小毛莨居群的遗传分化及其与空间隔离的相关性

采用聚丙烯酰胺凝胶电泳技术,对分布于华中地区的11个小毛莨（Ranunculus ternatus）居群的遗传分化进行了检测。对8个酶系统17个酶位点上的分析结果表明,该种各居群的各项遗传多样性指标处于一个相对较低的水平：多态位点比率（P）为0－53.0％,平均每位点等位基因数（A）为1－1.647,平均预期杂合度（He）和观察杂合度（Ho）分别为0－0.108和0－0.102。居群间遗传一致度甚高（I＝0.9754-0.9991）。根据Nei 's传距离所作出的聚灰分析表明,豫南信阳地区3个居群与湖北省武汉地区8个居群之间关系较远。而在武汉地区,长江以北的居群及长江以南的部分居群分别相聚在一起,用GPS定位方法得到居群间空间距离并据此聚类,该种的遗传分化与地理因素的相关性,并推测出长江的隔离作用加强了两岸居群间的遗传分化,同时发现一个生于独特生境的居群在表型和遗传结构上都已与其他邻近居群有了很大分异,由于该居群在所检测的酶位点上均无特有等位基因出现,作者认为不宜将其作为新种或新变种处理。     

小毛茛居群分化研究(Ⅰ)——居群内和居群间的形态变异

对小毛茛的 3个地点共 6个居群的的形态变异作了观测。该种的株高、叶形、花瓣数目等性状具有显著的居群内和居群间变异。用 31个形态及生境性状作出的聚类分析结果表明 :小毛茛居群遗传分化主要与居群所在生境因素相关 ,与地理位置之间仅有不显著的相关性。     

小毛茛居群分化研究(Ⅱ)——居群遗传变异的等位酶分析

采用聚丙烯酰胺凝胶电泳技术检测小毛茛的 3个地点共 6个居群的遗传变异。对 4个酶系统 7个酶位点的基因型频率的聚类分析 ,结果表明 :小毛茛居群遗传分化主要与居群所在生境因素相关 ,与地理位置之间仅有不显著的相关性。等位酶分析与形态变异研究的结果基本吻合     

小毛莨居群分化研究（Ⅰ）——居群内和居群间的形态变异

对小毛莨的3个地点共6个居群的形态变异作了观测,该种的株高、叶形、花瓣数目等性状具有显著的居群内和居群间变异。用31个形态及生境性状作出的聚类分析结果表明,小毛莨巨群遗传分化主要与居群所在生境因素相关,与地理位置之间仅有不显著的相关性。     

小毛莨居群分化研究（Ⅱ）——居群遗传变异的等位酶分析

采用聚丙烯酰胺凝胶电泳技术检测小毛莨的3个地点共6个居群的遗传变异。对4个酶系统7个酶位点的基因型频率的聚类分析。结果表明,小毛莨居群遗传分化主要与居群所在生境因素相关,与地理位置之间仅有不显著的相关性,等位酶分析与形态变异研究的结果基本吻合。     

小毛茛(Ranunculus ternatus Thunb.)花粉流潜能初探

在自然居群中对小毛茛传粉机制与距离作了观测,并对开花后花粉萌发能力的变化作了研究,结果是：该种兼具虫媒或风媒传粉机制,以虫媒传粉为主;传粉距离多数局限于２ｍ以内,但不排除远距离传粉的可能性;体外萌发试验表明,该种花粉萌发率在开花第一天甚低,开花后２４ｈ达到最高值。作者推测,小毛茛花粉以近距离散布为主,但具有远距离传播的潜能。     

小慈姑的遗传多样性和居群分化

小慈姑是中国南部狭域分布的易危水生植物。采用聚丙烯酰胺凝胶电泳和等位酶分析方法,研究了该种江西东乡、湖南茶陵、广西桂林和福建武夷山4个地点的8个自然居群的遗传分化及其与地理位置的相关性。9个酶系统18个等位酶位点的检测结果表明,小慈姑有较高水平的遗传多样性:多态位点百分率P=16.67%—38.89%,平均每位点等位基因数A=1.278—1.833,平均预期杂合度He=0.0941—0.1928,平均观察杂合度Ho=0.1461—0.2127。居群之间有较高的遗传一致度I=0.7161—0.9965。根据Nei s遗传距离所作出的聚类分析显示,同地居群之间有较紧密的遗传关系,居群间的遗传分化与空间距离呈正相关。     

小毛茛雌蕊群的授粉率及花粉管生长途径

为探讨毛茛属中是否具有与慈姑属中类似的花粉管再分配现象,对小毛茛开花后不同时期柱头的授粉率和花粉量进行了统计,并采用荧光显微术观察了其花粉在雌蕊群中的萌发及花粉管生长过程。该种的每朵花中含有39.2±9.9个离生心皮,开花过程常持续4~6d,开花2d后,柱头授粉率就可达到100%,平均每柱头的花粉量在3d后达到17.0±2.4粒。虽然开花的当天即有少数柱头落置有花粉粒,但花粉萌发常自开花的次日开始。花粉管先沿各雌蕊之向心一侧的组织中穿行至子房基部后部分花粉管转向胚珠,由珠孔进入珠心。从花粉粒落置于柱头到花粉管进入珠心大约需要24h。尽管毛茛属有着与慈姑属类似的多心皮雌蕊群,但大量的荧光显微观察表明,与慈姑属植物中不同的是,小毛茛的花粉管生长均局限于每一雌蕊中而不能穿过子房向其他雌蕊生长。雌蕊群的比较解剖发现野慈姑的子房基部有一条通向花托表面的孔道,这正是花粉管由一个雌蕊到另一个雌蕊的通路,但小毛茛的子房基部不存在此孔道。     

华东竹黄菌不同居群遗传分化的RAPD分析

为了解竹黄地理居群间的遗传分化,本研究采用随机引物扩增多态性DNA分子标记技术对江苏、安徽和浙江3省的8个居群共32个竹黄样本进行了遗传多样性分析.从50个RAPD引物中筛选得到了5个随机引物,对供试材料的DNA进行扩增,共检测出77个位点,其中多态性位点52个,多态性位点比率为67.53%.UPGMA聚类分析结果表明,这8个居群分为三类:安吉居群、临安居群、宜兴居群、广德居群和泾县居群聚为一类;宁国居群和休宁居群聚为一类;淳安居群单独为一类.遗传多样性分析表明8个竹黄居群中,淳安居群的遗传多样性水平最高,安吉居群的遗传多样性水平最低.Nei's基因多样性指数和Shannon信息指数均表明竹黄物种水平的遗传多样性高于居群水平.     

濒危植物连香树居群的遗传多样性和遗传分化研究

利用ISSR分子标记技术对濒危植物连香树10个居群的遗传多样性和遗传变异进行了分析,结果表明:连香树物种水平遗传多样性较高,多态位点百分率(PPB)达到69.59%,Nei’s基因多样性指数(H)和Shannon信息指数(I)分别为0.231 3和0.351 4;而在居群水平上,多态位点百分率(PPB)为30.61%,Nei’s基因多样性指数(H)和Shannon信息指数(I)分别为0.115 6和0.173 3。遗传变异分析表明,居群间遗传分化程度高,遗传分化系数(GST)为0.500 3,居群间基因流Nm为0.527 3。Mantel检测,居群间的遗传距离和地理距离之间不存在显著的相关性。生境的片断化使居群间的基因流受阻,可能是导致居群间高遗传分化和居群水平低遗传多样性的主要原因。     

Genetic differentiation among populations of marine algae

Most of the information for genetic differentiation among populations of marine algae is from studies on ecotypic variation. Physiological ecotypes have been described for individuals showing different responses to temperature and salinity conditions. Morphological ecotypes have also been found associated with areas differing in wave exposure or different intertidal positions. Little is known on how genetic variation is organized within and between populations of marine algae. The occurrence of ecotypic variation in some species is evidence for genetic differentiation among populations resulting from selection by the local environment. The rate of dispersal and subsequent gene flow will also affect the level of differentiation among populations. In species with low dispersal, differentiation can arise through chance founder events or random genetic drift. The few studies available have shown that species of algae exhibit a range of dispersal capabilities. This information can be useful for predicting the potential level of genetic differentiation among populations of these species. Crossing experiments with several species of algae have shown that populations separated by a considerable distance can be interfertile. In some cases individuals from these populations have been found to be morphologically distinct. Crosses have been used to study the genetic basis of this variation and are evidence for genetic differentiation among the populations sampled. Genetic variation of enzyme proteins detected by electrophoresis provides an additional method for measuring genetic variation within and between populations of marine algae. Electrophoretic methods have previously been used to study systematic problems in algae. However, there have been few attempts to use electrophoretic variation to study the genetic structure of populations of marine algae. This approach is outlined and includes some of the potential problems associated with interpreting electrophoretic data. Studies of electrophoretic variation in natural populations ofEnteromorpha linza from Long island Sound are used as an example. This species was found to reproduce only asexually. Despite a dispersing spore stage, genetic differentiation was found on a microgeographic scale and was correlated with differences in the local environment of some of the populations. Similar studies on other species, and especially sexually reproducing species, will add to a growing understanding of the evolutionary genetics of marine algae.Paper presented at the Seaweed Biogeography Workshop of the International Working Group on Seaweed Biogeography, held from 3–7 April 1984 at the Department of Marine Biology, Rijksuniversiteit Groningen (The Netherlands). Convenor: C. van den Hoek.     

Genetic differentiation processes among the populations in India

The genetic variability in Indian populations is examined on the basis of the study of Tf, Gc, Gm, and Km polymorphisms. This variability is not associated with fluctuations, but is related to population history (mainly to migrations, hybrydization and caste endogamy). When genetic distances are calculated, Northern, Southern and Western Indian poplations show closer resemblances to Western Asian populations, while Eastern Indian populations are more similar to Mongoloid peoples.     

Genetic differentiation among local populations of Asian elephant

Electrohoretically detectable enetic variation for 29 kinds of blood protein encoded by 33 loci was analyzed for 78 Asian eletants (Elephas maximus) which were collected from its four local populations: Sri Lanka, Souti India, Thailand and Nepal. Elehants in Sri Lanka are classified into the subspecies E.m. maximus, and those from the other tlree localities into the subspecies E. m. indicus. Six variable loci were detected, and one of them, the tetrazolium oxidase locus, was observed to show a complete allele substitution between the subspecies. Average heterozgosity within local populations were in a range of 0.0152 ? 0.0303. Whereas the Nei's genetic distance among three local populations of the subspecies indicus were 0.0013 ? 0.0031, the distance between the subspecies indicus and maximus were 0.0328 ? 0.0370, indicating that the two subspecies were well differentiated genetically.     

Genetic divergence without spatial isolation in polecat Mustela putorius populations

Understanding how genetic divergence could exist without spatial isolation is a fundamental issue in biology. Although carnivores have previously been considered as having a weak genetic variability, polecats Mustela putorius from eight distinct populations exhibited both a strong polymorphism (17.5–22.5%) and a substantial allele effective number reaching N_e=1.12. Heterozygosity ranging from H_o=0.031–0.063 significantly differed among populations, while the mean F_IS averaging 0.388 stressed a real deficiency of heterozygotes. Observed heterozygosity levels among populations did not correlate with any habitat types but were clearly associated with habitat diversity index. The habitat structure in polecat home range corresponded to habitat mosaic structure in which discrete habitat types alternated causing multifactorial constraints that may favour heterozygosity. Allozymic frequencies within populations did not vary with dominant habitat. But in the Tyrosinase‐1, the rare homozygote BB, resulting in a ‘dark’ phenotype, was found much more in deciduous woods than the homozygote AA showing the ‘typical’ pattern. Thus, the genetic basis for a character differentiation was here evidenced in a remarkable situation without spatial isolation. Further, the very low proportion of heterozygotes for this locus suggests a disruptive effect and supports the prediction of intermediate phenotypes being at a disadvantage. This heterozygote deficit may also result from an assortative mating intra phenotype (homogamy). The divergence in polecat phenotypes showed that genetic differentiation can be induced by subtle variations in environment, a situation that is likely to be frequent in most natural populations, and emphasized the adaptive nature of habitat preference.     

Karyotype differentiation and reproductive isolation among natural populations of Drosophila lacertosa

Drosophila lacertosa is widely distributed from northern India to Far East of Russia throughout China. We have studied geographical distributions of three kinds of chromosomal karyotypes, type D (2n=10, 4 pairs of V-shaped metacentric chromosomes and a pair of micro-chromosomes), type L (2n=10, 5V with a pair of large-sized hetero-chromatic autosomes) and type M (2n=10, 5V with middle-sized ones). Type D was found exclusively in local populations of D. lacertosa distributed in Yun-Gui Plateau, southwestern China. Both type L and M have a wide range of distribution, and the former occurred in subtropical regions of China including Taiwan Island, whereas the latter in cool temperate regions of East Asia covering Far East of Russia, Korea and the Japan Islands. A strong premating isolation was detected between flies with type D and those with type L or M. These data demonstrate that genetic differentiation leading to cryptic speciation might have occurred in natural populations of Drosophila lacertosa.     

Genetic differentiation among North Atlantic killer whale populations

Population genetic structure of North Atlantic killer whale samples was resolved from differences in allele frequencies of 17 microsatellite loci, mtDNA control region haplotype frequencies and for a subset of samples, using complete mitogenome sequences. Three significantly differentiated populations were identified. Differentiation based on microsatellite allele frequencies was greater between the two allopatric populations than between the two pairs of partially sympatric populations. Spatial clustering of individuals within each of these populations overlaps with the distribution of particular prey resources: herring, mackerel and tuna, which each population has been seen predating. Phylogenetic analyses using complete mitogenomes suggested two populations could have resulted from single founding events and subsequent matrilineal expansion. The third population, which was sampled at lower latitudes and lower density, consisted of maternal lineages from three highly divergent clades. Pairwise population differentiation was greater for estimates based on mtDNA control region haplotype frequencies than for estimates based on microsatellite allele frequencies, and there were no mitogenome haplotypes shared among populations. This suggests low or no female migration and that gene flow was primarily male mediated when populations spatially and temporally overlap. These results demonstrate that genetic differentiation can arise through resource specialization in the absence of physical barriers to gene flow.     

暗褐蝈螽不同地理种群间的遗传分化

利用线粒体COI基因片段研究了我国吉林、辽宁、内蒙古、河北和四川的暗褐蝈螽(Gampsocleis sedakovii)12个地理种群间的遗传分化。结果表明: 36条626 bp的mtDNA-COI基因片段中共检测到单倍型29种, 多态位点71个, 其中简约信号位点37个, 单一多态位点34个。分子变异等级分析(AMOVA)的计算结果显示, 群体内变异仅占总变异的37.23%, 明显小于群体间变异, Fst值为0.62770, 各群体间呈现明显的遗传分化。最大简约法(MP)系统发育分析结果显示, 暗褐蝈螽的12个地理种群以极高的自举支持度(100%)聚类, 形成两个独立的分枝。由于两个分枝的聚类结果与基于形态学特征划分的两个亚种(Gampsocleis sedakovii sedakovii和Gampsocleis sedakovii obscura)并不对应。综合采集地的生境, 初步推测暗褐蝈螽两个亚种间的形态学差异可能是由于它们所处生境不同所引起。在12个地理种群中, 只有内蒙古通辽(NTL)的个体在两个分枝中均有出现。单倍型分布格局研究发现, 单倍型H10是内蒙古通辽(NTL)、鄂温克(NEWK)和吉林吉林(JJL)3个地理种群的共享单倍型, 说明它们来自于共同的祖先。研究结果支持我国的东北地区是暗褐蝈螽遗传分化中心的观点, 但不支持基于形态学特征划分的两个亚种。