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151.
Hanna Kokko 《Behavioral ecology and sociobiology》1997,41(2):99-107
In various models of sexual selection mediated by the viability indicator (“good genes”) mechanism, a sexually selected trait
will truly reflect male quality if its expression is costly for the male. However, in long-lived species, the expression of
a trait often increases with age while the genotype of the male remains unchanged. This fact may obscure the indicator mechanism.
Hitherto, game theory models of honesty in sexual advertisement have not taken life-history effects into account, whereas
life-history models of reproductive effort have only seldom considered the dependence of mating success on the actions of
other individuals. Here, the two approaches are combined, and I examine whether honesty is maintained if males can divide
their advertisement effort over their lifetime. The model shows that an increase in the expression of the sexually selected
trait over several years is an evolutionarily stable strategy (ESS) under a wide range of situations, so that a correlated
preference for old age can emerge through a viability indicator mechanism. Honesty in the strict sense is not preserved: an
optimally behaving low-quality male will in some cases advertise more than a high-quality male of equal age, to the extent
that the strongest advertisement found in the population can be associated with a low-quality male. Due to life-history trade-offs,
however, honesty in an average sense holds true over the lifetime of individuals: “cheater” age classes will remain small
enough, that a female will obtain a higher expected mate quality if she trusts in the trait as an indicator of viability.
Received: 25 June 1996 / Accepted after revision: 15 April 1997 相似文献
152.
论述了云南怒江流域可持续发展的战略意义 ,分析了该区域生态经济格局与资源环境特征 ,并提出了怒江流域可持续发展的对策建议。 相似文献
153.
Sperm characteristics associated with different male reproductive tactics in bluegills (Lepomis macrochirus) 总被引:3,自引:0,他引:3
We examined the availability and motility of sperm from parental and sneaker male bluegills (Lepomis macrochirus), a colonially nesting sunfish (Family Centrarchidae) with male parental care and a high incidence of cuckoldry by both sneaker
and satellite males. We found no differences between sneakers and parentals in length and swimming speed of sperm, or percent
and duration of sperm activity. In sneaker milt, however, sperm was almost 50% more concentrated than in parental milt (16.5×106 vs 11.5×106 sperm/μl of milt, respectively). Despite this difference in sperm concentration, stripped ejaculates from sneakers contained
almost 400 million fewer sperm (only 32% as many sperm) than those from parentals due to their much smaller stripped ejaculate
volumes (only about 19% that of parentals). Thus unless sneakers can compensate by releasing more sperm or gaining closer
proximity to eggs at the time of spawning, they may be at a disadvantage with respect to sperm competition. We discuss these
results in relation to models for the evolution of alternative reproductive behaviours in this species and suggest that the
cuckolders may be making the best of a bad situation.
Received: 18 February 2000 / Revised: 23 March 2000 / Accepted: 14 September 2000 相似文献
154.
牛蛙入侵新案例与管理对策分析 总被引:3,自引:0,他引:3
牛蛙是ISSG/SSC公布的100种最危险的入侵种之一,也是进入我国最早、分布最广和危害最大的外来两栖动物.1980年以后,由于野外放养和人工驯养地区的迅速扩大,野化种群的数量增加很快,对土著蛙类和农田生态系统的稳定形成了严重威胁.本文依据近年来发现的3个新案例,初步分析了牛蛙在我国的分布状况和牛蛙成功入侵我国的主要原因,以及牛蛙在生物链中的位置和危害,并提出了3条相应的管理对策.图1表2参18 相似文献
155.
C. Cosmi V. Cuomo M. Macchiato L. Mangiamele S. Masi M. Salvia 《Environmental Modeling and Assessment》2000,5(1):19-27
Air pollution is one of the most pressing environmental problems which affects likewise urban, industrial and rural areas.
Environmental planners, regulators and decision makers need reliable, scientifically based tools to find out strategies for
controlling air pollution in a cost-effective way, taking into account the whole productive system. In this framework the
basic elements of energy-environmental planning have to be extended to include also waste processing technologies amongst
the usually considered pollution sources. Bottom-up optimizing models, based on linear programming techniques and customized
for specific cases, represent a powerful tool in energy-environmental management. This paper focuses on the integrated modeling
of material flows and energy system performed on a local scale case study (Basilicata Region, Southern Italy) using the linear
programming model IEA-MARKAL. We have evaluated the feasibility of the model in representing the waste management system to
estimate the environmental impact of the waste processing technologies in the context of the whole productive system. A sensitivity
analysis has been carried out to emphasize the connections between tariffs, waste disposal technologies assessment and atmospheric
emissions.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
156.
在一台六缸四冲程高压共轨柴油机上开展了乙醇/聚甲氧基二甲醚(PODE)/柴油混合燃料对内燃机燃烧和排放影响的试验研究.结果表明,在转速为1137 r·min-1,转矩为735 N·m的工况条件下,随着掺混PODE和乙醇比例的增大,双峰放热越来越明显,扩散燃烧速率增大,有效燃油消耗率增大,有效热效率降低,但降低幅度小于1%,其中,DPE5(PODE体积分数为20%,乙醇体积分数为5%)的有效热效率与D100(纯柴油)基本相当.提前主喷时刻、增大喷油压力均使有效热效率增大,CO和碳烟排放降低,NOx排放增大,而对降低HC排放的影响较小.相比D100,混合燃料可降低CO、HC、碳烟排放,在低喷油压力和较晚主喷时刻下,对碳烟的减排效果更为显著,最大降幅分别为85.5%(主喷时刻-1℃ A ATDC、喷油压力900 bar)和82.9%(主喷时刻-3℃ A ATDC、喷油压力600 bar),但不同混合燃料间的排放差异较小.综上所述,重型柴油机使用乙醇/PODE/柴油混合燃料可在热效率相当的前提下对排放有较大改善. 相似文献
157.
Climate change adaptation strategies that aim to minimize harm and maximize benefits related to climate change impacts have mushroomed at all levels of government in recent years. While many studies have explored barriers that stand in the way of their implementation, the factors determining their potential to mainstream adaptation into various sectors are less clear. In the present paper, we aim to address this gap for two international, six national, and six local adaptation strategies. Based on document analyses and 35 semi‐structured interviews, the 14 case studies also explore in how far the factors facilitating climate change adaptation are similar across levels of government or level‐specific. Although located at three different levels of government, we find that the 14 adaptation strategies analyzed here represent “one‐size‐fits‐all governance arrangements” that are characterized by voluntariness and a lack institutionalization. Since adaptation strategies are relatively weak coordination hubs that are unable to force adaptation onto sectoral policy agendas, they rely mainly on sectoral self‐interest in adapting to climate change, largely determined by problem pressure. We conclude that one‐size‐fits‐all governance arrangements are rarely adequate responses to complex challenges, such as climate change. Although climate change adaptation depends more on framework conditions such as problem pressure than on administrative or governance features, the findings presented here can help to understand under what circumstances adaptation is likely to make progress. 相似文献
158.
Globalization and climate change threaten the sustained provision of essential ecosystem services (ES) for people living in and downstream of mountain regions. The increasing evidence of the many vulnerabilities of mountain social-ecological systems has highlighted the urgent need for policy-relevant research into ways of coping with these trends. In this context, resilience has been emerging as a concept for both understanding and managing the complex social-ecological systems in which ES are provided and consumed. Yet, literature on resilience of social-ecological systems is mainly theoretical with limited application in real-world mountain case studies. In this paper, we present a comprehensive quantitative assessment of the social-ecological resilience of a case study in the Swiss Alps under global change. We model and evaluate an indicator for resilience that shows the capacity of the mountain social-ecological system to provide a set of demanded ES. In a first step, we model the development of this indicator in different scenarios of global change. In a second step, we test the effect of a rich set of policy strategies under all these scenarios to identify types and timing of interventions that are robust under multiple global change settings. Results indicate that the resilience of the mountain social-ecological system is endangered in all scenarios, especially if strong globalization is assumed. Robust strategies that buffer the system against these pressures require early spatial planning action in combination with more targeted direct payments to support the current regional structure and traditional mountain farming practices. Such information is crucial to guide decision-making processes in the era of highly uncertain future global change. 相似文献
159.
William A. H. Ellis Alistair Melzer Fred B. Bercovitch 《Behavioral ecology and sociobiology》2009,63(8):1181-1188
Animal movement patterns and use of space depend upon food and nonfood resources, as well as conspecific and heterospecific
interactions, but models of habitat use often neglect to examine multiple factors and rarely include marsupials. We studied
habitat use in an Australian population of koalas (Phascolarctos cinereus) over a 6-year period in order to determine how koalas navigate their environment and partition limited patchy food and nonfood
resources. Tree selection among koalas appears to be mediated by folar chemistry, but nonfood tree selection exerts a major
impact on home range use due to thermoregulatory constraints. Koalas moved on a daily basis, during both day and night, but
daytime resting site was not necessarily in the same location as nighttime feeding site. Koalas had substantial home range
overlap in the near absence of resource sharing with less than 1% of trees located in areas of overlap used by multiple koalas.
We suggest that koala spatiotemporal distribution and habitat use are probably based upon a community structure of individuals,
with a checkerboard model best describing overlap in home range area but not in resource use. Nonfood refugia and social networks
should be incorporated into models of animal range and habitat use. 相似文献
160.
A Standard Lexicon for Biodiversity Conservation: Unified Classifications of Threats and Actions 总被引:3,自引:0,他引:3
NICK SALAFSKY††† DANIEL SALZER† ALISON J. STATTERSFIELD‡ CRAIG HILTON-TAYLOR§ RACHEL NEUGARTEN† STUART H. M. BUTCHART‡ BEN COLLEN NEIL COX†† LAWRENCE L. MASTER‡‡ SHEILA O'CONNOR§§ DAVID WILKIE 《Conservation biology》2008,22(4):897-911
Abstract: An essential foundation of any science is a standard lexicon. Any given conservation project can be described in terms of the biodiversity targets, direct threats, contributing factors at the project site, and the conservation actions that the project team is employing to change the situation. These common elements can be linked in a causal chain, which represents a theory of change about how the conservation actions are intended to bring about desired project outcomes. If project teams want to describe and share their work and learn from one another, they need a standard and precise lexicon to specifically describe each node along this chain. To date, there have been several independent efforts to develop standard classifications for the direct threats that affect biodiversity and the conservation actions required to counteract these threats. Recognizing that it is far more effective to have only one accepted global scheme, we merged these separate efforts into unified classifications of threats and actions, which we present here. Each classification is a hierarchical listing of terms and associated definitions. The classifications are comprehensive and exclusive at the upper levels of the hierarchy, expandable at the lower levels, and simple, consistent, and scalable at all levels. We tested these classifications by applying them post hoc to 1191 threatened bird species and 737 conservation projects. Almost all threats and actions could be assigned to the new classification systems, save for some cases lacking detailed information. Furthermore, the new classification systems provided an improved way of analyzing and comparing information across projects when compared with earlier systems. We believe that widespread adoption of these classifications will help practitioners more systematically identify threats and appropriate actions, managers to more efficiently set priorities and allocate resources, and most important, facilitate cross‐project learning and the development of a systematic science of conservation. 相似文献