区域PRED模型在环境区划中的应用

通过分析区域ＰＲＥＤ模型的特点和结构,显示了该模型在环境区划中的广泛应用前景和重要意义．该模型既丰富了环境区划的理论基础,又使区划的指标体系增加了新的内容,使研究者能更多地着眼于系统的协调发展．     

Solar UV-B and visible radiation in tropical forest gaps: measurements partitioning direct and diffuse radiation

Solar ultraviolet-B (UV-B) radiation penetrates plant canopies to a different degree than photosynthetically active radiation (PAR) because UV-B is diffused to a greater degree by the atmosphere. We measured both global (total) and diffuse solar radiation in canopy gaps of a semideciduous tropical forest in Panama. Measurements were simultaneously made in the UV-B and PAR wavebands. Compared to unobstructed measurements taken outside the forest, the sunlit portions of gaps were depleted in the proportion of UV-B relative to PAR, especially at midday. Shaded areas, in contrast, were always richer in UV-B relative to PAR, but the magnitude of the change varied greatly. Presumably this variation was due to the differences in the directional nature of diffuse solar UV-B radiation as compared to diffuse PAR. Measurements in the gaps showed substantial reductions in the proportion of radiation in the diffuse components of both the UV-B and PAR wavebands. However, because of the greater proportion of UV-B which is diffuse, it tended to predominate in shaded areas. Similar patterns were seen in measurements taken at temperate latitudes. Response of shade- and gap-dwelling plants to these high UV-B:PAR ratios has received little attention.     

GENETIC VARIATION IN CRICKET CALLING SONG ACROSS A HYBRID ZONE BETWEEN TWO SIBLING SPECIES

The sibling ground crickets Allonemobius fasciatus and A. socius meet along a mosaic hybrid zone at ≈ 40°N latitude in eastern North America. In this paper we report the findings of a genetic analysis of calling-song variation within and among six cricket populations sampled along a transect through the hybrid zone in southern New Jersey. We compared aspects of the calling song of both wild-caught and laboratory-reared crickets to test the hypothesis that population differences in song observed in the wild were genetically based. We found significant, species-level differences in all aspects of the calling song, and these differences persisted even after a generation of common-garden rearing in the laboratory, supporting the hypothesis that interspecific variation observed in the wild largely reflects genetic differentiation between the two taxa. A discriminant function analysis indicated that individual crickets could be assigned to the proper taxon with less than 10% error, supporting the premise that calling song could be used by female crickets as a mechanism for species recognition. One population, collected from within the hybrid zone and containing significant numbers of hybrid individuals, was intermediate in its calling song, presumably reflecting this population's mixed genetic makeup. In this hybrid zone population, song phenotype was highly correlated to a hybrid index score generated using species-specific alleles at four diagnostic allozyme markers, suggesting a multigenic basis to calling-song variation in these crickets as well as linkage disequilibrium between markers and song. Based on an analysis of laboratory-reared full-sib families, broad-sense heritabilities for calling-song characteristics were generally significant in the two A. socius populations, whereas many components of song showed no significant family effects in the three A. fasciatus populations. The genotypically mixed, hybrid zone population showed very high heritabilities for most calling-song components, which likely reflect the influence of interspecific gene flow on genetic variation for quantitative traits.     

On the detection of environmental effects on complex matrices combining off-line liquid chromatography and 1H-NMR

An off-line combination of 400 MHz proton (1H)-NMR spectroscopy and liquid chromatography (LC) has been used for the multi-component comparison of low-molecular weight compounds (i.e., chemical fingerprinting) in model fluid broths and (processed) tomato. The focus of the research described is on (i) devising GLP-like methods for sample handling and NMR measurements that will ensure reproducibility, (ii) an automated handling of data, (iii) validity of the designed methodology and (iv) the interpretation of large amounts of data.     

Changes in otolith microchemistry of the Japanese eel, Anguitta japonica, during its migration from the ocean to the rivers of Taiwan

The newly recruited Japanese eel, Anguilla japonica , elvers and 1-year-old eels collected in estuaries and in rivers, respectively, were studied. The microstructure and chemical composition of the sagittal otolith of these eels were examined by SEM and wavelength-dispersive spectrometer (WDS), A transition zone or'elver mark'was observed in the otolith of the young eels. A comparison of the otoliths of elvers with those from the 1-year-old eels suggests that this transition zone was deposited during upstream migration, a change from a marine to freshwater environment. Strontium (Sr) content in the primordium of the otolith of both elvers and young eels was low, probably due to the maternal or freshwater origin of the oocyte. The concentration of Sr in the otolith increased gradually during marine life and reached a peak approximately 1 month before upstream migration. As the elvers entered the estuary, the Src concentration dramatically decreased and remained at a low level thereafter. These findings indicate that the history of the migratory environment of the eel can be reconstructed from a combined study of otolith microstructure and microchemistry analysis.     

Retrospective analysis of the relationships among the test environments of the Southern Queensland sugarcane breeding programme

Repeatability of aspects of genotype by environment (GxE) interactions is an important factor to be assessed in designing more efficient selection programmes. Sugar yield data from multi environment trials (METs) which were part of the sugarcane breeding programme in southern Queensland were analysed. Data were obtained from 71 environments consisting of trials planted from 1986 to 1989. Retrospective analysis on these data was conducted to assess the repeatability of the clone by environment (CxE) interactions over locations and years. This analysis focussed on identifying similarities among test environments in the way they discriminated among clones for sugar yield. Analyses of variance and pattern analyses on environments over years based on standardised data were conducted. The pattern analyses were done sequentially according to the accumulated data sets over years. Squared Euclidean distances among environments were averaged over data sets and years before pattern analyses across the data sets were conducted. A graphical methodology was developed to present the results of the cumulative historical analysis. CxE interactions of a magnitude which affected selection decisions were present in each data set studied. Pattern analyses on cumulative data sets identified environmental groupings that were based on geographical positions. Each location generated a different pattern of discrimination among the clones. These results emphasised the importance of clone by location (CxL) interactions in southern Queensland and the need to concentrate more on testing across locations than on ratooning ability within a location. The classifications identified similarities among ratoon crops within a location, differences among locations and differences between ratoon crops and their plant crop (PC). This suggested that some aspects of CxL and clone by crop-year (CxY) interactions were repeatable across years. The potential applications of these results to increase efficiency of the sugarcane breeding programme, such as the possibility of applying indirect selection among environments generating similar discrimination among clones, are discussed.Abbreviations GxE Genotype-by-environment interactions - METs multi-environment trials - CxE clone-by-en-vironment interactions - CxL clone-by-location interactions - PC plant crop - CxY clone-by-crop-year interactions - CxLxF clone-by-location-by-crop-year interactions - SYT substation yield trials - BSES Bureau of SugarExperiment Stations     

LONG-TERM LABORATORY EVOLUTION OF A GENETIC LIFE-HISTORY TRADE-OFF IN DROSOPHILA MELANOGASTER. 2. STABILITY OF GENETIC CORRELATIONS

Experiments in laboratory populations of Drosophila melanogaster have shown a negative genetic correlation between early-life fecundity on the one hand and starvation resistance and longevity on the other. Selection for late-life reproductive success resulted in long-lived populations that had increased starvation resistance but diminished early-life fecundity relative to short-lived controls. This pattern of differentiation proved, however, to be unstable. When assayed in a standard high-fecundity environment, the relative early fecundity of the long- and short-lived stocks reversed over a decade. That is, the long-lived populations came to have greater relative early-life fecundity, late-life fecundity, longevity and starvation resistance. Nevertheless, when these populations were assayed in other assay environments, the original trade-off was still present. We investigated the genetic structure of the short- and long-lived populations, to ask whether the inconstancy of the trade-off, as inferred from among population comparisons, is reflected in the pattern of genetic correlations within populations. For this purpose, lines from each of the short- and long-lived populations that had been selected for starvation resistance were compared with unselected controls. The direct and correlated responses of these starvation selected populations suggest that (1) the original genetic trade-off was still present in the ancestral short- and long-lived populations, even when it was no longer apparent from their comparison; (2) the trade-off was present in both assay environments; and (3) selectable genotype × environment variation exists for early fecundity. We suggest that a failure of the pattern of differentiation among populations to reflect the pattern of genetic correlations, if common in natural populations, will prevent the reliable inference of genetic trade-offs from comparisons of most natural populations.     

Carbohydrate transport in bacteria under environmental conditions,a black box?

A typical eubacterium carries a battery of substrate transport systems which are the ultimate pacemakers for growth. These systems reflect a billion year old selection for coping with rapidly changing conditions in the environment and each of them is optimised for specific growth conditions. Metabolic pathways in combination with transport systems can be interpreted as transient sensory systems, where a transport system corresponds to a sensor for external stimuli. Characteristic is a tightly linked common control between a carbohydrate metabolic pathway and the corresponding transport system. Many of the observed growth phenomena are a direct result of adaptation and regulation of transport capacity to rapid changes in environmental conditions. Some of the better understood examples are discussed. Nevertheless, knowledge on bacterial carbohydrate transport under environmental conditions as documented in the literature is still scarce.     

中国现代人群两性身高差异分布及其影响因素

本文对中国现代人群的两性身高差异分布状况及其影响因素进行了分析。选用152处中国现代人群（含69处汉族人群和83处少数民族人群）的男、女性身高数据,计算两性身高差异指数,并对比该指数在南、北方汉族和少数民族人群间的分布差异,同时分析纬度、气候、体格大小与城乡环境因素对两性身高差异程度的影响。结果表明,中国男性的平均身高比女性高出约7.16%(4.72%~9.26%）;南、北方汉族和少数民族之间的两性身高差异程度相似,北方汉族和南方汉族两性身高差异程度相似,但北方少数民族的两性身高差异明显大于南方少数民族。此外,两性身高差异程度与纬度、气温年较差和年均风速呈低度线性正相关,与年均气温、年均降水量和年均相对湿度呈低度线性负相关,而与体格大小和城乡环境并无显著关联。这提示遗传和自然环境因素在中国现代人群两性身高差异的区域化演变中更趋主导性,而社会环境因素的影响程度相对较低。     

Evolutionary coexistence in a fluctuating environment by specialization on resource level

Microbial communities in fluctuating environments, such as oceans or the human gut, contain a wealth of diversity. This diversity contributes to the stability of communities and the functions they have in their hosts and ecosystems. To improve stability and increase production of beneficial compounds, we need to understand the underlying mechanisms causing this diversity. When nutrient levels fluctuate over time, one possibly relevant mechanism is coexistence between specialists on low and specialists on high nutrient levels. The relevance of this process is supported by the observations of coexistence in the laboratory, and by simple models, which show that negative frequency dependence of two such specialists can stabilize coexistence. However, as microbial populations are often large and fast growing, they evolve rapidly. Our aim is to determine what happens when species can evolve; whether evolutionary branching can create diversity or whether evolution will destabilize coexistence. We derive an analytical expression of the invasion fitness in fluctuating environments and use adaptive dynamics techniques to find that evolutionarily stable coexistence requires a special type of trade-off between growth at low and high nutrients. We do not find support for the necessary evolutionary trade-off in data available for the bacterium Escherichia coli and the yeast Saccharomyces cerevisiae on glucose. However, this type of data is scarce and might exist for other species or in different conditions. Moreover, we do find evidence for evolutionarily stable coexistence of the two species together. Since we find this coexistence in the scarce data that are available, we predict that specialization on resource level is a relevant mechanism for species diversity in microbial communities in fluctuating environments in natural settings.