Biotic regionalization and climatic controls in western North America

New methods of weather analysis accompanied by microhabitat ‘bioassays’ have been applied in several case studies to demonstrate effects of atmospheric processes on patterns of community composition and structure and potential species evolution. Average spatial and seasonal airmass dynamics which determine regional and elevational patterns of relative microhabitat favorability, were found to vary between a recent global warming trend (ca 1900 to 1940) and the subsequent global cooling trend (ca 1940 to 1970). These apparently systematic spatial and temporal shifts in weather were related to plant establishment patterns and community composition and structure. The proposed causal mechanisms function, in part, through regional shifts in microhabitat size. These effects are similar to larger scale, longer term shifts deduced from the late Quaternary fossil record. By modifying the spatial approach, month-to-month and year-to-year variability of weather has been examined for the last 130 years at individual points in southwestern North America. Three climatic regimes (the end of the Little Ice Age, the recent warming trend and the recent cooling trend) exhibited distinct year-to-year patterns of weather that can be related to the establishment of different kinds of plants (e.g., C₄ grasses versus C₃ shrubs). Oscillations between different temporal climatic regimes appear to promote the episodic establishment of different life forms, but not necessarily their local extinction. The two methods of weather analysis have been combined in a regional assessment of climatic controls of different biomes in space and time with a primary focus on the Chihuahuan desert. Natural ecotones between the Chihuahuan desert and neighboring biomes are clearly related to large scale airmass dynamics associated with seasonal oscillations in jetstream position. The weather patterns controlling ecotonal positions result from seasonal topographic influences on the general circulation of the atmosphere. The apparent stability of these patterns allows causal hypotheses of biogeographic dynamics and the evolution of physiological traits and life history characteristics.     

蚕豆田节肢类群落特征的初步研究

经调查,蚕豆田的昆虫和蜘蛛,计有68种,其中属农作物害虫的有18种,天敌有50种。本文还对蚕豆田节肢类的优势种群、种群动态及其群落特征进行了分析,阐明了保护蚕豆田中的天敌对控制后茬作物害虫的重要意义。     

植物群落演替与土壤发展之间的关系

本文运用植物群落中植物优势种的重要值与相对应子群落的土壤特征值直接相关联的分析方法,对湖北宜昌大老岭的桦(Betula)、栎(Quercus)、栗(Castanea)七个群落类型的三个演替途径的土壤动态进行分析,结果表明:在植物群落的演替过程中,土壤中的Ca、pH值减少;离子代换量增加;Na、Mg、NH_4+-N、速效P、速效K、有机质的含量是随着物种的变化而呈不同的趋势。因此,植物群落的演替是生态系统的动态过程。     

Genetically-based plant resistance traits affect arthropods,fungi, and birds

We examine how the distribution of a leafgalling aphid (Pemphigus betae) affects other species associated with natural stands of hybrid cottonwoods (Populus angustifolia x P. fremontii). Aphid transfers on common-garden clones and RFLP analysis show that resistance to aphids in cottonwoods is affected by plant genotype. Because susceptible trees typically support thousands of galls, while adjacent resistant trees have few or none, plant resistance traits that affect the distribution of this abundant herbivore may directly and/or indirectly affect other species. We found that the arthropod community of aphid-susceptible trees had 31% greater species richness and 26% greater relative abundance than aphid-resistant trees. To examine direct and indirect effects of plant resistance traits on other organisms, we experimentally excluded aphids and found that abundances and/or foraging behavior of arthropods, fungi, and birds were altered. First, exclusion of gall aphids on susceptible trees resulted in a 24% decrease in species richness and a 28% decrease in relative abundance of the arthropod community. Second, exclusion of aphids also caused a 2- to 3-fold decrease in foraging and/or presence of three taxa of aphid enemies: birds, fungi, and insects. Lastly, aphidexclussion resulted in a 2-fold increase in inquilines (animals who live in abodes properly belonging to another). We also found that fungi and birds responded to variation in gall density at the branch level. We conclude plant resistance traits affect diverse species from three trophic levels supporting a bottom-up influence of plants on community structure.     

Comparison of fish assemblages among an artificial reef, a natural reef and a sandy-mud bottom site on the shelf off Iwate, northern Japan

Synopsis Fish assemblages at an artificial reef site, a natural reef site and a sandy-mud bottom site, on the shelf (depth 130 m) off Iwate Prefecture, northern Japan, were surveyed by using a bottom trammel net from May 1987 to March 1993. A total of 12 173 fishes of 48 species were recorded. Physiculus maximowiczi was dominant and comprised 69% of the total numerical abundance. Total fish number was lowest in March at all the 3 sites when P. maximowiczi migrated to deeper and warmer waters. Assemblage equitability and species diversity also varied seasonally in accordance with the abundance fluctuation of P. maximowiczi. P. maximowiczi, Alcichthys alcicornis and Hexagrammos otakii were more abundant at the artificial reef and natural reef sites, while Dexistes rikuzenius and Hemitripterus villosus were more abundant at the sandy-mud bottom site; total fish abundance was largest at the artificial reef site mainly due to the large number of P. maximowiczi. Species richness was similar among sites, but equitability, and consequently species diversity, was lowest at the artificial reef site. The main effect of the artificial reef seemed the attraction of P. maximowiczi from nearby bottoms, especially from natural rocky reefs; its large abundance determined the structure of the artificial reef fish community.     

Serological Characterization of Trichosporon cutaneum and Related Species

Recent molecular biological, chemical, physiological and morphological studies indicate that Trichosporon cutaneum and related species should be reclassified. In this study, antigenic characteristics of the species were determined. The results of adsorption experiments revealed that there were at least three serological types: I, II and III. Specific factor sera I, II and III were prepared on the basis of adsorption experiments and isolates were serotyped by cell slide agglutination (CSA). Since the CSA test was difficult to read in some strains, the results of the CSA test were compared with the findings from an enzyme-linked immunosorbent assay (ELISA). For the ELISA, crude polysaccharide antigens prepared from the culture supernatant were used as the antigen. The types determined by ELISA correlated well with those determined by the CSA test. These data suggest that T. cutaneum and related species have at least three serological types, and that the typing can be done by either CSA or ELISA.     

露水草的光合特性及其生态学意义

用盆栽和遮阴试验研究了露水草（Ｃｙａｎｏｔｉｓ ａｒａｃｈｎｏｉｄｅａ Ｃｌａｒｋｅ） 的光合作用特征,比较了不同遮光水平对光合速率、光合器官特性及光合产量的影响。结果如下：１．露水草是一种耐阴偏阳的Ｃ３ 类草木植物,其光合作用的光饱和点约为６５０ μｍ ｏｌ·ｍ － ２·ｓ－ １,光补偿点约为１７ μｍ ｏｌ·ｍ － ２·ｓ－ １,且具有高达１３０×１０－ ６的ＣＯ２ 补偿点。２．露水草的最大净光合速率为１２．４５ μｍ ｏｌ·ｍ － ２·ｓ－ １。叶片净光合速率的日变化规律呈双峰曲线,主峰在１１～１２ 时,次峰在１５时左右。３．遮光２０％ ～５０％ 有利于露水草的生长。与对照相比,叶片中叶绿素ｂ 的含量增加了４７％ ～８３％ ,并且由于净光合速率（相对光合速率）的提高,使光合生产量增加了１２％ ～１８％ 。     

Bacterial abundance and diversity in the Barbados Trench determined by phospholipid analysis

Abstract: The Barbados trench is characterized by large fields of volcanoes and mounds located over a distance of 30 km above the northern slope of a basement ridge corresponding to an inactive transform fault. Sediments from various locations were collected and analyzed for their lipid contents. Bacterial input to the overall biomass was estimated through the analysis of phospholipid ester-linked fatty acid (PLFA) profiles and glycerol ether lipids. Results indicated a eubacterial biomass estimated to be 10⁹cells (g dry wt)⁻¹. Individual fatty acid profiles revealed the presence of sulfur-oxidizing bacteria common to many deep-sea sites but also a large contribution of type I and type II methanotrophs to the eubacterial biomass. The presence of methanotrophs was further supported by the analysis of specific biomarkers of these microorganisms as well as some unusual trans fatty acid isomers. Anaerobic bacteria and presumbly sulfate reducing bacteria were also present, as well as archaebacteria and primarily methanogens, as indicated by glycerol ether lipid analysis.