獐牙菜种子萌发的研究

对温度、光照、植物激素（GA₃、NAA）条件对獐牙菜（Swertia bimaculata）种子萌发的影响进行了研究。结果表明,獐牙菜种子萌发的适宜温度为15～20℃,低温贮藏可促进其萌发,而有无光照对獐牙菜种子萌发没有明显影响,GA₃处理可提高其萌发势和萌发率,而NAA处理仅提高其萌发势。研究认为：獐牙菜种子具有休眠现象;激素及低温贮藏对打破种子的休眠具有重要作用。     

刈割留茬高度和不同播种组合对人工草地初级生产力和物种丰富度的影响

采用7种播种方式(3种单播和4种混播)和3种刈割留茬高度裂区试验,测定了青藏高原高寒地区人工建植3年的垂穗披碱草(Elymus nutans)、中华羊茅(Festuca sinensis)和羊茅(Festuca ovina)草地地上生物量、物种丰富度以及杂草生物量,以分析刈割对青藏高原人工草地初级生产力和物种丰富度的影响。结果显示:(1)在草地建植第2年,不刈割与刈割留茬60和20 mm的草地初级生产力均有显著差异;留茬60和20 mm刈割使单播草地的平均初级生产力分别降低20%和27%,使混播草地的平均初级生产力分别降低29%和37%。(2)草地建植第3年,不刈割、留茬60和20 mm 3个处理间的草地生产力均差异极显著;留茬60和20 mm刈割使单播草地的平均生产力分别降低19%和36%,使混播草地的平均生产力分别降低4%和18%。研究表明,刈割显著降低了人工草地的初级生产力,同时显著增加了垂穗披碱草单播草地的物种丰富度和杂草生物量以及3种牧草混播草地物种丰富度,其他播种草地的物种丰富度和杂草生物量与不刈割草地均无显著差异。     

“藏茵陈”的基原植物和药用亲缘学

详细比较藏药"藏茵陈"基原植物川西獐牙菜及其混淆品(代用品)抱茎獐牙菜、紫红獐牙菜、四数獐牙菜、红直獐牙菜、大籽獐牙菜、狭叶獐牙菜和椭圆叶花锚的外部形态特征及化学成分,澄清了这一类群在分类上的混乱,发现川西獐牙菜与紫红獐牙菜在习性,花部特征,种子形态和化学成分组成等方面相似性最高,印证了核基因ITS序列的结果。同时分析"藏茵陈"混淆的原因是多种来源和形态相似性造成的,讨论了"藏茵陈"鉴定的方法。通过对獐牙菜属系统关系的分析,提出紫红獐牙菜作为川西獐牙菜替代品的理论依据。     

水肥条件对新老两个春小麦品种竞争能力和产量关系的影响

采用de Wit替代系列实验研究了传统地方品种和尚头和现代品种定西-24在土壤水肥梯度下混播时的竞争结局以及竞争能力和单播产量之间的关系。在各个水肥处理条件下,混播时,虽然和尚头对定西-24的影响效应有所减弱,但是,和尚头对定西-24的竞争结局并没有发生改变:和尚头最终完全排除定西-24,成为竞争中的优胜者。在低水无肥和高水高肥条件下,定西-24的单播产量显著高于和尚头的单播产量,二者的竞争能力与其单播产量之间呈负相关;在低水低肥条件下,和尚头的单播产量与定西-24的单播产量几乎相等,二者的竞争能力与其单播产量之间没有特定的关系;在中水中肥条件下,和尚头的单播产量高于定西-24的单播产量,二者的竞争能力与其单播产量之间呈正相关,据此可以认为和尚头和定西-24混播时的竞争能力与其单播产量之间没有特定的关系。在低水无肥和高水高肥条件下,定西-24的单播地上生物量显著高于和尚头的单播地上生物量。在水分严重亏缺的条件下,和尚头的水分利用效率显著低于定西-24的水分利用效率;随着水分供给的改变,和尚头的水分利用效率得到了显著提高,然而当水分不再成为和尚头生长限制因子时,其水分利用效率降低,结果表明一定程度水分利用效率的提高有利于春小麦适应半干旱区的水分环境。     

四数獐牙菜的胚胎学及其系统学意义

四数獐牙菜花药四室,药壁发育为双子叶型;绒毡层腺质型。小孢子母细胞减数分裂为同时型, 四分体的排列方式为四面体形;成熟花粉为3-细胞。子房2心皮,2心皮连接处强烈内凸,4列胚珠。薄 珠心,单珠被,直生胚珠。胚囊发育为蓼型。胚乳发育为核型。胚胎发育为茄型酸浆I变型。反足细胞 在胚囊成熟时期宿存。果实成熟时,种子只发育至球型胚阶段。承珠盘存在。与已研究的獐牙菜种类 的胚胎特征相比较,该种存在三个显著的特点：直生胚珠,心皮连接处强烈内凸,承珠盘存在。这三个特 征目前仅在龙胆族中的花锚属中发现。经过性状分析,它们均是演征,此三个共有演征表明四数獐牙菜 与花锚属是一单系群,它们的亲缘关系最近。这与Yun &; Kupfer(1995)的分子证据部分吻合,因为分 子系统树上的花锚单系支包括花锚、四数獐牙菜和北美的密花属(广义獐牙菜属中的密花组),而后者的 胚胎学特征未有任何报道。胚胎学研究暗示四数獐牙菜的分类学等级有待重新评价,广义的獐牙菜属 有可能不是一单系发生群。     

基于MaxEnt模拟人类活动与环境因子对青藏高原特有植物祁连獐牙菜潜在分布的影响

以青藏高原特有植物祁连獐牙菜(Swertia przewalskii Pissjauk.)为材料,基于该物种18个种群分布点及8个生物气候变量、海拔变量以及人类活动强度变量,运用最大熵模型(Max Ent)和ArcGIS技术分别构建当前气候情景下及人类活动影响下祁连獐牙菜的适宜生境预测模型,研究人类活动及自然环境变量对祁连獐牙菜空间分布的影响。结果显示,人类活动影响下的训练集和测试集的AUC值均小于无人类活动干扰的AUC值,人类活动与祁连獐牙菜分布呈负相关。限制祁连獐牙菜分布的主要变量为海拔、等温性、人类活动足迹指数及平均温度日较差。当前气候情景下祁连獐牙菜的最适宜生境占祁连山国家公园青海片区总面积的36.6%,有利于该物种的保护和恢复,而位于门源县和祁连县保护区内一般控制区的潜在生境受到人为干扰的可能性较大,应加强关注和保护。     

基于ITS和matK序列的獐牙菜亚族 (龙胆科龙胆族)分子系统学

为探讨獐牙菜亚族（subtribe Swertiinae）各属之间和一些属内的系统关系,本研究选取了该亚族14属68种1变种,采用最大简约法（maximum parsimony）和贝叶斯法（Bayesian inference）对样品核基因ITS和叶绿体基因matK的两个片段进行独立和联合分析。结果显示：Bartonia位于亚族的最基部;喉毛花属（Comastoma）、肋柱花属（Lomatogonium）和假龙胆属（Gentianella）都非单系,处于同一个较为进化的分支中;獐牙菜属折皱组（Swertia sect. Rugosa）和獐牙菜组（S. sect. Swertia）亲缘关系最近,宽丝组（S. sect. Platynema）和藏獐牙菜组（S. sect. Kingdon Wardia）亲缘关系最近;口药花属（Jaeschkea）与獐牙菜属多枝组（S. sect. Ophelia）的大籽獐牙菜（Smacrosperma）亲缘关系最近。同时讨论了獐牙菜亚族形态分类与分子数据不一致的原因。     

黑荆（Acacia mearnsii）对几种林下植物种子萌发的化感作用

研究了入侵植物黑荆（Acacia mearnsii De Willd.）不同地上器官、不同浓度水浸提液对杜虹花（Callicarpa formosana Rolfe.）、紫薇（Lagerstroemia indica Linn.）、白花败酱（Patrinia villosa Juss.）、田麻（Corchoropsis tomentosa(Thunb.) Makino）4种植物种子的化感作用。结果表明黑荆茎、叶和豆荚水浸提液对4种植物的种子萌发均有不同程度的抑制作用。（1）黑荆不同地上器官对杜虹花、白花败酱、田麻的化感作用强度为叶>茎>豆荚,对紫薇的化感效应与浸提液的浓度有关,低浓度时茎>叶>豆荚,高浓度时豆荚>茎>叶。（2）同一器官的水浸提液对各植物化感效应不同,豆荚水浸提液对杜虹花、白花败酱、紫薇的种子萌发表现为较强的抑制作用,而对田麻则影响不显著。（3）高浓度茎水浸提液对种子萌发抑制作用的强度表现为田麻>杜虹花>紫薇>白花败酱。（4）随着浓度的增加,黑荆不同地上器官的水浸提液对杜虹花、白花败酱和田麻种子萌发的影响都呈现抑制作用增强的趋势。（5）黑荆的入侵可能通过化感作用抑制林下植物种子的萌发而对森林物种多样产生负面影响。     

獐牙菜亚族植物的系统发育分析

獐牙菜亚族(subtribe Swertiinae)是龙胆科(Gentianaceae)中分类处理较困难的一个亚族。为探讨该亚族各属之间和属内的系统关系,选取了该亚族86种及变种,采用ML和BI方法对样本的叶绿体基因mat K和rbc L片段进行分析,构建了该亚族的系统发育树,用马尔科夫蒙特卡洛算法(MCMC)的分子序列贝叶斯分析推算了该亚族的关键演化时间点。结果显示:①龙胆亚族和獐牙菜亚族各自为单系,且互为姐妹类群;②獐牙菜属、假龙胆属、肋柱花属和喉毛花属均不是单系群,各属的种在系统发育树上互有交叉,特别是獐牙菜属的多个种分别聚到不同的支上,与其它属是并系关系;③獐牙菜亚族49个种在约4 Ma开始形成;④分子数据支持何廷农分类系统对于獐牙菜亚属和多枝亚属的属间划分,部分支持多枝亚属下多枝组和宽丝组的划分;⑤异型花属、獐牙菜属、假龙胆属、喉毛花和肋柱花属的属间分类以及獐牙菜属肉根亚属密花组的系统位置仍需进一步讨论。     

青藏高原禾草混播对土壤微生物多样性的影响

土壤微生物多样性的形成、维持和变化机理是生态学研究的核心内容, 已有大量研究表明土壤微生物群落构建不仅受到土壤环境的深刻影响, 也与植物群落物种多样性密切相关。由于自然群落中土壤环境和植物多样性协同影响土壤微生物, 难以区分和厘清植物多样性和土壤环境对土壤微生物多样性构建的各自影响。该研究基于在青藏高原高寒草地构建的人工草地群落, 比较分析了3种优势禾本科牧草单播和混播及施肥处理13年后, 土壤细菌和真菌物种多样性及其与植物群落和土壤理化因子的关系。主要结果: 1)与各单播处理相比, 3种牧草两两混播一致显著降低了土壤细菌群落的丰富度和多样性, 其中变形菌门和放线菌门相对丰度显著增加, 而酸杆菌门、拟杆菌门和浮霉菌门相对丰度显著减小; 牧草混播对土壤真菌多样性没有显著影响。2)牧草混播显著降低了土壤pH和土壤全氮含量, 增加了土壤全磷含量; 施肥显著降低土壤pH, 增加了土壤速效磷含量; 但这些土壤理化因子的变化不足以解释土壤细菌和真菌多样性在处理间的差异。3)施肥显著提高了植物群落地上生物量, 降低了植物物种丰富度, 土壤细菌多样性随植物物种丰富度增加而减小, 而与植物生物量变化无关。该研究在野外条件下, 通过长期控制实验揭示了高寒草地禾草混播并不增加土壤微生物多样性, 为高寒地区牧草混播人工草地实践提供了科学依据。     

Population dynamics of species with gynogenetic sibling species

Models are formulated for the population dynamics of a monoecious or dioecious species with an all-female parthenogenetic sibling species which is also gynogenetic. Continuous, deterministic reproduction and mortality, a stationary age distribution, random mating, and limited sexual competence for all individuals are posited. It is also supposed that in the dioecious case males do not distinguish between true and gynogenetic females. Similarly, hermaphrodites do not differentiate hermaphrodites and gynogens. The model implies that extinction is highly likely in the dioecious situation, but much less so in the monoecious one. Empirical evidence is reviewed and related to the assumptions and conclusions.     

Helminth species diversity of mammals: parasite species richness is a host species attribute

Studies investigating parasite diversity have shown substantial geographical variation in parasite species richness. Most of these studies have, however, adopted a local scale approach, which may have masked more general patterns. Recent studies have shown that ectoparasite species richness in mammals seems highly repeatable among populations of the same mammal host species at a regional scale. In light of these new studies we have reinvestigated the case of parasitic helminths by using a large data set of parasites from mammal populations in 3 continents. We collected homogeneous data and demonstrated that helminth species richness is highly repeatable in mammals at a regional scale. Our results highlight the strong influence of host identity in parasite species richness and call for future research linking helminth species found in a given host to its ecology, immune defences and potential energetic trade-offs.     

物种概念及其界定

半世纪以来,物种概念的定义备受关注,不同研究方向的生物学家提出24种不同或至少有分歧的物种概念,根据其不同的物种概念,物种的界定和物种的数量会出现很大的差异。人们普遍认同:物种是进化分离的微居群谱系,但把谱系分离过程中获得的特征如生殖隔离、可鉴定性、单系统发生等视为鉴定物种次级特征却有不同的声音。该文提出统一的物种概念,把谱系进化分离作为物种界定的唯一而又必要的特征,把谱系分离过程中获得的次级特征作为界定谱系分离的证据。鉴于此,物种概念间的分歧就会化解。其一,物种概念化与物种界定明显分开,不再混淆;其二,谱系的次级特征只与物种界定有关,在某种程度上为谱系分离提供证据;第三,若能把合理解释的任何一个特征作为某物种客观存在的证据,这样更多的特征更能确定谱系分离;最后最重要的是,统一物种概念使我们解放思想,扬弃传统的物种界定标准,探求物种界定的新思路。     

Finding unknown species in the genomes of extant species

Although many species have gone extinct, their genetic components might exist in extant species because of ancient hybridization. Via advances in genome sequencing and development of modern population genetics, one can find the legacy of unknown or extinct species in the context of available genomes from extant species. Such discovery can be used as a strategy to search for hidden species or fossils in conservation biology and archeology, gain novel insight into complex evolutionary history, and provide the new sources of genetic variation for breeding and trait improvement in agriculture.     

Ring species as demonstrations of the continuum of species formation

In the mid‐20th century, Ernst Mayr (1942) and Theodosius Dobzhansky (1958) championed the significance of ‘circular overlaps’ or ‘ring species’ as the perfect demonstration of the gradual nature of species formation. As an ancestral species expands its range, wrapping around a geographic barrier, derived taxa within the ring display interactions typical of populations, such as genetic and morphological intergradation, while overlapping taxa at the terminus of the ring behave largely as sympatric, reproductively isolated species. Are ring species extremely rare or are they just difficult to detect? What conditions favour their formation? Modelling studies have attempted to address these knowledge gaps by estimating the biological parameters that result in stable ring species (Martins et al. 2013), and determining the necessary topographic parameters of the barriers encircled (Monahan et al. 2012). However, any generalization is undermined by a major limitation: only a handful of ring species are known to exist in nature. In addition, many of them have been broken into multiple species presumed to be evolving independently, usually obscuring the evolutionary dynamics that generate diversity. A paper in this issue of Molecular Ecology by Fuchs et al. (2015), focused on the entire genealogy of a bulbul (Alophoixus) species complex, offers key insights into the evolutionary processes underlying diversification of this Indo‐Malayan bird. Their findings fulfil most of the criteria that can be expected for ring species (Fig.  1 ): an ancestor has colonized the mainland from Sundaland, expanded along the forested habitat wrapping around Thailand's lowlands, adjacent taxa intergrade around the ring distribution, and terminal taxa overlap at the ring closure. Although it remains unclear whether ring divergence has resulted in restrictive gene flow relative to that observed around the ring, their results suggest that circular overlaps might be more common in nature than currently recognized in the literature. Most importantly, this work shows that the continuum of species formation that Mayr and Dobzhansky praised in circular overlaps is found in biological systems currently described as ‘rings of species’, in addition to the idealized ‘ring species’.     

On the measurement of species diversity incorporating species differences

When pairwise differences (relatedness) between species are numerically given, the average of the species differences weighted by relative frequencies can be used as a species diversity index. This paper first theoretically develops the indices of this type, then applies them to forestry data. As examples of diversity indices, this paper explores the taxonomic diversity and the newly introduced amino acid diversity, which is a modification of the nucleotide diversity in genetics. The first, mathematical part shows that both indices can be decomposed into three inner factors; evenness of relative frequencies (=the Simpson index), the simple average over species differences regardless of relative frequencies, and the taxonomic or genetic balance in relative frequencies. The taxonomic diversity has another decomposition: the sum over the Simpson indices at all the taxonomic levels. The second part examines the effects of different forest management techniques on diversity. It is shown that a thinning operation for promoting survival of specific desirable species also contributed to increasing the taxonomic diversity. If we calculated only conventional indices that do not incorporate species relatedness, we would simply conclude that the thinning did not significantly affect the diversity. The theoretical developments of the first part complement the result, leading us to a better interpretation about contrasting vegetation structures. The mathematical results also reveal that the amino acid diversity involves redundant species, which is undesirable when measuring diversity; hence, this index is used to demonstrates crucial points when we introduce species relatedness. The results suggest further possibilities of applying diversity indices incorporating species differences to a variety of ecological studies.     

Exotic species richness and native species endemism increase the impact of exotic species on islands

Aim Exotic species pose one of the most significant threats to biodiversity, especially on islands. The impacts of exotic species vary in severity among islands, yet little is known about what makes some islands more susceptible than others. Here we determine which characteristics of an island influence how severely exotic species affect its native biota. Location We studied 65 islands and archipelagos from around the world, ranging from latitude 65° N to 54° S. Methods We compiled a global database of 10 island characteristics for 65 islands and determined the relative importance of each characteristic in predicting the impact of exotic species using multivariate modelling and hierarchical partitioning. We defined the impact of exotic species as the number of bird, amphibian and mammal (BAM) species listed by the International Union for Conservation of Nature (IUCN) as threatened by exotics, relative to the total number of BAM species on that island. Results We found that the impact of exotic species is more severe on islands with more exotic species and a greater proportion of native species that are endemic. Unexpectedly, the level of anthropogenic disturbance did not influence an island's susceptibility to the impacts of exotic species. Main conclusions By coupling our results with studies on the introduction and establishment of exotic species, we conclude that colonization pressure, or invasion opportunities, influences all stages of the invasion process. However, species endemism, the other important factor determining the impact of exotic species, is not known to contribute to introduction and establishment success on islands. This demonstrates that different factors correlate with the initial stages of the invasion process and the subsequent impacts of those invaders, highlighting the importance of studying the impacts of exotic species directly. Our study helps identify islands that are at risk of impact by exotics and where investment should focus on preventing further invasions.     

外来树种对本地林业虫害的诱发作用

白蜡窄吉丁、萧氏松茎象、光肩星天牛、黄斑星天牛、云斑天牛和桑天牛等林业害虫均为我国本地林业生态系统中的昆虫种类,在北美白蜡树、北美松树和北美黑杨派杨树等外来树种引入和大量栽培之前,一直没有形成严重的危害,以至于白蜡窄吉丁和萧氏松茎象都没有引起人们的关注。这些重要林业害虫在我国的发生都是伴随着敏感外来树种的引进和大量不合理的种植而逐渐严重起来的。本文对外来树种的引进与本地林业虫害的发生之间的关系进行了分析,提出了外来树种的不合理引进可能诱发本地林业新虫害的观点,并对其发生机理以及相应的研究和治理对策进行了讨论。