Hibernation behavior of Rana lessonae and R. esculenta in their natural habitat

We studied the hibernation behavior of the water frog Rana lessonae and its hybridogenetic associate R. esculenta in their natural habitat during three successive winters. Animals caught in pitfall traps at a fenced pond were individually marked with PIT tags and some (n=36) were additionally equipped with radio transmitters. Of the animals caught, 85% left the fenced pond for hibernation. More R. esculenta remained inside the fenced area compared to R. lessonae. R. lessonae emigrated earlier in autumn and came back later in spring than R. esculenta, but the distance to their hibernation sites did not differ. Both species left the fenced pond earlier in the year when ambient temperatures were lower. All radio-tracked animals hibernated in woodland, 3–7 cm below the surface in soil, under moss, fallen leaves or small branches. Soil temperatures at the actual hibernation sites were significantly higher than at randomly chosen control sites. A surprising finding was that most frogs changed their hibernation sites during winter, and often more than once. Movements were more frequent in the warmer first half of the winter than in the cooler second half, but some animals were active even on days with mean temperatures below 1°C. These results show that both species do not spend the whole winter torpid in one particular hibernation site but move around, especially at higher temperatures. Most of the animals lost weight during the winter, and the weight loss was greater in females than in males and higher in warm than in cold winters. To what extent weight loss and survival is influenced by the chosen hibernation sites and the amount of movement during winter, and whether this contributes to the differences in species and sex ratios found in mixed populations, needs more investigation. Received: 4 August 1999 / Accepted: 15 November 1999     

Initiation of early breeding in a population of Microtus townsendii (Rodentia) with the secondary plant compound 6-MBOA

Summary Feeding the secondary plant compound 6-Methoxybenzoxazolinone (6-MBOA) during winter to a free living population of Microtus townsendii accelerated breeding in females. Both the recruitment of young and sexual maturation of these young were advanced by four weeks in comparison with a control population. Overwintered females supplied with 6-MBOA matured at a lower body weight than control females. But there was no such weightat-maturity difference between the grids for males. During April and May 72% of all juveniles captured came from the experimental population. Winter reproduction and early recruitment of young stimulated by 6-MBOA could have important population consequences for these voles.     

The first born,their dispersal,and vole cycles

Summary On the basis of some empirical data and the existing theory of vole cycles, a new hypothesis is proposed. It explains cyclicity as an effect of obligatory dispersal of the first seasonal cohort of young (Y1) from their natal (optimal) habitats into vacant (suboptimal) habitats. This behaviour could evolve, because it increases contribution of genetic lineages with dispersing Y1, to subsequent generation. It is assumed that the dispersal of Y1 is common among vole species, it does not change during consecutive phases of the cycle, and it does not vary between cyclic and non-cyclic populations. It results in multiannual cycles only under a certain set of spatial and climatic conditions, which are discussed in a paper. Otherwise it results in annual dynamics.     

Association between dwarfing genes ‘Rht1’ and ‘Rht2’ and resistance toSeptoria tritici Blotch in winter wheat (Triticum aestivum L. em Thell)

Summary Differences in levels of resistance toSeptoria tritici blotch were observed in plants with a specific height-reducing gene. When the gene Rht ₂ was present either as an isoline or in the progeny, a higher degree of resistance was found. The most susceptible plants were observed in populations carrying the Rht ₁ gene. Associations, as determined by phenotypic correlations, were detected betweenSeptoria tritici blotch and tall stature, late heading, and maturity. Plants having short stature, early heading, early maturity, and acceptable levels of resistance were identified in the F₂ population whenRht ₂ was present. Results of this study indicated that wheat breeders must select the appropriate dwarfing source that may confer resistance and grow large F₂ populations, in order to increase the probability of obtaining desired genotypes.     

Seed transmission of turnip yellow mosaic virus in winter turnip and winter oilseed rapes

This is the first record of seed transmission of turnip yellow mosaic virus (TYMV) in oilseed and turnip rapes. The seed transmission of TYMV in a naturally infected winter turnip rape (Brassica napus var. silvestris) cultivar Perko PVH was investigated. By ELISA 1.6%, 3.2% and 8.3% seed transmission of the virus was found in seed of plants from three localities. The proportion of infected seeds produced by artificially infected plants of winter oilseed rape (Brassica napus ssp. oleifera) and winter turnip rape cultivars was determined. The virus transmission rate, expressed as the proportion of virus-infected plants which germinated from the seed was for the oilseed rape cvs Jet Neuf 0.1%, Solida 0.4%, Silesia 0.8%, Darmor 1.2%, SL-507 0.2%, SL-509 0.0% and for the winter turnip rape cv. Perko 1.5%. ELISA cannot be used in direct tests on bulk seed lots to estimate proportion of infected seed, but must be used on germinated seedlings.     

Water potential gradients of tall and short cultivars of winter wheat

Summary Water and osmotic potentials were measured with thermocouple psychrometers, weekly after heading, two times each day at pre-dawn and at noon, in flag leaves and grain of tall and short cultivars of winter wheat grown in the field under rain-fed conditions.Water was held with less tension in the grain than in the leaf for both tall and short cultivars. The tall cultivars had lower leaf water potentials, but higher grain water potentials, than the short cultivars. The grain osmotic potential was lower in the short cultivars compared to the tall ones. Grain yield of short cultivars (1810 kg/ha) was more than that of tall cultivars (1730 kg/ha). Apparently higher leaf water potentials of short cultivars enabled more photosynthates to move into the grain.     

美洲鲽抗冻蛋白基因的克隆及在E.coli中的表达

本文报告了美洲鲽抗冻蛋白基因的克隆及在E.coli中表达的研究,以质粒P~(CT5)作为抗冻蛋白基因的供体,p~(ORF-2)作为表达载体。用HpaⅡ酶从质粒p~(CT5)上切下抗冻蛋白基因片段,再经Bal 31酶,绿豆核酸酶处理,连接上BglⅡ接头,然后插入到p~(ORF-2)的BglⅡ位点上,借助于p~(ORF-2)上的β-半乳糖苷酶基因的活性,使含正确插入抗冻蛋白基因的克隆呈现出蓝色菌落,共获得4000多个转化子,其中有201个蓝色克隆。对于50个蓝色克隆提取质粒DNA,电泳后发现均大于p~(ORF-2)。用BglⅡ消化后,可以发现有300—1500bpDNA片段,同时确定了抗冻蛋白基因在p~(ORF-2)中的插入方向,对于正确插入的克隆作出部分限制性内切酶图谱,测定出插入的抗冻蛋白基因片段的DNA序列,然后将重组质粒从E.coli MH1000菌株转化到E.coliTK1046中,研究分析表达产物,SDS—聚丙烯酰胺凝胶电泳结果证明插入的抗冻蛋白的基因已表达,有明显的融合蛋白带,分子量大于β-半乳糖苷酶、是由大肠杆菌的外膜蛋白F,抗冻蛋白和β-半乳糖苷酶组成。融合蛋白含量占总蛋白的20％左右。     

Studies on the population dynamics of a thistle-feeding lady beetle,Henosepilachna pustulosa (Kôno) in a cool temperature climax forest

1. A field study was carried out on the population dynamics of a thistle-feeding lady beetle, Henosepilachna pustulosa (Kôno ) living in a cool temperature climax forest in northern Kyoto Prefecture, central Japan.
2. Intensive marking, release and recapture program was carried out to estimate the adult population parameters by usingJolly-Seber method.
3. Sampling ratio was around 50%. Marking ratio rapidly rised as the census progressed and approached to 100%.
4. Sex ratio (% ♀) was 63–69% in both overwintered and new adults.
5. Daily survival rate was as high as 0.95 or more and constant throughout the season. Adult longevity in the spring was longer than 40 days.
6. Reproductive rate i. e., the ratio of the number of newly emerged adults in a given generation to that of overwintered adults in the preceding generation, is very small, ranging 1–3, whereas winter survival is higher than 50%, consequently the size of populations in the study area remain in a remarkably constant size and it never reached a level where intraspesific competition occurred.
7. The population characteristics of H. pustulosa are compared with those of the two closely related species, H. vigintioctopunctata and H. vigintioctomaculata, which are the pests of Solanaceous crops. Hp is more K-strategic than the two pest species.