川中丘陵地区大豆根瘤菌遗传多样性与系统发育关系

【目的】研究分离自川中丘陵地区大豆根瘤菌的遗传多样性和系统发育。【方法】采用16S rDNA PCR-RFLP和16S rRNA基因、glnII、共生基因(nodC)系统发育分析的方法进行研究。【结果】供试未知菌的16S rDNA用4种限制性内切酶(HaeⅢ、HinfⅠ、MspⅠ及TaqⅠ)酶切后获得5种16S遗传图谱类型。16S rDNA PCR-RFLP结果表明,所有供试菌株在83%水平分为慢生根瘤菌属(Bradyrhizobium)和中华根瘤菌属(Sinonrhizobium)两大类群,而75%的菌株为中华根瘤菌。6个代表菌株的16S rDNA、glnII和nodC三个位点基因的系统发育结果基本一致,4株与S.fredii USDA205T相似度最高;有2株分别与B.yuanmingense CCBAU10071T、B.diazoefficiens USDA110T相似度最高。4个Sinonrhizobium代表菌株16S rDNA、glnII序列相似度分别为98.3%-99.9%、98.2%-100%,但它们的nodC基因序列完全相同。【结论】川中丘陵地区大豆根瘤菌具有较丰富的遗传多样性,S.fredii为优势种。     

基于16S rDNA 和COI 基因序列初步探究角壳网纹溞的分类地位

在安徽升金湖中首次发现了角壳网纹溞。利用特异性分子标记, 对角壳网纹溞的16S rDNA 和COI 基因进行了PCR 扩增和测序, 并进行了相关的分子遗传学分析。结果表明: 角壳网纹溞的16S rDNA 和COI 基因中A+T 含量均超过60%, 明显高于C+G 的含量。角壳网纹溞不仅在形态上与其他同属种类相差校大, 在分子进化中也与其他同属种类的遗传距离相差较大。通过K-2P 双参数模型计算, 角壳网纹溞COI 基因的种间平均遗传距离高达20%, 种间遗传距离的范围为16.7%-23.9%。因此, 结合其形态学和分子遗传学的特征暗示角壳网纹溞的进化地位应为网纹溞属中一个相对独立的分支。     

温度对透明溞和隆线溞一亚种发育及生长的影响

透明溞(Daphnia hyalina)和隆线溞一亚种(D.carinata ssp.)的发育、生长与温度的关系极为密切。胚胎发育时间随温度升高而缩短。低温培养的个体普遍大于高温。龄期、寿命也随温度升高而变短。在15—30℃温度范围内,实验种群的内禀增长力(r_m)随温度升高而增加。透明溞的产卵率以20℃为最高,达1.4936;而隆线溞一亚种则在15℃为最高,达1.490。不同种类在各种温度下,卵一胚胎,幼体,成体3个发育阶段所需时间的百分比变化甚小。卵一胚胎占总发育时间(从卵进入孵育囊起至成体死亡止)的(5.08±0.42)%,幼体为(10.76±1.53)%,成体为(84.16+1.72)%。根据不同温度下总胚胎发育时间,并参考了文献中记载的资料,获得了溞属温度与总胚胎发育时间的曲线迥归方程: Ln D=3.5748+0.0769 LnT-0.3122(Ln T)~2对隆线溞一亚种的形态、生态进行了描述,对它的分类地位进行了讨论。     

安徽某淡水龙虾养殖群体分类的分子标记筛选

为筛选可用于淡水龙虾养殖群体物种分类的分子标记,对安徽省某水产养殖有限公司采集的淡水龙虾样本进行了线粒体COⅠ、16S rDNA、D-loop、Cyt b及12S rDNA基因的测序分析,并与GenBank中30个滑螯虾属(Cherax)物种的相应基因序列比对,同时,进行上述5种分子标记在种内个体间、属内种间、科内属间和目内科间的同源性变异范围比对分析。结果显示,本研究所采集淡水龙虾样本与四脊滑螯虾(C. quadricarinatus)的相似性最高,其中,1 113 bp的Cyt b相似性100%,COⅠ、16S r DNA及12S rDNA相似性都在99%以上;在以克氏原螯虾(Procambarus clarkii)为外类群构建的邻接系统发育树中,本研究样本与四脊滑螯虾聚为一支,然后与其他物种聚合构成系统树,确定本研究采集的淡水龙虾样本为四脊滑螯虾;通过同源性变异范围比对分析,在淡水龙虾养殖群体的分子分类工作中,16S rDNA、Cyt b及12S rDNA比COⅠ和D-loop这2种分子标记具有较强优势。本研究结果可为今后淡水龙虾养殖场中物种的分类鉴定工作提供参考。     

太湖梅梁湾沉积物中溞属卵鞍的垂直分布及其与总氮、总磷间的关系

本研究调查了太湖梅梁湾沉积物(25~1 cm)中溞属种类卵鞍(或休眠卵)的垂直分布及其与总氮、总磷的关系。结果表明:在梅梁湾的沉积物中,共鉴定出3种溞属种类(盔形溞(Daphnia galeata)、蚤状溞(Daphnia pulex)和中华拟同形溞(Daphnia similoides sinensis))的卵鞍,其中以盔形溞为优势种;溞属种类平均卵鞍密度及含休眠卵卵鞍密度分别为0.03~2.01和0~0.33 ind·g-1dw;T1和T2采样点的3种溞属种类的含休眠卵卵鞍密度明显高于T3采样点;在16~1 cm的沉积层中,T1采样点的总氮和T2采样点的总磷均呈明显增加的趋势,而T3采样点中的总氮和总磷变化幅度均较小;T1采样点中蚤状溞的卵鞍密度与总磷(TP)含量呈显著的相关性(P0.05),而T3采样点中中华拟同形溞的卵鞍密度和T2采样点中盔形溞的含休眠卵卵鞍密度与总氮(TN)总磷(TP)含量均呈显著的相关性(P0.05);湖泊沉积物中溞属种类的卵鞍(或休眠卵)密度的垂直分布能够再现湖泊溞属种类的历史演替过程,且与总氮、总磷含量之间存在一定的相关性。     

武汉东湖透明溞和隆线溞一亚种的种群变动和生产量

本文报道了1980—1982年东湖二种优势枝角类:透明溞(Daphnia hyalina)和隆线溞一亚种(Daphnia carinata ssp.)的种群变动和生产量的研究结果。分析了影响种群变动和生产量的生态因子。尽管这二种枝角类在一年中有一段共存时间,但高峰期从来是错开的。一般来说,透明溞的高峰期出现在春季或冬季;而隆线溞一亚种则出现在夏季或秋季源沓ㄋ蘑蛘纠此?1980—1982年透明溞的种群密度的年平均值为28.43(17.59—38.50)个/升;隆线溞一亚种为4.64(3.79—5.31)个/升。种群的瞬时出生率(b),;通常大于瞬时增长率(r);瞬时死亡率(d)与b的季节变动在大多数情况下是一致的。透明溞的年平均生物量为0.218(0.163—0.315)毫克干重/升,生产量为9.181(4.877—13.428)毫克干重/升·年,P/B系数为42.38(27.76—56.70)。隆线溞一亚种的年平均生物量为0.046(0.039—0.060)毫克干重/升,生产量为3.417(2.752—3.829)毫克干重/升·年,P/B系数为77.04(61.24—99.74)。     

线粒体COⅠ和16S rRNA片段确定近江蛏和缢蛏属的分类地位

对5种双壳类软体动物(近江蛏Sinonovacula rivularis、缢蛏Sinonovacula constricta、小刀蛏Cultellus attenuatus、尖刀蛏Cultellus scalprum和大竹蛏Solen grandis)的线粒体基因COⅠ和16S rRNA部分序列进行测序和分析, 并结合GenBank中其他竹蛏超科和樱蛤超科物种COⅠ和16S rRNA片段, 计算种间遗传距离, 构建系统发育树, 探讨近江蛏及缢蛏属的分类地位。结果表明, 5个物种COⅠ和16S rRNA片段A+T含量均远高于G+C含量, 近江蛏与缢蛏之间的碱基序列差异和遗传距离均已达到种间差异水平, 确定近江蛏为缢蛏属的一个种。分别构建COⅠ(砂海螂为外群)和16S rRNA片段(密鳞牡蛎为外群)的Neighbor-Joining系统树, 两者的拓扑结构都明确显示, 缢蛏属为灯塔蛤科一个属, 灯塔蛤科录属于竹蛏超科, 而不录属于樱蛤超科。       

基于mt DNA 16S rRNA、COⅠ及Cyt b部分基因序列的长颚斗蟋与迷卡斗蟋遗传差异分析

长颚斗蟋和迷卡斗蟋的遗传差异对于蟋蟀遗传多样性,分类鉴定等有重要意义。通过PCR技术扩增测定长颚斗蟋和迷卡斗蟋的mt DNA 16S r RNA、COⅠ与Cyt b部分基因序列。数据分析表明:长颚斗蟋和迷卡斗蟋16S r RNA,COⅠ和Cyt b的种间序列相似度分别约为91.5%、87.0%和85.5%。长颚斗蟋种内16S r RNA、COⅠ和Cyt b基因序列相似度分别为99.8%、98.9%和98.8%;迷卡斗蟋种内16S r RNA、COⅠ和Cyt b基因序列相似度分别为98.4%、98.4%、97.2%。研究结果表明:长颚斗蟋与迷卡斗蟋的种间遗传差异明显大于种内遗传差异;16S r RNA、COⅠ、Cyt b基因序列适合作为长颚斗蟋和迷卡斗蟋遗传差异研究及分类鉴定的分子标记;COⅠ和Cyt b基因较16S r RNA基因有更快的进化速度,其种间遗传差异也更为明显。     

北京白羊沟景区农林交错带蛾类DNA条形码鉴定

[目的]DNA条形码技术已经在多个类群中得到了广泛应用,但对数量巨大的鳞翅目昆虫而言,仍然缺失大量数据,尤其是形态鉴定较为困难的小蛾类和很多中型蛾类,尚无法构建较为完善的DNA条形码系统.本研究旨在为鳞翅目害虫DNA条形码系统的构建和完善提供数据来源及支撑,验证COⅠ基因作为DNA条形码通用基因的准确性,探讨28S rDNA的D2基因片段作为DNA条形码辅助基因的可行性,并检验目前BOLD系统的鉴定成功率.[方法]对采集自北京白羊沟风景区的小蛾类和中型蛾类490头标本进行形态鉴定和DNA测序,分别基于COⅠ及28S D2基因计算种内种间遗传距离,并构建了NJ系统发育树.[结果]BOLD系统的鉴定成功率为65％,对小蛾类和夜蛾类鉴定成功率较低.基于COⅠ基因的NJ树鉴定成功率为94.4％,基于28S D2基因的NJ树鉴定成功率为89.4％.[结论]结合种内与种间遗传距离结果,COⅠ基因适合作为鳞翅目蛾类DNA条形码通用基因,28S D2基因较为保守,不适合作为DNA条形码的辅助基因.     

四种散白蚁的分子鉴定及系统发育地位(等翅目:鼻白蚁科)

【目的】目前对白蚁的物种鉴定主要依赖形态学特征,本文从分子水平对4种散白蚁进行了鉴定和系统发育分析。【方法】对4种散白蚁(湖南散白蚁Reticulitermes hunanensis Tsai et Peng、平额散白蚁Reticulitermes planifrons Li et Ping、近暗散白蚁Reticulitermes perilucifugus Ping和侏儒散白蚁Reticulitermes minuts Ping et Xu)的线粒体16Sr DNA和COⅡ基因序列进行扩增和测序,对序列进行比对及碱基组成分析后上传至GeneBank,并构建系统发育树对4种散白蚁进行系统发育分析。【结果】16S rDNA和COⅡ基因片段长度分别约380bp和720bp,两个基因的AT碱基含量均远远大于GC,16S rDNA序列的遗传距离普遍大于COⅡ序列,且两者的系统发育情况不一致。【结论】COⅡ基因系统发育与地理位置差距相关较为明显,16S rDNA基因序列碱基差异较COⅡ多,推断COⅡ基因更适合于白蚁由于地理位置引起的系统发育和地理迁徙及传入情况的研究,16S rDNA基因更适合于白蚁种类的鉴别。     

Respiratory electron transport system (ETS) activity as an estimator of the thermal tolerance of two Daphnia hybrids

The influence of temperature on the activity of the respiratoryelectron transport system (ETS) was measured in one clone ofDaphnia hyalina x galeata and one of Daphnia cucullata x galeata,isolated from Lake Bled (Slovenia). The ETS activity of ovigerousfemales acclimated to 7, 20 and 25°C, was measured at 5,10, 15, 20, 25 and 30°C. Population growth experiments showedthat D. cucullata x galeata grew better at high rather thanlow temperatures. Daphnia hyalina x galeata, however, grew moresuccessfully at low temperatures than did D. cucullata x galeata.The highest Q₁₀ of ETS activity of D. cucullata x galeata atthe lowest temperature range of 5–15°C indicated theabsence of enzymes that could function sufficiently well atlow temperatures. The ETS activity of the warm-acclimated hybridD. hyalina x galeata reached a maximum at an incubation temperatureof 20°C, while D. cucullata x galeata had maximal ETS activityat 25°C. Thus D. cucullata x galeata has a more efficientenzyme system than D. hyalina x galeata at the higher temperature.The higher Arrhenius activation energy (E_a) for D. cucullatax galeata than for D. hyalina x galeata indicates that enzymesfrom D. cucullata x galeata are more temperature sensitive thanthose from D. hyalina x galeata. In conclusion, the ETS of D.cucullata x galeata is adapted to a higher temperature and tonarrower temperature fluctuations than that of D. hyalina xgaleata.     

南漪湖沉积物枝角类卵鞍密度的垂直变化及其与营养盐的关系

本文研究了南漪湖沉积物(1～28 cm)中枝角类卵鞍密度的垂直变化.共鉴定出中华拟同形溞、盔形溞、蚤状溞、网纹溞、微型裸腹溞、象鼻溞、船卵溞、粗刺大尾溞和盘肠溞9种枝角类的卵鞍.大型溞属种类和小型枝角类卵鞍密度的变化范围分别为0～2.0和0～10.0 ind·g^-1 DM.中华拟同形溞和网纹溞分别是南漪湖沉积物大型枝角类和小型枝角类的优势种.中华拟同形溞的卵鞍密度与1^#采样点沉积物中总磷含量呈显著负相关,与3^#采样点沉积物中总氮、总磷含量均呈显著正相关.在3个采样点中(除2^#采样点总氮外),网纹溞的卵鞍密度与沉积物中总氮、总磷含量均呈显著正相关.结果暗示,湖泊富营养化和鱼类捕食影响了南漪湖枝角类群落结构的历史演变.     

A taxonomic reappraisal of the Daphnia hyalina complex (Crustacea: Cladocera): an experimental and ecological approach

The paper is a taxonomic study of the limnetic Daphnia populations of the English Lake District, the populations upon which the most popular taxonomic scheme is based (Johnson, 1952).
Johnson treats these populations as three varieties of the species D. hyalina, namely D. hyalina s. str., D.h. var. galeata and D.h. var. lacustris .
Careful examination of the populations of Esthwaite reveals that what has previously been regarded as a population of a single variety of D. hyalina. includes three distinct forms. Experimental work confirms that these are genetically distinct. One of these forms corresponds to D. hyalina var. galeata , whilst the other two are designated the "toothed" and "round-headed" forms.
The first part of the paper is concerned with the taxonomic status of var. galeata . Brooks (1957) and some later workers treat this as a separate species (D. galeata) on morphological grounds. This is fully supported by the present work. Differences between var. galeata and co-existing forms in incidence of sexual reproduction, in vertical distribution and in seasonal abundance and average brood-size provide further support for the separation of D. galeata.
The second part of the paper is concerned with D. hyalina s.str. which, on the basis of morphology, ecology and reproductive behaviour, is shown to be at least as distinct from other members of the complex as is D. galeata . It is argued that other forms should therefore to be removed from D. hyalina . The taxonomic status and affinities of the remaining "toothed" and "round-headed" forms are discussed.     

Allochronic differentiation among Daphnia species, hybrids and backcrosses: the importance of sexual reproduction for population dynamics and genetic architecture

Seasonal dynamics of the abundance, sexual reproduction and genetic architecture in a Daphnia hyalina-galeata hybrid complex were studied in the large and deep Lake Constance. We found evidence for the occurrence of first and second order hybridization. Our study revealed strong differences between the parental species not only regarding their seasonal dynamics, genetic architecture and diversity, but also their sexual reproductive behaviour. The overwintering D. hyalina showed low genetic diversity, no genetic differentiation during the season, and reproduced sexually in autumn, whereas D. galeata reached higher levels of genetic diversity, reproduced sexually in early summer, and exhibited changes in genetic structure during the season, but was only present from spring to autumn. However, in both species sexual reproduction was a rare event, and daphnids, including hybrids, reproduced predominantly asexually. This allows long-term persistence of hybrids as well without continuing hybridization events. Within all variables studied, F1 and F2 hybrids showed an intermediate pattern, whereas proposed backcross hybrids were more similar to their respective parentals. These differences in phenotype as well as significant differences in pairwise Fst values between parentals suggest that gene flow seems to be relatively low in the Lake Constance hybrid system. We found evidence for unidirectional introgression by backcrossing from D. galeata to D. hyalina and found a decrease in at least one of the proposed introgressed alleles in the hyalina-backcross while the season progressed. Our findings suggest allochronic differentiation within this hybrid population and different microevolutionary trajectories of the parental species, which will be discussed in the light of the ongoing reoligotrophication process of Lake Constance.     

Genetic markers, genealogies and biogeographic patterns in the cladocera

Cladoceran crustaceans are an important component of zooplankton in a wide range of freshwater habitats. Although the ecological characteristics of several cladoceran species have been well studied, biogeographical studies have been hampered by problematic taxonomic affiliations. However, recently developed molecular techniques, provide a powerful tool to subject aquatic taxa to comparative analyses. Here we highlight recent molecular approaches in aquatic ecology by presenting a simple method of DNA preparation and PCR amplification of the mitochondrial DNA (16S rDNA) in species from nine different families within the cladocera. On a broad taxonomic scale, sequence analysis of this mtDNA fragment has been used to produce the first molecular based phylogeny of the cladocera. This analysis clustered the cladoceran families in a fashion similar to that suggested by previous systematic classifications. In a more detailed analysis of the family Daphniidae, nuclear randomly amplified polymorphic DNA (RAPD), mitochondrial restriction fragment length polymorphism (RFLP) and morphological analyses were combined to identify species and interspecific hybrids within the Daphnia galeata species complex across 50 lakes in 13 European countries and one lake in Africa. The study revealed interspecific hybridization and backcrossing between some taxa (D. cucullata and D. galeata) to be widespread, and species and hybrids to frequently occur in sympatry. Genetic, as well as morphological information, suggests the occurrence of D. hyalina outside the Holarctic.     

Molecular genetic diagnostics of some Daphnia species (Crustacea,Cladocera) from the Volga river

Population genetic structure of the widespread Daphnia species from Kuibyshev and Saratov reservoirs was examined by use of RAPD-PCR technique with four mitochondrial DNA (16S rRNA) specific primers. One of the examined Daphnia clones from the Volga region appeared to be conspecific to the North American Daphnia galeata, while another clone was most likely a hybrid between D. galeata and D. cucullata.     

Genetic assessment of species boundaries in the North American Daphnia longispina complex (Crustacea: Daphniidae)

Species boundaries in the North American Daphnia longispina group have proved difficult to establish on the basis of morphology alone. This confusion may be due to hydridization, phenotypic plasticity or the existence of sibling species. We therefore used genetic analysis to delineate species boundaries by examining 27 North American populations belonging to the longispina complex for variation at 15–26 allozyme loci. The populations consisted of Daphnia thorata from two western sites and two eastern sites, Daphnia galeata mendotae from its type location and seven sites across its range, and Daphnia rosea from eight temperate and seven arctic sites. Two populations from the Eurasian longispina complex were also included for reference. Populations assigned to D. galeata mendotae formed a genetically cohesive group, whereas a genetic dichotomy was found between temperate and arctic D. rosea , suggesting that this taxon includes two species. Genetic analysis also confirmed the distinctness of western D. thorata from other members of the longispina group. Unexpectedly, eastern populations resembling D. thorata were genetically more similar to temperate D. rosea than to any helmeted species ( D. galeata, Daphnia hyalina or D. thorata ). Our results suggest that the helmet character is a poor indicator of phylogenetic relationships, as the genetic ability to produce this feature has been lost or acquired several times in the evolution of the longispina group.     

Daphnia hybridization along ecological gradients in pelagic environments: the potential for the presence of hybrid zones in plankton

The relative homogeneity of pelagic environments has been regarded as the reason for the absence of hybrid zones for hybridizing planktonic Daphnia (Crustacea: Cladocera); occasional dominance of interspecific hybrids over parental species was explained by their temporal superiority in fluctuating environments. However, water bodies with spatially varying environmental conditions might facilitate the formation of hybrid zones in plankton. We studied the distribution of species and hybrids of the Daphnia longispina complex in 11 canyon-shaped reservoirs, localities characterized by horizontal environmental gradients (particularly of food supply and size-selective predation); we also analysed patterns of carapace size and fecundity among coexisting taxa. Spatial distribution of taxa agreed with their ecological characteristics; those showing different affinities along longitudinal reservoir profiles differed in size according to the presumed fish predation gradient. Only hybrids of Daphnia galeata with Daphnia cucullata and D. longispina (=hyalina) were recorded. The latter two species preferred opposite ends of gradients, such spatial segregation probably explaining the absence of their hybrids. Distributional patterns were relatively stable in two consecutive summers, apart from a substantial decline of D. galeata X cucullata in the second year. The observed pattern of a hybrid-dominated zone in intermediate conditions suggests that local Daphnia hybrid zones may indeed form within reservoirs.     

Predator-induced life-history changes and the coexistence of five taxa in a Daphnia species complex

Interspecific hybridization is common in water fleas of the Daphnia galeata species complex (e.g. D. galeata , D. cucullata , D. hyalina and their interspecific hybrids). We studied the effect of fish on the life histories of five taxa of this species complex originating from the Plußsee, northern Germany. Using four clones per taxon, we found that fish kairomones reduce size at birth and size at maturity significantly. For size at maturity larger taxa showed a significantly stronger reaction to fish kairomones than the smaller taxa. With respect to the intrinsic rate of increase, r , we compared two predation regimes (positive size selective and not selective). We found that under the fish predation regime most clones had a higher r when cultured with fish kairomones, leading to a higher r , and a stronger reaction for the smaller taxa. We conclude that fish predation might be an important factor influencing the co-occurrence of Daphnia parental taxa with their hybrids.