共查询到20条相似文献,搜索用时 171 毫秒
1.
ZHANGQuan Sodmergen HUYu-Shi LINJin-Xing 《Acta Botanica Sinica》2004,46(9):1075-1082
The ontogeny and vascular systems of female cones of the Fokienia, Oupressus, Ohamaecyparis and Juniperus were investigated in detail using scanning electron microscopy (SEM) and conventional light microscopy. In the species examined, in the axils of the bracts, the first recognizable structure was a broad meristematic swelling, from which ovules developed. No ovuliferous scales developed during the ontogeny of the female cones. The number of ovules and ovule developing sequence displayed considerable variation in different species. However, development of the bracts was similar in all of the investigated species. Following pollination, the foliage-like bracts became peltate bract scales due to intercalary expansion, and global cones formed. In addition, the vascular system in the bract scales became intricate, and inverted vascular bundles emerged in the adaxial of the mature bracts. Based on these observations, a morphological interpretation and possible evolutionary trend of the Cupressaceae female reproductive structures was discussed. 相似文献
2.
The taxonomic position of the monotypic conifer Pilgerodendron uviferum,an endemic species in southern South America,has been disputed on the basis of phylogenetic analysis using molecular data. These results suggest that P. uviferum is a species of Libocedrus. Phylogenetic analysis using morphological data appears to uphold its separate status. Characters of leaf cuticles are investigated and compared between four related genera including Pilgerodendron and further dis-tinctions between these are reported. The merits of these conflicting data sets for the taxonomy of the genus Libocedrus s. l. are discussed. It is concluded that the evidence for a merger of Pilgeroden-dron with Libocedrus is weak and that both morphology and biogeography support the separation of the two genera. 相似文献
3.
Jian-HuaLI Qiao-PingXIANG 《植物学报(英文版)》2005,47(6):651-659
In order to develop better insights into biogeographic patterns of eastern Asian and North American disjunct plant genera, sequences of nuclear ribosomal DNA internal transcribed spacer (nr DNAITS) region were used to estimate interspecific relationships of Thuja L. (Cupressaceae) and infer its biogeography based on the phylogeny. According to the phylogenetic analysis, two clades were recognized. The first clade included Thuja plicata D. Don (western North America) and T. koraiensis Nakai (northeastern Asia), and the second one contained T. occidentalis (Gord.) Cart. (Japan). The ancestral area of Thuja was inferred to be eastern Asia, and two dispersal events were responsible for the modern distribution of Thuja in North America. Both the North Atlantic land bridge and Bering land bridge were possible routes for the migration of ancestral populations to North America. 相似文献
4.
Biology Bulletin - The genus Allocricetulus at presently includes three taxa. The taxonomic status of two of them, A. eversmanni (Eversmann’s hamster) and A. curtatus (Mongolian... 相似文献
5.
The problem of whether the hominid fossil sample of habiline specimens is comprised of more than one species has received much attention in paleoanthropology. The core of this debate has significant implications about when and how variation must be explained by taxonomy. In this paper, we examine the problem of whether the observed variation in habiline sample must be interpreted to reflect species differences. We test the null hypothesis of no difference by examining the degree of variability in habiline sample in comparison with other single-species early hominid fossil samples from Sterkfontein and Swartkrans (Sterkfontein is earlier than the habiline sample; Swartkrans may be within the habiline time span). We use the standard error test for this analysis, a sampling statistic based on the standard error of the slope of regressions between pairs of specimens that relates all of the homologous measurements each pair shares. We show that the null hypothesis for the habiline sample cannot be rejected. The similarities of specimen pairs within the habiline sample are not more than those observed between the specimens in the two australopithecine samples we analyzed. 相似文献
6.
Ancestral Area Analysis of the Genus Caragara (Leguminosae) 总被引:1,自引:0,他引:1
ZHANGMing-Li 《Acta Botanica Sinica》2004,46(3):253-258
Caragana has a temperate Asian distribution. Based on the phylogeny and 13 distributionalareas of this genus, its ancestral area was studied via the ancestral area analysis suggested by Bremer(1992), Ronquist (1994) and Hausdorf (1997). The results indicate that three areas, Far East-NortheastChina, Altai-Sayan and North China-Qinling Mountains (Mts) are likely the ancestral areas. Linking to theviewpoints of the Holarctic origin for north temperate flora, Far East-Northeast China seems more likely tobe the ancestral area. According to the three ancestral areas isolated geographically and the analysis inthe present study, as well as former biogeographical analysis of this genus, it is suggested that Caraganaspeciation is mainly in the mode of vicariance rather than dispersal, and dispersed is often in shortdistance. 相似文献
7.
8.
ThierryDeuve博士(法国国家自然历史博物馆,巴黎)撰写的IllustratedCatalogueoftheGenusCarabusoftheWorld (Coleoptera:Carabidae)于2004年由Pensoft.Sofia Moscow出版。 该书系统地总结了鞘翅目步甲科Carabidae步甲属Carabus昆虫系统学方面的研究成果,共461页,24个图版。其内容分 3个部分:1)形态学(Morphology),分别对步甲属昆虫成虫和幼虫的形态特征进行了描述;2)系统学(Systematics),主要 讨论步甲属昆虫系统发育和分类研究现状和存在的问题,对近年步甲属分子系统学的研究进展及其意义重点进行了评述;3) 名录(Catalogue),根据作… 相似文献
9.
Árni Einarsson Gerdur Stefánsdóttir Helgi Jóhannesson Jón S. Ólafsson Gísli Már Gíslason Isamu Wakana Gudni Gudbergsson Arnthor Gardarsson 《Aquatic Ecology》2004,38(2):317-348
Ecological features of Lake Myvatn and the outflowing River Laxá show a wide range of spatial and temporal variations. The physical division of the lake into three main basins and the variation in chemical composition and temperature of the artesian springs feeding this shallow productive lake have large spatial effects. Variation in groundwater characteristics depends on percolation time and proximity to geothermal sources. Variation in precipitation is evened out by the porous volcanic soil and bedrock and the spring-water discharge is therefore very stable. A pulse of volcanic activity in 1975–1984 (the Krafla Fires) heated the groundwater entering the North Basin of the lake and changed its chemistry. Although much reduced, these effects have not disappeared yet, but overall the impact of the volcanic activity on the biota seemed minimal. Recycling of nutrients through internal loading is important and occurs on various time scales. In winter, when the lake is ice-covered, the topmost 5-cm layer of sediment pore water has a hundredfold concentration of nutrients relative to the overlying lake water. The nutrients are released during the ice-free period by sediment resuspension, diffusion, bioturbation and recycling. In spring, resuspension events sometimes lead to spikes in dissolved phosphorus and nitrogen, but there is little evidence of any major desorption of nutrients from suspended particles during such events later in the summer. In contrast to the stable groundwater, the biota show more or less regular fluctuations with no straightforward correlation with external signals. The most prominent fluctuations, those of the chironomid Tanytarsus gracilentus seem to be driven by interactions between the species and its sediment resources. Fluctuations in other invertebrates could be a consequence of the Tanytarsus cycles due to the large impact this species has on the benthic environment of this detritus-driven ecosystem. Temporal variation in epibenthic chironomids and Cladocera translates into variable production of vertebrate predators (Arctic charr, Salvelinus alpinus, and ducks), body condition and mortality of fish and sometimes into return rates of migrating adult ducks. The waterfowl show large temporal variation on a centennial scale, e.g., the invasion of the tufted duck (Aythya fuligula) which arrived by the end of the 19th century and has by now outnumbered other species. Fluctuations of Cyanobacteria (Anabaena) and the fish Gasterosteus aculeatus (three-spined stickleback) harmonize with the cycles in the benthic community. Palaeolimnological studies indicate that primary production in the South Basin became increasingly benthic as the lake depth was reduced by sedimentation (around 2 mm year–1). Other trends include a decrease in Tanytarsus and Daphnia and an exponential increase in green algae (Cladophorales, Pediastrum) and associated organisms. 相似文献
10.
Anna KUPARINEN Juha MERILA 《动物学报(英文版)》2009,55(5):342-349
The timing of river entry in the Atlantic salmon is known to depend on genetic, demographic and environmental factors, but little is known about the relative magnitude of among population and among year variation and covariation in this respect in natural state Atlantic salmon rives. To investigate this, variability in the timing of river entry in three historical Finnish Atlantic salmon populations were analyzed using salmon trap data collected during 1870- 1902. The analyses reveled that 1 ) the timing of river entry differed substantially and consistently among the rivers, and that 2) variation among the rivers was much larger than variation among years. Annual variations were not explained by regional environmental conditions, whereas in one river the timing of the local flood peak was a significant predictor of the timing of river entry. Differences in the timing of salmon entry to geographically closely situated rivers suggests that a regionally fixed opening date for coastal fisheries might not be the best management strategy as it may lead to uneven exploitation of salmon populations from different rivers [ Current Zoology 55 (5) : 342 - 349, 2009] . 相似文献
11.
Rehfeldt G 《American journal of botany》1997,84(2):190-200
Seedling populations of seven Cupressus taxa were compared in common gardens to assess relationships among taxa and to elucidate the genetic structure of three taxa with different distributions and demographics. Discriminant analyses of 15 quantitative traits separated C. sargentii and C. forbesii from taxa within the C. arizonica complex (C. arizonica, C. glabra, C. stephensonii, C. nevadensis, and C. montana); aligned a population of C. arizonica from Sierra de Arteaga, Mexico, with families of the same taxon from southwestern United States; and described a close relationship between C. nevadensis and C. glabra. but nevertheless separated taxa within the C. arizonica complex. Analyses of wind-pollinated progenies of single trees showed the narrow endemic, C. glabra, to have a greater degree of population differentiation than the more broadly dispersed C. arizonica. In addition, genetic variances within the numerically small populations of C. arizonica were about the same as in the much larger populations of C. glabra. The results also suggested that genetic variability in C. stephensonii, a taxon occurring in a single population, may occur primarily among inbred lines. While the genetic structures of C. arizonica and C. glabra have counterparts among broadly dispersed conifers, that of C. stephensonii appears to be unique. Together, the results support the view that genetic structure primarily reflects the uncertain, chance events that are interspersed throughout evolutionary history. 相似文献
12.
重新界定了栒子属(Cotoneaster)高山组(Sect.Alpigeni Hurusawa)黄杨叶系(Series BuxifoliiKlotz)的范围,仅含4种植物,即C. buxifolius Wall. ex Lindl.,C.delavayanus Klotz,C. insolitus Klotz和C. poluninii Klotz。将原作者建立该系时包含的5种,即C. argenteus Klotz; C. brevirameus Rehd.& Wils.; C. hodjingensis Klotz; C. lijiangensis Klotz; C. rockii Klotz,被原作者置另一系的C. marginatus Lindl. ex Schlecht.以及被俞德浚教授等误认为红花栒子小叶变种C. rubens var. miniatus Yu,一共7个名称归并为黄杨叶栒子(C. buxifolius Lindl.)的同物异名;又把C.buxifolius f. vellaea Franch.和C. astrophores J. Fryer et E.C. Nelson归并为绒毛细叶栒子C. poluninii Klotz同一种。经修订后的黄杨叶系在栒子属高山组中以普遍直立的习性,叶下表面、萼片和萼筒密被绒毛和常具2个小核等特征组成相对自然的一群。 相似文献
13.
通过对中国鸡头薯属大量标本的比较研究,作者认为种Eriosemahimalensis不能成立,应将其降为Eriosemachinensis的异名。本文还绘制了鸡头薯块根的形态变异图,作为进行分类学处理的重要依据之一。 相似文献
14.
松科冷杉属植物的化石历史和现代分布 总被引:2,自引:0,他引:2
冷杉是北半球阴暗针叶林的优势种和建群种,现全世界共有52种1亚种12变种,在北半球形成南欧、北美和东亚三个分布中心,这三个地区也是冷杉属化石最丰富的地区。在垂直分布上,冷杉集中分布于1000~2000m(15种)和2500~4000m(13种)两个海拔地段。在中国,冷杉植物呈南北间断分布,集中分布在横断山地区。冷杉属的特有现象和孑遗分布现象都十分突出,有7个种呈孑遗分布。根据冷杉属的地史分布和现代分布的研究并结合最新的系统演化资料,本文推测冷杉属于白垩世中期起源于北半球的中高纬度地区,始新世以后,随着全球气候的变冷,逐步向南迁移,由于喜马拉雅山脉、阿尔卑斯山、落基山脉抬升及东亚季风气候的出现以及第四纪冰期的影响而形成了现代间断的分布格局。冷杉与银杉、金钱松等其它松科植物的形成模式十分相似。 相似文献
15.
柏科4个属(Fokienia、Cupressus、Chamaecyparis和Juniperus)植物雌球果的发育(英文) 总被引:1,自引:0,他引:1
通过扫描电镜和常规石蜡切片技术,观察了柏科4个属(Fokienia、Cupressus、Chamaecyparis和Juniperus)植物雌球果中胚珠的发育及苞片的结构变化。在所有研究的种类中,可育苞片腋部最先观察到的结构是一扁平的突起,并在其上分化出发育为胚珠的胚珠原基。在雌球果的发育过程中,未观察到独立的珠鳞发育。不同的种中,胚珠的数量和发育顺序有所不同,但苞片的发育是相似的。传粉前,苞片的结构与叶相似。传粉后,由于剧烈的居间生长,苞片发育为盾形,形成球形的球果。另外,在发育后期,苞片内维管系统变得复杂,并且在近轴面有反向的维管束发育。我们还对柏科植物雌球果的形态学特性及其可能的演化趋势进行了讨论。 相似文献
16.
小鲵科为亚洲特有的有尾两栖动物,是现生有尾目10科中第三大科.中国是小鲵科动物属、种分布的主要区域,且研究其分类历史较久,学者较多,故导致学术观点差异较大.本文对中国小鲵科分类地位发生变更的部分属(巴鲵属Liua、拟小鲵属Pseudohynobius、肥鲵属Pachyhynobius)、种(秦巴巴鲵L. tsinpaensis、满洲小鲵Hynobius mantchuricus、豫南小鲵H. yunanicus、弱唇褶山溪鲵Batrachuperus cochranae和太白山溪鲵B. taibaiensis)的变更历史进行回顾,旨在为小鲵科动物的分类提供一个清晰的背景知识. 相似文献
17.
Gilda Nardi Antonio Canziani Palmira Striani Nicola Santini Carla Coccia Laura Seghetti Rita Kranic 《Aerobiologia》1996,12(4):269-271
The aim of this work is to study the incidence of pollinosis in the Health District of Ascoli Piceno, Central Italy (U.S.L.24),
this being an underestimated pathology from the clinical point of view and also as a result of the recent introduction of
this taxa in the National Aeroallergen Network. Since 1990, 5055 patients of both sexes with respiratory symptomatology of
suspected IgE mediated aetiology have been examined in our Centre with the Skin Prick Test (SPT) using allergen panels including
Cypress; 171 (3.38%) patients were found to be positive to this allergen. These results show that the subjects with symptoms
in the period January–March in most cases have a sensitization toCupressus pollen and new studies will evaluate the possibility of specific immunotherapy. 相似文献
18.
拟单性木兰属(木兰科)植物的分类学修订 总被引:2,自引:0,他引:2
根据标本研究和野外调查,对木兰科(Magnoliaceae)的拟单性木兰属(Parakmeria Hu &; Cheng)进行了分类学修订。回顾了此属的分类学简史,阐述了保留拟单性木兰属的理由,将Magnolia Linn. subgenus Gynopodium Figlar &; Noot. section Gynopodium 作为拟单性木兰属的新异名,将Magnolia yunnanensis (Hu) Noot. 和M. nitida W. W. Smith var. robusta B. L. Chen &; Noot.作为云南拟单性木兰(Parakmeria yunnanensis Hu)的新异名,将Magnolia omeiensis (Cheng) Dandy、M. lotungensis Chun &; C. H. Tsoong、M. nitida W. W. Smith var. lotungensis (Chun &; C. H. Tsoong) B. L. Chen &; Noot. 和Parakmeria lotungensis (Chun &; C. H. Tsoong) Law作为峨眉拟单性木兰(Parakmeria omeiensis Cheng)的新异名,确认拟单性木兰属含4种植物,列出了分种检索表,描述了各种的地理分布和生长环境。 相似文献
19.
Life History Evolution in the Genus Trillium 总被引:1,自引:0,他引:1
20.
R. Lücking 《Plant biology (Stuttgart, Germany)》1996,109(3):248-260
An analysis of character variation in species of the Porina rufula aggregate, i.e. P. rufula (Kremp.) Vain., P. limbulata (Kremp.) Vain., P. rubentior (Stirt.) Müll. Arg., and P. pseudofulvella Sérus., showed that the hitherto applied concepts of species delimitation - based on perithecial size and colour - are not appropriate and should be replaced by a concept which primarily regards perithecial colour and shape as specific characters. Revision of type specimens proved the identity of P. rufula and P. pseudofulvella, whereas P. limbulata sensu Santesson had to be split into P. limbulata s. str. and P. leptospermoides Müll. Arg. Evolutionary tendencies are seen in reduction of thallus morphology and perithecial pigments as an adaptation to shady habitats, indicating P. leptospermoides as a more primitive and P. rufula as a more advanced taxon. Judging from species distribution, the phylogenetic origin of the P. rufula aggregate might be in the Neotropics. 相似文献