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排序方式: 共有135条查询结果,搜索用时 31 毫秒
71.
Summary A number of aposematic butterfly and moth species sequester toxic substances from their host plants. Some of these insects can detect the toxic compounds during food assessment. Some pipevine swallowtails use aristolochic acids among the host finding cues during oviposition and larval feeding and accumulate the toxins in the body tissues throughout all life stages. Likewise, a danaine butterfly,Idea leuconoe, which sequesters high concentrations of pyrrolizidine alkaloids in the body, lays eggs in response to the specific alkaloid components contained in the apocynad host. Insect species sharing the same poisonous host plants may differ in the degree of sequestration of toxins. Two closely ralated aposematic geometrid moth species,Arichanna gaschkevitchii andA. melanaria, sequester a series of highly toxic diterpenoids (grayanotoxins) in different degrees, while a cryptic geometrid species,Biston robstus, does not sequester the toxins, illustrating the diversity in adaptation mechanisms even within the same subfamily. By contrast, a number of lepidopteran species store the same compounds though feeding upon taxonomically diverse plant species. A bitter cyanoglycoside, sarmentosin, was characterised from several moth species in the Geometridae, Zygaenidae and Yponomeutidae, and from the apollo butterflies,Parnassius spp. (Papilionidae), although each species feeds on different groups of plants.Interspecific similarities and differences in life history and ecology are discussed in relation to variable characteristics of sequestration of plant compounds among these lepidopteran insects. 相似文献
72.
Michael Wink Angelika Hofer Martin Bilfinger Elke Englert Martinus Martin Dietrich Schneider 《Chemoecology》1993,4(2):93-107
Summary The palatability of plants was studied in young, immature and adult geese of three species,Anser anser, Anser indicus andBranta canadensis, with respect to secondary plant metabolites. In their first 1–4 weeks of life, hand-reared goslings feed on a wide variety of plants, more or less irrespective of their allelochemical contents. Older birds become more selective, but still consume plants which are normally considered to be unpalatable or even toxic for other animals. Choice experiments were performed with pure secondary metabolites which were offered on otherwise highly palatable food items, such as leaves ofTaraxacum officinale. These experiments revealed a similar trend, in that very young goslings discriminate their food much less than older goslings or adult geese. In general, food contaminated with essential oils was rejected, whereas alkaloids, glycosides, amines and sulfur compounds were tolerated to a remarkable degree. In consequence, especially young, but also adult geese must have a high capacity to tolerate and/or to detoxify dietary allelochemicals. Another detoxification mechanism became evident during the experiments: geese ingest soil and mud quite regularly. It could be shown experimentally that the respective soil had a high capacity to bind alkaloids. We assume that geophagy is a means (besides a presumed active detoxification in the liver) to adsorb and thus reduce the contents of dietary allelochemicals. 相似文献
73.
Toxicity assays of ladybirds using natural predators 总被引:1,自引:0,他引:1
Nicola M. Marples 《Chemoecology》1993,4(1):33-38
Nestling blue titsParus caeruleus L. were given diets containing homogenized ladybirds, to assess the effects of their chemical defences. The 2spot, 10spot and water ladybirds produced no apparent toxic effects when small numbers were given at regular intervals.The pine and kidney-spot ladybirds slightly inhibit growth and may be toxic to very young nestlings. The Water ladybird is extremely distasteful to this predator, despite its lack of toxicity. The results are discussed with reference to the proposed Müllerian and Batesian mimetic relationships between the ladybird species. 相似文献
74.
This study reports the results of restoration management on sand dune environments along the coastal belt of the Castelporziano
nature reserve (Rome, Italy) and the subsequent monitoring phases to test the sustainability of the ‘soft techniques’ applied.
In the area concerned, over a length of ca. 3 km, 40 dunes were built up along with three belts located at <40 m, 40–70 m,
and >70 m, respectively, from the shoreline. On each of 38 dunes 20 individuals ofAmmophila littoralis were planted; this species is one of the local autochthonous species considered particularly suitable for stabilizing sand
dunes. After one year, two years and five years, respectively the changes in height and surface of each dune, the survival
rates ofA. littoralis, and its changes in cover, the appearance of new shoots and the establishment of new species were observed. A progressive
increase in species number, which five years after the restoration amounted to about 60% of those characterizing the natural
dunes, was reported indicating a progressive trend towards populations similar to natural ones. In the colonization of new
species there is a prevalence of theSporobolus-Elymetum farcti and theSalsolo Kali-Cakiletum maritimae association, while the species established successively refer to theEchinophoro spinosae-Ammophiletum arundinaceae association and theCrucianellion maritimae alliance as occurring in natural successions.
This succession runs parallel to the natural dune colonization processes. In particular, the data regarding survival, cover
and number of vegetative shoots indicate that the dune belt between 40 and 70 m from the sea is the one most suitable for
restoration.
Some changes in dune morphology was observed: the height of the artificial dunes tended to decrease considerably in the five
years of observation, whereas a progressive increase in their surface area was observed. During the study period.A littoralis favoured the establishment of new species, but as yet exercises no action on increasing dune height. 相似文献
75.
In cooperatively breeding birds, the presence of helpers is expected to increase the reproductive success of the breeding pair. However, some studies fail to find this effect. A positive effect of helpers may be restricted to cases in which a breeding pair has a poor likelihood of raising the entire brood on its own, as would be the case under stressful environmental conditions or with enlarged brood sizes. We conducted brood size manipulations in a cooperative breeder, the sociable weaver, Philetairus socius, to investigate the relationship between the difficulty of raising nestlings and the effort and impact of helpers. Overall, sociable weavers did not work harder to raise the enlarged broods. However, the presence of helpers significantly increased the feeding rates at enlarged nests, but not controls. This was insufficient to prevent generalised brood reduction in enlarged broods, whether attended by pairs alone or with helpers. Nonetheless, the presence of helpers was associated with decreased nestling mortality and an increase in the numbers of young fledged. Our results suggest that groups are better able to respond to the needs of enlarged broods than pairs alone and that the presence of helpers has a beneficial effect on overall reproductive success.Communicated by J. Dickinson 相似文献
76.
Summary Changes in the density of beech scale infestation (Cryptococcus fagisuga) of a mature beech stand (Fagus sylvatica) were investigated after gap-cutting in limed and unlimed areas bordering on the gaps and in untreated areas over a 5-year period. Parallelly the concentrations of sucrose, protein amino acids, and procyanidins were examined in the inner and outer bark of non-infested beech trees and beeches infested by beech scale.Irrespective of liming in the areas bordering on the gaps the proportion of beech trees with increasing beech scale infestation was significantly higher, the proportion of beeches with diminishing infestation was significantly lower than in the untreated control areas. Trees with the same infestation tendency occurred in clusters.Physiological defence reactions in the inner and outer bark of the infested beech trees were registrated as an increase in the procyanidin content and a decrease in the protein amino acid content. A change in the outer bark—inner bark—ratio of the infested beech trees showed a transfer of compounds between the inner and outer bark. During the period of observation long-lasting shifts occurred in the pattern of compounds of the bark irrespective of actual infestation intensity. 相似文献
77.
测试了聚四氟乙烯(PTFE)复合膜材料的透湿性和对氯化钠气溶胶、粉末状微生物枯草芽孢杆菌黑色变种(ATCC9372)、液体中脊髓灰质炎病毒疫苗株的防护性能。结果表明,该复合膜材料有良好的透湿性能,同时对氯化钠气溶胶、粉末状和液体中的微生物均具有良好的防护性能。 相似文献
78.
John Alcock 《Behavioral ecology and sociobiology》1996,39(3):181-188
I examine three alternative hypotheses on the male size dimorphism of Dawson’s burrowing bees (Amegilla dawsoni) in which there are large (major) and small (minor) males. One possibility is that minor males are simply the incidental
byproduct of environmental conditions that prevent females from provisioning brood cells optimally. This hypothesis is not
supported by the finding that males of intermediate size are consistently rare in populations sampled across years and in
different regions, nor can it easily account for the absence of a size dichotomy in females. A second possibility is that
minors represent a “best of a bad job” response of those females that are small or otherwise disadvantaged. However, presumptive
male siblings sometimes include both majors and minors, a result not predicted from this hypothesis. A third explanation is
that female brood provisioning strategy results in the production of minors and majors with equal fitness benefit to fitness
cost ratios. However, although it is true that minor males weigh on average about half what a major weighs, and so represent
approximately half the provisioning expense of a major, minor males on average appear to secure far fewer than half the number
of matings of majors. If the estimate of mating success of minors is accurate, the net gain to females from producing a minor
son is unlikely to equal that derived from a major son. Therefore the third hypothesis must also be tentatively rejected,
although with caution given the uncertainties in estimating the relative costs and benefits of producing major and minor sons.
Received: 12 January 1996/Accepted after revision: 27 April 1996 相似文献
79.
80.
How do birds recognize their own eggs? Do they have a stored template for their own egg characteristics, or do they use another mechanism? Intraspecific brood parasitism is considered to be an additional reproductive tactic where females can increase their own reproductive success. Because of the costs involved in rearing young that are not their own, it will pay females to detect and reject the eggs of a parasite, although it is not known how they do this. Here, we show experimentally that moorhens will cease laying in a nest when their first egg is replaced with another hen’s egg but not when it is replaced with their own egg taken from an earlier clutch. This provides good evidence that birds have an internal representation of their own eggs and use this in decisions about whether to reject foreign eggs. 相似文献