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821.
Seirian?SumnerEmail author William?O.?H.?Hughes Jacobus?J.?Boomsma 《Behavioral ecology and sociobiology》2003,54(3):256-263
Social parasites exploit the socially managed resources of social insect colonies in order to maximise their own fitness. The inquilines are among the most specialised social parasites, because they are dependent on being fully integrated into their host's colony throughout their lives. They are usually relatives of their host and so share ancestral characteristics (Emery's rule). Closely related inquiline-host combinations offer a rare opportunity to study trade-offs in natural selection. This is because ancestral adaptations to a free-living state (e.g. the production of a worker caste) become redundant and may be replaced by novel, parasitic traits as the inquiline becomes more specialised. The dynamics of such processes are, however, unknown as virtually all extant inquiline social parasites have completely lost their worker caste. An exception is Acromyrmex insinuator, an incipient permanent social parasite of the leaf-cutting ant Acromyrmex echinatior. In the present study, we document the size distribution of parasite and host workers and infer how selection has acted on A. insinuator to reduce, but not eliminate, its investment in a worker caste. We show that the antibiotic producing metapleural glands of these parasite workers are significantly smaller than in their host counterparts and we deduce that the metapleural gland size in the host represents the ancestral state. We further show experimentally that social parasite workers are more vulnerable to the general insect pathogenic fungus Metarhizium than are host workers. Our findings suggest that costly disease resistance mechanisms are likely to have been lost early in inquiline evolution, possibly because active selection for maintaining these traits became less when parasite workers had evolved the ability to exploit the collective immune system of their host societies. 相似文献
822.
Male spotted bowerbirds preferentially choose,arrange and proffer objects that are good predictors of mating success 总被引:2,自引:0,他引:2
Females from a wide range of species have been shown to prefer males producing exaggerated, elaborate sexual displays. The question of whether males can adapt their behaviour in order to accentuate these preferred aspects has received less attention. Male bowerbirds provide an excellent system in which to address this question. Males build and decorate structures--bowers--which females use to assess males. Males exhibiting high numbers of particular decorations on their bowers receive increased mating success. Males can choose what objects to place on bowers and where to put them. Therefore, their behaviour can directly influence their mating success. I studied a population of spotted bowerbirds Chlamydera maculata in central Queensland, Australia. I show, using two sets of observations and a choice experiment, that males exhibit strong and consistent preferences for certain objects. The male's preferences have an adaptive value, targeting objects that predict his mating success. Such behaviour operates at three levels. Fundamentally, object selection and acquisition is biased in favour of certain objects for use as decorations. These decorations are then placed prominently on the bower, within the avenue. Finally, males actively proffer influential decorations, used as props, to visiting females, ensuring that crucial components of the sexual display cannot be ignored. 相似文献
823.
Consensus building during nest-site selection in honey bee swarms: the expiration of dissent 总被引:3,自引:2,他引:1
This study addresses a question that lies at the heart of understanding how the scouts in a honey bee swarm achieve unanimity in their dances, and so reach agreement in their choice of a future nest site: what causes the scouts that perform dances for the non-chosen sites to stop dancing for these sites? One possibility is that a scout stops dancing for a non-chosen site only after she follows a lively dance for another site, such as the site that is ultimately chosen. This hypothesis is contradicted by the finding that 23 out of 27 scouts (in 6 swarms) that danced initially for a non-chosen site stopped their dancing before they followed a dance for another site. Evidently, a scout that supports initially one of the non-chosen sites is likely to withdraw her support for this site even before she learns about another site. What causes her to do so? Close examination of the behavior of scouts revealed that they reduce the strength of their dancing (waggle runs/return to the swarm) for a given site over consecutive returns to the swarm. On average, the pattern of this reduction in dancing is strikingly linear, which suggests that it arises from an internal, neurophysiological process that automatically drives down a scout's motivation to dance for a site. Other results suggest that scouts from inferior sites start their dancing less strongly, and so cease their dancing more rapidly, than do scouts from superior sites. If so, then during the consensus-building process of the scouts, it is the support (the dancing) for inferior sites that is most likely to die out while it is the support for a superior site that is most likely to prevail. 相似文献
824.
In species exhibiting egg guarding as well as communal egg laying, females may adopt the strategy of laying eggs in the nests of conspecifics and leaving without providing care (termed intraspecific brood parasitism). This study is the first to describe such a behavior in the insect Publilia concava (Hemiptera: Membracidae) through field studies that followed 849 marked females across 1,828 brood associations. While brood parasitism increased the total number of eggs in a host brood, it did not reduce the overall hatching success of host broods. Solitary females exhibited a range of guarding durations while parasitic females rarely remained to guard eggs. Females exhibiting the parasitic tactic increased their lifetime number of clutches without decreasing the number of solitary clutches that they were able to initiate. Estimates of egg number for these individual broods revealed that females adopting the parasitic tactic (in addition to solitary breeding) had higher lifetime fecundity relative to females that did not parasitize. In females that exhibited both tactics (solitary and parasitic), the parasitic tactic yielded a higher rate of oviposition. The major component of oviposition rate was the time to find hosts and this time decreased with increasing host availability across 222 replicate groups. Females exhibited a shift toward the parasitic tactic when host broods were more abundant (i.e. in larger groups and later in the season). However, the time to find hosts increased as the frequency of the parasitic tactic increased, suggesting that this tactic may be maintained through negative frequency dependence. The results of this study suggest that brood parasitism may be the preferred tactic, as part of a conditional strategy, when hosts are readily available with solitary breeding being the preferred tactic when hosts are in short supply. 相似文献
825.
Courting virtual rivals increase ejaculate size in sticklebacks (<Emphasis Type="Italic">Gasterosteus aculeatus</Emphasis>) 总被引:1,自引:0,他引:1
Marc?ZbindenEmail author Dominique?Mazzi Reto?Künzler Carlo?R.?Largiadèr Theo?C.?M.?Bakker 《Behavioral ecology and sociobiology》2003,54(3):205-209
Sperm competition occurs when sperm of two or more males compete to fertilize a given set of eggs. Game-theory models of sperm competition predict that males, which face an increased risk of sperm competition, will invest more sperm in a mating. In the pair-spawning three-spined stickleback ( Gasterosteus aculeatus), males attempt to steal fertilizations (i.e. to sneak) when they are in the courting phase, but not when they are parental. The behaviour of neighbouring males may therefore indicate the risk of sperm competition. We visually confronted males before spawning with computer animations of the same virtual stickleback showing two different behaviours: either courting (high risk of sperm competition) or brood-caring (low risk of sperm competition). We show that males invest significantly more sperm (absolutely and relatively with respect to available sperm in the testes) after the courting stimulus. The relative investment ratio between the courting and the brood-caring treatment was on average 1.75. Three-spined sticklebacks thus seem to assess the risk of sperm competition by the behaviour of neighbours and to adjust their ejaculate accordingly. This result suggests that the evolutionary force of sperm competition has led to precise mechanisms of future risk assessment. 相似文献
826.
Innate antipredator responses of Arctic charr (<Emphasis Type="Italic">Salvelinus alpinus</Emphasis>) depend on predator species and their diet 总被引:2,自引:0,他引:2
The ability to discriminate between more dangerous and less dangerous predators can have serious fitness advantages for fish juveniles. This is especially true for hatchery-reared fish young used for stocking, because their post-release mortality is often much higher than that of wild-born conspecifics. We tested whether two coexisting fish predators and their different diets induce innate behavioral responses in predator-naive Arctic charr (Salvelinus alpinus) young originating from an endangered hatchery-bred population used for re-introductions. We predicted the antipredator responses of charr to be stronger towards chemical cues of brown trout (Salmo trutta) and pikeperch (Stizostedion lucioperca) than towards odorless control water. More pronounced antipredator behavior was predicted in treatments with predators fed on charr than when their diet consisted of another sympatric salmonid, European grayling (Thymallus thymallus), or when they were food-deprived. The Arctic charr young showed strong antipredator responses in all brown trout treatments, whereas odors of the less likely predator pikeperch were avoided with conspecific diet only. Freezing was the most sensitive antipredator behavior, as it was completely absent in control treatments. We found considerable individual variation in the amount and strength of antipredator responses. Although almost half of the charr failed to show antipredator behavior towards the piscivores, those with the innate ability showed highly sensitive recognition of predator odors. Our results indicate that the innate antipredator behavior of the juvenile fish is already finely tuned to respond specifically to chemical cues from different fish predators and even their diets.Communicated by J. Krause 相似文献
827.
Michele?ArestaEmail author Angela?Dibenedetto Marcella?Narracci Immacolata?Tommasi 《Environmental Chemistry Letters》2003,1(1):13-18
A bench-scale pilot plant has been developed for the treatment of olive-mill water. The plant is fed in a continuous mode
and implements a primary treatment (sand filtering and irradiation with UV-rays) and a secondary treatment (anoxic and aerobic
biological treatment). Satisfactory results were obtained and the treated green water falls under the limits of the Italian
legislation. Veratric and ferulic acid biodegradation were studied under anoxic conditions in order to verify the requirements
for optimal biodegradation.
Electronic Publication 相似文献
828.
David?S.?LembergEmail author Rolland?Fraser 《Environmental Modeling and Assessment》2005,10(3):265-276
Residential lakeshore development is causing increasing pressure on the lacustrine environment. Traditional landscaping patterns
produce lakes ringed with lawns at the expense of the naturally occurring shoreline habitat. In this work, we present a mathematical
model to select path locations to minimize impacts on the lakeshore environment, while providing convenient access to the
landowners. 相似文献
829.
J.?Orestes?CerdeiraEmail author Kevin?J.?Gaston Leonor?S.?Pinto 《Environmental Modeling and Assessment》2005,10(3):183-192
The spatial relations of sites within networks of priority areas for conservation is critical to the long-term maintenance
of key genetic, population and ecosystem processes. However, these relations have received relatively little attention in
the development of mathematical methods for objectively identifying such networks. Here we present a novel heuristic for incorporating
connectivity explicitly as part of the model constraints, provide an integer linear programming formulation for the same problem,
describe an integer cutting procedure which defines a sequence of non-decreasing lower bounds on the optimal solution and
report the results of some computational experiments using these algorithms. 相似文献
830.
用国产ETLD-80型热释光环境剂量计调查了哈密地区环境天然贯穿辐射水平.结果表明,哈密地区室外、室内宇宙射线电离辐射空气吸收剂量率分别为(3.7±0.3 )、(3.3±0.3)×10~(-8)Gy/h,人口加权平均值分别为3.2和2.8×10~(-8)Gy/h.地球γ辐射空气吸收剂量率分别为(5.8±0.9)、(7.7±1.2)×10~(-8)Gy/h,人口加权平均值分别为5.0和6.6×10~(-8)Gy/h.天然贯穿辐射所致居民有效剂量当量为71.7μSv/a(宇宙辐射298μSv/a,地球γ辐射419μSv/a). 相似文献