Bushcricket song as a clue for spermatophore size?

Bushcricket males of Poecilimon zimmeri transfer large and protein-rich spermatophores during mating, which females directly ingest. There is correlational evidence that heavier males transfer larger nuptial gifts. In no-choice mating trials, females mated randomly with respect to male’s body weight. In contrast, in two-choice mating trials, female bushcrickets exhibit clear choice for the heavier male. This heavier male advantage was also found in pre-mating choice during phonotaxis. With manipulated mute males, females mated at random with regard to body weight of the competitors. The number of physical encounters between a female and males was low in all tests with a single male (no choice) and greater in choice-tests with two competing males. The latencies to mate also differed significantly between treatments. The time mating pairs spent in precopula was short in experiments where the males could hear rivals and significantly longer in all other tests using either a single male or mute males. Thus, acoustic signalling in male bushcrickets seems to signal male body weight. A preference for heavier males may reflect a female’s preference for a larger spermatophore and therefore a greater direct benefit.     

When is a male not a male? Sex recognition and choice in two sex-changing species

For dioecious species, choosing a mate of the same sex can have reproductive costs. For sex-changing animals, however, a lack of sex recognition may not carry a reproductive cost, as pairs that were initially same-sex can become opposite-sex pairs as one partner changes sex. The strength of sex discrimination in sex changers, then, should depend on the duration of mating associations and whether the time of sex change is influenced by social situation (“flexible” sex change). We studied two species of marine snails that change sex from male to female, one with flexible sex change and long-term or permanent mating associations (Crepidula fornicata) and one with short-term pairings and relatively fixed time of sex change (Crepidula convexa), to determine whether either species exhibits sex recognition and whether members of C. convexa show stronger sex discrimination. In laboratory experiments, small males, the choosing animals, were placed with either a male or a female conspecific (no-choice experiments) or given a choice of a male or female (choice experiments). We controlled for shell length in all experiments, as relative size may influence sex change or choice. Males of both species paired more often with females than males, but, as predicted, males of C. convexa showed stronger discrimination: When given a choice, no C. convexa male paired with another male. In contrast, some C. fornicata males always chose other males even when given the choice of a female. These results suggest that sex recognition can be adaptive even for sex changers but demonstrate that the level of sex recognition will depend on other aspects of reproductive behavior.     

旅游地旅游者忠诚度机制模型及实证研究——以黄山风景区为例

旅游地忠诚的旅游者是其发展的重要资源,旅游者忠诚度机制研究有利于更全面地认识旅游者忠诚现象,帮助旅游地管理者制定有效的旅游者忠诚培育的战略。在文献回顾的基础上,尝试从交易过程、关系过程相结合的视角分析影响旅游地忠诚的要素,并尝试构建旅游地旅游者忠诚度机制的理论模型。通过问卷调查获得旅游者感知价值、满意度、信任和忠诚度数据,采用结构方程模型方法,以黄山风景区为案例地进行实证分析,检验模型拟合度及各变量对旅游者忠诚度的影响。结果显示,在影响旅游者忠诚度的各因素中,满意度对旅游者忠诚度的影响最大,路径系数是0.41;信任是影响旅游者忠诚度的另一重要因素,路径系数是0.21。     

选择试验模型法在耕地资源保护中的应用——以浙江省温岭市为例

选择试验模型法是目前国际上用于评估具有公共物品特性的自然资源和环境物品经济价值的一种相对较新的方法。论文以浙江省温岭市耕地资源保护为例,探讨选择试验模型法在耕地资源保护经济价值评估实践的可行性。在专家咨询和小组讨论的基础上,确定耕地景观、田间设施、土壤肥力和耕地保护费为温岭市耕地资源保护的4个属性。在对温岭市246名居民进行随机抽样调查的基础上,分析了温岭市耕地资源保护不同属性的价值以及耕地资源保护不同替代方案的相对价值。结果表明,对于温岭市全体居民来说,今后耕地资源保护的实施应该重点改善田间设施和提高土壤肥力,而耕地景观的改善也同样可以增加温岭市居民的福利水平。     

The effect of perceived female parasite load on post-copulatory male choice in a sex-role-reversed pipefish

The last several decades of research in behavioral ecology have resulted in a deeper appreciation of post-mating processes and sexual conflict in sexual selection. One of the most controversial aspects of sexual selection is cryptic mate choice. Here, we take advantage of male pregnancy in a sex-role-reversed pipefish (Syngnathus typhle) to quantify cryptic choice based on perceived parasite load and other sources of variance in female fitness. Studies have shown that S. typhle males preferentially mate with females with lower parasite loads and that a male’s perception of female parasite load can be altered by tattooing females. We manipulated the apparent parasite load of females in controlled mating experiments to test the hypothesis that post-copulatory sexual selection is dependent on a male’s perception of female parasite load in pipefish. Our results provided no evidence for cryptic male choice based on perceived female parasite load. However, we found evidence that eggs from larger females were more likely to result in viable offspring than eggs from smaller females and that the first female to mate with a male transferred more eggs per copulation on average. Overall, our results show that potential for post-copulatory sexual selection does exist in pipefish, but the male’s perception of female parasite load does not play a major role in this process.     

Modelling predation by transient leopard seals for an ecosystem-based management of Southern Ocean fisheries

Correctly quantifying the impacts of rare apex marine predators is essential to ecosystem-based approaches to fisheries management, where harvesting must be sustainable for targeted species and their dependent predators. This requires modelling the uncertainty in such processes as predator life history, seasonal abundance and movement, size-based predation, energetic requirements, and prey vulnerability. We combined these uncertainties to evaluate the predatory impact of transient leopard seals on a community of mesopredators (seals and penguins) and their prey at South Georgia, and assess the implications for an ecosystem-based management. The mesopredators are highly dependent on Antarctic krill and icefish, which are targeted by regional fisheries. We used a state-space formulation to combine (1) a mark-recapture open-population model and individual identification data to assess seasonally variable leopard seal arrival and departure dates, numbers, and residency times; (2) a size-based bioenergetic model; and (3) a size-based prey choice model from a diet analysis. Our models indicated that prey choice and consumption reflected seasonal changes in leopard seal population size and structure, size-selective predation and prey vulnerability. A population of 104 (90–125) leopard seals, of which 64% were juveniles, consumed less than 2% of the Antarctic fur seal pup production of the area (50% of total ingested energy, IE), but ca. 12–16% of the local gentoo penguin population (20% IE). Antarctic krill (28% IE) were the only observed food of leopard seal pups and supplemented the diet of older individuals. Direct impacts on krill and fish were negligible, but the “escapement” due to leopard seal predation on fur seal pups and penguins could be significant for the mackerel icefish fishery at South Georgia. These results suggest that: (1) rare apex predators like leopard seals may control, and may depend on, populations of mesopredators dependent on prey species targeted by fisheries; and (2) predatory impacts and community control may vary throughout the predator's geographic range, and differ across ecosystems and management areas, depending on the seasonal abundance of the prey and the predator's dispersal movements. This understanding is important to integrate the predator needs as natural mortality of its prey in models to set prey catch limits for fisheries. Reliable estimates of the variability of these needs are essential for a precautionary interpretation in the context of an ecosystem-based management.     

Speed choice versus celeration behavior as traffic accident predictor

INTRODUCTION: The driver celeration behavior theory predicts that this variable is superior to all other variables as a predictor of individual traffic accident involvement, including the ever-important speed parameter. The study was undertaken to test this prediction. Also, it was expected that most variables would associate fairly strongly. METHOD: The use of speed choice as a predictor of individual traffic accident record was discussed, and four different variants of this variable (maximum, net mean, gross mean, and standard deviation of speed) identified. These variables were then compared to celeration behavior as predictors of accident record of bus drivers in the same set of data. RESULTS: Celeration behavior was found to be slightly superior, in accordance with the prediction made from the driver celeration behavior theory, although the differences were not significant. Furthermore, the predictor variables were found to associate fairly strongly between themselves, with the exception of gross mean speed, and to have fair stability over time, especially when aggregated. CONCLUSIONS: These results tentatively confirm some of the predictions made from the driver celeration behavior theory. As the results for accidents were in the expected direction, but not significant, and the maximum speed variable may have suffered from a ceiling effect, the conclusion is provisional. Impact on industry: The correlations found were strong enough to warrant the use of celeration behavior as a predictive variable for transportation companies in their safety work.     

大城市郊区典型区域农户作物种植选择行为及其影响因素对比研究——基于沈阳市苏家屯区238户农户的调查研究

研究从农户作物种植选择行为角度出发,以马斯洛需求层次理论为基础,通过构建社会经济及政策变化对农户种植选择行为影响机理分析框架和理论模型,基于沈阳市苏家屯区238户农户调查数据,采用统计分析法和Logistic回归分析,研究结果表明:工业化、城市化进程的加快促进了大城市郊区非农就业机会的增多和对农产品需求的增加,导致农户作物种植业选择行为出现了明显的"非粮化"和"非农化"趋势,不同区域农户作物选择行为存在明显的差异,在空间上形成近郊区以种植粮食作物为主→远郊区兼种粮食作物和经济作物为主→纯农村区以种植经济作物为主的"反杜能圈"式的种植模式特征。在此研究基础上,从外部环境包括城市扩展、经济结构、市场价格变化、政策制度安排和内部环境包括个人特征、家庭特征、资源禀赋等7类因素13个因子对产生差异的影响机理进行分析,结果显示不同区域、不同因子的作用方向、影响程度与显著性表现均有所不同。根据以上的研究结果,政府应该从鼓励农户发展休闲农业、合理引导农户把握市场和培养新型农民等方面入手,优化农业结构调整,促进农村土地合理利用,提高土地利用效率,实现农村土地资源的持续利用。     

Urban riverbank residents' evaluation of flood evacuation policies in Winnipeg,Manitoba, Canada

The results of a discrete choice experiment (DCE) as a part of a survey among the urban riverbank residents on the Red River in Winnipeg, Manitoba, Canada, indicated that the risk of over-dike flooding, set at 2ft above the 1997 flood water level, was a significant determinant of both voluntary and mandatory evacuation, compared to those set at the 1996 or 1997 levels. Mandatory evacuation was more preferred over voluntary evacuation when the likelihood of flooding was at its most severe, and the opposite relationship was the case when the likelihood was low. The notification time for evacuation, suggested as 1, 2, and 4 days, proved to be an insignificant attribute, whereas the respondents indicated significant preference for full flood compensation over an offer of either 80% or 90% flood relief, irrespective of the alternatives of voluntary or mandatory evacuation.     

级联失效特性下的危险品运输路径选择研究

基于复杂网络的级联失效特性,构建危险品运输网络的级联失效模型,提出用路段重要度来度量某条路段上发生危险品事故后引起网络其他路段失效的规模。以路径风险最小化和路径总重要度最小化为目标,建立危险品运输路径的多目标决策模型,并利用标号法进行求解。算例结果表明,危险品运输网络确实存在级联失效现象。选择危险品运输路径时,应尽量避开重要度高的路段,以降低危险品事故对普通道路网络的不良交通影响。