Divergent selection along climatic gradients in a rare central European endemic species,Saxifraga sponhemica

Background and Aims The effects of habitat fragmentation on quantitative genetic variation in plant populations are still poorly known. Saxifraga sponhemica is a rare endemic of Central Europe with a disjunct distribution, and a stable and specialized habitat of treeless screes and cliffs. This study therefore used S. sponhemica as a model species to compare quantitative and molecular variation in order to explore (1) the relative importance of drift and selection in shaping the distribution of quantitative genetic variation along climatic gradients; (2) the relationship between plant fitness, quantitative genetic variation, molecular genetic variation and population size; and (3) the relationship between the differentiation of a trait among populations and its evolvability.Methods Genetic variation within and among 22 populations from the whole distribution area of S. sponhemica was studied using RAPD (random amplified polymorphic DNA) markers, and climatic variables were obtained for each site. Seeds were collected from each population and germinated, and seedlings were transplanted into a common garden for determination of variation in plant traits.Key Results In contrast to previous results from rare plant species, strong evidence was found for divergent selection. Most population trait means of S. sponhemica were significantly related to climate gradients, indicating adaptation. Quantitative genetic differentiation increased with geographical distance, even when neutral molecular divergence was controlled for, and Q_ST exceeded F_ST for some traits. The evolvability of traits was negatively correlated with the degree of differentiation among populations (Q_ST), i.e. traits under strong selection showed little genetic variation within populations. The evolutionary potential of a population was not related to its size, the performance of the population or its neutral genetic diversity. However, performance in the common garden was lower for plants from populations with reduced molecular genetic variation, suggesting inbreeding depression due to genetic erosion.Conclusions The findings suggest that studies of molecular and quantitative genetic variation may provide complementary insights important for the conservation of rare species. The strong differentiation of quantitative traits among populations shows that selection can be an important force for structuring variation in evolutionarily important traits even for rare endemic species restricted to very specific habitats.     

日本海太平洋褶柔鱼生物学特征的年际变化

根据2010~2013年连续4个年度在日本海进行鱿钓生产采集的样本,利用SSPS软件统计拟合生长和Logistic曲线的方法,分析了太平样褶柔鱼(Todarodes pacificus)的胴长、体重、性别、性成熟度和摄食强度等生物学特征,以及日本海太平洋褶柔鱼群体结构和组成的年际变化。太平洋褶柔鱼总样本数量为388尾,其中雌、雄个体的平均胴长分别为231 mm和230 mm,优势胴长组为220~250 mm。各年度样本的雄雌性比均接近1︰1,总性比为0.89。胴长和体质量关系呈幂函数变化。Logistic曲线拟合个体初次性成熟胴长,其中雌性为216.04 mm,雄性为216.71 mm。样本以性成熟个体为主,成熟率(Ⅲ、Ⅳ和Ⅴ期)高达78.35%。摄食强度主要分布在Ⅰ、Ⅱ、Ⅲ等级,从胃含物组成的出现频率来看,以鱼类最高且主要是沙丁鱼类和灯笼鱼类,频率达70%以上;头足类次之,甲壳类较少。日本海太平洋褶柔鱼各年度的群落结构稍有差异,推测其生长发育与海洋环境因子有关,如温度、海流、盐度、饵料丰度等不同变化造成。     

Switching roles: the functional plasticity of adult tissue stem cells

Adult organisms have to adapt to survive, and the same is true for their tissues. Rates and types of cell production must be rapidly and reversibly adjusted to meet tissue demands in response to both local and systemic challenges. Recent work reveals how stem cell (SC) populations meet these requirements by switching between functional states tuned to homoeostasis or regeneration. This plasticity extends to differentiating cells, which are capable of reverting to SCs after injury. The concept of the niche, the micro‐environment that sustains and regulates stem cells, is broadening, with a new appreciation of the role of physical factors and hormonal signals. Here, we review different functions of SCs, the cellular mechanisms that underlie them and the signals that bias the fate of SCs as they switch between roles.     

基于微卫星标记的印度中部Madhya Pradesh地区疟疾强化控制和非强化控制区的斯氏按蚊基因流和种群遗传结构分析

[目的]斯氏按蚊Anopheles stephensi是亚洲东南部城市人体疟疾的主要媒介,印度12％的疟疾病例由其引起.本实验研究了印度中部Madhya Pradesh地区东北部的疟疾强化控制(EMCP)区和非强化控制(非EMCP)区斯氏按蚊的基因流.在EMCP区,由于采用了各种疟疾防控措施因而疟疾病例首先降低,但是很快回升,说明总的疟疾风险维持稳定.[方法]应用7个微卫星位点,对印度中部Madhya Pradesh地区东北部的4个EMCP区和非EMCP区采集的斯氏按蚊进行基因分型,以分析各种群参数.[结果]发现各标记在所有种群中表现出高度的多态性.在两区间未发现很大的遗传多样性.观察到EMCP区的东部种群(FST=0.0485,RST =0.1112)比非EMCP区的北部种群(FST=0.020,RST =0.0145)具有较高的遗传分化,在EMCP区和非EMCP区之间观察到较高的基因流(12.90,6.16,5.06和2.38).RST的灵敏度高于FST,说明分化可能是由于突变而非遗传漂变引起的.[结论]本研究表明,在EMCP区和非EMCP区内以及EMCP区和非EMCP区之间存在很高的基因流.基因流水平高以及抗虫性的发展似乎是EMCP区和非EMCP区疟疾病例发生增加的重要原因.     

Glucosylceramides are critical for cell‐type differentiation and organogenesis,but not for cell viability in Arabidopsis

Glucosylceramides (GlcCer), glucose‐conjugated sphingolipids, are major components of the endomembrane system and plasma membrane in most eukaryotic cells. Yet the quantitative significance and cellular functions of GlcCer are not well characterized in plants and other multi‐organ eukaryotes. To address this, we examined Arabidopsis lines that were lacking or deficient in GlcCer by insertional disruption or by RNA interference (RNAi) suppression of the single gene for GlcCer synthase (GCS, At2g19880), the enzyme that catalyzes GlcCer synthesis. Null mutants for GCS (designated ‘gcs‐1’) were viable as seedlings, albeit strongly reduced in size, and failed to develop beyond the seedling stage. Heterozygous plants harboring the insertion allele exhibited reduced transmission through the male gametophyte. Undifferentiated calli generated from gcs‐1 seedlings and lacking GlcCer proliferated in a manner similar to calli from wild‐type plants. However, gcs‐1 calli, in contrast to wild‐type calli, were unable to develop organs on differentiation media. Consistent with a role for GlcCer in organ‐specific cell differentiation, calli from gcs‐1 mutants formed roots and leaves on media supplemented with the glucosylated sphingosine glucopsychosine, which was readily converted to GlcCer independent of GCS. Underlying these phenotypes, gcs‐1 cells had altered Golgi morphology and fewer cisternae per Golgi apparatus relative to wild‐type cells, indicative of protein trafficking defects. Despite seedling lethality in the null mutant, GCS RNAi suppression lines with ≤2% of wild‐type GlcCer levels were viable and fertile. Collectively, these results indicate that GlcCer are essential for cell‐type differentiation and organogenesis, and plant cells produce amounts of GlcCer in excess of that required for normal development.     

The origin and genetic differentiation of the socially parasitic aphid Tamalia inquilinus

Social and brood parasitisms are nonconsumptive forms of parasitism involving the exploitation of the colonies or nests of a host. Such parasites are often related to their hosts and may evolve in various ecological contexts, causing evolutionary constraints and opportunities for both parasites and their hosts. In extreme cases, patterns of diversification between social parasites and their hosts can be coupled, such that diversity of one is correlated with or even shapes the diversity of the other. Aphids in the genus Tamalia induce galls on North American manzanita (Arctostaphylos) and related shrubs (Arbutoideae) and are parasitized by nongalling social parasites or inquilines in the same genus. We used RNA sequencing to identify and generate new gene sequences for Tamalia and performed maximum‐likelihood, Bayesian and phylogeographic analyses to reconstruct the origins and patterns of diversity and host‐associated differentiation in the genus. Our results indicate that the Tamalia inquilines are monophyletic and closely related to their gall‐forming hosts on Arctostaphylos, supporting a previously proposed scenario for origins of these parasitic aphids. Unexpectedly, population structure and host‐plant‐associated differentiation were greater in the non‐gall‐inducing parasites than in their gall‐inducing hosts. RNA‐seq indicated contrasting patterns of gene expression between host aphids and parasites, and perhaps functional differences in host‐plant relationships. Our results suggest a mode of speciation in which host plants drive within‐guild diversification in insect hosts and their parasites. Shared host plants may be sufficient to promote the ecological diversification of a network of phytophagous insects and their parasites, as exemplified by Tamalia aphids.     

Multilocus analysis of nucleotide variation and speciation in three closely related Populus (Salicaceae) species

Historical tectonism and climate oscillations can isolate and contract the geographical distributions of many plant species, and they are even known to trigger species divergence and ultimately speciation. Here, we estimated the nucleotide variation and speciation in three closely related Populus species, Populus tremuloides, P. tremula and P. davidiana, distributed in North America and Eurasia. We analysed the sequence variation in six single‐copy nuclear loci and three chloroplast (cpDNA) fragments in 497 individuals sampled from 33 populations of these three species across their geographic distributions. These three Populus species harboured relatively high levels of nucleotide diversity and showed high levels of nucleotide differentiation. Phylogenetic analysis revealed that P. tremuloides diverged earlier than the other two species. The cpDNA haplotype network result clearly illustrated the dispersal route from North America to eastern Asia and then into Europe. Molecular dating results confirmed that the divergence of these three species coincided with the sundering of the Bering land bridge in the late Miocene and a rapid uplift of the Qinghai‐Tibetan Plateau around the Miocene/Pliocene boundary. Vicariance‐driven successful allopatric speciation resulting from historical tectonism and climate oscillations most likely played roles in the formation of the disjunct distributions and divergence of these three Populus species.     

云南蕨类植物的物种多样性和区系组成

在一定实地调查和分类的基础上,采用统计分析及区系地理分析法,对云南地区蕨类植物进行研究。结果表明:云南地区共有蕨类植物60科193属1 530种(包括变种和变型),科、属、种分别占中国蕨类植物科总数的58.8%,属的83.9%和种的95.2%;在这60个科中含30种以上的有13个,含5个属以上的有11个,分别占该蕨类植物区系属、种数的56.5%和79.2%,特别是鳞毛蕨科、蹄盖蕨科、水龙骨科和金星蕨科,这4个科共拥有70属761种,分别占总属数、总种数的36.3%、49.7%;193属中含30种以上的有11个,分别占总属、总种数的5.7%和41.7%,最具优势的是鳞毛蕨属和耳蕨属、蹄盖蕨属、铁角蕨属、卷柏属,这5个属共有403种,占总种数的26.3%;该区系中无云南特有科,但具有4个亚洲特有科:雨蕨科、稀子蕨科、柄盖蕨科和骨碎补科;该区系以热带、亚热带性质为主,科的区系成分中热带亚热带分布的科占66.6%,热带成分的属有112个,占68.7%(除世界分布类型);该区系是东亚地区蕨类植物区系的重要组成部分,东亚分布31属和中国特有分布6属,分别占总属数(除世界分布属外)的19.0%和3.7%;该地区蕨类植物区系与西藏、台湾具有共同的区系起源和物种分化形成的背景,属的相似性系数约为70%,种的相似性系数约为30%,均起源于热带亚热带地区;属的热带区系成分与温带区系成分所占比例分别为68.7%和27.6%,存在一定的区系过渡性;该区系科的分化强度为3.2,属的分化强度为7.9,在科、属水平上均表现出较强的区系分化特征。