破碎生境中影响植物种群进化动态的因素

综述了生境破碎中植物种群进化的影响因素。生境破碎会导致遗传漂变、近交衰退、基因流下降,降低种群的遗传变异,增加种群间遗传分化,不利于物种的进化前景。生境破碎形成许多隔离的小种群,小种群面临高的局部灭绝的风险,应当加强对破碎生境中小种群的监测,分析其进化趋势,采取必要的保护措施。     

基于线粒体Cyt b基因的南海北部金钱鱼种群遗传结构分析

【目的】分析南海北部金钱鱼（Scatophagus argus）遗传多样性,明确其群体演化历史和分布动态,为金钱鱼养殖育种及其种质资源的合理开发利用提供科学依据。【方法】以采自福建东山（DS）、广东阳江（YJ）、海南海口（HK）、广西北海涠洲岛（BH）、广西钦州（QZ）、广西防城港（FC）及越南清化（TH）等南海北部的7个金钱鱼地理群体为研究对象,基于线粒体DNA细胞色素b基因（Cyt b）序列分析,利用DnaSP 5.10统计南海北部金钱鱼群体的单倍型、单倍型多样性指数（H_d）和遗传多样性指数（π）,通过邻接法（NJ）构建单倍型的系统发育进化树,以Network 4.6中的中介连接网络法构建单倍型网络图,并综合Tajima’s D检验、Fu’s Fs检验及核苷酸错配分布等方法分析金钱鱼群体的历史动态。【结果】7个金钱鱼地理群体的291条Cyt b基因序列定义为33个单倍型（Hap1~Hap33）,其中单倍型Hap1、Hap2和Hap7是南海北部金钱鱼在长期进化过程中形成的稳定优势基因型。7个金钱鱼地理群体的H_d为0.54103~0.77436,π为0.00112~0.00171,群体内遗传距离为0.00113~0.00171,遗传分化系数（F_st）为-0.01734~0.00364,基因流（Nm）为137.03888~inf。不同地理群体的单倍型均无规律地散布在单倍型系统发育进化树上,不存在与地理群体明显对应的系统分支,也未表现出明显的地理聚群分布特征。金钱鱼群体内个体间的遗传变异为100.74%,说明遗传变异全部来源于群体内个体间,即南海北部金钱鱼群体既无群体分化,也无以琼州海峡分隔的组群分化。Tajima’s D检验和Fu’s Fs检验结果均为显著负值,且核苷酸错配分布呈单峰分布,推测南海北部金钱鱼群体发生过群体扩张,且扩张事件约发生在3.4万年前,属于更新世晚期。【结论】南海北部7个金钱鱼地理群体的遗传多样性符合高单倍型多样性低核苷酸多样性类型,群体间遗传距离较小,亲缘关系较近,遗传分化不明显,且群体间存在频繁的基因交流,具有高度的遗传同质性,符合南海北部金钱鱼是一个随机交配种群的假设。     

木荷种群遗传多样性的ISSR分析

利用ISSR分子标记技术,对木荷种群的遗传多样性和遗传分化进行分析.用12个引物对9个木荷种群共180个个体的样品进行扩增,共测到245个位点,其中多态位点221个,多态位点百分率(P)为90.20%.9个种群的P平均为53.02%.木荷种水平的Shannon信息指数(Ⅰ)为0.4548,Nei指数(h)为0.3016.各种群Ⅰ平均为0.2914,h平均为0.1974.表明木荷物种以及种群水平均具有较高的遗传多样性.AMOVA分子差异分析表明木荷种群的遗传变异34.37%存在于种群间,65.63%存在于种群内,种群间的基因分化系数(Gst)为0.3454.木荷种群间的基因流(Nm)为0.9476.木荷9个种群间的遗传距离平均为0.1547.利用算术加权平均数法(UPGMA)对木荷9个种群进行聚类,结果可分为3大类群.     

九节茶种质遗传多样性ISSR分析

为进一步研究九节茶的遗传特性,为育种工作提供理论指导,利用ISSR分子标记试验方法研究了37个九节茶种源的遗传多样性,从100条引物中筛选出17条引物,分别利用POPGENE 1.32软件及NTSYS软件对九节茶种源进行了基于ISSR的遗传多样性分析及种源聚类分析。结果表明：17条引物共扩增出105个位点,其中多态性位点87个,多态性位点百分率65.71%;37个种源间遗传多样性较低,福建、广东、江西、浙江和广西5个种群之间的遗传多样性为0.1770,种内遗传多样性为0.0990,基因分化系数为0.4405,即种群间遗传变异占种群遗传变异的44.05%,55.95%的遗传变异在种内进行。由种群间的遗传分化系数计算的基因流Nm=0.6350。遗传相似系数为0.7048~0.9143,平均0.8096。聚类分析表明,在遗传相似系数为0.81处,37个种源可以分为5类,聚类结果并不能完全反映出种源的地理分布,但可以部分反映地理分布的特点,为种质资源的鉴定打下良好基础。     

New ways to study developmental genes in spore-forming bacteria

The regulated activation of numerous sets of genes in multiple chromosomal locations is a hallmark of cellular differentiation in both eukaryotes and prokaryotes. Certain species of bacteria that experience complex developmental cycles are especially attractive as systems in which to study the mechanisms of this kind of gene regulation because they are highly amenable to both biochemical and genetic approaches. Bacillus subtilis, which undergoes extensive cellular differentiation when it sporulates, is one such system. Many new methods are now available in this Gram-positive species for identifying, manipulating, and studying the regulation of genes involved in spore formation, including the use of transposable genetic elements that create gene fusions in vivo as an automatic consequence of insertions into genes.     

Gene flow and population differentiation

There are many possible spatial patterns of selection and gene flow that can produce a given cline structure; the actual geography of natural selection and gene flow must be worked out before an attempt is made to explain a given natural cline in terms of a model. The results of experimental and theoretical models show that it is possible for local differentiation to evolve parapatrically in spite of considerable gene flow if the selection gradients are relatively uniform. Irregularities in environmental gradients increase the sensitivity of clines to the effects of gene flow in proportion to the increase in the differences in gene frequencies between the emigrants and the demes receiving the immigrants. It is not necessary for a sharp spatial environmental change to be present for distinct differentiation to occur. In some cases even a gentle environmental gradient can give rise to marked spatial differentiation along a genetically continuous series of demes; such environmental differences may be below the practical limits of resolution in field studies. Any asymmetry in gene flow does not lead to dedifferentiation if the environmental gradient is smooth; it merely shifts the position of the transition zone between the differentiated areas from that which would be expected if there were no asymmetry. Abrupt geographic differences in gene, genotype, or morph frequencies should not, therefore, be interpreted as evidence for environmental changes in the immediate vicinity of the steepest part of the cline; neither should they be interpreted as evidence for geographic barriers, sharp environmental differences, or sexual isolation among the differentiated groups of populations when there are no other sources of evidence for these phenomena. Gene flow may be unimportant in the differentiation of populations along environmental gradients.     

Local selection and latitudinal variation in a marine predator-prey interaction

Although pairs of species often interact over broad geographic ranges, few studies have explored how interactions vary across these large spatial scales. Surveys along 1500 kilometers of the Pacific coast of North America documented marked variation in the frequency of predation by the snail Nucella canaliculata on the intertidal mussel Mytilus californianus. Laboratory rearing experiments suggest that regional differences in drilling behavior have a genetic basis, and mitochondrial sequence variation confirms that gene flow is low among these snail populations. Marine communities separated by hundreds of kilometers may have intrinsically different dynamics, with interactions shaped by restricted gene flow and spatially varying selection.     

正选择驱动褪黑激素受体MT1与MT2基因的分化

【目的】研究褪黑激素受体（melatonin receptor,MTNR）基因的进化模式,为褪黑激素受体基因相关功能的研究提供理论参考。【方法】利用生物信息学的方法和软件对来自11个物种的褪黑激素受体1a（MT1）和褪黑激素受体1b（MT2）基因的系统发生关系、基因相似性、选择压力、选择方向等进行系统地分析。【结果】MT1和MT2基因可能由共同祖先基因通过基因重复产生, MT1可能保持着源基因的功能,MT2为新产生的功能基因。MT1基因在物种间的相似性极显著高于MT2基因（P＜0.01）;MT1基因主要受纯化选择,MT2基因受到显著的正选择;MT1与MT2基因均承受着较强的选择压力,且选择压力在2基因间无显著差异（P＞0.05）。【结论】MT1基因主要受纯化选择可能是MT1基因与动物季节性繁殖关联研究结论不统一的原因,MT2基因受正选择提示正选择可能是驱动MT2与MT1发生分化的重要动力。     

浙江仙居长叶榧自然居群遗传多样性的ISSR分析

采用ISSR分子标记技术,对中国特有树种长叶榧的遗传多样性和遗传分化进行分析.用10个引物对浙江省仙居县的5个长叶榧居群共100个样品进行扩增,共测到136个位点,其中多态位点72个,多态位点百分率（P）为52.97%.长叶榧总的Shannon信息指数(I)为0.269 1,Nei指数（h）为0.175 8,表明种水平的遗传多样性较高,而居群水平的遗传多样性较低,P平均为28.09%,I平均为0.138 9,h平均为0.091 2.AMOVA分子差异分析表明长叶榧居群间遗传分化程度高,45.72%的变异存在于居群间,54.28%的变异存在于居群内,居群间的基因分化系数（Gst）为0.489 1.长叶榧居群间的基因流很低,为0.522 4.瓶颈效应、居群隔离和遗传漂变可能是造成长叶榧居群低遗传多样性和居群间较高遗传分化的主要原因.5个居群间的平均遗传距离为0.128 0.利用算权平均数法（UPGMA）对长叶榧居群进行聚类,结果可分为两大类群:下辽和龙潭坑2个居群组成一个类群;石舍与石长坑居群先聚在一起,再与夹坟坑居群组成另一个类群.      

Microsatellites reveal strong genetic structure in the common cutworm,Spodoptera litura

The common cutworm, Spodoptera litura(Lepidoptera: Noctuidae), is a voracious agricultural pest. To increase understanding of the migration patterns and genetic diversity of different geographic populations of this species, we analyzed genetic variation in nine microsatellite loci among 576 individuals collected from 17 locations in China and one in Myanmar during 2011–2012. We successfully identified 162 alleles, with an average of 18 alleles per locus and a range of 5 to 34. The mean observed heterozygosity of the 18 populations ranged from 0.18 to 0.98, and the expected heterozygosity ranged from 0.19 to 0.89. For the nine microsatellite markers studied, polymorphism information content ranged from 0.18 to 0.88(mean=0.64). We found low genetic differentiation among the 18 populations(mean F-statistics(F_(ST))=0.05) and high genetic diversity among individuals. Principle coordinates analysis indicated no significant correlation between geographic and genetic distance(r=0.04). The value of N_m(N_m4) estimated using coalescent-based methods suggests strong gene flow with migration. The nine microsatellite markers identified in this study will be beneficial for further investigation of migration patterns and genetic diversity in S. litura.     

基于28S rDNA D2区序列的陕南凹缘菱纹叶蝉分子系统学与遗传多样性研究

为探讨陕南桑园凹缘菱纹叶蝉(Hishimonus sellatus Uhler)系统关系与遗传多样性,对陕南7个主要蚕桑产区共132头凹缘菱纹叶蝉的 28S rDNA基因D2区序列进行核苷酸多样性和遗传差异分析,同时研究单倍型之间的分子系统关系和网络进化图。结果表明,总群体共存在多态性位点63个,单倍型8个,优势单倍型H_1占单倍型总数的74.2%,遗传分化程度较低。分子方差分析显示:种群内变异占总组分的98.94%,差异不显著,且其基因流系数Nst和种群地理距离之间不存在相关性(R~2=0.019 7),说明各个地理种群之间存在渐渗杂交。     

Community diversity: relative roles of local and regional processes

The species richness (diversity) of local plant and animal assemblages-biological communities-balances regional processes of species formation and geographic dispersal, which add species to communities, against processes of predation, competitive exclusion, adaptation, and stochastic variation, which may promote local extinction. During the past three decades, ecologists have sought to explain differences in local diversity by the influence of the physical environment on local interactions among species, interactions that are generally believed to limit the number of coexisting species. But diversity of the biological community often fails to converge under similar physical conditions, and local diversity bears a demonstrable dependence upon regional diversity. These observations suggest that regional and historical processes, as well as unique events and circumstances, profoundly influence local community structure. Ecologists must broaden their concepts of community processes and incorporate data from systematics, biogeography, and paleontology into analyses of ecological patterns and tests of community theory.     

利用微卫星标记分析云南省6个东方蜜蜂(Apis cerena)群体遗传多样性及遗传分化

利用21对微卫星标记对来自于腾冲、无量山、迪庆、武定、泸水、西双版纳6个云南东方蜜蜂Apis cerana群体进行遗传多样性及遗传分化分析.通过计算多态信息含量、平均杂合度、等位基因数、遗传距离、基因流、F-统计量等参数,评估各东方蜜蜂群体遗传多样性和各群体间遗传分化.各座位的等位基因数为4(AP313)至18(AT003).除迪庆群体外,其余群体均显示较高水平的期望杂合度,其中,武定群体最高,为0.696;迪庆群体最低,为0.367.各东方蜜蜂群体间存在极显著的遗传分化,平均分化系数Fst为0.264.云南6个东方蜜蜂群体的遗传分化显著,除迪庆群体外,其余5个群体遗传多样性较高;分析遗传分化与地理距离的关系发现,云南6个东方蜜蜂群体间的遗传分化与地理距离不存在显著相关.     

利用荧光SSR分子标记评估中国栗属植物遗传多样性

【目的】利用SSR分子标记研究中国栗属植物遗传多样性、亲缘关系和群体遗传结构的特点,为栗属植物的资源改良、种质创新与利用提供理论依据。【方法】利用不同产区的12个板栗品种对330个SSR分子标记进行筛选,获得高质量的12对SSR引物。随后在高分辨率的毛细管电泳上对栗属4个种的96份资源进行位点信息检测。用Power Marker 3.25、GenAlEx 6.51、FigTree v1.4.3和Structure 2.3.3对全部资源进行群体遗传多样性的相关分析。【结果】对96份资源进行检测,共获得129个等位变异,每个标记平均有10.750个位点变异。位点多样性（GD）变幅为0.656（CmSI0396）—0.877（CmSI0930）,平均为0.800;观察杂合度（Ho）变幅为0.329（CmSI0742）—0.769（CmSI0702）,平均为0.615;期望杂合度（He）变幅为0.489（CmSI0742）—0.789（CmSI0922）,平均为0.672;多态信息含量（PIC）变幅为0.586（CmSI0396）—0.868（CmSI0930）,平均为0.774。从不同栗属植物种群间的遗传多样性来看,茅栗种群的观察位点数（Na）、有效等位变异（Ne）和Shannon多样性指数最高,其次是板栗种群,最低是日本栗种群。从两两群体间的遗传分化指数（Fst）可知,栗属植物种间的遗传分化值在0.077—0.180,整体种群间存在中等以上程度的分化,板栗种群、锥栗种群与日本栗种群间的遗传分化值分别为0.165和0.180,表现出较大的遗传分化。同时,栗属植物种群的基因流（Nm）为1.580>1,也说明种群间存在较频繁的基因交流,由此降低了由基因遗传漂变所引起的各种群间遗传分化程度。分子方差分析（AMOVA）结果表明,变异主要发生在种群内,占总变异量的73%,种群间的变异占27%。UPGMA聚类分析、主坐标分析和群体遗传结构结果较一致,各资源的遗传背景存在明显的种间界限,部分资源在世代遗传中继承了不同祖先种的遗传信息。例如,资源65、71和82号为混合类型资源,包含有茅栗和日本栗的遗传背景,而现在的两种间存在地理隔离。在相同生态区域的栗属植物种间存在一定的基因交流,没有形成完全的生殖隔离。48号资源‘广东矮生’同时含有板栗和茅栗的遗传背景,在地理分布上该资源原生地正处于板栗和茅栗资源的重叠生态区。【结论】筛选的12对SSR引物能够准确地评估中国栗属植物的遗传多样性,综合聚类分析可确定栗属植物的类群划分与种间信息高度一致且种间存在一定的基因交换。     

Evidence for a one-allele assortative mating locus

Theoretical models have shown that speciation with gene flow can occur readily via a "one-allele mechanism," where the spread of the same allele within both of two diverging species reduces their subsequent hybridization. Here we present direct genetic evidence for such an allele in Drosophila pseudoobscura. Alleles conferring high or low assortative mating in D. pseudoobscura produce the same effects when inserted into D. persimilis. This observation suggests that the type of genetic variation that is most conducive to controversial modes of speciation with gene flow, such as reinforcement or sympatric speciation, is present in nature.     

Genetic Variation in Rhizome Lotus （Nelumbo nucifera Gaertn. ssp. nucifera） Germplasms from China Assessed by RAPD Markers

To estimate genetic variation in rhizome lotus （Nelumbo nucifera Gaertn. ssp. nucifera） germplasms in China, a total of 94 rhizome lotus germplasms collected from 18 provinces in China were assessed. The RAPD （randomly amplified polymorphic DNA） marker was employed. The selected 17 random primers detected 139 polymorphic alleles out of a total 207 （67.15%）. Nei＇s gene diversity statistics and region differentiation parameters indicated that all germplasms had a relatively high level of genetic diversity with ne = 1.3202, h = 0.1937, I= 0.2982 and the gene flow among all regions was Nrn = 5.5742. The UPGMA dendrogram clustered all 94 germplasms into two clusters： One contained eight commercial cultivars and major landraces, and the other included the wild and some special landraces from five regions, and the PCA analysis exhibited the similar result. Those germplasms from southwestern and eastern China had higher genetic diversity than those from the southern, northern and central China. Predominant proportion of genetic variation （95.61%） was found significant within rather than among （4.39%） regions, as revealed by AMOVA analysis. The data analysis also revealed that the genetic diversity of rhizome lotus germplasms among different regions is positively related to their geographic distances, though it is ambiguous to find the trend from the UPGMA dendrogram and the PCA analysis. A relatively high genetic diversity and gene flow resided in the root lotus germplasms; about 96% of the variation was found within region; accessions from southwest and eastern China have higher genetic diversity than those from the southern, northern and central China.     

Plant speciation

Like the formation of animal species, plant speciation is characterized by the evolution of barriers to genetic exchange between previously interbreeding populations. Prezygotic barriers, which impede mating or fertilization between species, typically contribute more to total reproductive isolation in plants than do postzygotic barriers, in which hybrid offspring are selected against. Adaptive divergence in response to ecological factors such as pollinators and habitat commonly drives the evolution of prezygotic barriers, but the evolutionary forces responsible for the development of intrinsic postzygotic barriers are virtually unknown and frequently result in polymorphism of incompatibility factors within species. Polyploid speciation, in which the entire genome is duplicated, is particularly frequent in plants, perhaps because polyploid plants often exhibit ecological differentiation, local dispersal, high fecundity, perennial life history, and self-fertilization or asexual reproduction. Finally, species richness in plants is correlated with many biological and geohistorical factors, most of which increase ecological opportunities.     

A mosaic of chemical coevolution in a large blue butterfly

Mechanisms of recognition are essential to the evolution of mutualistic and parasitic interactions between species. One such example is the larval mimicry that Maculinea butterfly caterpillars use to parasitize Myrmica ant colonies. We found that the greater the match between the surface chemistry of Maculinea alcon and two of its host Myrmica species, the more easily ant colonies were exploited. The geographic patterns of surface chemistry indicate an ongoing coevolutionary arms race between the butterflies and Myrmica rubra, which has significant genetic differentiation between populations, but not between the butterflies and a second, sympatric host, Myrmica ruginodis, which has panmictic populations. Alternative hosts may therefore provide an evolutionary refuge for a parasite during periods of counteradaptation by their preferred hosts.