沿海岛屿与内陆藓类植物遗传多样性和分化的比较研究——以真藓(Bryum argenteum Hedw.)为例

基于11个内陆居群和32个岛屿居群的252份标本,采用ISSR分子标记技术对真藓（Bryum argenteum Hedw.）的遗传多样性进行了研究。结果显示：岛屿与内陆居群间的遗传多样性差异显著,岛屿居群间的分化程度（G_st=0.453）大于内陆居群（G_st=0.387）,岛屿居群的遗传分化与地理来源间存在极显著相关性（r=0.478,n=175,P<0.001）。地理隔离效应是导致岛屿居群间遗传分化的重要因素。岛内居群间的遗传分化水平较低,仅有29.4%~29.7%的遗传多样性存在于居群间。聚类分析表明,43个居群可划分为10大类群,真藓遗传关系受地理因素和生境异质性的影响,水域隔离影响了真藓繁殖体在岛屿间的传播。     

Evidence of horizontal gene transfer between land plant plastids has surprising conservation implications

Background and AimsHorizontal gene transfer (HGT) is an important evolutionary mechanism because it transfers genetic material that may code for traits or functions between species or genomes. It is frequent in mitochondrial and nuclear genomes but has not been demonstrated between plastid genomes of different green land plant species.MethodsWe Sanger-sequenced the nuclear internal transcribed spacers (ITS1 and 2) and the plastid rpl16 G2 intron (rpl16). In five individuals with foreign rpl16 we also sequenced atpB-rbcL and trnL_UAA-trnF_GAA.Key ResultsWe discovered 14 individuals of a moss species with typical nuclear ITSs but foreign plastid rpl16 from a species of a distant lineage. None of the individuals with three plastid markers sequenced contained all foreign markers, demonstrating the transfer of plastid fragments rather than the entire plastid genome, i.e. entire plastids were not transferred. The two lineages diverged 165–185 Myr BP. The extended time interval since lineage divergence suggests that the foreign rpl16 is more likely explained by HGT than by hybridization or incomplete lineage sorting.ConclusionsWe provide the first conclusive evidence of interspecific plastid-to-plastid HGT among land plants. Two aspects are critical: it occurred at several localities during the massive colonization of recently disturbed open habitats that were created by large-scale liming as a freshwater biodiversity conservation measure; and it involved mosses whose unique life cycle includes spores that first develop a filamentous protonema phase. We hypothesize that gene transfer is facilitated when protonema filaments of different species intermix intimately when colonizing disturbed early succession habitats.     

不同灌水量下限对高羊茅绿期及抗寒性生理指标的影响

采用盆栽试验的方法,研究了秋末冬初不同灌水量下限\[分别占田间持水量(FC)的80%、70%、60%、50%\]对高羊茅绿期及抗寒性生理指标的影响.结果表明：在冬季低温条件下,80%和70%FC灌水处理使高羊茅叶片相对含水量、保护酶(SOD、POD和CAT)活性、叶绿素、可溶性糖和游离脯氨酸含量维持在较高水平,丙二醛含量和电解质外渗率降低,高羊茅的抗寒性增强.80%FC灌水处理分别较70%、60%和50%FC处理的草坪草绿期延长4、22和28 d,到达枯黄休眠的时间最晚,完成返青的时间最早.综合考虑节水和提高水分利用效率等多种因素,70%FC灌水处理为高羊茅秋末冬初季节最佳的灌水下限.     

Filling the interspace—restoring arid land mosses: source populations,organic matter,and overwintering govern success

Biological soil crusts contribute to ecosystem functions and occupy space that could be available to invasive annual grasses. Given disturbances in the semiarid shrub steppe communities, we embarked on a set of studies to investigate restoration potential of mosses in sagebrush steppe ecosystems. We examined establishment and growth of two moss species common to the Great Basin, USA: Bryum argenteum and Syntrichia ruralis from two environmental settings (warm dry vs. cool moist). Moss fragments were inoculated into a third warm dry setting, on bare soil in spring and fall, both with and without a jute net and with and without spring irrigation. Moss cover was monitored in spring seasons of three consecutive years. Both moss species increased in cover over the winter. When Bryum received spring irrigation that was out of sync with natural precipitation patterns, moss cover increased and then crashed, taking two seasons to recover. Syntrichia did not respond to the irrigation treatment. The addition of jute net increased moss cover under all conditions, except Syntrichia following fall inoculation, which required a second winter to increase in cover. The warm dry population of Bryum combined with jute achieved on average 60% cover compared to the cool moist population that achieved only 28% cover by the end of the study. Differences were less pronounced for Syntrichia where moss from the warm dry population with jute achieved on average 51% cover compared to the cool moist population that achieved 43% cover by the end of the study. Restoration of arid land mosses may quickly protect soils from erosion while occupying sites before invasive plants. We show that higher moss cover will be achieved quickly with the addition of organic matter and when moss fragments originate from sites with a climate that is similar to that of the restoration site.     

Two remarkable moss species new to Turkey and South-west Asia

Bryum blindii and Dicranella crispa are reported new to Turkey and South-west Asia following a recent bryological excursion to the Ardahan and Burdur regions of Turkey. Illustrations, geographic distribution and comparisons with morphologically similar taxa are given.     

沿海岛屿与内陆藓类植物遗传多样性和分化的比较研究——以真藓(Bryum argenteum Hedw.)为例

基于11个内陆居群和32个岛屿居群的252份标本,采用ISSR分子标记技术对真藓( Bryum argenteum Hedw.)的遗传多样性进行了研究。结果显示:岛屿与内陆居群间的遗传多样性差异显著,岛屿居群间的分化程度( G st = 0. 453)大于内陆居群( G st = 0. 387),岛屿居群的遗传分化与地理来源间存在极显著相关性( r = 0. 478, n = 175, P < 0. 001)。地理隔离效应是导致岛屿居群间遗传分化的重要因素。岛内居群间的遗传分化水平较低,仅有29. 4%~ 29. 7%的遗传多样性存在于居群间。聚类分析表明,43个居群可划分为10大类群,真藓遗传关系受地理因素和生境异质性的影响,水域隔离影响了真藓繁殖体在岛屿间的传播。     

垂蒴真藓原丝体发育特征的研究

在室内培养垂蒴真藓(Bryum uliginosum)孢子的基础上,对其孢子萌发、原丝体发育及配子体发生的全过程进行了跟踪观察。结果表明：该种孢子萌发后直接产生绿丝体。而轴丝体和假根仅在绿丝体上产生;配子体原始细胞产生于绿丝体基部细胞或轴丝体上。由此可以看出：垂蒴真藓属于真藓型孢子萌发型(Bryum-type)。     

中国新记录种——摩拉维采真藓(新拟)

该文首次报道了摩拉维采真藓(新拟)在中国的分布。研究表明:(1)摩拉维采真藓的主要识别特征为:叶常聚集在茎顶成莲座状,叶倒卵状披针形至匙形,具长毛尖,具分化边缘,中肋消失于叶尖下,叶细胞长菱形至六边形,叶腋处着生大量单列细胞构成的分枝或不分枝的丝状芽胞。(2)通过对摩拉维采真藓的命名和系统位置的讨论,确认该种是真藓属细叶真藓组的有效种。(3)摩拉维采真藓与近缘种细叶真藓和幽美真藓有诸多相似特征:莲座状的茎顶、有分化边和菱形至六边形中上部细胞的倒卵形叶,但该种以具有大量叶腋生丝状芽胞和叶中肋不及顶等特征区别于细叶真藓的无腋生芽胞、叶中肋突出叶尖成长芒状,以具有叶湿时平展、干时卷曲和叶腋有芽胞等特征区别于幽美真藓的叶湿时内凹、干时紧贴于茎和无腋生芽胞;拟三列真藓、圆叶真藓和灰黄真藓的部分种群都曾报道有与摩拉维采真藓相似的腋生丝状芽胞,但摩拉维采真藓的假根集生于植株基部、叶有狭分化边、叶缘平直、中肋消失于叶尖下而区别于拟三列真藓的茎中下部密被假根、叶有宽分化边、叶缘背卷、中肋及顶或短出,摩拉维采真藓有分化边和长毛尖的倒卵状披针形区别于圆叶真藓叶有无分化边和圆钝叶尖的卵圆形叶,区别于灰黄真藓有中肋及顶和短尖的卵状披针形叶;柔叶真藓有与摩拉维采真藓相似、中肋不及顶的叶,但无芽胞而易与新记录种区分。(4)该种在北温带有较广泛分布,形成欧洲-北亚-中亚-西亚和北美两个主要分布区;作者在四川和新疆等地的发现可以推测摩拉维采真藓在中国可能有更广泛的分布。     

Haplodontium zangii X.R.Wang & J.C.Zhao,sp. nov. (Bryaceae,Bryopsida) from Xizang,China

Haplodontium zangii X.R.Wang &; J.C.Zhao, a new moss species from Xizang, China, is described and illustrated. Previously, specimens of H. zangii have been identified as Mielichhoferia himalayana Mitt. However, H. zangii is distinctly different from M. himalayana in having excurrent costae with short awns (vs long denticulate awns), short-pyriform capsules, 0.8–1?mm (vs long-pyriform capsules, 2.5–3?mm), and densely papillose exostome teeth (vs smooth or vertically striped exostome teeth). Haplodontium zangii is similar to H. macrocarpum (Hook.) J.R.Spence, which was traditionally placed in Mielichhoferia Nees &; Hornsch. as M. macrocarpa (Hook.) Bruch &; Schimp. The main differences between H. zangii and H. macrocarpum are in the morphology of the leaves, capsules, guide cells, and stomata. Mielichhoferia himalayana and another Chinese species of Mielichhoferia, M. sinensis Dix., are also transferred to Haplodontium Hampe, a new genus in the bryoflora of China, as H. himalayanum (Mitt.) X.R.Wang &; J.C.Zhao and H. sinensis (Dix.) X.R.Wang &; J.C.Zhao. A morphological comparison and a key to the three species of Haplodontium in China as well as to H. macrocarpum, a species that is likely to be found in China, are provided.