香椿种质生长及叶部表型性状的遗传变异分析

以84个香椿(Toona sinensis(A.Juss.)Roem.)种质为材料,对其2个生长性状和18个叶部性状(包含6个质量性状和12个数量性状)进行测定。结果显示,香椿6个叶部质量性状变异类型丰富,呈现出多态化特点,单一性状的主要表型多为1~2个。苗高、地径及叶部表型等14个数量性状在种质间的差异均达到极显著水平,且除地径外,其他性状的遗传方差分量均大于环境方差分量,表明此类性状主要受遗传控制。参试的14个数量性状的平均表型变异系数为20.35%,平均遗传变异系数为16.36%;综合表型和遗传变异系数,叶柄长度较其他性状变异大,而叶片夹角稳定性最高,各数量性状(除地径外)遗传变异系数与表型变异系数之差小于7%。香椿种质各性状间Shannon-Weaver遗传多样性指数相差不大(1.892~2.069),遗传多样性水平高,具有良好的遗传改良基础。聚类分析可将84个香椿种质分为5类,类群Ⅰ表现为生长旺盛、小比叶重型;类群Ⅱ生长较快、叶片较大;类群Ⅲ种质数量最多,属生长缓慢、大比叶重型;类群Ⅳ特征为大叶片、多叶型;类群Ⅴ为小叶片、稀叶型。研究结果表明参试香椿种质变异丰富,遗传多样性水平高,能为良种选育、遗传改良等研究提供丰富的遗传材料。     

Evaluation of genetic variation in the daylily (Hemerocallis spp.) using AFLP markers

The daylily (Hemerocallis spp.) is one of the most economically important ornamental plant species in commerce. Interestingly, it is also one of the most heavily bred crops during the past 60 years. Since the American Hemerocallis Society began acting as the official registry of daylily cultivars in 1947, more than 40 000 registrations have been processed. In order to determine the effects of intensive breeding on cultivar development, and to study relationships among different species, genetic variation in the daylily was estimated using AFLP markers. Nineteen primary genotypes (species and early cultivars) and 100 modern cultivars from different time periods were evaluated using 152 unambiguous bands (average 79% polymorphism rate) derived from three AFLP primer combinations. Overall, pairwise similarity estimates between entries ranged between 0.618 and 0.926 (average=0.800). When comparing cultivar groups from different time periods (1940–1998), genetic similarity was initially increased, compared to the primary diploid genotypes, remained constant from 1940 to 1980, and then steadily increased as breeding efforts intensified and hybridizers began focusing on a limited tetraploid germplasm pool derived by colchicine conversion. Among modern (1991–1998) daylily cultivars, genetic similarity has increased by approximately 10% compared to the primary genotypes. These data were also used to evaluate recent taxonomic classifications among daylily species which, with a few minor exceptions, were generally supported by the AFLP data. Received: 15 March 2000 / Accepted: 13 June 2000     

Oenanthe aquatica (L.)Poir.: Seed reproduction,population structure,habitat conditions and distribution in Czechoslovakia

The paper summarizes data concerning the biology and ecology ofOenanthe aquatica. The species is commonly distributed all over Czechoslovakia, from lowlands to the submontane belt, especially in fishpond and river basins.O. aquatica shows no special relationship to the chemical and physical soil properties, and is well adapted to habitats with a changing water level. The reproduction ofO. aquatica depends on emerging of the bottom. The most developed populations are formed by biennial plants and arise in the year following summer or autumn drainage.     

Genetic variation and habitat conditions in Betula humilis Schrk. populations in Poland,Belarus and Latvia

A rapidly growing human population and the extirpation of numerous species make modern wetlands among the most threatened of ecosystems. One of the endangered wetland plants in central and eastern Europe is Betula humilis. B. humilis forms comparably abundant populations on both well-preserved and drained fens; thus, we aimed in this paper to investigate the relationships between habitat quality parameters (e.g. concentrations of calcium and magnesium, groundwater levels, pH and conductivity) and genetic diversity in 12 populations of B. humilis from Poland, Belarus and Latvia. For the purposes of this study, alcohol dehydrogenase (ADH) gene sequences and nuclear microsatellites were chosen as molecular markers. Analyses revealed that only the Ca²⁺ concentration was significantly negative relative to the observed heterozygosity of microsatellites, which suggests that calcium access is the only factor influencing genetic variation at B. humilis localities. No genetic differentiation was detected between populations occupying wet and dry habitats in different parts of the species range. A minimum spanning tree based on ADH gene haplotypes appears to confirm the B. humilis population history previously inferred from analyses of nuclear microsatellites and chloroplast markers.     

Genetic variation in the soil phthiracarid mite, Steganacarus (S.) magnus (Nicolet, 1855) (Acarida, Oribatida) (Notulae Oribatologicae XL)

Genetic divergence and variability at 14 enzyme loci were examined in and between Italian populations of two edaphic Oribatid (Acarida, Oribatida) species, Steganacarus (Steganacarus) magnus (8 populations) and S. (S.) hirsutus (1 population). The seven populations belonging to S. (S.) magnus can be divided into two groups according to their phenotype, form anomala (A) (MON, ARG, AST, CDO) and form magna (M) (MAL, MAM, RIF) while another can be considered as hybrid between the two preceding groups (ZOC). Genetic identity (I) values between the S. (S.) magnus populations in spite of their morphological differences ranged from 0.977 to 1.000 showing the great genetic similarity of simple local populations while those of S. (S.) hirsutus indicated two distinct morphological species. The genetic distances between all the populations examined were very low despite the ecological differences and geographical distances between the collecting sites. Genetic variability estimates in all the populations of both species were very low when compared to those reported for most arthropods. Some explanatory considerations are suggested.     

Reproductive fitness,population size and genetic variation in Muscari tenuiflorum (Hyacinthaceae): The role of temporal variation

In plant populations a positive correlation between population size, genetic variation and fitness components is often found, due to increased pollen limitation or reduced genetic variation and inbreeding depression in smaller populations. However, components of fitness also depend on environmental factors which can vary strongly between years. The dry grassland species Muscari tenuiflorum experiences long term habitat isolation and small population sizes. We analyzed seed production of M. tenuiflorum in four years and its dependence on population size and genetic variation. Genetic diversity within populations was high (AFLP: H_e = 0.245; allozymes: H_e = 0.348). An analysis of molecular variance revealed considerable population differentiation (AFLP: 26%; allozyme: 17%). An overall pattern of isolation by distance was found, which, however was not present at distances below 20 km, indicating stronger effects of genetic drift. Genetic diversity was positively correlated to population size. Self pollination reduced seed set by 24%, indicating inbreeding depression. Reproductive fitness was not correlated to genetic diversity and a positive correlation with population size was present in two of four study years. The absence of a general pattern stresses the importance for multi-year studies. Overall, the results show that despite long term habitat isolation M. tenuiflorum maintains seed production in many years independent of population size. The long term persistence of populations is thus expected to depend less on intrinsic genetic or demographic properties affecting seed production but on successful plant establishment and persistence, which latter are based on conservation and protection of suitable habitats.     

Pelage color variation in pocket gophers (Rodentia: Geomyidae) in relation to sex,age and differences in habitat

Pelage coloration is a phenotypic characteristic in mammals that could be associated with an individual's survival and fitness; thus coloration gains adaptive importance. In geomyids, pelage coloration shows a relationship with the color of soils on which they live, mainly freshly dug soil of their burrows. This characteristic could be due to a camouflage adaptation to avoid predators. Pocket gophers disperse aboveground to establish a territory before they reach reproductive condition, and males disperse longer distances than females. The aim of this study was to evaluate pelage color variation in pocket gophers (Thomomys anitae) in relation to habitat differences, sex, and age, and determine its association to the color of the soil on which they live. Brightness of T. anitae's dorsal pelage coloration and that of soil samples from five different habitats in the Baja California peninsula, Mexico were measured to test four hypotheses: (1) Subadults show a wide coloration range, but extreme colors are lost in adulthood due to natural selection. (2) Males are more vulnerable to depredation than females; therefore, males’ coloration is more homogenous as a protective camouflage. (3) In open habitats pocket gophers are more exposed to being detected by predators, therefore their pelage coloration pattern is less variable than that of individuals from habitats with more vegetation cover. (4) Pelage coloration better matches soil coloration in moist conditions similar to that of freshly dug soil of their burrows. The results confirmed our predictions; however, selection does not impose an equal pressure on pelage coloration on the five habitats evaluated; other factors such as population density and predator presence need to be assessed. The strongest effects are found in the most open habitat, and there is less strong support for predictions in habitats where predator assemblage is diminished.     

Sexual reproduction, clonal diversity and genetic differentiation in patchily distributed populations of the temperate forest herb Paris quadrifolia (Trilliaceae)

Clonal plant species have been shown to adopt different strategies to persist in heterogeneous environments by changing relative investments in sexual reproduction and clonal propagation. As a result, clonal diversity and genetic variation may be different along environmental gradients. We examined the regional and local population structure of the clonal rhizomatous forest herb Paris quadrifolia in a complex of forest fragments in Voeren (Belgium). Relationships between population size (the number of shoots), shoot density (the number of shoots per m²) and local growth conditions were investigated for 47 populations. Clonal diversity and genetic variation within and among 19 populations were investigated using amplified fragment length polymorphism markers. To assess the importance of sexual reproduction, seed set, seed weight and germination success were determined in 18 populations. As predicted, local growth conditions largely affected population distribution, size and density of P. quadrifolia. Populations occurring in moist and relatively productive sites contained significantly more shoots. Here, shoots were also much more sparsely distributed compared to populations occurring in dry and relatively unproductive sites, where shoots showed a strongly aggregated distribution pattern. Clonal diversity was relatively high, compared with other clonal species (G/N ratio = 0.43 and Simpson’s D=0.81). Clonal diversity significantly (P<0.01) decreased with increasing shoot density while molecular genetic variation was significantly (P<0.01) affected by population size and local environmental conditions. Lack of recruitment and out-competition of less-adapted genotypes may explain the decreased genetic variation in dry sites. Analysis of molecular variance revealed significant genetic variation among populations (Φ _ST=0.42, P<0.001), whereas pairwise genetic distances were not correlated to geographic distances, suggesting that gene flow among populations is limited. Finally, the number of generative shoots, the number of seeds per fruit and seed weight were significantly and positively related to population size and local growth conditions. We conclude that under stressful conditions populations of clonal forest plant species can slowly evolve into remnant populations characterized by low levels of genetic variation and limited sexual reproduction. Conservation of suitable habitat conditions is therefore a prerequisite for effective long-term conservation of clonal forest plant species.     

Microgeographic variation in allozyme frequencies in relation to the degree of exposure to wave action in the dogwhelk Nucella lapillus (L.) (Prosobranchia: Muricacea)

Nucella lapillus from 15 sites 50 m to 21 km apart in S. Devon, S. W. England were analysed for allozyme variation at eight soluble enzyme loci. Sites were classified as either Exposed or Sheltered and a hierarchical analysis of allozyme variation carried out using Wright's Fixation Index, F_ST. Whelks from Sheltered sites segregated for alleles at the Est-3, Lap-2, Pep-2 and Mdh-1 loci which were virtually absent from exposed sites resulting in high F_ST values (0.289–0.506) when all samples were included. Consequently mean heterozygosity of the Sheltered samples was roughly twice that of the Exposed. Between Sheltered sites the frequencies of these 'additional' alleles varied substantially, even on a microgeographic scale and were found to be highly correlated with exposure. Within individuals the presence of the 'sheltered' alleles was correlated with the possession of the 'sheltered' shell shape as indicated by length divided by aperture height. This must necessarily be the case, however, if both are related independently to exposure. Although these correlations imply the action of selection there is evidence within the data for stochastic factors affecting the pattern observed. Complicating the picture further is the correspondence observed in the distribution of the 'sheltered' alleles with the known distribution of chromosomal translocations. Phenotypic associations within individuals also support the hypothesis that variation at the Est-3, Lap-2, Mdh-1 and Pet-2 loci is related to variation in chromosome number. However, the nature of the relations of karyotype and allozyme variation with shell shape and exposure remain speculative.     

苦瓜主要品质性状的遗传变异、相关和通径分析

对23份苦瓜材料的10个品质性状进行了研究。结果表明,苦瓜维生素C、还原糖、有机酸、果瘤、果色、果刺和苦味遗传变异系数大,遗传力高;水分含量遗传变异系数很小;风味遗传变异系数较小,遗传力低。苦瓜4个内在营养品质之间相关性小,而4个外观品质性状之间关系密切。两个味觉品质与4个内在营养品质之间相关性小,但与4个外观品质之间关系密切。内在营养品质与外观品质之间有一定关系。通径分析提出通过降低果实的苦味和有机酸含量来提高风味品质;通过水分含量和果瘤两性状的直接选择来实现对维生素C的间接选择。     

Sexual vs. vegetative reproduction in relation to forest dynamics in the understorey shrub,Hydrangea paniculata (Saxifragaceae)

In the forest understorey, shrubs usually reproduce vegetatively rather than sexually, but the relative contribution of these two reproductive modes may vary with temporal changes in environmental conditions (e.g., light, substrates of forest floor) that are closely related to forest dynamics. To evaluate the occasional changes in reproductive modes of the clonal understorey shrub Hydrangea paniculata, the reproductive characteristics (i.e., flowering, seedling establishment, vegetative propagation, reproductive size and age) were investigated in four different developmental stages in a Japanese beech forest (early gap, EG; late gap, LG; building, BU; mature, MA). Flowering individuals occurred only in EG and LG, and a much greater number of seedlings was observed in both EG and LG than in BU and MA, mainly because canopy gaps provided sufficient light for flowering and suitable substrates (fallen trees and exposed mineral-soil) for seedling establishment. The flowering individuals originated from plants that had persisted in the shaded understorey until gap formation. In contrast to sexual reproduction, clonal fragmentation increased with forest development in the order LG, EG, BU, MA. This is because, in later stages of forest dynamics (BU and MA), large individuals, some of which had previously flowered in gap stages, were layered on the forest floor and subsequently produced a substantial number of clonal fragments by separation of the buried branches from the main stems which had decayed. This resulted in a large number of clonal fragments originating from a single mother plant. These results suggest that the reproductive modes of H. paniculata is strongly influenced by the changes in environmental conditions with respect to the dynamics of canopy trees. Reproduction from seed in gap stages, despite their short period, provide new genets in established populations, whereas vegetative propagation via fragmentation in closed-canopy stages enhance the stability of the population until the next disturbance.     

Genetic variation of ticks (Ixodes ricinus L.) in the Lithuanian and Norwegian populations

RAPD markers were used to measure the genetic diversity of 119 individuals of Ixodes ricinus collected from Lithuania and Norway. The samples were analysed within and also between the populations. We analysed 74 loci in each of 6 populations. Our results show high levels of diversity within the populations. The percentage of polymorphic loci of the six analysed populations: Birzai, Vilnius, Kretinga, Tjore, Kjosvik and Odderoya were 68.9%, 58.1%, 78.38%, 62.2%, 44.6% and 68.9%, respectively. The percentage of polymorphic loci in the Lithuanian populations was 93.2%, and in the Norwegian populations 81.08%. The genetic distance ranged from 0.019 to 0.079 within Norwegian populations and from 0.005 to 0.0967 within Lithuanian populations and between the countries from 0.022 to 0.146. The genetic variation of I. ricinus among Norwegian populations was lower than among Lithuanian populations. The highest part of genetic variation in I. ricinus ticks depends on variation within Kretinga (Lithuania) and Odderoya (Norway) populations situated in coastal areas where many migratory and sea birds are aggregated.     

Offspring fitness in relation to population size and genetic variation in the rare perennial plant species Gentiana pneumonanthe (Gentianaceae)

Seeds were sampled from 19 populations of the rare Gentiana pneumonanthe, ranging in size from 5 to more than 50,000 flowering plants. An analysis was made of variation in a number of life-history characters in relation to population size and offspring heterozygosity (based on seven polymorphic isozyme loci). Life-his-tory characters included seed weight, germination rate, proportion of seeds germinating, seedling mortality, seedling weight, adult weight, flower production per plant and proportion of plants flowering per family. Principal component analysis (PCA) reduced the dataset to three main fitness components. The first component was highly correlated with adult weight and flowering performance, the second with germination performance and the third component with seed and seedling weight and seedling mortality. The latter two components were considered as being maternally influenced, since these comprised life-history traits that were significantly correlated with seed weight. Multiple regression analysis showed that variation in the first fitness component was mainly associated with heterozygosity and not with population size, while the third fitness component was only correlated with population size and not with heterozygosity. The latter relationship appeared to be non-linear, which suggests a stronger loss of fitness in the smallest populations. The second (germination) component was neither correlated with population size nor with genetic variation. There was only a weak association between population size, heterozygosity and the population coefficients of variation for each life history character. Most correlation coefficients were negative, however, which suggests that there is more variation among progeny from smaller populations. We conclude that progeny from small populations of Gentiana pneumonanthe show reduced fitness and may be phenotypically more variable. One of the possible causes of the loss of fitness is a combination of unfavourable environmental circumstances for maternal plants in small populations and increased inbreeding. The higher phenotypic variation in small populations may also be a result of inbreeding, which can lead to deviation of individuals from the average phenotype through a loss of developmental stability.     

Microsatellite and chloroplast DNA analyses reveal no genetic variation in a beach plant Surianana maritima on the Paracel Islands,China

Genetic variation within and among six natural populations of beach plant Suriana maritima on the Paracel Islands of China was assessed using SSR and chloroplast DNA sequence analysis. The results showed a complete absence of genetic variation between individuals either within or among populations. The cumulative consequences of a founder effect, selfing, and inbreeding may be responsible for the loss of genetic diversity in S. maritima.     

Mycorrhizal symbiosis increases growth,reproduction and recruitment of Abutilon theophrasti Medic. in the field

We examined in the field the effect of the vesicular-arbuscular (VA) mycorhizal symbiosis on the reproductive success of Abutilon theophrasti Medic., an early successional annual member of the Malvaceae. Mycorrhizal infection greatly enhanced vegetative growth, and flower, fruit and seed production, resulting in significantly greater recruitment the following year. In addition, the seeds produced by mycorrhizal plants were significantly larger and contained significantly more phosphorus than seeds from non-mycorrhizal plants, an effect which may improve offspring vigor. Infection by mycorrhizal fungi may thus contribute to the overall fitness of a host plant and strongly influence long-term plant population dynamics.     

Review: Risk assessment implications of variation in susceptibility to perchloroethylene due to genetic diversity,ethnicity, age,gender, diet and pharmaceuticals

Current cancer risk assessments do not adequately consider impacts of human inter-individual variability on susceptibility to environmental pollutants like perchloroethylene (PCE). PCE is metabolized through both oxidative and glutathione (GSH) conjugation pathways. Toxicity criteria derived using both pathways are 23-fold more stringent than those calculated using only oxidative metabolism. While toxicokinetic modeling of PCE metabolism predicted very high variability through the GSH conjugation pathway, it is unclear if the range in estimates is due to human variability or uncertainty. Thus, the variation in the GSH conjugation pathway of PCE metabolism due to genetics, ethnicity, age, gender, diet, and pharmaceutical co-exposures is examined. Genetic polymorphisms were found at several loci including, GSTT1, GSTM1, CCBL1, AGXT2, NAT8, ACY3, MRP2, OAT1/3, FMO3, and CYP3A that code for enzymes/transporters in the GSH conjugation pathway. Genetic diversity in GSTT1, GSTM1, and CCBL1 between ethnic populations, as well as age, gender, diet, and pharmaceutical co-exposures influences toxic and mutagenic metabolites produced through this pathway. Given this diversity, large differences in PCE metabolism through the GSH conjugation pathway are expected. To be health protective for diverse ethnic populations and lifestyles, both the oxidative and GSH conjugation pathways need to be considered in developing PCE toxicity criteria.     

The length weight relationship, age, growth and reproduction of the roach Rutilus rutilus (L.) in Lake Volvi

The length-weight relationship of a sample of 233 roach ( Rutilus rutilus ) can be described by the following equations: y =0·0356 x ^3·405 and y =0·0215 ×^3·606 for males and females respectively. In both equations y equals the body weight in grams and × is the standard length in centimetres. The average condition factor K was 2·01 with a range of 1·71 to 2·26. The roach's span of life was 13 years for both sexes. The growth increment is greater during the first year of life (about 56 mm), decreasing to approximately 17 mm at the end of the sixth year of life and then becoming constant at about 12 mm per year. Roach become sexually mature at age 1 + for males and one year later for females. The mean absolute fecundity was 9294 eggs; with a range from 920 to 32 810. The growth of the gonads is related to the age of the fish. Spawning occurs during the first half of April, at a mean water temperature of 10° C.     

Clinal genetic variation and isolation by distance in the European eel Anguilla anguilla (L.)

The genetic variability and structure of the European eel ( Anguilla anguilla L.) in populations throughout Europe was reassessed using 15 allozymic loci, seven of which were polymorphic. Seven sites were sampled on a latitudinal gradient across the natural continental range, extending from southern France to southern Norway. Heterozygosity ( H _e = 0.05) and level of polymorphism (P = 0.43) were comparable to other marine fish. Populations were poorly differentiated ( G _ST = 0.014, F _ST = 0.002), which is not surprising considering the high dispersal capability of the European eel. However, a significant geographical cline was detected at two alleles ( IDH-1 * 100 and GPI-1 * 110 ), and genetic distances ( D _CE) were concordant with geographical coastal distances. Mantel tests, pairwise F _ST's and multidimensional scaling analyses identify three distinct groups: Northern Europe, Western Europe and the Mediterranean Sea. We propose that the clinal genetic structure in the European eel may be due to (1) isolation by distance (as recently detected with microsatellites), (2) temporal reproductive separation, (3) post-larval selective forces, (4) contact between formerly separated groups or (5) some combination thereof.  © 2002 The Linnean Society of London, Biological Journal of the Linnean Society , 2002, 77 , 509–521     

The age, growth and reproduction of the stone loach Noemacheilus barbatulus (L.) in a Dorset chalk stream

SUMMARY.

• 1 In this highly productive chalk stream the stone loach, sampled by electrofishing over a 30 month period, had a high growth rate reaching a mean length of 65 mm in 1 year and 93 mm in 2 years. The fish were short-lived in contrast to most slow-growing populations in the U.K. and Finland with 11 group fish comprising 8.8% and III group fish only 1.1% of the total number.
• 2 The loach were fractional spawners: a 75 mm female produced an estimated 10,620 eggs between late April and early August totalling 46% of the loach's initial weight.
• 3 In March and April some small 0 group females contained only poorly developed eggs and up to 10% of 0 group fish may have failed to spawn.
• 4 Amongst loach >52 mm in length in March and April there was an exponential relationship between absolute fecundity and fish length but no relationship between relative fecundity and length. There was. however, a relationship between fish length and both gonadosomatic index and maximum egg size, which may indicate that large fish began to spawn first.

     

Development of EST-PCR markers and monitoring their intrapopulational genetic variation in Picea abies (L.) Karst.

Fifteen cDNA sequences are reported for the European coniferous forest tree species Norway spruce [Picea abies (L.) Karst.], including the results of similarity searches in public electronic databases. The sequences were subsequently employed for the design of specific primer pairs and PCR-based amplification of genomic fragments. For seven primer pairs, polymorphic EST-PCR markers were identified among 18 trees. Their mode of inheritance was verified by analysing single-tree offspring and studying segregation among haploid endosperms in comparison to diploid tissue. Codominant inheritance was indicated for six markers, while one marker was apparently dominant. Variation of the six codominant EST markers was tested by genotyping 110 randomly selected trees in a Bavarian Norway spruce population. For comparison, the same trees were genotyped at 18 enzyme coding gene loci. There were 3.33 alleles per locus for EST markers and 3.00 for isoenzyme gene markers. In general, a trend to more even frequency distributions and larger intrapopulational variation, including observed heterozygosities, was indicated more for EST markers than for isoenzyme gene markers. The benefits of these newly developed EST-PCR markers are outlined with respect to population genetics and ecological genetics. Received: 29 April 2000 / Accepted: 25 August 2000