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25 August 2021, Volume 43 Issue 04
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  • Articles
    Are phylogenies resolved at the genus level appropriate for studies on phylogenetic structure of species assemblages?
    Hong Qian, Yi Jin
    2021, 43(04):  255-263.  doi:10.1016/j.pld.2020.11.005
    Abstract ( 48 )   HTML ( )   PDF (3104KB) ( 43 )   Save
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    Phylogenies are essential to studies investigating the effect of evolutionary history on assembly of species in ecological communities and geographical and ecological patterns of phylogenetic structure of species assemblages. Because phylogenies well resolved at the species level are lacking for many major groups of organisms such as vascular plants, researchers often generate a species-level phylogenies using a phylogeny well resolved at the genus level as a backbone and attaching species to their respective genera in the phylogeny as polytomies or by using a megaphylogeny well resolved at the genus level as a backbone and adding additional species to the megaphylogeny as polytomies of their respective genera. However, whether the result of a study using species-level phylogenies generated in these ways is robust, compared to that based on phylogenies fully resolved at the species level, has not been assessed. Here, we use 1093 angiosperm tree assemblages (each in a 110×110km quadrat) in North America as a model system to address this question, by examining six commonly used metrics of phylogenetic structure (phylogenetic diversity and phylogenetic relatedness) and six climate variables commonly used in ecology. Our results showed that (1) the scores of phylogenetic metrics derived from species-level phylogenies resolved at the genus level with species being attached to their respective genera as polytomies are very strongly or perfectly correlated to those derived from a phylogeny fully resolved at the species level (the mean of correlation coefficients is 0.973), and (2) the relationships between the scores of phylogenetic metrics and climate variables are consistent between the two sets of analyses based on the two types of phylogeny. Our study suggests that using species-level phylogenies resolved at the genus level with species being attached to their genera as polytomies is appropriate in studies exploring patterns of phylogenetic structure of species in ecological communities across geographical and ecological gradients.
    Topography and soil content contribute to plant community composition and structure in subtropical evergreen-deciduous broadleaved mixed forests
    Qichi Yang, Hehe Zhang, Lihui Wang, Feng Ling, Zhengxiang Wang, Tingting Li, Jinliang Huang
    2021, 43(04):  264-274.  doi:10.1016/j.pld.2021.03.003
    Abstract ( 26 )   HTML ( )   PDF (10460KB) ( 15 )   Save
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    Topography and soil factors are known to play crucial roles in the species composition of plant communities in subtropical evergreen-deciduous broadleaved mixed forests. In this study, we used a systematic quantitative approach to classify plant community types in the subtropical forests of Hubei Province (central China), and then quantified the relative contribution of drivers responsible for variation in species composition and diversity. We classified the subtropical forests in the study area into 12 community types. Of these, species diversity indices of three communities were significantly higher than those of others. In each community type, species richness, abundance, basal area and importance values of evergreen and deciduous species were different. In most community types, deciduous species richness was higher than that of evergreen species. Linear regression analysis showed that the dominant factors that affect species composition in each community type are elevation, slope, aspect, soil nitrogen content, and soil phosphorus content. Furthermore, structural equation modeling analysis showed that the majority of variance in species composition of plant communities can be explained by elevation, aspect, soil water content, litterfall, total nitrogen, and total phosphorus. Thus, the major factors that affect evergreen and deciduous species distribution across the 12 community types in subtropical evergreen-deciduous broadleaved mixed forests include elevation, slope and aspect, soil total nitrogen content, soil total phosphorus content, soil available nitrogen content and soil available phosphorus content.
    Phylogenetic and functional structures of succession in plant communities on mounds of Marmota himalayana in alpine regions on the northeast edge of the Qinghai-Tibet Plateau
    Xinhui Li, Tao Yang, Dandan Wang
    2021, 43(04):  275-280.  doi:10.1016/j.pld.2021.04.005
    Abstract ( 26 )   HTML ( )   PDF (7746KB) ( 12 )   Save
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    Few studies have examined the succession of plant communities in the alpine zone. Studying the succession of plant communities is helpful to understand how species diversity is formed and maintained. In this study, we used species inventories, a molecular phylogeny, and trait data to detect patterns of phylogenetic and functional community structure in successional plant communities growing on the mounds of Himalayan marmots (Marmota himalayana) on the southeast edge of the Qinghai-Tibet Plateau. We found that phylogenetic and functional diversities of plant communities on marmot mounds tended to cluster during the early to medium stages of succession, then trended toward overdispersion from medium to late stages. Alpine species in early and late stages of succession were phylogenetically and functionally overdispersed, suggesting that such communities were assembled mainly through species interactions, especially competition. At the medium and late stages of succession, alpine communities growing on marmot mounds were phylogenetically and functionally clustered, implying that the communities were primarily structured by environmental filtering. During the medium and late stages of succession the phylogenetic and functional structures of plant communities on marmot mounds differed significantly from those on neighboring sites. Our results indicate that environmental filtering and species interactions can change plant community composition at different successional stages. Assembly of plant communities on marmot mounds was promoted by a combination of traits that may provide advantages for survival and adaptation during periods of environmental change.
    Comparative analysis of plastomes in Oxalidaceae: Phylogenetic relationships and potential molecular markers
    Xiaoping Li, Yamei Zhao, Xiongde Tu, Chengru Li, Yating Zhu, Hui Zhong, Zhong-Jian Liu, Shasha Wu, Junwen Zhai
    2021, 43(04):  281-291.  doi:10.1016/j.pld.2021.04.004
    Abstract ( 42 )   HTML ( )   PDF (15623KB) ( 9 )   Save
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    The wood sorrel family, Oxalidaceae, is mainly composed of annual or perennial herbs, a few shrubs, and trees distributed from temperate to tropical zones. Members of Oxalidaceae are of high medicinal, ornamental, and economic value. Despite the rich diversity and value of Oxalidaceae, few molecular markers or plastomes are available for phylogenetic analysis of the family. Here, we reported four new whole plastomes of Oxalidaceae and compared them with plastomes of three species in the family, as well as the plastome of Rourea microphylla in the closely related family Connaraceae. The eight plastomes ranged in length from 150,673 bp (Biophytum sensitivum) to 156,609 bp (R. microphylla). Genome annotations revealed a total of 129-131 genes, including 83-84 protein-coding genes, eight rRNA genes, 37 tRNA genes, and two to three pseudogenes. Comparative analyses showed that the plastomes of these species have minor variations at the gene level. The smaller plastomes of herbs B. sensitivum and three Oxalis species are associated with variations in IR region sizes, intergenic region variation, and gene or intron loss. We identified sequences with high variation that may serve as molecular markers in taxonomic studies of Oxalidaceae. The phylogenetic trees of selected superrosid representatives based on 76 protein-coding genes corroborated the Oxalidaceae position in Oxalidales and supported it as a sister to Connaraceae. Our research also supported the monophyly of the COM (Celastrales, Oxalidales, and Malpighiales) clade.
    Rhododendron kuomeianum (Ericaceae), a new species from northeastern Yunnan (China), based on morphological and genomic data
    Yu-Hang Chang, Gang Yao, Jens Neilsen, De-Tuan Liu, Lu Zhang, Yong-Peng Ma
    2021, 43(04):  292-298.  doi:10.1016/j.pld.2021.04.003
    Abstract ( 43 )   HTML ( )   PDF (6658KB) ( 34 )   Save
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    Rhododendron kuomeianum Y.H. Chang, J. Nielsen & Y.P. Ma, a new species of Rhododendron (Ericaceae) within subsect. Maddenia in sect. Rhododendron from Yiliang County, NE Yunnan, China, is described and illustrated. The new species is similar to R. valentinianum, but it can be easily distinguished by its sparse scales on the abaxial surface of the leaf blade, fewer flowers per inflorescence and white corolla with pale red margins. There are also differences in the widths of calyx lobes, leaf blade shape and indumentum characteristics of the petiole between the new species and Rhododendron linearilobum. We confirmed that R. kuomeianum is a new species closely related to R. valentinianum and R. changii with phylogenomic studies of 10 species within this subsection based on restriction site-associated DNA sequencing (RAD-seq) data. These phylogenomic analyses also clarified additional taxonomic problems in this subsection previously raised by morphological analysis. Our findings make a strong case for using next-generation sequencing to explore phylogenetic relationships and identify new species, especially in plants groups with complicated taxonomic problems.
    Phylogenetic estimation and morphological evolution of Alsineae (Caryophyllaceae) shed new insight into the taxonomic status of the genus Pseudocerastium
    Gang Yao, Bine Xue, Kun Liu, Yuling Li, Jiuxiang Huang, Junwen Zhai
    2021, 43(04):  299-307.  doi:10.1016/j.pld.2020.11.001
    Abstract ( 24 )   HTML ( )   PDF (20927KB) ( 10 )   Save
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    Pseudocerastium is a monotypic genus in Caryophyllaceae endemic to China. The genus has been widely accepted since it was described in 1998, however its phylogenetic position within Caryophyllaceae has never been studied. In the present study, the whole plastid genome and nuclear ribosomal internal transcribed spacer (ITS) sequences of Pseudocerastium stellarioides was obtained through genome skimming, and the phylogenetic position of the species was studied for the first time. Plastid phylogenomic analysis of Caryophyllaceae revealed that Pseudocerastium is clustered within the tribe Alsineae with strong support. Phylogenetic analyses based on an enlarged taxon sampling of Alsineae using five DNA regions (matK, rbcL, rps16 intron, trnL-F and ITS) revealed that P. stellarioides was nested deeply within Cerastium with strong support. Analyses of morphological character evolution suggest that the ancestral states in Alsineae include three styles and a six-lobed capsule at the apex, while both Cerastium and Pseudocerastium have five styles and ten lobes at the apex of the capsule, further supporting their close relationship. The species Pseudocerastium stellarioides is similar to Cerastium wilsonii in morphology, but differs in having villous indumentum on the lower part of the filaments and compressed globose seeds. Therefore, based on the present molecular and morphological evidence, the generic name Pseudocerastium is reduced here as a new synonym of Cerastium and the species P. stellarioides is transferred to Cerastium as C. jiuhuashanense.
    Pollination adaptations of group-by-group stamen movement in a meadow plant with temporal floral closure
    Aysajan Abdusalam, Reyilamu Maimaitituerxun, Halibinuer Hashan, Gulzar Abdukirim
    2021, 43(04):  308-316.  doi:10.1016/j.pld.2021.04.001
    Abstract ( 30 )   HTML ( )   PDF (3458KB) ( 9 )   Save
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    Floral sexual organ (stamen and pistil) movements are selective adaptations that have different functions in male-female reproduction and the evolution of flowering plants. However, the significance of stamen movements in the spatial-temporal function and separation of male and female organs has not been experimentally determined in species exhibiting floral temporal closure. The current study investigated the role of slow stamen (group-by-group) movement in male-female sexual function, and the effect of stamen movement on pollen removal, male-male and male-female interference, and mating patterns of Geranium pratense, a plant with temporal floral closure. This species uses stamen group-by-group movement and therefore anther-stigma spatial-temporal separation. Spatial separation (two whorls of stamen and pistil length) was shown to be stronger than temporal separation. We found that stamen movements to the center of the flower increase pollen removal, and the most common pollinators visited more frequently and for longer durations during the male floral stage than during the female floral stage. Petal movements increased both self-pollen deposition rate and sexual interference in G. pratense. The fruit and seed set of naturally and outcrossed pollinated flowers were more prolific than those of self-pollinated flowers. Group-by-group stamen movement, dehiscence of stamens, pistil movement, and male-female spatial-temporal functional separation of G. pratense before floral temporal closure may prevent male-female and stamen-stamen interference and pollen discounting, and may increase pollen removal and cross-pollination.
    Repellent, larvicidal and adulticidal activities of essential oil from Dai medicinal plant Zingiber cassumunar against Aedes albopictus
    Ming-Xiang Li, Yong-Peng Ma, Hong-Xia Zhang, Hong-Zheng Sun, Hong-Hai Su, Sheng-Ji Pei, Zhi-Zhi Du
    2021, 43(04):  317-323.  doi:10.1016/j.pld.2020.11.008
    Abstract ( 24 )   HTML ( )   PDF (383KB) ( 8 )   Save
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    Zingiber cassumunar is an important plant used in traditional medicine and as a natural mosquito repellent. However, the compounds responsible for the repellent activity of the plant are still unknown. The aim of the study is to identify the components of Z. cassumunar essential oil that show repellent activity against Aedes albopictus. We also evaluated the larvicidal and adulticidal activities of Z. cassumunar essential oil against Ae. albopictus. In-cage mosquito repellent experiments showed that Z. cassumunar essential oil possessed moderate repellent activity with a minimum effective dose (MED) of 0.16 ±0.01 mg/cm2, compared to reference standard N,N-diethyl-3-methylbenzamide (DEET, 0.03 ±0.01 mg/cm2). Bioassay-guided fractionation identified the major active compound of Z. cassumunar essential oil as (-)-terpinen-4-ol (1) (MED:0.19 ±0 mg/cm2). We also found that Z. cassumunar essential oil showed moderate larvicidal activity against first instar larvae of Ae. albopictus with a LC50 (50% lethal concentration) of 44.9 μg/L after 24 h. Fumigation bioassays showed that Z. cassumunar essential oil exhibits moderate adulticidal activity against Ae. albopictus with a LC50 of 5.44%, while (-)-terpinen-4-ol showed significant adulticidal activity with a LC50 of 2.10% after 24 h. This study verifies that the Z. cassumunar essential oil has mosquito repellent activity, and that (-)-terpinen-4-ol is mainly responsible for this activity. Furthermore, this study provides scientific support for the folk usage of Z. cassumunar essential oil as mosquito repellent and indicates that Z. cassumunar essential oil and (-)-terpinen-4-ol can be used as plant-derived repellents and insecticides for mosquito control.
    Cavitation resistance of peduncle, petiole and stem is correlated with bordered pit dimensions in Magnolia grandiflora
    Feng-Ping Zhang, Jiao-Lin Zhang, Timothy J. Brodribb, Hong Hu
    2021, 43(04):  324-330.  doi:10.1016/j.pld.2020.11.007
    Abstract ( 25 )   HTML ( )   PDF (6760KB) ( 4 )   Save
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    Variation in resistance of xylem to embolism among flowers, leaves, and stems strongly influences the survival and reproduction of plants. However, little is known about the vulnerability to xylem embolism under drought stress and their relationships to the anatomical traits of pits among reproductive and vegetative organs. In this study, we investigated the variation in xylem vulnerability to embolism in peduncles, petioles, and stems in a woody plant, Magnolia grandiflora. We analyzed the relationships between water potentials that induced 50% embolism (P50) in peduncles, petioles, and stems and the conduit pit traits hypothesized to influence cavitation resistance. We found that peduncles were more vulnerable to cavitation than petioles and stems, supporting the hypothesis of hydraulic vulnerability segmentation that leaves and stems are prioritized over flowers during drought stress. Moreover, P50 was significantly correlated with variation in the dimensions of inter-vessel pit apertures among peduncles, petioles and stems. These findings highlight that measuring xylem vulnerability to embolism in reproductive organs is essential for understanding the effect of drought on plant reproductive success and mortality under drought stress.
    AtWRKY75 positively regulates age-triggered leaf senescence through gibberellin pathway
    Haiyan Zhang, Liping Zhang, Songguo Wu, Yanli Chen, Diqiu Yu, Ligang Chen
    2021, 43(04):  331-340.  doi:10.1016/j.pld.2020.10.002
    Abstract ( 32 )   HTML ( )   PDF (8186KB) ( 16 )   Save
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    WRKY transcription factors play essential roles during leaf senescence. However, the mechanisms by which they regulate this process remains largely unknown. Here, we identified the transcription factor WRKY75 as a positive regulator during leaf senescence. Mutations of WRKY75 caused a delay in age-triggered leaf senescence, whereas overexpression of WRKY75 markedly accelerated this process. Expression of senescence-associated genes (SAGs) was suppressed in WRKY75 mutants but increased in WRKY75-overexpressing plants. Further analysis demonstrated that WRKY75 directly associates with the promoters of SAG12 and SAG29, to activate their expression. Conversely, GAI and RGL1, two DELLA proteins, can suppress the WRKY75-mediated activation, thereby attenuating SAG expression during leaf senescence. Genetic analyses showed that GAI gain-of-function or RGL1 overexpression can partially rescue the accelerated senescence phenotype caused by WRKY75 overexpression. Furthermore, WRKY75 can positively regulate WRKY45 expression during leaf senescence. Our data thus imply that WRKY75 may positively modulate age-triggered leaf senescence through the gibberellin-mediated signaling pathway.