Study On Origin And Migration Of Three Desert Plants: Gymnocarpos Przewalskii(Caryophyllaceae), Tetraena Mongolica(Zygophyllaceae), Tugarinovia Mongolica(Compositae)

Gymnocarpos przewalskii Maxim.,Tetraena mongolica Maxim.and Tugarinovia mongolica Iljin are three types of typical desert plants.Former researches showed that these three plant species were relic plants after the retreat of Tethys.Because of their morphological particularity,Gymnocarpos przewalskii is determined as two species' genus,Tetraena mongolica and Tugarinovia mongolica is determined as monotypic genus.Molecular,morphological and geographical distribution characters of these three plant species and their relative species are studied in this paper.Many relative species can be found in Africa.By analyses of geographic distribution of these species,we confirm that Gymnocarpos przewalskii originated in Tethys.Both Tetraena mongolica and Tugarinovia mongolica originated in Gondwanaland.Then we analyze geologic history since Mesozoic to make sure the migratory routes of these three plant species.Prior to Oligocene age,Gymnocarpos was distributed in the northern bank of the Tethys.Because of the uplift of Qinghai-Xizang Plateau,Gymnocarpos' distribution area was separated into two sections and geographic isolation was formed.Gymnocarpos przewalskii and Gymnocarpos decandrus distributed respectively in the northeast and southwest of the Qinghai-Xizang Plateau.Most of the relative species of Tetraena mongolica and Tugarinovia mongolica distributed widely in Africa continent,so we infer that they originated in Gondwanaland.Since Mesozoic Era,because of the universal ancient continent disintegration,following with the movement of the Qiangtang and Gangdise blocks,Tetraena mongolica and Tugarinovia mongolica immigrated into Eurasia.These two species distribute narrowly in western part of Inner Mongolia nowadays.The causes include the uplift of Qinghai-Xizang Plateau,uplift of Northwest-inner Mongolia-Loess Plateau-Yungui Plateau,survival environment worsening,crowding-out Effect of native plants and so on.Analyses of migratory route of Tetraena mongolica,Tugarinovia mongolica and Gymnocarpos decandrus shows that all of these plants experienced high salinity habitats.Obviously,before the plants survive well in a new habitat,they should undergo a pro-adaptation process.Salt tolerance of island plants can transform into drought tolerance.Therefore we can infer that xerophytes originated from halophyte.According to the origination of these three plant species,we conjecture that the origination of angiosperm taken place in Permian or more early.