Fishing as a Supergame

This paper considers how cooperative solutions to games of sharing fish resources can be supported by threat strategies. With highly mobile fish stocks, the number of agents compatible with a cooperative self-enforcing solution is not very high for reasonable values of the discount rate, but sensitive to changes in the discount rate and costs and to cost heterogeneity. With migrating stocks, where growth and reproduction depend on how much all agents leave behind after harvesting, the likelihood of a cooperative, self-enforcing equilibrium is increased. With a dominant player and a competitive fringe the rents and optimum stock level of the dominant player fall quickly as the share of the competitive fringe increases.     

Sustainable development as freedom

There has been considerable debate about how best to define sustainable development. In this commentary, I argue that Amartya Sen's concept of 'development as freedom' is the appropriate theoretical framework for understanding sustainable development. Environmentalists should consider defining their goal as 'sustainable development as freedom,' the achievement of the greatest possible level of freedom without restricting the access of future generations to these same freedoms. The adoption of this framework has implications for the work of environmental NGOs, which are briefly discussed.     

Parasites as conservation tools

Parasite success typically depends on a close relationship with one or more hosts; therefore, attributes of parasitic infection have the potential to provide indirect details of host natural history and are biologically relevant to animal conservation. Characterization of parasite infections has been useful in delineating host populations and has served as a proxy for assessment of environmental quality. In other cases, the utility of parasites is just being explored, for example, as indicators of host connectivity. Innovative studies of parasite biology can provide information to manage major conservation threats by using parasite assemblage, prevalence, or genetic data to provide insights into the host. Overexploitation, habitat loss and fragmentation, invasive species, and climate change are major threats to animal conservation, and all of these can be informed by parasites.     

Humic substances as surfactants

Humic substances from soils and sediments can be defined as surface active substances based on the surface tension measurements. Although there are several micellar structural models of humic substances currently available, few studies evaluating humic substances as surfactants have been conducted to date. Therefore, we evaluated the ability of humic substances and their derivatives to influence surface tension. We found that the ability of a humic substance to influence the surface tension of a solution depends on its origin. Many industrially produced humic materials exerted little or no impact on surface tension, whereas humic substances isolated from natural environments (water, soil, peat, sediments, sludge from wastewater treatment facilities) exerted a large impact on surface tension. These findings indicate that the modification of humic substances can enable their use as surfactants. In addition, these findings indicate that solutions of humic substances and their derivatives can be used to increase the solubility of organic compounds.     

Territory defence in tropical birds: are females as aggressive as males?

Much of our knowledge concerning the functions of territorial behaviour and how territories are defended by individuals comes from research on birds. The vast majority of this work has focused on temperate zone breeding territoriality in which territories are defended most obviously by males. Our understanding of the female role in territory defence is limited because they are less conspicuous and much harder to observe. We studied sex roles in territory maintenance and defence in a duetting, resident neotropical passerine, the white-bellied antbird (Myrmeciza longipes). This species maintains territories and pair bonds year round and both sexes sing and actively participate in territory defence. We performed a series of playback experiments throughout the dry (non-breeding) and wet (breeding) seasons. We exposed territorial pairs to three types of stimuli including: (1) single sex, male only songs, (2) single sex, female only songs, and (3) both sex songs/duets. Contrary to findings for most other tropical species, individuals defended their territories with equal levels of aggression regardless of stimuli. Furthermore, sex roles were very different, with males responding more aggressively than females to all stimuli throughout both seasons. Both males and females consistently responded more aggressively to territorial intrusions during the dry season than during the wet season, likely because food abundance is low in the dry season and territory value is high. Our analysis of duetting behaviour suggests that duets do not serve a significant role in mate guarding, or territory defence.     

Evidence for broadcast spawning as well as brooding in the scleractinian coral Pocillopora damicornis

The reproductive activity of 88 colonies of Pocillopora damicornis at Rottnest Island, Western Australia, was examined over 12 mo (20 August 1988 to 20 August 1989). Larvae were found close to the three new moons of February, March and April, 1989, but in large numbers only during March; 67% of all corals produced larvae. There was no obvious connection between gametogenesis and the production of brooded larvae; however, those corals which did not produce, larvae also did not produce ova but did produce, sperm, and must be considered male colonies. All colonies which produced ova went on to produce planulae. Spermatogenesis occurred throughout the year, but oogenesis occurred between September 1988 and April 1989. Dramatic declines in the percentage of polyps containing eggs and sperm occurred in early February and early April 1989. On these dates the amount of lipid in the tissue of the corals decreased, which suggests that the decline in the percentage of polyps with sperm and eggs was not due to the gametes being resorbed by the polyps. Therefore, P. damicornis at Rottnest Island appears to be both a brooder and a broadcaster with asexual reproduction through brooded larvae and sexual reproduction through spawning of gametes. This accounts for earlier evidence in the literature that some input from sexual reproduction had been occurring in the populations of P. damicornis at Rottnest Island. There is no direct evidence for spawning, as broadcasting of gametes has not been observed, but the indirect evidence provides a strong argument for the existence of this dual reproduction.     

Population as an oscillating system

In this paper we present a new approach describing population dynamics based on the view of a population as an oscillating system. To develop a mathematical model of an oscillating population, we applied a third-order differential equation. Our model describes population dynamics within a parametric-temporal continuum, formed by the relative values of population growth and decrease over time. In this paper we also illustrate how our oscillative model effectively compliments the existing suite of models in population dynamics.     

Biota as toxic metal indicators

Metal in the environment arises from both natural sources and human activities. Toxic metals in air, soil, and water have become a global problem. They are potential hazards to aquatic, animal, and human life because of their toxicity, bioaccumulative, and non-biodegradable nature. The major impacts of metal pollutants can be stated as ecosystem contamination and health problems of exposed human populations. Those problems have been a cause of increasing public concern throughout the world. Some trace metals are used by living organisms to stabilize protein structures, facilitate electron transfer reactions, and catalyze enzymatic reactions. But even metals that are biologically essential can be harmful to living organisms at high levels of exposure. An increasing concentration of heavy metals in the environment can modify mineral and enzyme functions of human beings. During the last two decades, the interest in using bioindicators as monitoring tools to assess environmental pollution with toxic metals has increased. Bioindicators are flora and fauna members, which are collected and analyzed to measure the levels of metal contaminants. Bioindicators therefore identify health hazards. Various living organisms, such as microbes, fungi, plants, animals, and humans, are used to monitor toxic metals from air, water, sediment, soil, and food chain. Here, we review recent bioindicators, toxicity assessment, and ecological effects.     

Age cohorts as paternal sibships

Summary Characteristics of a populations's reproductive system affect the degree of relatedness within the age cohorts and maternal sibships of that population. Two consequences of a small litter size, particularly of size one, a relatively polygynous mating system at any one time period, and frequent replacement of reproductively active males over successive periods, are that (1) the set of offspring that each female produces (a maternal sibship) will usually consist of halfsiblings, and (2) within a social group the members of each age cohort will be closely related, either all forming one paternal sibship (half-siblings) if there is only one reproductively active male at a time, or in the case of several reproductively active males, a set of individuals whose mean relatedness is some-what ower than in the one-father case. In the present paper, degree of relatedness within each of these two subgroups is calculated on the basis of a simple model. I then examine effects of the various reproductive parameters on this relatedness and compare maternal sibships and age cohorts in the relative degree of relatedness within them. Age cohorts will often be identifiable, closely related units, paternal sibships in the extreme case. Age cohorts may be important in the evolution of family altruism. They differ from maternal sibships in interesting ways that may affect the kinds of behaviors that are likely to evolve.     

Macroinvertebrates as indicators of pollution

Various pollution indicators of stream Ban-Ganga have been identified on the basis of presence/absence/numerical abundance at various stations. They have been categorized as pollution tolerant, facultative and pollution intolerant groups in relation with the water quality at different stations of stream.     

超积累植物在时空、科属内的分布特点及寻找方法

探讨了超积累植物在时空、科属内的分布特点和正常植物演化出镍超积累特性必备的 2个基本条件 ,介绍了国外 2种常用的寻找超积累植物的方法。