Reproductive systems in conifer seed orchards

Summary In order to quantify female and male fitness values of clones in a Pinus sylvestris L. seed orchard, multilocus-genotypes of parental clones were compared with those of open pollinated seeds in the bulked orchard crop. Female and male contributions to individual seeds were distinguished by observing enzyme gene loci active in both endosperm and embryo tissue. Seed probes from two successive flowering periods were surveyed. The female and male fitnesses of five parental clones measured relative to the population mean were derived. The contributions of four clones were found to be sexually asymmetric. One clone, for instance, made exclusively female contributions in one flowering period. Variations existed in fitness values between clones. Deviations in sex specificity occurred between flowering periods: one clone contributed asymmetrically in both periods, but in sexually reversed proportions. A method to comprehensively quantify and illustrate the observed phenomena is proposed.     

Host-attacking behavior of a eulophid parasite,Kratochviliana sp., to the leaf mining host,Phytomyza ranunculi (Diptera: Agromyzidae) during its stay on the leaf

The present paper studies how the female parasite of Kratochviliana sp. visits and attacks its host larvae of Ranunculus leaf mining fly, P. ranunculi at a single leaf visit. The parasite visited its hosts at random on the leaf. The frequency of host visits was independent of the host density and the proportion of hosts survived from the parasite attack, in a leaf and its distribution was expressed as a single straight line. It almost always attacked living hosts at the first host visit after isolated from them for one day but with the rate of about 0.5 at the subsequent visits. In consequence, the relationships of the number of host attacks and killed hosts to the host density drew satulated curves in each. A model of host attack by this parasite at its single leaf visit was formulated by modifyingBakker et al.'s model (1972) basing upon these observations and the attack avoidance by the parasite to already attacked hosts previously reported.     

Infanticide and fertility among Eskimos: A computer simulation

Until recently, certain Eskimo groups were reported to practice female infanticide in the belief that the time spent suckling a girl would delay the mother's next opportunity to bear a son, males being preferred to females because of their future role as providers in a hunting economy. From sex ratios in census data, rates of female infanticide of up to 66% for some groups have been inferred, leading some ethnographers to conclude that these groups were headed for extinction. Eskimo beliefs regarding the effects of infanticide on fertility, however, are in accord with the results of research on the relation of fertility and lactation: The cessation of lactation following infanticide would significantly shortern the expected interval until the next birth. Given this fact and available field data regarding the parameters of Eskimo population growth, the present computer simulation indicates that Eskimo populations could sustain a rate of 30% female infanticide and still survive. Higher reported rates are explained as the combined result of female infanticide plus the tendency of ethnographers to overestimate to overestimate the ages of juvenile females relative to juvenile males.     

Regulation of growth in larvae of the crab : The effect of cyclic temperatures

Experiments were designed to demonstrate that growth is precisely regulated in crustacean larvae and that cyclic temperatures act as a perturbation on growth regulation. Newly hatched larvae were exposed to either the specific a cyclic temperature, cumulative growth was significantly inhibited. Also, the specific growth rate ( ) of larvae in the cyclic temperature regime was found to oscillate with decreasing amplitude around the of the larvae exposed to constant temperature. This oscillatory pattern has been observed in a wide variety of self-regulating systems. Evidence is presented to demonstrate that this regulatory mechanism also adapts to long-term exposure to cyclic temperatures. These findings increase our understanding of how larvae cope with and adapt to changing environmental temperatures. More significantly, the mechanism could provide a sensitive tool for estimating the effects of specific environmental disturbances on fitness.     

Ultrastructural characterization and three-dimensional reconstruction of isolated maize (Zea mays L.) egg cell protoplasts

Summary Isolated egg cell protoplasts ofZea mays L., inbred line A 188, have been studied at the transmission electron microscope level. Their preparation for electron microscopy has been performed by embedding in ultra-low gelling agarose as a preliminary step. Five isolated egg cell protoplasts were serially ultrathin sectioned and studied in detail. One of these protoplasts was reconstructed in three dimensions to provide additional information on its structure. After enzymatic digestion and microdissection, isolated egg cells are true, highly vacuolized protoplasts. The structure of their organelles agrees with in situ observations, indicating an ultrastructural intactness after isolation: the mitochondria are polymorphic, form reticulate networks, and have well developed cristae; the plastids contain starch grains; and the spherical nucleus is euchromatic. As in situ, the organelles of the isolated egg cell protoplasts are aggregated near the nucleus. The complete picture provided by this work should serve as a comparative base for studies on in vitro fertilization products.     

The influence of the social environment on sexual maturation of female deermice (Peromyscus maniculatus bairdi)

Population Ecology - Female deermice housed from weaning with groups of five females, five males or five males plus five females had significantly smaller uteri at 35–38 days of age compared...     

四合木种群的生态适应性

通过四合木异地播种生长量比较、以及四合木对土壤的适应性和对水热综合因子的适应性分析,得到如下结果：（1）四合木生长量高低的顺序为乌海区的东胜土（12．12g）〉乌海区的乌海土（10．62g）〉东胜区的乌海土（3．10g）〉东胜区的东胜土（2．59g）。同一地区不同土壤间四合木生长量之间没有差异（P≥0．05）,不同地区相同土壤间的生长量之间却有十分显著的差异,说明了土壤条件对四合木的生存影响是次要的,气候条件是保证四合木生存的最重要的条件。（2）四合木分布区与异地保护区之间9种土壤微量元素具有差异,但由于四合木植株中的微量元素含量均高于土壤中的有效量,说明四合木对微量元素具有富集作用,土壤微量元素含量不是四合木成活与生长的限制因子。（3）四合木分布区与异地保护区之间各月平均温度差异显著;全年气温日较差以及温暖指数、寒冷指数、湿润指数和水热综合因子指数差异显著;生长季地表地温昼夜温差具有特殊性,这可能是异地保护不易成功的限制因子之一。     

鼎突多刺蚁群体结构和生活史的研究

本文报告了鼎突多刺蚁(Polyrhachis vicina Roger)的群体结构和生活史。通过研究表明,鼎突多刺蚁一年发生一代,以蚁后、雄蚁、工蚁、幼虫和卵越冬。卵和幼虫在冬天发育停滞(或极慢)。到了春天,随着气温的上升,卵和幼虫又恢复正常发育。据室内人工饲养观察,卵的发育历期为23.8±2.5天(平均温度26℃)幼虫为20.4±4.4天(26℃),工蚁蛹为19.8±5.5天(27℃)。成长工蚁在5—11月出现;8—11月,雄蚁从蛹中羽化;10月,雌蚁从蛹中羽化。雌蚁分飞交尾后,进入邻近蚁巢或回到原巢,脱翅成为蚁后。蚁巢内存在着多后现象。     

长白落叶松生殖生物学特性研究──Ⅰ．球花芽分化与早期发育

本文研究了长白落叶松（ＬａｒｉｘｏｌｇｅｎｓｉｓＨｅｎｒｙ）大小孢子叶球的分化及其分布规律．获得如下结果：（１）６月下旬芽鳞形成期终止,７月初进入小孢子叶分化期,７月未至８月上旬小孢子叶分化期结束．８月上旬进入小孢子囊分化期,８月下旬出现造孢细胞,９月中旬形成小孢子母细胞．１０月底小孢子母细胞保持在细线期阶段,小孢子叶球进入冬季休眠期．（２）９月初苞片原基开始形成,９月中旬珠鳞原基形成;１０月上旬出现胚珠原始体,１０月下旬大孢子母细胞形成,１０月底大孢子叶球芽进入冬季休眠．（３）小孢子叶球芽主要分布在树冠的中、下部．数量上远远大于大孢子叶球芽的数量,约为大孢子叶球芽的１９倍。大孢子叶球芽主要集中分布在树冠中部,而且树冠下部多于树冠上部。     

麦长管蚜抗吡虫啉品系和敏感品系的生殖力比较

通过建立抗性品系和敏感品系的种群生命表,比较麦长管蚜Sitobion avenae(Fabricius)抗吡虫啉品系和敏感品系的生殖力差异,结果表明,抗性品系适合度显著下降,世代历期延长,成蚜寿命缩短;在繁殖上表现为产仔量下降,生殖期缩短。以净生殖率(R0)和内禀增长率(rm)来评价抗性品系的相对生物适合度,抗性品系分别是敏感品系的0.5200和0.7481。因此,麦长管蚜对吡虫啉的抗性品系存在显著的生殖劣势。