披碱草属及其近源属植物种子胚乳细胞多样性研究

披碱草属不仅是小麦、大麦等作物的重要基因库,也是优良牧草的重要组成部分。胚乳是麦类作物种子的重要组成部分,其重量占籽粒重量在90%以上。胚乳特性是一个相对稳定的遗传性状,可以将胚乳特性作为植物分类和系统关系的一个指标。胚乳细胞特征作为植物的一类微形态特征,在麦类植物系统分类与进化研究中具有一定的价值。该研究对小麦族的6个披碱草属(Elymus)物种、2个拟鹅观草属(Pseudoroegneria)物种、1个大麦属(Hordeum)物种和2个冰草属(Agropyron)物种,共4属11份材料的胚乳细胞特征进行解剖观察并测量相关指标。结果表明:(1)不同属、种的植物种子胚乳细胞之间存在丰富的多样性,属间差异大于属内种间差异;(2)同样具有P染色体组的Agropyron cristatum和A.mongolicum与同样具有St染色体组的Pseudoroegneria libanotica和P.spicata各自在细胞形状和大小上的差异很小;(3)不同物种的胚乳细胞在大小、形状和数量上均表现出差异,但不能很好地反映属以及基因组间的差异,研究结果为揭示披碱草属植物的系统关系提供了胚乳细胞方面的证据,同时也为利用该属植物改良麦类作物品质积累资料。     

赖草属种子胚乳细胞多样性研究

对赖草属21个物种的胚乳细胞特征进行了解剖观察,发现赖草属植物种子胚乳细胞存在丰富的多样性,不同物种的胚乳细胞在大小、形状和数量上均表现出明显的差异,其胚乳细胞的特征具有类群鉴分的价值。属于较原始的sect．Leymus Hochst．组的沙生赖草、大赖草和滨麦具有较大而多的胚乳细胞,属于较进化的sect. Anisopyrum(Griseb．)Tzvel．组的多枝赖草和灰赖草具有较小而少的胚乳细胞。     

青海鹅观草属的叶片表皮微形态特征及其分类意义的探讨

通过青海鹅观草属叶片表皮的解剖观察,结合外部形态,表明了该属植物在小麦族中共族分属的合理性,同时对青海地区属下类群重新进行了确认,共划分2组16种,即拟技碱草组,包括6种;弯穗草组,包括10种．过去处理的种短柄鹅观草和多秆鹅观革分别作为短颖鹅观草和缘毛鹅观草的变种。此外,类群间的演化水平和属的地理起源也作了初步探讨。     

鹅观草属部分种的叶表皮微形态特征及其分类学意义

在过去叶表皮实验的基础上,本从鹅观草属不同组、系中新增解剖了１６个有代表性的种。根据这些种叶片反映的表皮微形态特征,进一步证实了鹅观草属共族分属以及属下类群划分的正确性,揭示了属中各主要类群的演化水平和系统发育关系。研究结果最后表明：鹅观草属的半颖组最原始,在系统发育中它可能既派生了较进化的小颖组和大颖组,又派生了最进化的长颖组;在大颖组中,齿草系较原始,纤毛草系较进化,宽叶草系最进化,纤毛草系     

鹅观草属部分种的叶表皮微形态特征及其分类学意义

在过去叶表皮实验的基础上 ,本文从鹅观草属不同组、系中新增解剖了 1 6个有代表性的种。根据这些种叶片反映的表皮微形态特征 ,进一步证实了鹅观草属共族分属以及属下类群划分的正确性 ,揭示了属中各主要类群的演化水平和系统发育关系。研究结果最后表明 :鹅观草属的半颖组最原始 ,在系统发育中它可能既派生了较进化的小颖组和大颖组 ,又派生了最进化的长颖组 ;在大颖组中 ,齿草系较原始 ,纤毛草系较进化 ,宽叶草系最进化 ,纤毛草系和宽叶草系可能相继起生于齿草系。并且 ,鹅观草属的这种进化关系同过去细胞学和形态学提供的证据是基本一致的。     

鹅观草属的地理分布

鹅观草属是禾本科小麦族中的最大的属,现知全世界有4组,20系,126种,分布于北半球的温带和寒带,中国有4组,18系,79种,主要分布于西北,西南,华北和东北,是鹅观草属植物种类最为集中的区域,尤其高原东北部的唐古特地区又是我国鹅观草属分布相对密集之地,有3组,12系,30种,而且其间不同等级,不同演化水平的类群均有分布,该地可能就是该属的现代分布中心,同时,唐古特地区多汇聚有鹅观草属不同等级的原始类群和与原始类群有很缘的短柄草属植物,其中最原始的大柄鹅观草特产于该区,而该区缺乏的是高级的大颖组类群,故推测唐古特地区可能又是该属的起源地,起源时间大约在青藏高原明显增高,气候转凉的晚第三纪初的中新世,鹅观草属起源后,在中国境内地质活动比较剧烈的地区得到了进一步的发展和分化,但只有少数适应性较强的类群大概以3条路径扩展到国外,并向东到在北美的巴芬岛,向西延伸到大西洋滨岸,向北进入寒冻的北极地区。     

鹅观草属五个类群的核型与进化

报道了鹅观草属５个类群的核型,即长芒鹅观草,核型２ｎ＝４ｘ＝２８＝２２ｍ＋６ｓｍ（２ＳＡＴ）;短颖鹅观草,核型２ｎ＝４ｘ＝２８＝２０ｍ（２ＳＡＴ）＋８ｓｍ（２ＳＡＴ）;短柄鹅观草,核型２ｎ＝４ｘ＝２８＝２２ｍ（２ＳＡＴ）＋６ｓｍ;纤毛鹅观草,核型２ｎ＝４ｘ＝２８＝２０ｍ＋８ｓｍ（４ＳＡＴ）;毛盘鹅观草,核型２ｎ＝４ｘ＝２８＝１８ｍ＋６ｓｍ（４ＳＡＴ）＋４ｓｔ。同时,通过核型重要性状的递变分析,揭示了鹅观草属５个类群的相对进化程度以及宏观分类中４个组的系统发育关系,表明鹅观草属的半颖组在系统发育中可能既派生了颖体短小的小颖组,又派生了颖体长大的大颖组和长颖组。     

根据外部形态特征试论鹅观草属的亲缘演化关系

鹅观草属的一些性状是有演化意义的,其中外部形态上小穗柄、颖、芒的演趋势不仅和为判断属下类群演化的依据,而且可以作为推证属间类群渊源的下。     

伞形科藁本属20种植物的果实特征及其分类学意义

采用扫描电镜方法对中国藁本属20种及山芎属1种植物的果实表面微形态进行首次研究,并对其中15种进行果实解剖特征观察。结果表明:藁本属植物果实微形态在外果皮表面突起度、细胞轮廓、表面纹饰和表皮分泌物上表现出丰富的多样性;在果实解剖特征上,果棱形状、油管数目、胚乳形状等种间差异明显且稳定,而种内居群间无变异,可作为藁本属种间鉴定及种间关系探讨的重要参考性状。结合前人对伞形科其他类群果实微形态与解剖结构特征的研究及近年来分子系统学的证据,得出如下结论:(1)藁本属不是一个自然类群;(2)支持拟藁本属归入藁本属;(3)对藁本属部分种的系统位置和种间亲缘关系进行了讨论。     

宁夏枸杞的胚胎发生和胚乳发育

宁夏枸杞的胚胎发生属茄型,由顶细胞参与胚体的形成,基细胞仅形成六细胞胚柄。胚乳发育为细胞型,但也观察到少数核型胚乳的现象。初步探讨了核型胚乳与细胞型胚乳的关系。     

Phylogenetic indices for measuring the diet breadths of phytophagous insects

Prevailing methods of measuring diet breadth of phytophagous insects are not consistent between studies and generally rely on counts of a variety of higher plant taxa (e.g. genera, families, orders). Results derived from them can be inconsistent if different taxonomic levels are used between studies. In any case, such indices do not include information from the whole branching structure of the host plant phylogeny, and do not address the fact that higher taxa are not necessarily phylogenetically equivalent. Here we present novel phylogeny-based methods which address these shortcomings. Although a previously proposed index (the Phylogenetic Diversity index) may be employed, it cannot be used to measure diets of strictly monophagous insects (i.e. those which utilise a single host species). We therefore introduce a modification of this index (the Root Phylogenetic Diversity index) which may be applied to all diets. In addition, we propose a Clade Dispersion index as a branch-length-independent measure of the degree to which hosts are scattered across the host phylogeny. We describe how these indices could be employed in studies of insect diet breadth and discuss potential problems which may be encountered in their use. Received: 16 November 1998 / Accepted: 10 February 1999     

Stability in abundance and niche breadth of gamasid mites across environmental conditions, parasite identity and host pools

There is substantial variability among populations of the same species in basic features such as abundance or niche breadth, and it is unclear to what extent these are true species traits as opposed to the product of local environmental factors. In parasites, abundance and niche breadth, i.e. host specificity, show repeatability among different populations of the same species, but may also be influenced by external forces, depending on the parasite taxa studied. We tested whether the abundance and host specificity of gamasid mites parasitic on small mammals from 26 different geographic regions of the Palaearctic, are species-specific or instead determined by host identity and/or parameters of the biotic and abiotic environment. Values of abundance and host specificity (measured as the number of host species used) were significantly more similar among populations of the same mite species than among different mite species; despite also showing consistency within particular host species or regions independently of mite species identity, both abundance and the number of host species used appear to be true mite species traits. In contrast, the taxonomic distinctness of host species used by a mite showed little repeatability among populations of the same mite species, and appears mostly determined by the local pool of available host species. Within given mite species, all three variables (abundance, number of host species used, and their taxonomic distinctness) covaried to some extent with one or more environmental factors (e.g., nature of the local host assemblage, temperature, precipitation) across geographical regions, but there was no universal pattern among results from different mite species. These results are similar to those obtained earlier on other taxa, e.g. fleas, and suggest that there are general laws acting on spatial patterns of parasite abundance and host specificity.     

Systematic embryology of the Scilla siberica alliance (Hyacinthaceae)

Eleven species of the Scilla siberica alliance, a well defined monophyletic group within the "genus by tradition" Scilla , have been investigated embryologically with special reference to embryo sac and endosperm development. Data are now available for 15 out of 20 known species. In most species embryo sacs develop according to the bisporic Allium-type, only in Scilla rosenii according to the tetrasporic Drusa-type. Endosperm development is either nuclear or helobial (in 10 and 4 species respectively, unknown in 1). The taxonomic significance of these traits is evaluated after character polarisation by out-group comparison. Among the out-group taxa, S. persica may be considered as the sister group of the S. siberica alliance because only these two groups have an Allium-type embryo sac, a synapomorphy derived from the plesiomorphic Polygonurn-type. The Drusa-type in S. rosenii is an autapomorphy for that species and evolved from an Allium-type embryo sac. S. rosenii is distinct from its sister species S. koenigii , previously thought to be conspecific. Nuclear endosperm is considered to be plesiomorphic rather than apomorphic within the S. siberica alliance, with respect to its occurrence in the presumed sister group and other outgroup taxa (S. hohenackeri group, S. bifolia alliance), but some doubt remains because of a helobial endosperm occurring in the out-group taxon S. messeniaca . The distribution of other synapomorphies within the S. siberica alliance suggests that a helobial endosperm evolved as a synapomorphy for S. bithynica, S. melaina and S. mischtschenkoana , but as a parallel trait in S. leepii . Species status for S. leepii is supported.     

应用RAMP分子标记探讨拟鹅观草属的种间关系

采用RAMP (random amplified microsatellite polymorphism) 标记技术, 分析了拟鹅观草属9种1亚种和鹅观草属6 种植物之间的遗传变异和亲缘关系。33 个引物组合产生的310 条DNA扩增片段中, 286条(92 25%) 具有多态性, 每个引物组合产生5~13条多态性带, 平均为8 67条。利用310个RAMP标记, 在NTSYS pc软件中, 计算Jaccard遗传相似系数, 建立UPGMA聚类图。结果表明: (1) 物种间遗传差异明显, 具有丰富的遗传多样性; (2) 阿拉善鹅观草和大丛鹅观草与拟鹅观草属的物种聚类在一起, 表明它们与拟鹅观草属的亲缘关系较近, 而与本试验所分析的另外4个鹅观草属物种的亲缘关系较远; (3) RAMP分子标记可以将拟鹅观草属的物种分开, 而且形态相似、地理分布相同或相近的物种聚类在一起;(4) RAMP结果与形态学和细胞学的分析结果一致, 表明RAMP标记是评价拟鹅观草属种间关系十分有效的方法。     

Polyploidy associated with altered and broader ecological niches in the Claytonia perfoliata (Portulacaceae) species complex

? Premise of the study: Polyploids are often hypothesized to have distinct and broader niches than their diploid progenitors. Differences in geographic distributions between diploid and polyploids are frequently used to infer niche differentiation and increased breadth, but they are seldom used to test these hypotheses explicitly. ? Methods: Niche overlap and breadth were compared for diploids, tetraploids, and hexaploids of three taxa in the Claytonia perfoliata complex (C. parviflora, C. perfoliata, and C. rubra) with the use of species distribution models. Resampling and randomization approaches were used to test hypotheses of niche differentiation, breadth, and conservatism. ? Key results: Niche differentiation was detected between polyploid and diploid cytotypes assigned to the same taxon (e.g., C. parviflora 2× vs. 4×) but not between hexaploids and tetraploids within a taxon (e.g., C. parviflora 4× vs. 6×). Individual hexaploid cytotypes had broader ecological niches than individual diploid cytotypes. However, as a group the three hexaploid taxa did not exceed the combined niche breadth of the three diploids, suggesting that polyploidy does not result in transgressive niche breadth for this group. Niche overlap was lowest among diploids and was highest among the three hexaploid cytotypes, consistent with introgression associated with polyploidy resulting in greater ecological similarity. Although cytotypes possessed nonidentical niches, after accounting for environmental differences among ranges, cytotypes were more similar than expected, suggesting niche conservatism and similar responses to environmental characteristics. ? Conclusions: These results suggest that polyploids occupy distinct and broader niches relative to diploids but that cytotypes also share fundamentally similar responses to environmental variation across ploidy levels.     

以礼草属的分类研究

以礼草属Kengyilia Yen et J. L. Yang 是禾本科Poaceae小麦族trib．Triticeae中新近建立的屑,针对其存在问题,对它进行了全面清理,提出了一个新的分类系统。新系统含3组、26种、6变种,其中3个组为新设立,并包括1新种、7个新等级、新组合及新异名。此外,还报道了一些类群的分布新记录。     

A taxonomical study on the genus Kengyilia Yen et J. L. Yang

Kengyilia Yen et J L Yang is a recently established genus in trib. Tritieeae of Poaceae. In this paper, this genus is taxonomically revised, and a new taxonomic system is presented. The new system includes 3 sections, 26 species and 6 varieties, of which 3 sections and 1 species are described as new, 7 taxa are treated respectively in the ways of new status or combination and reduction. Three new sections, sect. Kengyilia, sect. Stenachyra L. B. Cai and sect. Hyalolepis (Nevski) L. B. Cai, are differentiated by the length and width of spike, the growing position of spikelet, the relative length of glume, the colour of anther and so on. The sect. Kengyilia contains 9 species, distributed in northwestern China, extending westward to Kazakhstan, Kirghizia, Tadzhikistan, Afghanistan and Iran; the sect. Stenachyra L. B. Cai comprises 10 species and 3 verieties, distributed in western China, mainly in the Qinghai-Xizang Plateau; and the sect. Hyalolepis (Nevski) L. B. Cai consists of about 7 species and 3 varieties, distributed in western China, extending westward to Kirghizia and Tadzhikistan. Twenty-six species of Kengyilia are recognized on the basis of the same criterion of specific concept, and the other taxa below the rank of species are also checked in terms of their external morphology. As a result, Kengyilia pen~ dula L. B. Cai is reported as a new species; K. hirsuta var. obviaristata L. B. Cai is raised to a species; K. melanthera (Keng) J. L. Yang, Yen et Baum is reduced to a variety under K. thoroldiana (Oliver) J. L. Yang, Yen et Baum; Roegneria hirsuta var. leiophylla Keng et S. L. Chen is reduced as a synonym of K. hirsuta var. hirsuta; Agropyron thoroldianum var. lasciusculum Melderis is reduced to K. grandiglumis (Keng et S. L. Chen) J. L. Yang, Yen et Baum; Roegneria rigidula var. intermedia Keng et S. L. Chen to K. rigidula (Keng et S. L. Chen) J. L. Yang, Yen et Baum; R. hirsuta var. variabilis Keng et S. L. Chen and R. rnelanthera var. tahopaica Keng et S. L. Chen to K. hirsuta (Keng et S. L. Chen)J. L. Yang, Yen et Baum. In addition, new records onthe geographical distributions of some taxa are also reported in this paper.