芦芽山寒温性针叶林冠层下植被beta多样性格局及其成因

群落构建机制是生态学的中心议题之一。对山地植被beta多样性格局及其成因的探究有助于加深对此问题的认识。以芦芽山寒温性针叶林群落冠层下植被为研究对象,结合野外调查与室内实验获取的详细数据,运用Mantel检验、普通最小二乘回归和典范对应分析(CCA)等统计方法,探讨了林下植被的beta多样性格局及其成因,结果显示:(1)沿海拔梯度相邻群落间草本层物种周转率呈现递减格局,而灌木层变化规律不明显;(2)灌、草层beta多样性与海拔差异、地理距离呈显著正相关关系,而与局地环境异质性关系不显著。控制海拔作用后发现,灌、草层beta多样性与地理距离关系依然显著,而当消除地理距离的线性影响后,beta多样性与海拔关系也变得不显著(3)CCA模型中,环境因子共解释了物种组成变异的74.4%,其中,海拔、坡度、凋落物厚度、乔木密度与总干面积对林下灌、草植被物种组成具有显著影响,但土壤因子的作用未见显著。综上,生境筛滤与扩散限制共同主导了芦芽山寒温性针叶林冠层下群落构建过程,但扩散限制的影响强于生境筛滤作用。     

The role of temporal sensing in bioelectromagnetic effects

Experiments were conducted to see whether the cellular response to electromagnetic (EM) fields occurs through a detection process involving temporal sensing. L929 cells were exposed to 60 Hz magnetic fields and the enhancement of ornithine decarboxylase (ODC) activity was measured to determine cellular response to the field. In one set of experiments, the field was turned alternately off and on at intervals of 0.1 to 50 s. For these experiments, field coherence was maintained by eliminating the insertion of random time intervals upon switching. Intervals ≥ 1 s produced no enhancement of ODC activity, but fields switched at intervals ≥ 10 s showed ODC activities that were enhanced by a factor of approximately 1.7. These data indicate that it is the interval over which field parameters (e.g., amplitude or frequency) remain constant, rather than the interval over which the field is coherent, that is critical to cellular response to an EMF. In a second set of experiments, designed to determine how long it would take for cells to detect a change in field parameters, the field was interrupted for brief intervals (25–200 ms) once each second throughout exposure. In this situation, the extent of EMF-induced ODC activity depended upon the duration of the interruption. Interruptions ≥ 100 ms were detected by the cell as shown by elimination of field-induced enhancement of ODC. That two time constants (0.1 and 10 s) are involved in cellular EMF detection is consistent with the temporal sensing process associated with bacterial chemotaxis. By analogy with bacterial temporal sensing, cells would continuously sample and average an EM field over intervals of about 0.1 s (the “averaging” time), storing the averaged value in memory. The cell would compare the stored value with the current average, and respond to the EM field only when field parameters remain constant over intervals of approximately 10 s (the “memory” time). Bioelectromagnetics 18:388–395, 1997. © 1997 Wiley-Liss, Inc.     

Significance and Interspecific Variability of Accumulated Trace Metal Concentrations in Antarctic Benthic Crustaceans

Trace metals (Cd, Cu, Pb and Zn) were analysed in crustaceans collected on Polarstern cruises ANT XVI/2 (1999) and ANT XXI/2 (2003/04, BENDEX) to the Weddell Sea. Our study provides further evidence for the frequently reported “Cd anomaly” in polar crustaceans, with data ranging from 1.2 (Ceratoserolis trilobitoides) to 6.2 mg Cd kg^–1 DW (Notocrangon antarcticus) in 1999 and from 1.2 (Waldeckia obesa) to 20.3 mg Cd kg^–1 (Tryphosella murrayi) in 2003. Pb concentrations well below 1 mg kg^–1 in most of the samples analysed might serve as a regional or even global background value for comparison in biomonitoring studies. Increasing Cu concentrations from eggs of decapods (e.g., 5 vs. 51 mg kg^–1 in N. antarcticus) or juveniles in the brood pouch of an amphipod species to adult females indicate that the enzymatic requirements and haemocyanin component demand for Cu in early life‐history stages is probably not met without a distinct bioaccumulation of this essential element after hatching. Most interestingly, Cd also increases (<0.1 vs. 6.2 mg kg^–1 in N. antarcticus). This could be the consequence of efficient uptake mechanisms for Cu that cannot discriminate between this element and Cd. Cu and Zn concentrations in decapods of this study are largely within the range reported worldwide (40–90 mg Cu kg^–1 and 40–80 mg Zn kg^–1), indicating that these elements are regulated. The enormous heterogeneity of Cd and Zn in many amphipod species investigated (e.g., from 0.6 in Gnathiphimedia mandibularis to 34.4 mg Cd kg^–1 in Orchomenopsis acanthura and from 41 in Eusirus antarcticus to 1244 mg Zn kg^–1 in Iphimediella bransfieldi) supports the hypothesis of the “Cd anomaly” and suggests that there is probably no consistent metabolic demand for the essential element Zn in this taxonomic group. The heterogeneity of Cu in amphipods is less pronounced. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Reproductive patterns in galagos (Galago zanzibaricus and Galago garnettii) in relation to climatic variability

The reproductive patterns (birth seasonality, litter size, litters per year) of two sympatric species of galago (Galago zanzibaricus and G. garnettii) were studied in a coastal forest in Kenya for a two-year period. Trap-retrap and radio tracking methods were employed. G. zanzibaricus has one infant twice per year; G. garnettii has one infant once per year. Both species are seasonal breeders. These East African galagos are intermediate in reproductive patterns when compared with galagos from South African woodland (G. senegalensis moholi and G. crassicaudatus umbrosis) and West African rainforest (G. alleni and G. demidovii). Climatic patterns (total annual rainfall, seasonal variability of rainfall, variability in total annual rainfall, and annual temperature variability) are also compared for the three regions. Climatically, East Africa is intermediate between West and South Africa in total annual rainfall and in seasonality of rainfall, but not in year-to-year variability in rainfall. East Africa shows the highest variability in annual rainfall. South Africa has the coldest dry seasons and highest variability in temperatures. The results of this study suggest that “r-selection” and “K-selection” do not provide adequate explanations of galago reproductive patterns.     

Growth of an Insect Trypanosomatid at 37 C in a Defined Medium*

SYNOPSIS. A defined medium for an insect trypanosomatid, “Leptomonas pessoai” (probably a member of the genus Herpetomonas) isolated from the reduviid Zelus leucogrammus, allows growth up to 37 C. No marked differences were evident for growth at 37 C. The requirements for amino acids, vitamins, purine, and hemin, and pH range were like those established for Crithidia fasciculata. Again like C. fasciculata, it remains alive at 4 C for at least 3 months in a çlycerolated defined medium.     

The skull attributed to Mozart—craniosynostosis or not?

The results of a detailed morphological analysis of the skull attributed to Mozart are presented which refute a recent claim that the skull as well as several of Mozart's portraits show indications of uncomplicated trigonocephaly. These indications according to the present analysis are within the limits of normal variation and derive from retention of part of the long arm of the anterior fontanelle.     

Is the Prevalence of Successful Weight Loss and Maintenance Higher in the General Community than the Research Clinic?

BARTLETT, SUSAN J., MYLES S. FAITH, KEVIN R. FONTAINE, LAWRENCE J. CHESKIN, AND DAVID B. ALLISON. Is the prevalence of successful weight loss and maintenance higher in the general community than the research clinic? Obes Res. Objective: The prevalence of successful weight loss remains unclear. In 1982, Schachter concluded that in the general population, the rate of “self-cured” obesity approached 63%–much higher than the rate from clinical trials. Several subsequent studies have addressed this issue. Research Methods and Procedures: Our initial goal was to meta-analyze these studies to evaluate the validity of the original hypotheses and the extent to which additional investigations supported the findings. We began by restating Schachter's hypotheses in precise, testable terms. Results: A systematic review of these studies found many methodological limitations and much heterogeneity among the samples studied, hypotheses addressed, and operational definitions. Some of these limitations appear to stem from the lack of clear, precise statements of the exact hypotheses tested. Differences among studies are delineated, and we outline why meta-analytic pooling of these data appears inappropriate. Conclusions: The current data are inadequate to draw any definite conclusions regarding the cure rate of obesity. Criteria for the adequate study of success rates with “self-cure” in the general population are proposed.     

Proboscis monkey (Nasalis larvatus) social organization: Group structure

Proboscis monkey (Nasalis larvatus) social organization was studied at the Tanjung Puting National Park in Kalimantan Tengah, Indonesia, for 12 months. Data were collected on one-male groups and all-male groups by using scan sampling and event sampling while following groups. Evening census surveys were also conducted. Proboscis monkeys were found to follow the typical Asian colobine pattern of one-male social groups, with extra-group males forming all-male groups. These groups appear stable, with few changes in membership. One-male groups appear to be “female bonded”; adult females direct affiliative behaviors towards their offspring and other adult females, not towards the male. Nearest-neighbor data indicate some peripheralization of juvenile animals.