The Future of Tropical Species on a Warmer Planet

Abstract: Modern global temperature and land cover and projected future temperatures suggest that tropical forest species will be particularly sensitive to global warming. Given a moderate greenhouse gas emissions scenario, fully 75% of the tropical forests present in 2000 will experience mean annual temperatures in 2100 that are greater than the highest mean annual temperature that supports closed‐canopy forest today. Temperature‐sensitive species might extend their ranges to cool refuges, defined here as areas where temperatures projected for 2100 match 1960s temperatures in the modern range. Distances to such cool refuges are greatest for equatorial species and are particularly large for key tropical forest areas including the Amazon and Congo River Basins, West Africa, and the upper elevations of many tropical mountains. In sum, tropical species are likely to be particularly sensitive to global warming because they are adapted to limited geographic and seasonal variation in temperature, already lived at or near the highest temperatures on Earth before global warming began, and are often isolated from cool refuges. To illustrate these three points, we examined the distributions and habitat associations of all extant mammal species. The distance to the nearest cool refuge exceeded 1000 km for more than 20% of the tropical and less than 4% of the extratropical species with small ranges. The biological impact of global warming is likely to be as severe in the tropics as at temperate and boreal latitudes.     

Shouting the odds: vocalization signals status in a lizard

Many species possess multiple sexually dimorphic traits, which incorporate different sensory modalities (e.g., acoustic, olfactory and visual), although their relative roles in sexual selection and in determining reproductive success are still poorly understood for most taxa. We assessed the role of multiple male traits, including one acoustic (dominant call frequency) and one visual (yellow throat patch) trait, in residency advertisement, contest behavior, and breeding success in barking geckos (Ptenopus garrulus garrulus). We show that male barking geckos maintain largely exclusive home ranges, with a trend for larger males to maintain larger home ranges. We also show that larger males have a lower dominant calling frequency. When aggressive behavior was elicited in the field using a recorded call of average frequency, resident males with low frequency calls were more likely to respond aggressively and charge the speaker compared to males with high frequency calls. However, body size and small relative throat patch size, rather than call frequency, were the best predictors of overall aggressiveness. Body size was also the best predictor of whether males bred. We suggest that call frequency in this crepuscular species constitutes an effective long-range signal of body size, used by males for remote rival assessment and to advertise home range boundaries in low-light environments.     

Null-Hypothesis Significance Testing and the Critical Weight Range for Australian Mammals

Abstract:  The critical weight range hypothesis for Australian terrestrial mammals states that species in the intermediate size range 35–5500 g are particularly susceptible to extinction. In a 2001 study Cardillo and Bromham found no statistically significant evidence for this hypothesis and suggested that research should instead focus on why small species are resistant to extinction. We used a similar data set of body sizes of Australian mammals grouped by conservation classification, but we used test statistics (mean deviation above and below the median body size) that are more statistically powerful than those of Cardillo and Bromham (quartiles, maxima, and minima of body size distributions). We found strong evidence in favor of the critical weight range hypothesis: the body size distribution of threatened species was more clustered toward the median body size from above and below. This pattern was statistically significant at the continental scale and in the arid zone, but not in the mesic zone. Confusing statistical significance with evidence of no effect, as Cardillo and Bromham did, can have negative implications for conservation biology because it can result in failure to act when action is warranted or provision of incorrect advice that affects policy and planning decisions.     

Data ranges in aquatic toxicity of chemicals

A significant problem for effect assessment of aquatic ecosystems arises from the large ranges of toxicity data, which can be found in different databases and literature. Here, ranges are given for the aquatic toxicity of 27 high production volume chemicals. Based on these illustrative examples and on the current literature on uncertainty in aquatic effect assessment, toxicity ranges are discussed for their possible causes (variation in experimental condition, species, endpoint, time) and ways to handle them (safety factors). Implications and recommendations on the procedure of risk analysis of chemical substances are drawn. Two main requirements for a comprehensive risk assessment are identified, which often play a minor role in current practice (as they are often neglected) as well as in scientific discussion (as they are meant to be trivial). First, data quality must be checked critically before applying any result of a toxicity test. Secondly, experimental data should take into account different species and acute as well as chronic data. If these aspects are considered in risk analysis, which is common practice in ecotoxicology but not always in the context of practical applications in risk engineering, a more comprehensive picture of the environmental toxicity of a chemical substance can be obtained.     

气孔运动机理研究进展

本综述讨论了Ｋ＋在气孔运动中的作用、有机代谢物对气孔运动的影响、渗透调节物质的转动机理、内源和外源信号对气孔运动的影响等方面的研究进展，并结合作者的工作，首次提出微管、微丝在气孔运动中可能具有重要调控作用的设想．     

A simple method for preparing prometaphase chromosomes from amniotic fluid cell cultures

A simple method for preparing prometaphase chromosomes from amniotic fluid cell cultures is described. The technique is based upon several key steps including: (1) reduced colcemid concentration, (2) reduced exposure to trypsin-EDTA, and (3) maintaining cells in single suspension by adjusting cell concentration appropriately. Chromosomes with banding resolution up ot 800 bands per haploid set can be routinely produced. The described methodology is particularly useful in defining and establishing the clinical significance of subtle structural aberrations.     

DDSC振动控制器的功能、指标及技术分析

DDSC（双数据处理振动控制器）系统是美国Dactron公司90年代研制的用于振动试验控制的新型振动控制器，具有硬件可靠，指标先进，功能完善的特点，在振动控制中具有很高的实用性和性价比，本文从使用的角度对其功能和技术特点进行展开分析。