambiente & Recursos Nat, Bogota, Colombia. [Zhang, Hong-Xiang] Chinese Acad Sci, Xinjiang Inst Ecol & Geog, Key Lab Biogeog & Bioresource Arid Land, Urumqi, Peoples R China. [Silvestro, Daniele; Antonelli, Alexandre] Gothenburg Global Biodivers Ctr, Gothenburg, Sweden. [Antonelli, Alexandre] Univ Gothenburg, Dept Biol & Environm Sci, Gothenburg, Sweden. [Antonelli, Alexandre] Gothenburg Bot Garden, Gothenburg, Sweden. [Antonelli, Alexandre] Harvard Univ, Dept Organism & Evolutionary Biol, Cambridge, MA 02138 USA. [Gogna, Elena; Erkens, Roy H. J.] Maastricht Univ, Maastricht Sci Programme, Maastricht, Netherlands. [Dupont-Nivet, Guillaume] Univ Rennes, Geosci Rennes UMR CNRS, Rennes, France.
Woutersen, A; Hoorn, C (reprint author), Univ Amsterdam, IBED, Amsterdam, Netherlands.
amberwoutersen@gmail.com; m.c.hoorn@euva.nl |