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11.
A. Roulin J. Gasparini P. Bize M. Ritschard H. Richner 《Behavioral ecology and sociobiology》2008,62(4):507-519
One hypothesis for the maintenance of genetic variation states that alternative genotypes are adapted to different environmental
conditions (i.e., genotype-by-environment interaction G×E) that vary in space and time. Although G×E has been demonstrated
for morphological traits, little evidence has been given whether these G×E are associated with traits used as signal in mate
choice. In three wild bird species, we investigated whether the degree of melanin-based coloration, a heritable trait, covaries
with nestling growth rate in rich and poor environments. Variation in the degree of reddish-brown phaeomelanism is pronounced
in the barn owl (Tyto alba) and tawny owl (Strix aluco), and variation in black eumelanism in the barn owl and Alpine swift (Apus melba). Melanin-based coloration has been shown to be a criterion in mate choice in the barn owl. We cross-fostered hatchlings
to test whether nestlings sired by parents displaying melanin-based colorations to different extent exhibit alternative growth
trajectories when raised by foster parents in poor (experimentally enlarged broods) and rich (experimentally reduced broods)
environments. With respect to phaeomelanism, barn owl and tawny owl offspring sired by redder parents grew more rapidly in
body mass only in experimentally reduced broods. With respect to eumelanism, Alpine swift offspring of darker fathers grew
their wings more rapidly only in experimentally enlarged broods, a difference that was not detected in reduced broods. These
interactions between parental melanism and offspring growth rate indicate that individuals display substantial plasticity
in response to the rearing environment which is associated with the degree of melanism: at least with respect to nestling
growth, phaeomelanic and eumelanic individuals are best adapted to rich and poor environments, respectively. It now remains
to be investigated why eumelanism and phaeomelanism have a different signaling function and what the lifelong consequences
of these melanism-dependent allocation strategies are. This is important to fully appraise the role played by environmental
heterogeneity in maintaining variation in the degree of melanin-based coloration. 相似文献
12.
Lisa E. Schwanz 《Behavioral ecology and sociobiology》2008,62(8):1351-1358
Parasitized animals may alter their life histories to minimize the costs of parasitism. Organisms are predicted to decrease
investment in current reproduction when parasitism has the greatest impact on current reproductive ability. In contrast, if
parasitism decreases residual reproductive value, hosts should increase current reproductive investment, referred to as fecundity
compensation or terminal investment. In mammalian hosts, parasitic infection most often leads to reductions in current host
reproduction, perhaps attributable to the emphasis on parasites that are unlikely to impact the host’s residual reproductive
value. In this study, the life history response of a rodent, Peromyscus maniculatus, to infection with a parasite that should strongly impact the residual reproductive value of its host (Schistosomatium douthitti, Trematoda) was examined. Infection decreased survival for hosts exposed to a high dose of parasites and was chronic in survivors,
confirming that infection had strong impacts for the residual reproductive value of the host. As predicted, infected mice
increased their reproductive output, producing litters of greater mass due to heavier offspring. However, this increased output
was observed after a greater delay to begin breeding in infected mice and was not observed in animals that suffered early
mortality. The deer mouse S. douthitti system may provide a rare example of fecundity compensation in mammals. 相似文献
13.
入侵种喜旱莲子草对土壤养分的表型可塑性反应 总被引:9,自引:1,他引:9
对外来入侵种喜旱莲子草(Alternanthera philoxeroides(Mart.)Griseb.)在不同土壤氮养分处理中的表型可塑性反应进行了研究。结果表明:土壤中氮养分水平对喜旱莲子草克隆生长有显著影响,如分枝强度、苇节长度随氮含量升高均有不同程度的增加;氮养分最高的处理中根系生物量投资最小,而茎、叶生物量投资最大,对照处理中则表现山根冠比最大。研究结果表明,在不同土壤养分条件下,喜旱莲子草不同表型结构有可能同时对环境选择作出反应,在种群生存与维持、生长、繁殖等功能方面实现种群个体各器官生物量投资的优化配置来适应多样化的环境,以增强其入侵能力, 相似文献
14.
C. H. Schilling S. B. Biner H. Goel J. Jane 《Journal of Polymers and the Environment》1995,3(3):153-160
Traditional methods for the shape-forming of engineering ceramics entail plastic deformation of powder slurries containing hazardous organic liquids as suspending media. Replacing these organic with aqueous media requires the development of environmentally benign, water-soluble additives which serve as plasticizers and binders. Fundamental studies were performed with aqueous suspensions of colloidal-Al2O3 to evaluate the role of sucrose and maltodextrin on viscosity, sedimentation, and filtration characteristics, plastic flow behavior of filter cakes, and sinterability. Maltodextrin systems exhibited superior results, including filtration to high packing densities and clay-like plasticity with minimal cracking.Paper presented at the Bio/Environmentally Degradable Polymer Society—Third National Meeting, June 6–8, 1994, Boston, Massachusetts.Ames Laboratory is operated for the U.S. Department of Energy by Iowa State University under Contract W-7405-Eng-82. 相似文献
15.
The age at which worker honey bees begin foraging varies under different colony conditions. Previous studies have shown that
juvenile hormone (JH) mediates this behavioral plasticity, and that worker-worker interactions influence both JH titers and
age at first foraging. These results also indicated that the age at first foraging is delayed in the presence of foragers,
suggesting that colony age demography directly influences temporal division of labor. We tested this hypothesis by determining
whether behavioral or physiological development can be accelerated, delayed, or reversed by altering colony age structure.
In three out of three trials, earlier onset of foraging was induced in colonies depleted of foragers compared to colonies
depleted of an equal number of bees across all age classes. In two out of three trials, delayed onset of foraging was induced
in colonies in which foragers were confined compared to colonies with free-flying foragers. Finally, in three out of three
trials, both endocrine and exocrine changes associated with reversion from foraging to brood care were induced in colonies
composed of all old bees and devoid of brood; JH titers decreased and hypopharyngeal glands regenerated. These results demonstrate
that plasticity in age-related division of labor in honey bee colonies is at least partially controlled by social factors.
The implications of these results are discussed for the recently developed ‘‘activator-inhibitor” model for honey bee behavioral
development.
Received: 8 November 1995/Accepted after revision: 10 May 1996 相似文献
16.
Cédric Alaux Malvina Boutot Pierre Jaisson Abraham Hefetz 《Behavioral ecology and sociobiology》2007,62(2):213-222
Worker sterility in the bumblebee Bombus terrestris is conditional and is linked to the social development of the colony. Workers refrain from reproducing or overtly challenging
the queen until gyne production has initiated, at the so-called competition point (CP). It is not known whether this behavior
is hard-wired or workers show reproductive plasticity. It also remains unclear whether worker reproductive decision is under
queen and/or worker control. In this study, we tested worker reproductive plasticity in an attempt to assess whether and under
which conditions worker sterility/fertility are reversible. We introduced egg-laying workers into colonies with different
social structures for 1 week then monitored their reproductive status. We revealed a remarkable reproductive plasticity in
the introduced workers that was social-condition-dependent. In the presence of a pre-CP queen, the introduced workers reverted
to sterility, whereas in the presence of a post-CP queen, such workers remained egg-layer. Reversion to sterility does not
occur when direct contact with the queen is prevented, as the introduced workers remained egg-layer in the queenright colonies
with a confined queen. Egg-laying workers that were introduced into queenless colonies mostly maintained their fertility regardless
of colony social phase. This shows that worker transition from cooperative to selfish behavior is reversible depending on
the social context. 相似文献
17.
18.
Lürling M 《Chemosphere》2011,82(3):411-417
Active growth is a prerequisite for the formation of grazing-protective, mostly eight-celled colonies by the ubiquitous green alga Scenedesmus in response to chemical cues from zooplankton. Colonies can also be evoked by chemically quite similar manmade anionic surfactants, such as FFD-6. In this study, it was hypothesized that growth-inhibiting concentrations of the herbicide metribuzin impair the ability of Scenedesmus obliquus to form colonies in response to the surfactant morphogen FFD-6. The results confirmed that the formation of colonies in S. obliquus was hampered by metribuzin. EC50 values of metribuzin for colony inhibition (approximately 11 μg L−1) were similar to those for growth and photosynthesis inhibition (12-25 μg metribuzin L−1). In the absence of the colony-inducing surfactant FFD-6, S. obliquus populations were comprised of 92% unicells, having on average 1.2 cells per colony at all tested metribuzin concentrations (0-100 μg L−1). In contrast, in the presence of FFD-6 and at low metribuzin concentrations (0 and 5 μg L−1), S. obliquus had more than five cells per colony with a high portion of eight-celled colonies. However, increasing concentrations of metribuzin decreased the number of colonies in the FFD-6-exposed populations and caused them to remain mostly unicellular at the highest concentrations (50 and 100 μg L−1). This study revealed that metribuzin impeded growth and by doing so, also obstructed the possibility for unicellular Scenedesmus to form colonies. Consequently, an increase in mortality of Scenedesmus from grazing is expected. 相似文献
19.
基于双剪屈服条件的输油管道腐蚀剩余强度可靠性研究 总被引:2,自引:1,他引:1
提出基于双剪屈服塑性极限条件的管道可靠性爆破压力可靠度模型,在基于剩余强度可靠性理论基础上,着重分析随机参数,即腐蚀深度、腐蚀长度和运行压力的分布情况,通过经典可靠性计算方法、JC法将非正态分布转化成标准正态分布,从而建立起基于双剪屈服条件的管道腐蚀可靠性计算模型。通过提取现场实验数据进行验算,其结果表明:双剪屈服强度理论算得的爆破压力更接近实验结果,该方法降低API579的保守性,大大提高了可靠性的计算精度。 相似文献
20.
Hirofumi Michimae 《Behavioral ecology and sociobiology》2006,60(2):205-211
Alternative phenotypes in natural populations can arise from either genetic polymorphism or an environmentally induced phenotype, that is, polyphenism. Evolutionary models of polyphenism developed by theoretical studies predict that polyphenism is favored when there are environment-dependent fitness trade-offs between alternatives and that the threshold frequency for a facultative switch between alternative phenotypes is adjusted in accordance with different selection regimes. The broad-headed (alternative) larval morph of Hynobius retardatus, which is induced by crowding with conspecifics or heterospecific anuran (Rana pirica) larvae, is a representative example of cannibalistic polyphenism. Morph induction by such proximate factors must reflect evolutionary (conditional frequency-dependent) processes. To clarify the role of frequency-dependent processes in polyphenism, I investigated the occurrence rate of the broad-headed morph under experimental crowding conditions (low conspecific, high conspecific, and high heterospecific densities) using larvae from eight natural populations with different larval densities of conspecifics and heterospecifics, and found interpopulational differences in the expression of the morph. Thus, there is a larval density-dependent equilibrium frequency of the morph in each pond, suggesting that the local switch point for morph induction was modified by selection to produce evolved differences between ponds. The evolution of such interpond differences has three necessary conditions: (1) There are pond-dependent fitness trade-offs between alternatives, (2) The maintenance of the morph is costly, and (3) The presence of conspecific or, especially, heterospecific larvae provides a reliable cue to the receiver. 相似文献