Liu W.-Z.,Northwest University, China |
Hilu K.,Virginia Polytechnic Institute and State University |
Wang Y.-L.,Xian Botanical Garden
Botanical Studies | Year: 2014
Background: In the classical doctrines, Magnolia was frequently considered the archetype among flowering plants, and its conduplicate carpel with marginal placentation was assumed to be derived from a leaf-like organ bearing ovules along its margins. Although the robustness of this concept has been seriously questioned by advances in botanical research, especially the emergence of Magnolia deeper in the angiosperm tree of life in molecular systematics, it remains the most-taught interpretation for the origin of carpels. Results: To test the validity of this classical doctrine, we performed comparative anatomical analyses of the vascular bundles in the flowers of Magnolia using fine (8-μm) paraffin -sections. We document the presence of two independent vascular systems in the carpels: the collateral bundles of the dorsal and ventral veins arising from the stelar bundle, and the amphicribral ovular bundles arising from the cortical bundles. This observation in conjunction with data from other fields concurrently suggests that the ovary wall is equivalent to a foliar organ whereas the placenta represents an ovule-bearing shoot. Conclusions: Our observation on the former model plant, Magnolia, nullifies the classical doctrine of carpel evolution and supports the Unifying Theory. This conclusion prompts a reconsideration of the concept of angiosperm flower evolution. © 2014 Liu et al.
Wang Y.L.,Chinese Academy of Sciences |
Ejder E.,Swedish Magnolia Group |
Yang J.F.,Chinese Academy of Sciences |
Kang Y.X.,Northwest Agriculture and Forestry University |
And 2 more authors.
Blumea: Journal of Plant Taxonomy and Plant Geography | Year: 2013
Magnolia biondii var. purpurascens var. nov. and Magnolia cylindrica var. purpurascens var. nov. (Magnoliaceae) are described as two new varieties endemic to China. Magnolia biondii var. purpurascens is mainly restricted to forests of Shaanxi and SE Gansu provinces. It differs from the typical variety, M. biondii var. biondii, in the dense indumentum of white hairs on twigs and the cup-shaped purplish red flowers. Magnolia cylindrica var. purpurascens occurs in secondary forests of Jingning and Songyang counties of southern Zhejiang province. It differs from the typical variety, M. cylindrica var. cylindrica, in the cup-shaped flowers of purplish red colour. The two new varieties are distinct in their distributions in both cases but share the chromosome numbers with their typical varieties. Magnolia biondii var. purpurascens is a diploid with 2n = 38, whereas M. cylindrica var. purpurascens is a tetraploid with 2n = 76. © 2013 Naturalis Biodiversity Center.
Wang Y.-L.,Northwest University, China |
Wang Y.-L.,Shanxi Normal University |
Li X.,Northwest University, China |
Li X.,University of Western Australia |
And 4 more authors.
Molecular Phylogenetics and Evolution | Year: 2010
In this paper, we report the phylogeographic history of Clintonia udensis Trautv. & Mey. (Liliaceae) inferred from two types of chloroplast DNA markers, polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and DNA sequences. Eighty samples were collected from 20 natural populations, 19 located in China and one in Japan, across the entire range of the species in East Asia. High genetic diversity (hT(PCR-RFLP) = 0.972, hT(sequencing) = 0.874) and significant differentiation (NST(PCR-RFLP) = 0.893, NST(sequencing) = 0.988 and GST(PCR-RFLP) = 0.777, GST(sequencing) = 0.978) were detected at the species level. These findings are consistent with a scenario of clonal reproduction and locally restricted gene exchange. The level of diversity of tetraploid populations was slightly greater than that of diploid populations. Significant molecular variation was found between tetraploids and diploids. Tetraploids may be autopolyploids and may have formed repeatedly in different locations. At least three regions of origin could be recognized. Twenty-six distinct haplotypes were identified. Haplotype frequency distributions were strongly skewed, with most haplotypes (n = 25) represented by only one sample each and thus restricted to a single population. Non-overlapping distributions of cpDNA haplotypes and strong genetic differentiation among populations and/or different ploid level were consistent with the findings of a nested clade analysis, which inferred long-distance colonization as the major process influencing the spatial haplotype distribution of this species. Nested clade analysis showed that the 26 haplotypes formed two 3-step, four 2-step and eleven 1-step clades, with twelve clades showing significant geographical associations. Higher NST than GST (P < 0.05) suggested a distinct phylogeographical pattern. Based on mismatch distribution analysis and neutrality tests, we found no evidence of population expansion in the species. Our analyses indicate that the history of C. udensis involved both long-distance migration and the tectonic events of Mountains in East Asia. © 2010 Elsevier Inc. All rights reserved.
Xiang X.,CAS Institute of Botany |
Li D.,CAS Kunming Institute of Botany |
Jin X.,CAS Institute of Botany |
Hu H.,Xian Botanical Garden |
And 3 more authors.
PLoS ONE | Year: 2012
Recently, there have been a lot of intense debates about the acceptance/rejection of paraphyletic groups in biological classification. On the one hand, evolutionary classification states that similarity and common descent are two criteria for biological classification and paraphyletic groups are natural units of biological classification. On the other hand, cladistic classification considers that common descent is the only criterion in biological classification and monophyly should be strictly adhered to. Holcoglossum is used herein as a case to illustrate this problem. Although Holcoglossum is a small orchid genus of less than 20 species, there is little consensus about its generic circumscription since it was established, which leads to confusion in taxonomic treatments in the Aerides-Vanda group. Based on the analyses of molecular and morphological evidence, our results suggest that the clade comprising Holcoglossum s.s., Ascolabium, Penkimia and Ascocentrum himalaicum is strongly supported as a monophyly, and that the three taxa are nested within different subclades of Holcoglossum s.s. Thus, it is reasonable to recognize a monophyletic circumscription of Holcoglossum, which is also well supported by some vegetative and floral characters. The Holcoglossum s.l. would facilitate a better understanding of pollinator-driven floral divergence and vegetative stasis than a paraphyletic and narrowly defined genus. © 2012 Xiang et al.