云南乌头属牛扁亚属的核形态研究

对云南乌头属牛扁亚属３种、１变种共９个居群的核形态进行了研究。其中弯短距乌头、粗花乌头和滇川乌头的染色体数目和核型为首次报道。所有种类的静止核和前期染色体形态基本相似,分别属于复杂中央染色微粒型和中国型;分裂中期染色体数目为２ｎ＝４ｘ＝３２,染色体类型通常为ｓｍ或ｍ,ｓｔ染色体少见,染色体从大到小逐渐过渡,核型的二型性不明显。结合有关资料,重点指出了乌头属不但在亚属之间,而且在牛扁亚属内也存在着较     

GENOTYPIC VARIATION AND CLONAL STRUCTURE IN CORAL POPULATIONS WITH DIFFERENT DISTURBANCE HISTORIES

Genotypic diversity in six populations of the endemic Hawaiian reef coral, Porites compressa, was directly related to habitat-disturbance history. The highest diversity (lowest amount of clonal proliferation) was found in populations that had been intensely or recently disturbed. In these populations, space was not limited and mean colony size was small (< 500 cm²), suggesting early stages of recolonization. In an undisturbed, protected habitat, lower genotypic diversity was a result of a significant degree of clonal replication of established genotypes. Unoccupied substratum was rare in this habitat, and average colony size was large (> 2500 cm²). Populations in intermediately disturbed habitats showed intermediate levels of diversity and clonal structure as a result of the combined contributions of sexual and asexual reproduction. Individual clones were distributed over small areas (< 4 m²) or distances (< 1 m) in young populations, and more broadly (> 256 m²) and over longer distances (> 90 m) in the older, undisturbed population. Interpretations of life-history parameters and estimates of total genetic variability in species that have the potential to reproduce asexually are dependent upon an assessment of the overall clonal structure of populations. The power of genotypic assays to reliably detect clonal versus unique colonies, as well as the spatial scales over which clonal populations are sampled, are critical to such assessments.     

RESOURCE ALLOCATION AND REPRODUCTION IN POPULATIONS OF AMPHICARPUM PURSHII (GRAMINEAE)

Five New Jersey populations of Amphicarpum purshii (an annual panicoid grass) were investigated as to total allocation of biomass to reproduction and its distribution between aerial chasmogamous and subterranean cleistogamous inflorescences. Germination of both types of seed was documented, for the first time, in not only the field but under three laboratory temperature regimes. Overall, approximately 29 % of the shoot biomass was allocated to reproduction. On a population basis, subterranean inflorescences accounted for 37–100 % of the reproductive biomass, and these seed (5 × heavier but fewer in number) were the source of most surviving seedlings. Subterranean spikelets contained caryopses significantly more frequently than aerial spikelets. The ratio of the number of viable aerial seed to the number of viable subterranean seed increased from 0/4 to 4/2 with recentness and/or frequency of disturbance. As a pioneer species in secondary succession, Amphicarpum purshii produces a larger subterranean propagule, with greater seedling vigor and a higher probability of local reproductive success, and also a smaller aerial propagule in larger numbers with potentially greater genetic variability.     

REPRODUCTION, SURVIVAL AND TAG LOSS IN CALIFORNIA SEA OTTERS

We observed 40 California sea otters, Enhydra lutris , that were instrumented with implanted radio transmitters and flipper-tagged, and obtained additional data on the reproduction of tagged female otters from the California Department of Fish and Game.
The proportion of instrumented females accompanied by a pup peaked in the spring, with a secondary peak in the fall. Two methods of estimating the annual reproductive rate gave comparable values of 0.90 and 0.94. The average inter-birth interval was 389 d. Two methods of estimating pup survival to weaning gave values of 0.46 and 0.58. Pups either remained with a female less than 80 or more than 120 d. Early mortality of dependent pups appears to be more frequent in California than in Prince William Sound, Alaska.
Two methods of estimation indicated that adult females had the highest survival rates and adult males the lowest. Juvenile females had lower survival rates than adult females but juvenile males had higher survival rates than adult males. The survival rate of juvenile females was lower than that of juvenile males.
The estimated annual loss rate for flipper-tags, based on the instrumented individuals, was 0.26. More individuals lost two tags than would be expected by chance. It is unlikely that accurate estimates of sea otter survival rates can be derived from observations of tagged individuals.     

光周期对飞蝗三个地理种群胚胎滞育和生殖的影响(英文)

本文研究了光周期对飞蝗三个地理种群胚胎滞育和生殖的影响。结果表明飞蝗不同地理种群胚胎滞有特性存在显著差异。新疆和硕飞蝗种群无论在长光照还是短光照下均产滞育卵,属于专性滞育;天津北大港和新疆哈密飞蝗种群的胚胎滞育随光周期的不同而变化,长光照和短光照下分别产非滞有卵和滞育卵,属于不同类型的兼性滞育。在纬度等条件差别不大的情况下,海拔高度对滞有特性的影响可能起主导作用。长光照延长哈密和北大港飞蝗种群的产卵前期、降低其产卵频率及产卵量;但对和硕飞蝗种群的这些特性无明显影响。和硕飞蝗种群胚胎打破滞育所需的低温处理时间较哈密和北大港飞蝗种群所需时间长。     

HETEROPHYLLY IN POPULUS GRANDIDENTATA (SALICACEAE) WITH EMPHASIS ON RESIN GLANDS AND EXTRAFLORAL NECTARIES

Big-tooth aspen displays heterophylly on twigs of saplings and on upper, vigorously growing twigs of larger trees. Early leaves, those present in overwintering buds which expand in spring, differ from late leaves, those that are mostly initiated and developed during the late spring and summer of the same year. The two sets of leaves differ in size, shape, number of teeth, number of marginal resin glands, and number and size of basilaminar extrafloral nectaries. Secretory structures are generally more prominent and active on late leaves. Marginal resin glands, resin-secreting stipules, and basilaminar nectaries of both early and late leaves are similar anatomically, having a secretory epidermis of cytoplasmically dense palisade-like cells separated from vascular bundle endings by several layers of isodiametric parenchyma. These secretory structures, and the dense mat of trichomes which cover the leaf until it fully expands, may help to protect the young leaves from insect damage. The basilaminar nectaries seem especially effective because they attract ants that probably discourage visits by other insects.     

THE RELATIONSHIPS BETWEEN SEASONAL VARIATION IN LIGHT INTENSITY,RAMET SIZE,AND SEXUAL REPRODUCTION IN NATURAL AND EXPERIMENTAL POPULATIONS OF ASTER ACUMINATUS (COMPOSITAE)

We conducted experiments to evaluate the effects of different patterns of seasonal light availability on ramet size and sexual reproduction in the understory herb, Aster acuminatus. In April 1982, 200 potted rhizomes were divided equally between a high light and a shaded site. Twice during the growing season subsets of pots were reciprocally transferred between the sites, resulting in eight different light treatments. There was significant variation among treatments in mean ramet weight (0.41–1.21 g), height (15.0–23.4 cm), number of flowers (0.4–7.9) and percentage of ramets flowering (14–95). Periods of high light increased ramet height, weight, rhizome production and flowering, but high light earlier in the season increased ramet height more than did high light later in the season, while high light later had pronounced effects on the other three traits. Measurements taken in nine natural patches experiencing different patterns of seasonal light availability are consistent with the experimental results. The results provide new insights into the general phenomenon of size-dependent reproduction in herbs and illustrate how the phenology of biomass allocation can affect growth and reproduction.     

INTRASEASONAL VARIATION IN SEED PRODUCTION AMONG FLOWERS AND PLANTS OF THALICTRUM THALICTROIDES (RANUNCULACEAE)

Intraseasonal variation in ovule and seed production per flower and per plant of the perennial herb Thalictrum thalictroides (L.) Eames and Boivin was documented at three sites during three spring flowering seasons. Shading and pollen-addition experiments were used to assess the impact of variation in pollination and light availability on seed production. Mean seed number and percent seed set were lower in flowers open late in the season than in those open earlier. The lower percent seed set occurs primarily in flowers that are positioned laterally on the inflorescence and which open later than center flowers. Plants flowering early in the season produce more flowers, ovules and seeds than those flowering later. Mean percent seed set per plant did not change, however, indicating that temporal differences in total seed output can be traced largely to variation in total ovule number. Seed production may be limited by lack of pollination during periods of inclement weather. At least late in the season, seed output may also be resource-limited: the decline in percent seed set among flowers coincided with the decline in light availability, and hand-pollination of late-opening flowers did not increase percent seed set to earlier levels. Artificial shading led to a significant reduction in percent seed set of lateral flowers, and decreased the probability of flowering again the following year. Thus, the relative selective roles of resource and pollination limitations may vary during the flowering season.     

EFFECTS OF PHOTOPERIOD ON EMBRYONIC DIAPAUSE AND REPRODUCTION IN THE MIGRATORY LOCUST IN THREE GEOGRAPHIC POPULATIONS1

Abstract The three investigated populations of migratory locust, Locusta migratoria L. (Orthoptera, Acrididae), reported in this paper show significant variation in diapause characteristics. The insects of the Heshuo Xinjiang population show diapause in egg stage regardless of the photoperiod of rearing condition, while the adults of the Beidagang Tianjin and the Hami Xinjiang populations produce diapause or nondiapause eggs according to the short or long photoperiod. From this research, we infer altitude plays an important role in inducing diapause. The long photoperiod which extends the duration of pre-oviposition period and reduces the oviposition frequency in the Beidagang and Hami populations shows no effect on those features of the Heshuo population. The duration at low temperature to end diapause in the Heshuo population is longer than that in the other two populations.     

CLINAL VARIATION ASSOCIATED WITH EDAPHIC ECOTONES IN HYBRID POPULATIONS OF GAILLARDIA PULCHELLA

The variety pulchella of the outcrossing annual plant species Gaillardia pulchella consists of two edaphic races in central Texas which are divergent for one morphological and four electrophoretic characters. Reduced pollen stainability in F₁ hybrids suggests the races are also divergent in chromosome structure. The recent proliferation of this species on roadsides and in pastures has led to hybridization between these races. An analysis of character variation in three hybrid populations revealed significant clinal variation associated with edaphic ecotones, and the width of these clines was found to vary among characters in a consistent pattern. It is argued that this pattern is the result of different characters experiencing different effective selection regimes, with narrower clines reflecting greater differentials in effective selection. Several mechanisms are discussed by which selection may impede the transgression of alleles across the ecotones in these populations. The results of this study are compared to the results of parallel studies on the autogamous annual species Avena barbata in California, and it is suggested that the difference between these two species in the width of clines separating edaphic ecotypes may be accounted for by their different breeding systems.