Testing the role of phenotypic plasticity for local adaptation: growth and development in time-constrained Rana temporaria populations

Phenotypic plasticity can be important for local adaptation, because it enables individuals to survive in a novel environment until genetic changes have been accumulated by genetic accommodation. By analysing the relationship between development rate and growth rate, it can be determined whether plasticity in life-history traits is caused by changed physiology or behaviour. We extended this to examine whether plasticity had been aiding local adaptation, by investigating whether the plastic response had been fixed in locally adapted populations. Tadpoles from island populations of Rana temporaria, locally adapted to different pool-drying regimes, were monitored in a common garden. Individual differences in development rate were caused by different foraging efficiency. However, developmental plasticity was physiologically mediated by trading off growth against development rate. Surprisingly, plasticity has not aided local adaptation to time-stressed environments, because local adaptation was not caused by genetic assimilation but on selection on the standing genetic variation in development time.     

Re‐examining extreme longevity of the cave crayfish Orconectes australis using new mark–recapture data: a lesson on the limitations of iterative size‐at‐age models

1. Centenarian species, defined as those taxa with life spans that frequently exceed 100 years, have long been of interest to ecologists because they represent an extreme end point in a continuum of life history strategies. One frequently reported example of a freshwater centenarian is the obligate cave crayfish Orconectes australis, with a maximum longevity reported to exceed 176 years. As a consequence of its reported longevity, O. australis has been used as a textbook example of life history adaptation to the organic‐carbon limitation that characterises many cave‐stream food webs. 2. Despite being widely reported, uncertainties surround the original estimates of longevity for O. australis, which were based on a single study dating from the mid‐1970s. In the present study, we re‐evaluated the growth rate, time‐to‐maturity, female age‐at‐first‐reproduction and longevity of O. australis using a mark–recapture study of more than 5 years based upon more than 3800 free‐ranging individuals from three isolated cave streams in the south‐eastern United States. 3. The results of our study indicate that accurate estimates of the longevity of O. australis are ≤22 years, with only a small proportion of individuals (<5%) exceeding this age. Our estimates for female time‐to‐maturity (4–5 years) and age‐at‐first‐reproduction (5–6 years) are also substantially lower than earlier estimates. 4. These new data indicate that the age thresholds for life history events of O. australis are comparable to other estimates for a modest assemblage of cave and surface species of crayfish for which credible age estimate exists, suggesting that a cave environment per se is not required for the evolution of extreme longevity in crayfish.     

Simulating the SARS outbreak in Beijing with limited data

We propose a mathematical model to simulate the SARS outbreak in Beijing. The model consists of six subpopulations, namely susceptible, exposed, quarantined, suspect, probable and removed, as China started to report SARS cases as suspect and probable separately from April 27 and cases transferred from suspect class to probable class from May 2. By simplifying the model to a two-compartment suspect-probable model and a single-compartment probable model and using limited data, we are able to simulate the SARS outbreak in Beijing. We estimate that the reproduction number varies from 1.0698 to 3.2524 and obtain certain important epidemiological parameters.     

亚胺培南临床用药与非发酵菌群分离率和耐药性的关系

目的了解亚胺培南临床用药和非发酵菌群分离率与耐药性变迁的关系,有利于非发酵菌感染的预防与治疗。方法统计分析浙江省人民医院2000～2003年临床分离非发酵菌的菌株分布、与亚胺培南的临床用药的相关性及耐药率。结果4年来非发酵菌的分离以铜绿假单胞菌(30．7％)、乙酸钙-鲍曼不动复合杆菌(19．％)及嗜麦芽糖寡养单胞菌(19．1％)为主．其分离率与亚胺培南用药存在相关性。对各菌属的主要菌种进行耐药性分析,嗜麦芽糖寡养单胞菌、脑膜脓毒性金黄杆菌和洋葱伯克霍尔德菌的耐药率极高,铜绿假单胞菌和乙酸钙-鲍曼不动复合杆菌的耐药率呈现明显升高的趋势。结论非发酵菌的检出率与亚胺培南使用关系密切,耐亚胺培南的菌株迅速升高。临床应合理使用抗生素,并加强对耐药菌株的监控。     

Robustness of Multiple Comparison Procedures: Treatment versus Control

Computer simulation techniques were used to investigate the Type I and Type II error rates of one parametric (Dunnett) and two nonparametric multiple comparison procedures for comparing treatments with a control under nonnormality and variance homogeneity. It was found that Dunnett's procedure is quite robust with respect to violations of the normality assumption. Power comparisons show that for small sample sizes Dunnett's procedure is superior to the nonparametric procedures also in non-normal cases, but for larger sample sizes the multiple analogue to Wilcoxon and Kruskal-Wallis rank statistics are superior to Dunnett's procedure in all considered nonnormal cases. Further investigations under nonnormality and variance heterogeneity show robustness properties with respect to the risks of first kind and power comparisons yield similar results as in the equal variance case.     

The biennial life strategy in a random environment

In a previous paper (J. Math. Biol. 26, 199–215 (1988)) we calculated the mean and variance of the long-run geometric growth rate of a discrete-time population model with two age classes in a random environment. The formula which was used in that paper as the starting point for the computation of the variance represents only the contribution of the one-period variances. Here we supplement these results by a calculation of the exact variance. All qualitative conclusions reached before are unaffected.     

广西柳州市1976—1990年蛇伤流行病学研究

本文对柳州市１９７６～１９９０年１５年蛇伤流行病学作了一次回顾性调查,在全市五区两县共查２０５０６９２７人次（年均人口数１３６７１２８．４０人）蛇伤数为１４１９人,总死亡６９人,年均发病率为：６．９２／１０万,年均死亡率为０．３４／１０万,年均病死率为：４．８６％。总致残８４人,年均致残率为０．４３／１０万。通过调查知道柳州市毒蛇种类有：银环蛇、金环蛇、竹叶青蛇、蝰蛇、烙铁头蛇、眼镜蛇、眼镜王蛇等七种。并掌握了蛇伤的季节、致伤的人群、时间、场所及转归,为今后开展蛇伤的防治、教学、科研及蛇类资源的综合利用提供了科学的依据。     

Parameter identification in epidemic models

Starting from a recent paper of Pollicott, Wang and Weiss we try to obtain improved representation formulas for the estimation of the time-dependent transmission rate of an epidemic in terms of either incidence or prevalence data. Although the formulas are (trivially) mathematically equivalent to previous formulas, the new representations need no additional estimates and they should be more stable numerically.We review the discrete time and the stochastic continuous time approach. We replace the assumption that recovery follows an exponential distribution and get estimates for the transmission rate for constant duration of the infectious phase.     

大型多钩槽绦虫在黄鳝体内寄生的研究

解剖检查了５００尾黄鳝。统计表明：黄鳝感染大型多钩槽绦虫的感染率为７．６％,感染强度是２．７,黄鳝感染此种绦虫为一个随机过程。大型钩槽绦虫在宿主种群中的分布符合负二项分布图式,其负二项分布参数ｋ＝０．０３４５,ｐ＝５．９０７８,长度在５ｃｍ以上的绦虫对宿主的正常生长有影响。