Origin And Diversification Of Important Character Taxa In The East Asian Flora

East Asia is a natural floristic region, and is one of the most species rich, and housed a complete flora since the Paleogene (even Cretaceous). East Asian flora not only harbors numerous groups of ancient relics, but also represents many newly formed lineages that evolved as a result of adaptive radiation. The Tethys retreat, Qinghai-Tibet Plateau uplift, insolated and young monsoon climate, coupled with dynamic geological history and diversity substrates, topography, and climates have been implicated in extensive evolutionary activity of the flora. The East Asian flora provides an outstanding system for exploring origin and patterns of biodiversity, and the contribution of dispersal and diversification to the assembly of a regional flora. In this study, under the framework of global flora analysis, we studied molecular phylogeny and biogeography of five taxa of East Asian flora:Adenocaulon, Meehania, Theligonum, tribe Urticeae and Mazaceae. Our goal is to understand evolution and assembly of East Asian plant flora. We specifically focus on assessing the timing and origin of the biome, and futher Meta-analysis based on a multi taxon approach to reconstruct the historical assembly of this biome.1) Meehania (Lamiaceae)Despite considerable progress, many details regarding the evolution of the Arcto-Tertiary flora, including the timing, direction, and relative importance of migration routes in the evolution of woody and herbaceous taxa of the Northern Hemisphere, remain poorly understood. Meehania (Lamiaceae) comprises seven species and five subspecies of annual or perennial herbs, and is one of the few Lamiaceae genera known to have an exclusively disjunct distribution between eastern Asia and eastern North America. We analyzed the phylogeny and biogeographical history of Meehania to explore how the Arcto-Tertiary biogeographic hypothesis and two possible migration routes explain the disjunct distribution of Northern Hemisphere herbaceous plants. Parsimony and Bayesian inference were used for phylogenetic analyses based on five plastid sequences (rbcL, rps16, rpl32-trnH, psbA-trnH and trnL-F) and two nuclear (ITS and ETS) gene regions. Biogeographic inferences were performed using a Bayesian method as implemented in BEAST and S-DIVA. Analyses including11of the12known Meehania taxa revealed incongruence between the chloroplast and nuclear trees, particularly in the position of Glechoma, possibly indicating allopolyploidy with chloroplast capture in the late Miocene. Based on nrDNA, Meehania is monophyletic, and the North American species M. coradata is sister to a clade containing the eastern Asian species. The divergence time between the North American M. cordata and the eastern Asian species occurred about9.81Mya (95%HPD:6.70-13.07Mya) according to the Bayesian relaxed clock methods applied to the combined nuclear data. Biogeographic analyses suggest a primary role of the Arcto-Tertiary flora in the study taxa distribution, with a northeast Asian origin of Meehania. Our results suggest an Arcto-Tertiary origin of Meehania, with its present distribution most probably being a result of vicariance and southward migrations of populations during climatic oscillations in the Tertiary with subsequent migration into eastern North America via the Bering land bridge in the late Miocene.2) Theligonum and Kelloggia (Rubiaceae)Theligonum and Kelloggia, two small genera from the coffee family (Rubiaceae), have a disjunct distribution along the Madrean-Tethyan belt and across the two sides of the QTP. Theligonum is a prostrate herbaceous genus occupying humid microenvironment and comprising four species:three are found at high elevations of2500-2800m in temperate regions in eastern Asia and one occurs at low altitude around600-900m in Macaronesia, the Mediterranean and Near East. Kelloggiaincludes only two species, K. chinensis Franchet, that occurs in alpine meadows or forest clearances at about3000m on the eastern Tibetan Plateau and K. galioides Torrey that grows in open places of coniferous forests (1100-3000m) in the western North America. Thus, these two small genera are very unique and excellent models to infer the role of the QTP uplift in the Northern Hemisphere. Phylogenetic relationships within and between Theligonum and Kelloggia as well as their relatives were inferred using chloroplast (rbcL, rps16, atpB-rbcL,psbA-trnH, and trnT-F) and nuclear ribosomal ITS sequences with Parsimony and Bayesian methods. Migration routes and evolution of these taxa were reconstructed using Bayesian relaxed molecular clock, ancestral area reconstruction, and bioclimatic niche modeling. Phylogenetic and biogeographic analyses suggested the monophyly of both Theligonum and Kelloggia, and that the ancestor of Theligonum arose in late Eocene (35.57Mya), while Kelloggia separated from Rubieae in early Oligocene (30.1Mya). Combined with our ecological niche modeling results, a Tethyan origin was hypothesized for the ancestor of both taxa in the late Ecoene to early Oligocene. Both Kelloggia and Theligonum are Tethyan floristic relicts, with the common Ancestor distributed in warm tropical to subtropical environments along the Tethys coast. The rapid uplift of the QTP in early Miocene and subsequent aridification in Central Asia that separated eastern and western Tethyan, are the probable causes of the disjunct distributions of the two investigated taxa. Our results also agree with a view that the QTP could reach an elevation of2,000m in the middle Miocene.3) The tribe Urticeae (Urticaceae)This study examines phylogenetic relationships among the12genera of Urticeae (Urticaceae) and investigates the pattern of morphological evolution based on analysis of nuclear ribosomal internal transcribed spacer (nrITS) and two plastid DNA regions (rbcL exon and trnL-F spacer). Sequence data were analyzed using maximum parsimony and Bayesian inference, and selected morphological traits were mapped onto the molecular tree. The molecular results strongly supported monophyly of Urticeae, excluding Gyrotaenia, which is related to Elatostemateae. All genera were monophyletic except for Urtica, Laportea, and Urera. Two Hesperocnide species are nested within Urtica. Laportea and Urera are divided into three groups with a strong geographical signal. The inferred phylogeny indicates six well-supported clades in Urticeae:clade A including Urtica (with Hesperocnide), Zhengyia, Laportea I, and Nanocnide; clade B comprising Laportea II; clade C including Dendrocnide and Discocnide; clade D including only Girardinia; clade E including Laportea III; and clade F including Obetia, Urera I, II, III, and Poikilospermum. Although it is difficult to identify morphological synapomorphies for these well-defined clades within Urticeae, character analysis shows that the herbaceous habit and alternate leaves are the ancestral states in the tribe. The presence of stinging hairs is the derived status in Urticeae, and it might have been a key innovation triggering species diversification in the tribe. Biogeographical analysis indicates the tropic Aisa origin of Uritceae in the early Eocene. The predominantly southwards migrations inferred here for the Uritceae conform to the boreotropics hypothesis, apparently driven by cooling and drying climates in the later Cenozoic.4) MazaceaeThe family Mazaceae, including three genera (Mazus, Lancea and Dodartia), was mainly distrubtued in East Aisa, Australia and New Zealand. These three genera were traditionaly included in the family Scrophulariaceae s.l., and have been transferred to Phrymaceae, and as a new family Mazaceae. Based on four chloroplast markers (matK, rpsl6, rbcL and trnL-F), our analysis confirmed the monophyly of Mazaceae, which are sister to Orobanchaceae-Rehmannia-Triaenophora-Phrymaceae-Paulowniaceae clade. The sister group of Mazus is the clade composed with Lancea and Dordartia with the highest support. Mazus is divided into two clades, corresponding exactly to their distribution in the Australian and E and SE Asian. Our analyses revealed six major clades of Mazus from E Asia. The estimated divergence times place the origin of the genus in the early Miocene (c.18Ma) and the divergence of theEast Asia and Australia speices in the middle to late Miocene. Migration from East Asia to Australia was possible after the collision of the Asian and Australian plates in the Miocene, which led to the uplift of high mountain chains along Malaysia, northeastern Australia, and the Highlands of New Guinea, and created "stepping stones" for the Northern Hemisphere species penetrating into Australasia. 5) Adenocaulon (Asteraceae)Adenocaulon (Mutisieae, Asteraceae) has5species and attained cosmopolitan distributions except Europe. Phylogenetic relationships in Adenocaulorrwere inferred using nuclear and plastid DNA regions. Reconstruction of spatiotemporal evolution was estimated using parsimony, Bayesian inference and likelihood methods, a Bayesian relaxed molecular clock and ancestral area reconstructions. Our results support the monophyly of Adenocaulon, which was siter to the Gerbera complex. Our biogeographical reconstruction suggests that Adenocaulon have originated in South America and then dispersed to North America during Miocene. Adenocaulon most likely migrated from North America to East Asia by the Bering land bridge after it arrived North America. Adenocaulon is well adapted for animal dispersal. The prominent glandular hairs on the cypselae are very sticky and cling readily to fabrics, fur, and feathers. The intercontinental disjunctions within the range of Adenocaulon are probably a result of dispersal of cypselae on the feathers of birds.To sum up, the research contains five typical taxa of East Asian flora, from family to tribe and genus level, including herbal, woody, vine and other life forms, and representing endemic, north and south temperate and pantropical hemisphere distribution modes. Integrated geology and fossil data, molecular phylogenetic studies spanning the flora indicate that East Asian plant groups represent a wide diversity of biogeographic sources, including north temperate (Arcto-Tertiary), Tethyan-Tertiary and Boreotropical elements. We compiled data for dated endemic clades of East Asia flora from our own studies and published literature, and found that the studied taxa originated and developed in mid to late Miocene, and represent a relatively young biome. Uplift of Qinghai-Tibet plateau, the East Asian monsoon formation and the formation of the Yangtze River system, as well as the arid retreat in east and central China maybe greatly promoted the development of the East Asian flora. Both vicariance and dispersal (including long-distance dispersal) are important on the diversification of the East Asian flora.