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251.
Jennifer E. Smith Sandra K. Memenis Kay E. Holekamp 《Behavioral ecology and sociobiology》2007,61(5):753-765
When social partners vary in their relative value, individuals should theoretically initiate partnerships with conspecifics
of the highest value. Here, we tested this prediction in a wild population of spotted hyenas (Crocuta crocuta). Crocuta live in complex, fission–fusion societies structured by dominance hierarchies in which individuals vary greatly in their
value as social companions. Because patterns of association among Crocuta reflect social preferences, we calculated association indices (AIs) to examine how social rank influences intrasexual partner
choice among unrelated adults of both sexes. The highest-ranking individuals were generally most gregarious in both sexes.
Females associated most often with dominant and adjacent-ranking females. Females joined subgroups based on the presence of
particular conspecifics such that subordinates joined focal females at higher rates than did dominants. Dominants benefit
from associations with subordinates by enjoying priority of access to resources obtained and defended by multiple group members,
but the benefits of these associations to subordinates are unknown. To investigate this, we tested three hypotheses suggesting
how subordinates might benefit from rank-related partner choice among unrelated females. We found that subordinates who initiated
group formation benefited by gaining social and feeding tolerance from dominants. However, rates at which dominants provided
coalitionary support to subordinates did not vary with AIs. Overall, our data resemble those documenting patterns of association
among cercopithecine primates. We consider our results in light of optimal reproductive skew theory, Seyfarth’s rank attractiveness
model, and biological market theory. Our data are more consistent with the predictions of Seyfarth’s model and of biological
market theory than with those of skew theory. 相似文献
252.
Andra Thiel Gerard Driessen Thomas S. Hoffmeister 《Behavioral ecology and sociobiology》2006,59(5):614-623
The parasitic wasp, Venturia canescens (Gravenhorst) (Hymenoptera: Ichneumonidae), has two reproductive modes, namely, thelytoky or arrhenotoky, and occurs in habitats
with highly variable or relatively stable host abundances, respectively. Since information processing is costly, we expected
that information indicating resource availability would be mainly used by the thelytokous wasps and less so by the arrhenotokous
type. This idea was explored by two different approaches. In a study on patch-time allocation, we used females from ten populations
and measured patch-residence times of individuals that visited multiple patches at different encounter rates. In a more detailed
approach, thelytokous and arrhenotokous females from a single location were observed continuously while foraging, and all
behaviors were recorded. Wasps of both reproductive modes (i.e., both habitat types) used information for the assessment of
habitat quality. However, the way that the information was used differed between them. Whereas thelytokous females used foraging
information to maximize their efficiency at high patch-encounter rates, arrhenotokous females merely reduced the number of
offspring produced without changing patch times. The behavior of the arrhenotokous females should result in a spreading of
offspring across the habitat and, thus, reduced sib-mating. The foraging strategy of these wasps might therefore be an adaptation
to reduce costs associated with inbreeding. 相似文献
253.
Incorporating the Effects of Socioeconomic Uncertainty into Priority Setting for Conservation Investment 总被引:1,自引:0,他引:1
MARISSA F. McBRIDE † KERRIE A. WILSON† MICHAEL BODE‡ HUGH P. POSSINGHAM† 《Conservation biology》2007,21(6):1463-1474
Abstract: Uncertainty in the implementation and outcomes of conservation actions that is not accounted for leaves conservation plans vulnerable to potential changes in future conditions. We used a decision-theoretic approach to investigate the effects of two types of investment uncertainty on the optimal allocation of global conservation resources for land acquisition in the Mediterranean Basin. We considered uncertainty about (1) whether investment will continue and (2) whether the acquired biodiversity assets are secure, which we termed transaction uncertainty and performance uncertainty, respectively. We also developed and tested the robustness of different rules of thumb for guiding the allocation of conservation resources when these sources of uncertainty exist. In the presence of uncertainty in future investment ability (transaction uncertainty), the optimal strategy was opportunistic, meaning the investment priority should be to act where uncertainty is highest while investment remains possible. When there was a probability that investments would fail (performance uncertainty), the optimal solution became a complex trade-off between the immediate biodiversity benefits of acting in a region and the perceived longevity of the investment. In general, regions were prioritized for investment when they had the greatest performance certainty, even if an alternative region was highly threatened or had higher biodiversity value. The improved performance of rules of thumb when accounting for uncertainty highlights the importance of explicitly incorporating sources of investment uncertainty and evaluating potential conservation investments in the context of their likely long-term success. 相似文献
254.
Szabolcs Lengyel 《Behavioral ecology and sociobiology》2007,61(4):589-598
When reproductive success is constant in one breeding phase, different tactics that increase variation in reproductive success
among individuals may evolve in other phases. For instance, in shorebirds, which usually have a limited clutch size of four
eggs, variation in reproductive tactics among individuals is expected either before egg-laying (e.g. diverse mating systems)
or after hatching of the young (e.g. diverse parental care). In this paper, I studied the pied avocet (Recurvirostra avosetta), a shorebird with a modal clutch size of four eggs, to test whether post-hatch chick adoption as an alternative tactic can
be linked to increased variation in annual reproductive success. When predation was high, naturally adopting pairs produced
more filial fledglings than did pairs not adopting chicks and not losing chicks to adoption. The number of filial fledglings
increased with the number of adopted young, possibly through diluting the chances of predation on filial young. Experimental
chick addition did not lead to more fledged young due to low brood integrity as shown by the frequent loss of chicks from
some experimental broods. When predation was low, larger broods occupied feeding territories with higher prey abundance than
smaller broods, possibly due to their dominance over smaller ones. Pairs that lost chicks to adoption (donors) fledged as
many filial young in their broods as did non-adopters/non-donors, whereas the total number of donors’ filial fledglings, including
those raised in adopting broods, approached that of adopters. These findings show, for the first time, that post-hatch alternative
reproductive tactics can lead to variation in annual reproductive success and to higher success for some pairs even in species
where past adaptations limit variation in reproductive success in a certain phase of reproduction. 相似文献
255.
假设近场地面运动由体波产生(忽略面波的影响),根据弹性半空间的平面谐波理论,提出了利用平动分量加速度记录合成地面转动加速时程的方法。该方法考虑了由于实际介质的不均匀性而产生的地震波频散现象。 相似文献
256.
Jason C. Burckhardt Brian L. Todd 《Journal of the American Water Resources Association》1998,34(1):179-184
ABSTRACT: Dendrochronology analyses of point bar complexes were used to quantify the effects of riparian forests on local lateral migration of bends in seven streams in the glacial till plains of north central Missouri. Stream bends were paired with similar bank height, midchannel radius of curvature, soil composition, and watershed size. In each pair, one concave bank was forested and one was unforested. Stream bends with unforested concave banks had an average local migration rate three times greater than stream bends that had forested concave banks. 相似文献
257.
冰对斜体结构作用的二维和三维力学模型分析 总被引:3,自引:0,他引:3
通常情况下,作用在斜体结构表面的冰力小于垂直结构,因此斜体结构成为有冰海区海洋结构的优选结构,冰对斜体结构作用力学机制的分析是近些年来国际上研究的热点问题。本文运用简单的二维理论及较为复杂的三维理论,依据辽东湾环境条件,采用计算与作图分析的手段,对摩擦系数、坡角、冰强度及冰厚如何影响作用在斜体结构上的水平冰力进行了讨论,并验证了相应结论 相似文献
258.
郑州市大气监测优化布点的研究 总被引:4,自引:0,他引:4
利用物元分析法,在大气污染普查基础上,以郑州市污染最严重的季节(冬季)的数据为准,构造大气环境监测的标准物元矩阵,求出关联函数值,进行了大气监测点的优选,并与用模糊聚类选出的点位相比较,来验证郑州市目前已有测子丫建立的合理性,并以此证明物元分析法是环境监测优化布点的一种可靠的方法。 相似文献
259.
总量控制费用分摊的多目标规划模型及解法 总被引:1,自引:0,他引:1
文章指出了污染物总量控制规划中公平合理分摊优化治理投资费用的重要性,分析了现有的优化治理投资费用分摊方法存在的问题,建立了公平合理分摊优化治理投资费用的多目标规划模型,提出用最短距离理想点法加以求解,并通过实例验证了该方法的合理性。结果表明该模型及解法既可以保证总量控制规划方案的社会整体效益最大,又不失公平,从而确保总量控制规划方案的顺利实施。 相似文献
260.
排污总量控制的最优化原则探讨 总被引:4,自引:0,他引:4
从环境经济学的最优化原则出发,对上海市推行的排污总量控制,超量排污罚款和对允许排放量限度内的排污征收生态环境补偿费进行了论述。根据最优化原则,污染物排放总量应该设置在最佳污染物排放量点,并且不同的河段应该设置相应的允许排放量;单位超量排污罚款价格不可过低,并且应该随着超量排污的增长而增加,以一个合适的费率征收生态环境补偿费会促使企业不断改进它的污染物治理技术,从而减少对水体的污染。因此,这三才是将 相似文献