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Xun Gong - One of the best experts on this subject based on the ideXlab platform.
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genetic characterization of the entire range of cycas panzhihuaensis Cycadaceae
Plant Diversity, 2020Co-Authors: Siyue Xiao, Jian Liu, Xun GongAbstract:Cycas panzhihuaensis L. Zhou & S. Y. Yang (Cycadaceae) is an endangered gymnosperm species endemic to the dry-hot valley of the Jinsha River basin in southwest China. Although the wild C. panzhihuaensis population from Panzhihua Cycad Natural Reserve is well protected and its genetic diversity has been well assessed, the genetic characteristics of populations outside the nature reserve, which face larger risks of extinction, remain unknown. Furthermore, the population genetics and historical dynamics of this endemic and endangered species have not been examined across its entire range. In this study, to analyze the genetic diversity, phylogeographical structure and demographic history of C. panzhihuaensis from all its seven known locations, we sequenced and compared molecular data from chloroplastic DNA (psbA-trnH, psbM-trnD, and trnS-trnG), single-copy nuclear genes (PHYP, AC5, HSP70, and AAT) from 61 individuals, as well as 11 nuclear microsatellite loci (SSR) from 102 individuals. We found relatively high genetic diversity within populations and high genetic differentiation among populations of C. panzhihuaensis, which is consistent with the patterns of other Asian inland cycads. Although no significant phylogeographical structure was detected, we found that small and unprotected populations possess higher genetic diversity and more unique haplotypes, which revises our understanding of diversity within this species and deserves due attention. Analysis of demographic dynamics suggest that human activity might be the key threat to C. panzhihuaensis. Based on the genetic characterization of C. panzhihuaensis, we propose several practical guidelines for the conservation of this species, especially for the populations with small sizes.
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phylogeny of the gymnosperm genus cycas l Cycadaceae as inferred from plastid and nuclear loci based on a large scale sampling evolutionary relationships and taxonomical implications
Molecular Phylogenetics and Evolution, 2018Co-Authors: Jian Liu, Yu-chung Chiang, Anders J Lindstrom, Shouzhou Zhang, Nathalie S Nagalingum, Xun GongAbstract:Abstract The gymnosperm genus Cycas is the sole member of Cycadaceae, and is the largest genus of extant cycads. There are about 115 accepted Cycas species mainly distributed in the paleotropics. Based on morphology, the genus has been divided into six sections and eight subsections, but this taxonomy has not yet been tested in a molecular phylogenetic framework. Although the monophyly of Cycas is broadly accepted, the intrageneric relationships inferred from previous molecular phylogenetic analyses are unclear due to insufficient sampling or uninformative DNA sequence data. In this study, we reconstructed a phylogeny of Cycas using four chloroplast intergenic spacers and seven low-copy nuclear genes and sampling 90% of extant Cycas species. The maximum likelihood and Bayesian inference phylogenies suggest: (1) matrices of either concatenated cpDNA markers or of concatenated nDNA lack sufficient informative sites to resolve the phylogeny alone, however, the phylogeny from the combined cpDNA-nDNA dataset suggests the genus can be roughly divided into 13 clades and six sections that are in agreement with the current classification of the genus; (2) although with partial support, a clade combining sections Panzhihuaenses + Asiorientales is resolved as the earliest diverging branch; (3) section Stangerioides is not monophyletic because the species resolve as a grade; (4) section Indosinenses is not monophyletic as it includes Cycas macrocarpa and C. pranburiensis from section Cycas; (5) section Cycas is the most derived group and its subgroups correspond with geography.
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highly diverse endophytes in roots of cycas bifida Cycadaceae an ancient but endangered gymnosperm
Journal of Microbiology, 2018Co-Authors: Ying Zheng, Tzen Yuh Chiang, Chao Li Huang, Xun GongAbstract:As an ancient seed plant, cycads are one of the few gymnosperms that develop a root symbiosis with cyanobacteria, which has allowed cycads to cope with harsh geologic and climatic conditions during the evolutionary process. However, the endophytic microbes in cycad roots remain poorly identified. In this study, using next-generation sequencing techniques, we investigated the microbial diversity and composition of both the coralloid and regular roots of Cycas bifida (Dyer) K.D. Hill. Highly diverse endophytic communities were observed in both the coralloid and regular roots. Of the associated bacteria, the top five families were the Nostocaceae, Sinobacteraceae, Bradyrhizobiaceae, Bacillaceae, and Hyphomicrobiaceae. The Nectriaceae, Trichocomaceae, and Incertae sedis were the predominant fungal families in all root samples. A significant difference in the endophytic bacterial community was detected between coralloid roots and regular roots, but no difference was observed between the fungal communities in the two root types. Cyanobacteria were more dominant in coralloid roots than in regular roots. The divergence of cycad root structures and the modified physiological processes may have contributed to the abundance of cyanobionts in coralloid roots. Consequently, the colonization of cyanobacteria inhibits the assemblage of other endophytes. Our results contribute to an understanding of the species diversity and composition of the cycad-endophyte microbiome and provide an abbreviated list of potential ecological roles of the core microbes present.
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Genetic structure and demographic history of Cycas chenii (Cycadaceae), an endangered species with extremely small populations
KeAi, 2017Co-Authors: Rui Yang, Xiuyan Feng, Xun GongAbstract:Geological activities and climate oscillations during the Quaternary period profoundly impacted the distribution of species in Southwest China. Some plant species may be harbored in refugia, such as the dry-hot valleys of Southwest China. Cycas chenii X. Gong & W. Zhou, a critically endangered cycad species, which grows under the canopy in subtropical evergreen broad-leaved forests along the upstream drainage area of the Red River, is endemic to this refugium. In this study, 60 individuals of C. chenii collected from six populations were analyzed by sequencing two chloroplast intergenic spacers (cpDNA: psbA-trnH and trnL-trnF) and two nuclear genes (PHYP and RBP-1). Results showed high genetic diversity at the species level, but low within-population genetic diversity and high interpopulation genetic differentiation. A Bayesian phylogenetic tree based on cpDNA showed that five chloroplast haplotypes were clustered into two clades, which corresponds to the division of the western and eastern bank of the Red River. These data indicate a possible role for the Red River as a geographic barrier to gene flow in C. chenii. Based on our findings, we propose appropriate in situ and ex situ conservation strategies for C. chenii
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pollen mediated gene flow promotes low nuclear genetic differentiation among populations of cycas debaoensis Cycadaceae
Tree Genetics & Genomes, 2016Co-Authors: Yiqing Gong, Xun GongAbstract:Cycas debaoensis is a critically endangered cycad species endemic to China. This species is found on two kinds of habitats according to the edaphic differences, sand and karst. A previous chloroplast DNA (cpDNA) study indicated that C. debaoensis had low genetic variation within populations and high genetic differentiation among populations. Because maternally inherited cpDNA does not fully characterize genetic structure of the species, we screened seven low-copy nuclear genes and 17 nuclear microsatellite loci to detect the nuclear genetic diversity, differentiation, and the population structure of C. debaoensis. The nuclear genes revealed higher level of genetic diversity. There were both the same and region-specific haplotypes or alleles between the karst and sand regions. Nuclear gene flow among all the populations was much greater than that of cpDNA, which indicated that pollen-mediated gene flow was much greater than seed-mediated gene flow. This promoted low nuclear genetic differentiation among populations of C. debaoensis. The study suggests that both genetic and anthropogenic disturbances have resulted in the critically endangered status of C. debaoensis.
Masumi Kono - One of the best experts on this subject based on the ideXlab platform.
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Is Cycas revoluta (Cycadaceae) wind- or insect-pollinated?
American journal of botany, 2007Co-Authors: Masumi Kono, Hiroshi TobeAbstract:Among the Cycadales (Cycadaceae and Zamiaceae), the Zamiaceae are known to be insect-pollinated. In contrast, the Cycadaceae are still considered wind-pollinated, although some doubt has been cast on several species, including Cycas revoluta. Using a large population of C. revoluta on Yonaguni Island (Okinawa, Japan), we performed exclusion experiments, documented insects from male and female cones, and analyzed the morphology of the apical part of the ovule to determine the pollination method of this species. Insect exclusion resulted in a notable reduction in seed set, except in a few individuals growing near male cones. The amount of airborne pollen was abundant within a 2-m radius of male cones but decreased markedly beyond this distance. Pollen grains of C. revoluta were found on the body of Carpophilus chalybeus (Nitidulidae, Coleoptera), one of a few species of insects collected from both male cones and female cones far from males. We conclude that C. revoluta relies on both wind (anemophily) and insect pollination (entomophily), although such anemophily is restricted to female trees growing within a 2-m radius of male trees. The nitidulids are not host specific to this cycad and primarily feed on plant tissue but serve as pollinators during pollen release. Cycas revoluta appears to be in an initial mode of animal pollination, as opposed to the host-specific insect pollination observed in most Zamiaceae.
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Estragole (4-allylanisole) is the primary compound in volatiles emitted from the male and female cones of Cycas revoluta.
Journal of plant research, 2006Co-Authors: Hiroshi Azuma, Masumi KonoAbstract:The genus Cycas (Cycadaceae; gymnosperm) have circumstantially been considered to be wind-pollinated. The cones of Cycas revoluta Thunb., however, emit a strong unpleasant odor. The chemical profiles of floral scents often correlate with various pollination modes (pollinators). We collected and analyzed the volatiles emitted from male and female cones of C. revoluta native to Iriomote and Yonaguni Islands, Japan. The analyses indicated that estragole (4-allylanisole) dominated in the volatiles (67.0–92.7%), with small amounts of other benzenoids, e.g., anethole, methyl salicylate, methyl eugenol, and ethyl benzoate. Several fatty acid esters were also detected in the samples from Iriomote Island. The function of estragole in the reproductive biology of C. revoluta is discussed.
Hiroshi Tobe - One of the best experts on this subject based on the ideXlab platform.
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Is Cycas revoluta (Cycadaceae) wind- or insect-pollinated?
American journal of botany, 2007Co-Authors: Masumi Kono, Hiroshi TobeAbstract:Among the Cycadales (Cycadaceae and Zamiaceae), the Zamiaceae are known to be insect-pollinated. In contrast, the Cycadaceae are still considered wind-pollinated, although some doubt has been cast on several species, including Cycas revoluta. Using a large population of C. revoluta on Yonaguni Island (Okinawa, Japan), we performed exclusion experiments, documented insects from male and female cones, and analyzed the morphology of the apical part of the ovule to determine the pollination method of this species. Insect exclusion resulted in a notable reduction in seed set, except in a few individuals growing near male cones. The amount of airborne pollen was abundant within a 2-m radius of male cones but decreased markedly beyond this distance. Pollen grains of C. revoluta were found on the body of Carpophilus chalybeus (Nitidulidae, Coleoptera), one of a few species of insects collected from both male cones and female cones far from males. We conclude that C. revoluta relies on both wind (anemophily) and insect pollination (entomophily), although such anemophily is restricted to female trees growing within a 2-m radius of male trees. The nitidulids are not host specific to this cycad and primarily feed on plant tissue but serve as pollinators during pollen release. Cycas revoluta appears to be in an initial mode of animal pollination, as opposed to the host-specific insect pollination observed in most Zamiaceae.
Ken D Hill - One of the best experts on this subject based on the ideXlab platform.
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the genus cycas Cycadaceae in vietnam
Botanical Review, 2004Co-Authors: Ken D Hill, Hiep T Nguyen, Phan Ke LocAbstract:The genusCycas is revised for Vietnam. Twenty-four species are enumerated, nine of them described as new (C.aculeata, C. brachycantha, C. collina, C. condaoensis, C. pachypoda,C. dolichophylla, C. fugax, C. hoabinhensis, andC. tropophylla). Descriptions of two Chinese species known to occur close to the China-Vietnam border are also provided. A new combination is made forC. bifida (formerlyC. rumphii vanbifida). The species are placed within an infrageneric classification previously outlined. Distribution of all taxa is mapped, and a key to species is provided. Illustrations are provided for new and poorly known taxa where adequate material has been available. Previous reports ofC. circinalis andC. rumphii from Vietnam are discussed. Lectotypes are designated forC. balansae, C. chevalieri, andC. elongata, and a neotype is designated forC. pectinata.
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new species and a new record of cycas Cycadaceae from thailand
Brittonia, 2002Co-Authors: A. J. Lindstrom, Ken D HillAbstract:Abstract New species and a new record of Cycas (Cycadaceae) from Thailand. Brittonia 54:298–304. 2002.—Two new Cycas species from Thailand are here described. C. petraea and C. elephantipes. A noteworthy extension of the range of C. macrocarpa into southeastern Thailand is recorded. New taxa are illustrated, distributions of the new taxa are mapped, and a key to the species of Cycas in Thailand is provided.
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the genus cycas Cycadaceae in thailand
Brittonia, 1999Co-Authors: Ken D Hill, S L YangAbstract:The genusCycas is revised for Thailand. Ten species are enumerated, five of them described as new (C. chamaoensis, C. clivicola, C. litoralis, C. nongnoochiae, C. tansachana), with one new subspecies (C. clivicola subsp.lutea). The species are placed within an infrageneric classification previously outlined. Distributions of the taxa are mapped, eight of the species are illustrated, and a key to species is provided. Previous records ofC. circinalis andC. rumphii from Thailand (here not regarded as indigenous in Thailand) are discussed.
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cycas pranburiensis Cycadaceae a new cycad from thailand
Brittonia, 1999Co-Authors: S L Yang, Ken D Hill, W Tang, P VatcharakornAbstract:A new species of cycad allied to theC. circinalis group,Cycas pranburiensis, is described from the southeast karst area of Thailand near Pranburi, Prachuap Khiri Khan province. It is distinguished by its short leaves with broad, coriaceous leaflets and mostly unarmed petioles, and the extended, gently curved sterile apices of the microsporophylls. The cone beetle fauna of the new species, believed to be involved in pollination, is distinct from that of other southeast Asian species ofCycas.
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cycas lindstromii Cycadaceae a new species from southern vietnam
Novon, 1997Co-Authors: Silin Yang, Ken D Hill, Nguyen Tien HiepAbstract:A new species, Cycas lindstromii, is described from Binh Thuan in southern Vietnam. It is allied to C. siamensis, but distinguished by its subterranean trunk, elongated megasporophyll, and shorter, keeled leaf. The new species is illustrated, and its distribution, ecology, and conservation status are discussed. The senior author studied wild cycad populations in Vietnam during the periods 16 October to 2 December 1994 and 18 February to 1 March 1995 (Yang, 1996). One discovery was a distinct species occurring in arid coastal areas in southern Vietnam, where it is under threat of extinction from land clearing and collection for sale as a garden plant. Systematic studies by the authors have shown that this taxon is as yet undescribed. It is here described as a new species in order to draw attention to its conservation requirements, and to provide a valid name for regulatory usage. Cycas lindstromii S.-L. Yang, K. D. Hill & N. T. Hiep, sp. nov. TYPE: Vietnam. Binh Thuan, Tuy Phong, Xa Chi Cong, near Doc Bao Da, 11013'N, 108038'E, alt. 25 m, 11 Nov. 1994, S.-L. Yang 557 (holotype, FTG; isotypes, NSW, S). Figure 1. Species similis C. siamensis Miquel, sed trunco subterraneo, foliis brevibus, megasporophylla lamina terminali elongata angusta differt. Stem subterranean, often branched at apex, to 15-23 cm long, 13-25 cm diam., base swollen, surface white-gray, smooth. Leaves 2-12 , deep green adaxially, yellowish green abaxially, highly glossy, 50-78 cm long, strongly keeled (opposite pinnae inserted at 40-600 on rachis), with 18-60 pinnae. Petiole 6.0-15 cm long, glabrous, spinescent for 50-100% of length. Basal pinnae not gradually reducing to spines, occasionally forked. Median pinnae simple, glabrous, 100-130 x 7-10 mm, crowded and overlapping, 7-12 mm apart on rachis; section flat, margins flat, apices acute. Tomentum on cataphylls brown. Cataphylls narrowly triangular, soft, 20-50 x 3-7 mm at base. Microsporangiate cones fusiform, coriaceous, yellow, 1620 cm long, 4-5 cm diam., peduncle length 3.0 cm. Microsporophyll lamina 10-16 X 11-15 mm, apical spine sharply upturned, 1-8 mm long. Megasporangiate cones 12 cm high, 7-9 cm diam.; megasporophylls 8-12 cm long, lamina ovate, 5.5-10 X 1.8-3.0 cm, deeply pectinate, with 6-13 pairs of soft lateral spines 8-12 x 4-5 mm; apical spine distinct from lateral spines, 30 x 4-5 mm at base. Ovules 2, glabrous. Seeds ovoid, 31-35 X 20-30 mm; sarcotesta reddish orange, not pruinose, 3-7 mm thick; fibrous layer present; spongy layer absent. Cycas lindstromii is nearest to C. siamensis (Miquel, 1863) but differs in its subterranean and frequently branched trunk, its shorter, keeled leaves with basal pinnae not progressively reducing to spines, its more slender male cone, and its relatively narrower and more elongated megasporophyll lamina. The two are placed in Cycas sect. Indosinenses. This section is defined by the pectinate megasporophyll lamina, the coriaceous male cone, and the glabrous ovules. Within the section, these two species make up subsection Indosinenses, defined by the small, narrow male cones and the short NovoN 7: 213-215. 1997. This content downloaded from 157.55.39.120 on Mon, 05 Sep 2016 06:04:20 UTC All use subject to http://about.jstor.org/terms
Shaotian Chen - One of the best experts on this subject based on the ideXlab platform.
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development of seven novel est ssr markers from cycas panzhihuaensis Cycadaceae
American Journal of Botany, 2010Co-Authors: Fangming Zhang, Ying Yang, Yanhong Zhai, Shaotian ChenAbstract:Premise of the study: Cycas panzhihuaensis L. Zhou & S. Y. Yang is a vulnerable gymnosperm endemic to China, where its range represents the northernmost occupation of Cycas L. We developed EST-derived SSR markers to investigate its genetic diversity and population structure.
