浑善达克沙地榆树疏林幼苗更新空间格局

榆树疏林广泛分布于浑善达克沙地,是适应半干旱、半湿润气候的沙地植被类型.采用Ripley的K函数统计方法,分析了浑善达克沙地固定沙丘与丘间低地封育状态下的榆树幼苗空间分布及更新格局.结果表明:两种生境下榆树幼苗密度分别为88株/hm2和77株/hm2,丘间低地更适合幼苗的生长.固定沙丘和丘间低地榆树幼苗均呈聚集分布,但丘间低地的幼苗聚集强度更高.固定沙丘上榆树幼苗与成熟树种群在小尺度上呈负关联,而丘间低地幼苗与成熟树种群呈现较显著的正关联,但二者在大尺度上均无关联性.研究对揭示浑善达克沙地榆树幼苗分布、更新空间格局及其恢复保护具有重要意义.     

基于28S, COI和Cytb基因序列的薜荔和爱玉子传粉小蜂分子遗传关系研究

薜荔和爱玉子均属于桑科榕属植物,二者为同一物种的原变种与变种的关系,早期研究认为这两种榕树与同一种传粉榕小蜂(Wiebesia pumilae (Hill))建立了稳定的互利共生关系,但近期在形态学、生态学、传粉生物学等方面对二者的研究结果表明,薜荔传粉小蜂和爱玉子传粉小蜂之间可能发生了遗传分化。实验用核糖体28SrDNAD1-D3区、线粒体Cytb及COI基因部分序列,对采自福建3个不同样地的薜荔传粉小蜂和3个不同品系的栽培爱玉子的传粉小蜂进行分析,结果表明:(1)薜荔传粉小蜂和爱玉子传粉小蜂的核糖体28S序列的碱基组成中A,T,G,C 4种含量较平均,C+G的平均含量(56%)稍高于A+T的含量(44%)。线粒体Cytb序列中A+T的含量(76.1%)明显高于C+G的含量(23.9%),COI序列中A+T的含量(71.9%)也明显高于G+C的含量(28.1%),这是膜翅目昆虫线粒体基因的普遍特征。在薜荔和爱玉子传粉小蜂的线粒体Cytb及COI基因中,密码子第三位点A+T的含量最高。(2)比较薜荔和爱玉子传粉小蜂的3种分子标记的变异范围显示,28S进化速度较Cytb及COI序列慢,比较保守,更适合科、亚科等较高分类单元的研究。薜荔传粉小蜂与爱玉子传粉小蜂之间的亲缘关系较近,采用Cytb与COI序列进行分析更为精确。(3)用Cytb及COI序列对薜荔传粉小蜂与爱玉子传粉小蜂之间的遗传距离进行分析显示,薜荔传粉榕小蜂个体间Cytb序列平均遗传距离为0.0054,爱玉子传粉小蜂个体间的Cytb遗传距离为0.0164;薜荔传粉小蜂与爱玉子传粉小蜂群体之间的Cytb序列平均遗传距离为0.1385;COI序列的薜荔传粉榕小蜂个体间遗传距离为0.0048,爱玉子传粉小蜂各样本间平均遗传距离为0.0102;薜荔传粉小蜂与爱玉子传粉小蜂群体间COI序列平均遗传距离为0.1896,两群体间的遗传距离(差异大于10%以上)明显大于群体内各样本之间的遗传距离,表明薜荔传粉小蜂与爱玉子传粉小蜂之间已经发生了很大的遗传分化,其变异水平达到了种间分化水平,即薜荔传粉小蜂与爱玉子传粉小蜂为两个不同的种。     

Population genetic structure of banana corm weevil Cosmopolites sordidus (Germar) in India

The population genetic structure of Cosmopolites sordidus (Germar), an economically important pest of bananas, was studied using the sequence data of the internal transcribed rDNA (ITS1+ITS2) and the mitochondrial ‘COI-tRNA^Leu-COII’ region from seventy nine individuals collected from six sampling locations in India. The ITS data revealed 70% within population variation and non-significant genetic differentiation estimates suggesting lack of phylogeographic sub-structuring. 49% within population variation and highly significant genetic differentiation values were obtained with the mitochondrial data. The Mantel test revealed lack of correlation between genetic and geographic distance with both the markers. Demographic expansion of the populations was confirmed by the star shaped haplotype networks, demographic tests and mismatch distribution curves using both the markers. Molecular diversity indices show a high haplotype diversity (Hd) but low nucleotide diversity (π) suggesting that the populations are closely related. Considering the low self-dispersal ability of the weevils, these results suggest that the range expansion of this banana pest in India has taken place mainly through transport of infested corms and plant material resulting in the weevils forming localised populations which are not genetically distinct from each other. The high gene diversity (Hd) has enabled the weevils to adapt to varying environmental conditions which could explain the range expansion of this pest in India. The observed discrepancy in the genetic differentiation estimates using these two markers can be attributed to the evolutionary dynamics of the nuclear and mitochondrial genomes.     

Population structure and genetic diversity of black redhorse (Moxostoma duquesnei) in a highly fragmented watershed

Dams have the potential to affect population size and connectivity, reduce genetic diversity, and increase genetic differences among isolated riverine fish populations. Previous research has reported adverse effects on the distribution and demographics of black redhorse (Moxostoma duquesnei), a threatened fish species in Canada. However, effects on genetic diversity and population structure are unknown. We used microsatellite DNA markers to assess the number of genetic populations in the Grand River (Ontario) and to test whether dams have resulted in a loss of genetic diversity and increased genetic differentiation among populations. Three hundred and seventy-seven individuals from eight Grand River sites were genotyped at eight microsatellite loci. Measures of genetic diversity were moderately high and not significantly different among populations; strong evidence of recent population bottlenecks was not detected. Pairwise F_ST and exact tests identified weak (global F_ST = 0.011) but statistically significant population structure, although little population structuring was detected using either genetic distances or an individual-based clustering method. Neither geographic distance nor the number of intervening dams were correlated with pairwise differences among populations. Tests for regional equilibrium indicate that Grand River populations were either in equilibrium between gene flow and genetic drift or that gene flow is more influential than drift. While studies on other species have identified strong dam-related effects on genetic diversity and population structure, this study suggests that barrier permeability, river fragment length and the ecological characteristics of affected species can counterbalance dam-related effects.     

Disturbance by mowing affects clonal diversity: the genetic structure of Ranunculus ficaria (Ranunculuaceae) in meadows and forests

To study the impact of disturbance by mowing on clonal variation, we compared the genetic structure of Ranunculus ficaria (Ranunculaceae) in meadows and forests located in southeast Germany. We applied random amplified polymorphic DNA (RAPD) analysis to investigate the clonal and genetic diversity and analysed a total of 117 samples from three study plots in each habitat type. Polymerase chain reaction with six primers resulted in 57 fragments. Clonal diversity differed clearly between the two analysed habitat types and was significantly higher in the study plots from meadows than in those from forests. The mean percentage of distinguishable genotypes (PD) was 0.80 in meadow plots and 0.36 in forest plots, and the detected genets were smaller in meadow plots than in forest plots. Mean genetic diversity measured as percentage of polymorphic bands, Shannon’s information index and Nei’s gene diversity was also higher in meadows (44.4, 0.22 and 0.14) than in forests (25.1, 0.09 and 0.05). The higher level of clonal diversity in meadow plots is most likely due to the effects of disturbance by mowing, which increases the dispersal of bulbils and promotes the establishment of new plants in meadows compared to forests.     

干旱荒漠区狭叶锦鸡儿灌丛扩展对策

通过对内蒙古干旱荒漠区狭叶锦鸡儿集群的灌丛结构、分株特征、繁殖倾向和分枝特征的调查,探讨荒漠区狭叶锦鸡儿的繁殖特点和灌丛扩展对策。研究表明：在荒漠区,狭叶锦鸡儿的营养繁殖占主导地位,主要是由根萌蘖产生无性系分株,其克隆生长构型为密集型。根系萌蘖、枝条的不定根繁殖、地上枝条不断分枝和新老个体形成复合灌丛是荒漠区狭叶锦鸡儿冠幅增大的主要原因。狭叶锦鸡儿通过克隆繁殖、灌丛扩大化和发达的根系适应荒漠区的干旱贫瘠环境,使其成为荒漠区的优势种。     

The ants of the southern Sonoran desert: community structure and the role of trees

In contrast to other North American deserts, the southern Sonoran desert is dominated by trees that provide shaded microhabitats necessary for the establishment and survival of several plant species. Near the southern limit of the Sonoran desert in Sonora, Mexico, we evaluated the role that tree microhabitats may play in structuring ant communities. We recorded 39 species and 21 genera of ants from a 9.7-ha area. Total species richness was estimated to be between 47 and 49 species, a much greater species richness than that reported for other North American arid-zone habitats. Although species richness did not differ between open ground and tree-shaded microhabitats, species composition did. Opportunistic species, Camponotus species, Pheidole sciophila and P. titanis were more common near trees, whereas Pheidole sp. A and granivorous species were more active in open areas. The imperilment of trees in the Sonoran desert due to commercial cutting and the spread of buffelgrass Pennisetum ciliare may alter the existing composition of ant communities.     

Diaspore structure and germination ecophysiology of the babassu palm (Attalea vitrivir)

Both germination and seedling establishment in palm trees are strongly influenced by the morphoanatomy of the fruits, although the interactions of these processes with ecophysiological aspects are not yet well understood. The present work evaluated structural and physiological aspects of seed germination in Attalea vitrivir, a species living under the seasonal climate of the Cerrado (Brazilian savanna) biome. We studied morphology, anatomy and histochemistry of the fruits and seedlings, the effects on germination of the pericarp, of diaspore storage conditions, germination temperature, removal of the operculum, and of gibberellic acid (GA3) application, and characterized the imbibition process of the seeds. Germination depends on a series of complex interactions between structures and physiological processes. The pericarp protects the seed and also causes physical dormancy that, when interacting with the temperature regime, can delay germination until subsequent rainy periods. Some seeds demonstrated non-profound physiological dormancy associated with restricted germination imposed by the operculum. Germination and initial development result from the elongation of the cotyledon cells and are affected by the activities of two distinct meristems in the proximal region of the embryo. The haustorium develops an invaginated secretory epithelium and aerenchyma, and actively participates in seed reserve mobilization. The adaptation of A. vitrivir to the Cerrado environment, with a strongly seasonal climate, is favored by its diaspore structure, by the abundance of endosperm reserves that allow the seedlings to survive for a long period above soil level, and by a seedling development pattern that protects the vegetative axis by deep burial.     

Microsatellite diversity and population genetic structure of redfin culter ( Culter erythropterus ) in fragmented lakes of the Yangtze River

Redfin culter (Culter erythropterus) is a small lethic freshwater fish and widely distributed in the adjacent lakes of the Yangtze River of China. Five microsatellite loci were applied to investigate the genetic variation and population structure of redfin culter from seven lakes in the middle-and-lower reaches of the Yangtze River. The gene diversity was high among the populations (H > 0.9), the average number of alleles among seven populations was low with a range from 2.00 to 3.87. The mean observed (H _O) and expected (H _E) heterozygosity ranged from 0.111 to 0.419 and from 0.162 to 0.750, respectively. Significant deviations from Hardy-Weinberg Equilibrium expectation were found in 50% of the total locus-population combination tests in which heterozygote deficits were apparent. The analysis of molecular variance (AMOVA) indicated that the percentage of variance among and within these populations were 6.18 and 93.82, respectively. The Fst values (0.062, P < 0.001) among studied populations indicated that there were significant genetic differentiations among redfin culture populations from the scattered lakes with different connections to the Yangtze River. These results are useful for the evaluation and conservation of small freshwater fishes. The factors that may be involved in low intra-population polymorphism and the pattern of the population genetic structure of redfin culter from the Yangtze River were discussed. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. Handling editor: C. Sturmbauer     

宁夏荒漠草原植物群落结构和物种多样性研究

采用样方法对宁夏荒漠草原植物群落进行了调查,对群落结构、功能群物种组成和物种多样性以及群落生产力的关系进行探讨。结果表明,群落生产力除受物种多样性的影响外,也受物种本身特征和环境资源的影响。在荒漠草原中功能群盖度与群落初级生产力无显著的相关关系。功能群内物种多样性、物种数和个体数量上呈现一定的互为消长关系。     

Mating system and population genetic structure of Bruguiera gymnorrhiza (Rhizophoraceae), a viviparous mangrove species in China

In order to explain the diversity patterns and develop the conservation strategies, the population genetic structures and the mating systems of Bruguiera gymnorrhiza from the coastlines of south China were investigated in this study. The mating system parameters were analyzed using progeny arrays for allozyme markers. The multilocus outcrossing rates (tm) ranged from 0.845 (Fugong) to 0.267 (Dongzhai harbor). High allozyme variations within the five collected populations were determined and compared with the published data of other plant species with the mixed mating systems. At species level, the percentage of polymorphic loci (P) was 80%, the average number of alleles per locus (A) was 2.440, and the heterozygosity (He) was 0.293. The total gene diversity within each population (H_S = 0.2782) and the coefficient of genetic differentiation (G_ST = 0.0579) among the populations were estimated. On the basis of this population genetic structure, it is suggested that the gene flow (Nm = 3.85) is quite high, which is possibly related to its water-dispersed hypocotyls. It is also suggested that the mating system of this species is of mixed mating.     

Spatial genetic structure in continuous and fragmented populations of Pinus pinaster Aiton

Habitat fragmentation, i.e., the reduction of populations into small isolated remnants, is expected to increase spatial genetic structure (SGS) in plant populations through nonrandom mating, lower population densities and potential aggregation of reproductive individuals. We investigated the effects of population size reduction and genetic isolation on SGS in maritime pine ( Pinus pinaster Aiton) using a combined experimental and simulation approach. Maritime pine is a wind-pollinated conifer which has a scattered distribution in the Iberian Peninsula as a result of forest fires and habitat fragmentation. Five highly polymorphic nuclear microsatellites were genotyped in a total of 394 individuals from two population pairs from the Iberian Peninsula, formed by one continuous and one fragmented population each. In agreement with predictions, SGS was significant and stronger in fragments ( Sp  = 0.020 and Sp  = 0.026) than in continuous populations, where significant SGS was detected for one population only ( Sp  = 0.010). Simulations suggested that under fat-tailed dispersal, small population size is a stronger determinant of SGS than genetic isolation, while under normal dispersal, genetic isolation has a stronger effect. SGS was always stronger in real populations than in simulations, except if unrealistically narrow dispersal and/or high variance of reproductive success were modelled (even when accounting for potential overestimation of SGS in real populations as a result of short-distance sampling). This suggests that factors such as nonrandom mating or selection not considered in the simulations were additionally operating on SGS in Iberian maritime pine populations.     

Population genetic structure of the ascidian Styela rustica at Kongsfjorden, Svalbard, Arctic

The actual Arctic biota shows a strong affinity with that of the Boreal Atlantic and Pacific ones, as a result of an active recolonization process after the Quaternary glaciations. The geographic distribution of sessile species is usually linked to larvae dispersive capabilities which can be directly related with time spent in the plankton. Ascidians larvae are lecitothorphic and short-lived, which suggest that ascidians could be not efficient dispersers. However, the solitary ascidian Styela rustica (Linnaeus, 1767) (Tunicata, Ascidiacea) shows a wide distribution pattern from the North Atlantic to the Arctic that, together with the relatively recent colonization of the Arctic system could indicate that this species efficiently disperses and colonizes new habitats. In this study we used ISSR-PCR markers to study the genetic structure of five populations of the ascidian Styela rustica at Kongsfjorden, west Spitsbergen (Svalbard archipelago). We analyzed whether this species presents a low genetic structure, as can be expected due to the historical process of recent post glaciations colonization, or if there is genetic differentiation at a local scale, caused by short-lived larvae and limited dispersal potential. The genetic diversity in each population assessed using the marker diversity index (M) ranged from 0.288 to 0.324. Population HN, situated close to a fast retreating glacier, showed the lowest diversity. Processes associated with deglatiation (icebergs calving from the glacier that scour the benthos and the increment of inorganic particulate matter on the water column) would drive to reduced population sizes and explain the reduced genetic variability observed in the HN population with respect to the others in the fjord. This suggests a possible linkage with the global warming process. Although the weak genetic structure found among the studied populations could indicate a founder effect, the genetic landscape shape analysis together with a positive relationship between genetic and geographic distances also suggest possible current gene flow among populations in the fjord.     

Spatio-environmental determinants of the genetic structure of three steppe species in a highly fragmented landscape

Habitat fragmentation can lead to substantial genetic depletion. As a consequence, restoration schemes often involve the introduction of propagules into isolated plant populations to improve genetic diversity. To avoid introducing maladapted seed material, such measures need to account for landscape genetic processes. However, surprisingly little is known as to whether different species within a distinct fragmented ecosystem respond similarly or idiosyncratically to eco-geographical variation.Using AFLP markers, we studied the population genetic structure in three species of the highly fragmented Kulunda steppe (South Siberia): Adonis villosa, Jurinea multiflora and Paeonia hybrida. In each population, we conducted a vegetation survey. We performed Mantel tests and an RDA approach to investigate how genetic structure was affected by three spatio-environmental variables: spatial distance, floristic composition and climate.Despite strong fragmentation, genetic diversity was moderate (A. villosa, J. multiflora) to high (P. hybrida), while differentiation was weak (A. villosa) to moderate (P. hybrida, J. multiflora). Mantel tests showed that spatial distance correlated with genetic distance in A. villosa and P. hybrida. Floristic composition was significantly associated with genetic differentiation in A. villosa. Climate did not have an effect on genetic structure in any species.All three species are long-lived, which may contribute to explaining why genetic effects of recent fragmentation are still limited. We highlight that floristic composition can be a powerful predictor of population differentiation in species that show rather stable conditions in their recent population histories (e.g. A. villosa). This can have important implications for identifying source populations where restoration actions involve the (re)introduction of propagules. In contrast, for P. hybrida and J. multiflora, we could not identify deterministic drivers of differentiation. We advocate that future studies should aim at disentangling the interactive effects of varying life cycles, eco-evolutionary population histories and spatio-environmental heterogeneity in fragmented landscapes.     

新疆阜康荒漠地区叉毛蓬居群的遗传结构和分化

应用RAPD技术,对新疆阜康荒漠地区叉毛蓬进行了居群遗传分析。结果表明：①用14个随机引物对5个叉毛蓬亚居群的98个个体进行了RAPD扩增,共检出3919条扩增片段,多态带3868条,总的多态位点百分率为98．7％;②Shannon多样性指数(HPOP／HSP＝0．6933)和Nei基因多样性指数(HS／HT＝0．6948)显示出大部分的遗传变异存在于叉毛蓬亚居群内,遗传分化系数(GST＝o．3052)表明亚居群问的分子变异占居群总遗传变异的30％以上;②5个叉毛蓬亚居群间的平均遗传距离为0．1817,变异范围从0．1258到0．2445,与同一物种亚种间遗传距离的变幅较一致(0．02—0．20),表明5个亚居群间产生了遗传分化;④叉毛蓬亚居群的基因流Nm＝1．138,低于一般广布种的基因流水平(Nm＝1．881),且远低于毛乌素沙地柠条的基因流(Nm＝5．9529),相对有限的基因流可能在叉毛蓬居群遗传分化的维持中起着作用。以上分析表明,尽管大部分的遗传多样性存在于叉毛蓬亚居群内,但5个亚居群间已有明显遗传分化的趋势。     

台湾海峡鲐鱼种群遗传结构

以往研究表明,台湾海峡的鲐鱼分属2个地理种群,即东海种群和闽南——粤东地方种群.为研究这2个种群的遗传结构,对鲐鱼闽东(30尾)和闽南(30尾)种群进行了AFLP分析,8对选择性引物在2个种群60个个体中,共扩增出497个位点,其中多态位点343个.闽东和闽南种群的多态位点比例、Nei遗传多样性指数和Shannon遗传多样性指数分别为57.75％、64.59％,0.1779、0.2123,0.2725和0.3228,2个种群的遗传多样性处于同一水平.与其他鱼类对比显示,台湾海峡鲐鱼种群的遗传多样性水平高.生境广及生命周期短被认为是台湾海峡鲐鱼具有较高遗传变异水平的原因;基因分化系数Gst、Shannon遗传多样性指数和AMOVA分析均显示鲐鱼的遗传变异主要来源于种群内,而种群间无明显的遗传分化.Nm显示2个种群间基因交流频繁.种群的显性基因型频率分布显示2个种群有基本相同的种群遗传结构.结果表明,鲐鱼闽东和闽南种群间无明显的遗传差异.幼体较强的扩散能力、海洋环流及洄游特性可能是造成台湾海峡鲐鱼种群间遗传同质性较高的原因.     

荒漠柠条锦鸡儿AM真菌多样性

为了阐明荒漠柠条锦鸡儿(Caragana korshinskii Kom.)根围AM真菌群落组成及其分布特点,2010年7月从河北省与内蒙古交界荒漠带选择多伦湖、黑城子和二羊点3个样地,按0—10、10—20、20—30、30—40、40—50 cm 5个土层采集柠条根围土壤样品,研究了柠条根围AM真菌物种组成、生态分布及与土壤因子的相关性。共分离鉴定出4属24种AM真菌,其中球囊霉属(Glomus)16种,是3个样地共同优势属;无梗囊霉属(Acaulospora)5种,是3个样地共有属;盾巨孢囊霉属(Scutellospora)2种;多孢囊霉属(Diversispora)1种;网状球囊霉(G.reticulatum)是黑城子和多伦湖样地优势种,二羊点亚优势种;黑球囊霉(G.melanosporum)是黑城子和二羊点样地优势种,多伦湖亚优势种;二羊点的AM真菌种类和孢子密度最高;黑城子和多伦湖样地无明显差异。AM真菌孢子密度与土壤碱解N、有机质和速效P含量极显著正相关,其中土壤碱解N影响最大。结果表明,柠条根围AM真菌物种多样性丰富,具有明显空间异质性,并与土壤因子关系密切,这为进一步分离筛选优势AM真菌菌种,充分利用AM真菌资源促进荒漠柠条生长提供了依据。     

短花针茅荒漠草原土壤微生物群落组成及结构

为详细了解内蒙古短花针茅荒漠草原生态系统中土壤微生物群落组成与结构。对其土壤中微生物的总DNA提取后,采用高通量测序技术对土壤中细菌的16Sr DNA和真菌的ITS基因进行了序列测定,分析了短花针茅荒漠草原土壤中微生物群落结构特征。结果表明,共获得细菌OTUs13711个,真菌OTUs 5929个。物种分类显示,细菌种类隶属于29门57纲111目191科485属,其中优势类群为Gammaproteobacteria和Thermoleophilia,它们的相对丰度分别为32.68%和26.83%。真菌隶属于4门16纲45目78科105属,优势类群为Ascomycota和Basidiomycota,它们的相对丰度分别为35.76%和25.90%。土壤中细菌群落的多样性和丰富度均高于真菌。     

Chloroplast DNA variation and genetic structure of Miscanthus sinensis in southwest China

Miscanthus sinensis is a dominant perennial C4 grass with the potential to being a feedstock crop in North America, Europe, and China. Variation in chloroplast DNA sequence was used to obtain information regarding the genetic diversity and structure of populations of M. sinensis in southwest China. Chloroplast DNA, trnL-F and rpl20-rps12 sequences from seventy-five individuals representing 14 populations of M. sinensis were used to study the sequence variation. Seven haplotypes and 16 polymorphic sites (2.7%) were identified. Five substitutions, 6 indels, and 5 existing substitutions and indels sites, were detected through splicing these two gene segments. The genetic diversity within the studied populations (diversity of haploids, h = 0.561, nucleotide diversity, π = 0.00504) was low, this may be affected by the relatively larger effect of genetic drift on the chloroplast DNA, reflecting smaller effective populations than nuclear DNA. Genetic variance within the populations was higher than that between the populations, suggesting that higher gene flow may exist within these populations. The results of parsimony network in seven haplotypes indicated that H1 and H2 may be ancient haplotypes, which may help guide future research on the origin of M. sinensis. Our results provide information on the genetic diversity and structure of M. sinensis and may assist future studies on the phylogeography of M. sinensis.