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771.
Is avian humoral immunocompetence suppressed by testosterone? 总被引:2,自引:2,他引:0
Dennis Hasselquist James A. Marsh Paul W. Sherman John C. Wingfield 《Behavioral ecology and sociobiology》1999,45(3-4):167-175
A key issue in sexual selection theory is how a correlation between male secondary sexual characters and male genetic quality
can be maintained. The immunocompetence-handicap hypothesis proposes that testosterone-dependent male characters remain honest
signals because of the immunosuppressive effect of elevated steroid hormone levels. The hypothesis requires that physiological
levels of testosterone depress immune system function. We quantified testosterone titers and humoral immunocompetence of captive
male and female red-winged blackbirds (Agelaius phoeniceus) at three points in the annual cycle (autumn, prebreeding, and breeding). We also conducted an implant experiment on the
males to assess the effects of prolonged, above-normal testosterone titers on humoral immune responses. Humoral immunocompetence
was measured as secondary antibody production to a non-pathogenic protein antigen, keyhole limpet hemocyanin, using an enzyme-linked
immunosorbent assay we developed for A. phoeniceus. Secondary antibody responses of individuals were highly repeatable between sampling periods. Neither physiological nor above-normal
levels of plasma testosterone suppressed secondary antibody production. In paired tests of the same individuals between prebreeding
and breeding, and between breeding and implant, plasma testosterone increased significantly but secondary antibody responses
were unaffected. We are confident in these results because with 80% power, an 11–14% difference in antibody titers would have
been detected. There was no relationship between plasma testosterone levels and humoral immunocompetence in free-ranging males
tested at the peak of breeding. These results cast doubt on a key assumption of the immunocompetence-handicap hypothesis.
Received: 13 April 1998 / Accepted after revision: 7 October 1998 相似文献
772.
Exaggerated male eye span influences contest outcome in stalk-eyed flies (Diopsidae) 总被引:3,自引:0,他引:3
Evolution of male weapons or status signals has been hypothesized to precede evolution of female mating preferences for those
traits. We used staged male fights among three species of Malaysian stalk-eyed flies (Diptera: Diopsidae) to determine if
elongated eye span, which is preferred by females in two sexually dimorphic species, influences contest outcome. Extreme sexual
dimorphism, with large males possessing longer eye span than females, is shared by Cyrtodiopsis whitei and C. dalmanni. In contrast, C. quinqueguttata exhibits a more ancestral condition – short, sexually monomorphic eye stalks. Videotape analysis of 20-min paired contests
revealed that males with larger eye span and body size won more fights in the dimorphic, but not monomorphic, species. To
determine if males from the dimorphic species use eye span directly to resolve contests, we competed male C. dalmanni from lines that had undergone artificial selection for 30 generations to increase or decrease eye span. We found that eye
span, independently of body size, determines contest outcome in selected-line males. Furthermore, in both dimorphic species,
the average encounter duration declined as the eye span difference between contestants increased, as expected if males use
eye span to assess opponent size. The number of encounters also increased with age in dimorphic, but not monomorphic, species.
Selected-line males did not differ from outbred males in either fight duration or number of encounters. We conclude that exaggerated
male eye stalks evolved to influence both competitive interactions and female mating preferences in these spectacular flies.
Received: 20 July 1998 / Received in revised form: 2 February 1999 / Accepted: 12 March 1999 相似文献
773.
We studied the correlation between male-male aggressive behavior of the spider mite, Schizotetranychus miscanthi and winter coldness, a factor hypothesized to correlate with the degree of relatedness of the interacting males through the
frequent occurrence of mother-son mating in the spring. Thirty-one samples from various populations throughout Japan were
added to previous data. A cluster analysis revealed two clinal trends for male-male aggression in S. miscanthi in regions of light or no snowfall. The two clines may represent a dimorphism within the species, each having a similar clinal
trend within Japan. Further support for the hypothesis that male overwintering survival affects male-male aggressiveness came
from a comparison between regions of heavy snowfall and those of light or no snowfall. In regions with heavy snow insulation,
overwintering survival may not be as high as in other areas, and there was no correlation between male aggressiveness and
the minimum winter temperature. However, there was a significant correlation in regions of light snow.
Received: 26 May 1998 / Received in revised form: 16 December 1998 / Accepted: 30 December 1998 相似文献
774.
Effects of male dominance and courtship display on female choice in the ring-necked pheasant 总被引:7,自引:0,他引:7
Male traits and behaviours acting in mate choice and intrasexual competition are expected to be congruent. When studying
their evolution, this often makes it difficult to differentiate between these two components of sexual selection. Studies
are therefore needed on mate choice in conjunction with the role of displays and dominance. We present the results from two
experiments conducted to investigate the effects of male dominance and courtship displays on female choice in the ring-necked
pheasant, Phasianus colchicus, controlling for differences in morphological male traits. We found: (1) different courtship behaviours had different effects
on female choice: females were mainly attracted by the feeding courtship behaviour, while another courtship display (the lateral
display) was effective in producing the copulation-acceptance response by the females; (2) subordinate males performed the
courtship behaviour before females less frequently than dominant males, and females reinforced intrasexual selection by choosing
dominant males, and (3) subordinate males in visual contact with a dominant became less attractive to females. The results
support the idea (armament-ornament model) that female pheasants may benefit from using traits selected in male-male competition
as clues for mate choice.
Received: 23 October 1997 / Accepted after revision: 7 October 1998 相似文献
775.
Kin conflict over caste determination in social Hymenoptera 总被引:2,自引:0,他引:2
We argue that caste determination, the process whereby females in the social Hymenoptera develop into either queens or workers,
is subject to kin-selected conflict. Potential conflict arises because developing females are more closely related to their
would-be offspring than to those of other females. Therefore, they may favour becoming queens contrary to the interests of
other developing females and of existing queens and workers. We suggest two contexts leading to potential caste conflict.
The first occurs when queens are reared in a reproductive phase following an ergonomic phase of worker production, while the
second occurs when queens and workers are reared simultaneously. The first context assumes that workers' per capita contribution
to colony survival and productivity falls with rising colony size. A critical feature influencing whether potential conflict
is realized is the extent to which developing females can determine their own caste (“self-determination”). Self-determination
is facilitated when female larvae control their own food intake and when queen-worker size dimorphism is low. We know of no
strong evidence for actual conflict over caste fate arising in the first context. However, stingless bees and polygynous ants
with excess queen-potential larvae that are either forced to develop as workers or are culled as adults demonstrate actual
caste conflict in the second context. Caste conflict does not preclude caste regulation for “the good of the colony”, but
such regulation is contingent on either the absence of potential conflict or on developing females losing control of their
caste fate.
Received: 22 March 1999 / Received in revised form: 15 June 1999 / Accepted: 19 June 1999 相似文献
776.
We manipulated availability of food and nesting sites in one population of the forest ant Myrmica punctiventris. The manipulations produced significant changes in relatedness structure, reproductive allocation, and response to hierarchical
selection. Food availability appeared to have a consistently stronger influence on these aspects of social organization than
did availability of nesting sites. We interpret our experimental results in light of observed differences between populations,
and discuss implications for kin selection dynamics.
Received: 30 July 1998 / Accepted after revision: 31 October 1998 相似文献
777.
Li Chen 《Journal of the American Water Resources Association》2003,39(5):1157-1165
ABSTRACT: An optimization and simulation model holds promise as an efficient and robust method for long term reservoir operation, an increasingly important facet of managing water resources. Recently, genetic algorithms have been demonstrated to be highly effective optimization methods. According to previous studies, a real coded genetic algorithm (RGA) has many advantages over a binary coded genetic algorithm. Accordingly, this work applies an RGA to obtain the 10‐day (the traditional period of reservoir operation in Taiwan) operating rule curves for the proposed reservoir system. The RGA is combined with an effective and flexible scheme for coding the reservoir rule curves and applied to an important reservoir in Taiwan, considering a water reservoir development scenario to the year 2021. Each rule curve is evaluated using a complex simulation model to determine a performance index for a given flow series. The process of generating and evaluating decision parameters is repeated until no further improvement in performance is obtained. Many experiments were performed to determine the suitable RGA components, including macro evolutionary (ME) selection and blend‐α crossover. Macro evolution (ME) can be applied to prevent the premature problem of the conventional selection scheme of genetic algorithm. The purpose of adjusting a of a crossover scheme is to determine the exploratory or exploitative degree of various subpopulations. The appropriate rule curve searched by an RGA can minimize the water deficit and maintain the high water level of the reservoir. The results also show that the most promising RGA for this problem consists of these revised operators significantly improves the performance of a system. It is also very efficient for optimizing other highly nonlinear systems. 相似文献
778.
定量风险评价(QRA)中的危险辨识方法 总被引:2,自引:1,他引:1
危险辨识是进行定量风险评价(QRA)的关键步骤,QRA分析区域内的危险设备设施可能很多,但并不是每台设备设施都一定要包含并进行定量风险计算,这不仅涉及到QRA的效率和成本问题,也涉及到评价结论准确性、安全投入有效性等问题。本文简要介绍并比较了欧盟ARAMIS和挪威Purple book中推介的2种危险辨识方法,有助于国内QRA分析人员参照比较及提升QRA分析的一致性。 相似文献
779.
新型水处理活性炭选型技术 总被引:8,自引:5,他引:3
活性炭依其原料不同、生产工艺不同,而有不同的吸附性能.使用简易的活性炭选型方法,可以减少应用测试时的备选炭型,从而大大降低活性炭水处理技术的运行成本.以碘值、甲基蓝值、苯酚值和丹宁酸值4种吸附容量性能指标为依据的活性炭选型技术,可以有效地预测活性炭对于水中各种大小不同污染物的去除能力.BET测试结果证明了这4项指标数据对于活性炭孔径分布预测的准确性.2,4-二氯苯酚和腐殖酸等目标化合物的吸附容量实验结果也都验证了这4项指标的预测功用,说明这种简便的活性炭选型技术有着广泛的应用价值. 相似文献
780.
工程方案选择的权重-属性决策分析方法 总被引:9,自引:0,他引:9
工程方案的选择是工程项目的战略决策问题 .从认知学原理出发 ,提出方案选择决策的 3个要素 :目标、权重和属性 .对决策目标体系的建立、权重的调查和赋值、属性的分析和规范化进行了讨论 ,提出了解决问题的思路和方法 .文中引用了一项工程方案决策实例 ,进一步说明权重 -属性分析方法的应用 . 相似文献