摘要:

Summary1. In order to understand fully the evolution of a behavioural trait one must not only consider whether it is adaptive in its present environment but also whether it originated as an adaptation to existing selective forces or as a fortuitous consequence of selection for a different role in other environments (i.e., as a pre‐adaptation) or of selection for different traits (e.g., as a pleiotropic effect). In this paper interspecific territorialism is examined in species of humming‐birds, sun‐birds, tropical reef fishes, stingless bees, stomatopods, crayfish, and limpets as a means of determining its adaptiveness and its origins.2. Humming‐birds form complex assemblages with species sorted out among the available resources. Dominant species establish feeding territories where flowers provide sufficient nectar. A few large, dominant species, usually uncommon, are marauders on others' territories. Subordinate species establish territories where flowers are more dispersed or produce less nectar, or they fly a circuit from nectar source to nectar source when flowers are even more dispersed, a foraging pattern called ‘traplining’, or they steal nectar from the territorial species by being inconspicuous while foraging. Two species,Amazilia saucerotteiandSelasphorus sasin, subordinate in one‐to‐one encounters, are able to take over rich resources by establishing several small territories within a territory of a dominant and forcing it to forage elsewhere.3. Among humming‐birds, territorial individuals attacked not only subordinate competitors but marauding humming‐birds and some insects, which stayed in the territory and foraged at will, and seemingly inappropriate targets, such as non‐competitors. This suggests that the stimulus for aggression is ‘any flying organism near the food resources’, regardless of its appearance. The behaviour rather than the identity of the intruder is the stimulus.4. Sun‐birds resemble humming‐birds to the extent that dominants establish territories on rich nectar sources and subordinates establish territories on less rich nectar sources or steal from the territories of dominants. The diversity of foraging patterns is not so great as in humming‐birds, perhaps because so few species of sun‐birds have been studied. However, the advantage of territorialism has been measured in the sun‐birdNectarinia reichenowi.Individuals with territories lose much less nectar to competitors than do those without territories.5. Field work on three species of tropical reef fishes involved a single aggressive species whose individuals attacked a wide range of species intruding on their territories. The stimulus for aggression inPomacentrus jenkinsiseemed to be an “object moving through [its] territory”. As suggested for humming‐birds, the stimulus is the behaviour rather than the identity of the intruder.6. The relationships found in stingless bees, stomatopods, crayfish, and limpets are simpler. The dominant and subordinate species divide the resources in their habitat, the dominants' aggression preventing the subordinates from using resources that were otherwise available to them.7. A general pattern emerges. Mutual interspecific territorialism occurs between species that (i) have different geographic ranges, (ii) occupy different habitats, or (iii) use different resources within the same habitat. Examples of two species holding separate territories on the same resources within the same habitat are rare and occur when the dominant species is rare relative to the available resources. These observations are contrary to the usual view that interspecific territorialism is an adaptation that permits co‐existence of potential competitors within the same habitat.8. Interspecific territorialism is sometimes adaptive and sometimes maladaptive, depending upon the species and the situation.9. The general pattern of occurrence of the behaviour and the general nature of the stimulus for aggression, i.e., the behaviour rather than the identity of the intruder, suggest that interspecific territoriality is a fortuitous consequence of selection for intraspecific territorialism, the latter being not only an adaptation to the presence of conspecific competitors but a pre‐adaptation to the presence of co

ISSN:1464-7931    

DOI:10.1111/j.1469-185X.1981.tb00341.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Summary1. Lipids deposited on the surface or embedded within the cuticle of terrestrial plants and arthropods are primarily responsible for the observed low rates of water loss through the cuticle.2. These lipids are a mixture of long‐chain compounds which include hydrocarbons (saturated, unsaturated, branched), wax esters, free fatty acids, alcohols, ketones, aldehydes, and cyclic compounds.3. The cuticle of both plants and arthropods is a continuous, non‐cellular multilayered membrane which overlies the epidermal cells.4. In arthropods, horizontal division of the cuticle into layers is clearly visible. In plants, the layers comprising the cuticle are not sharply demarcated.5. The substance responsible for the structural integrity of the plant cuticle (cutin) is composed of cross‐esterified fatty acids; structural integrity in arthropod cuticle is provided by a chitin‐protein complex.6. Cuticular lipids are probably formed near the surface in both plants and arthropods; however, specific sites of synthesis are known for only a few species and little is known about their transport from these sites to the surface. The elaborate pore canal and wax canal system of arthropod cuticle is absent from plants.7. The physical structure and arrangement of the lipid deposits on the cuticular surface that are so important in controlling water movement depend on both quantity and chemical composition, and are, in turn, specific to each species in relation to its environment.8. Different lipid components are not equally efficient in reducing transpiration. Maximum waterproofing effectiveness is provided by long‐chain, saturated, non‐polar molecules containing few methyl branches.9. Plants and arthropods can, within genetic constraints, alter the composition of their cuticular waxes to improve impermeability when conditions require increased water conservation.10. None of the models proposed to explain the change in arthropod cuticular permeability which occurs at a species‐specific temperature (‘transition temperature’) in many species is supported by the experimental d

ISSN:1464-7931    

DOI:10.1111/j.1469-185X.1981.tb00342.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Summary1. There is convincing evidence that a number of agents such as bacteria, viruses, endotoxins, foreign proteins, smokes and chemicals come into contact under physiological conditions with the lymphoid tissue associated with the gut and/or bronchial systems. Endogenous lectins and proteases may also act as mitogens on the central and peripheral immune system.2. It is suggested that these agents act as inducers of interferon (and some also as immunogens), so that local production of interferon is turned on successively from cell to cell depending upon their responsiveness and upon the periodic inflow of inducers.3. On the basis of a number of different features, it is proposed to distinguish between an ‘acute’ and a ‘physiological’ interferon response. In the latter, the interferon‐producing cell influences the neighbouring cells by short‐range humoral transmission (paracrine control) and possibly by cellular interaction, while the route of the general circulation is preferentially used in the former response.4. It is suggested that the physiological interferon response, although previously overlooked, has great biological importance because production of interferon at strategic sites can maintain active defence systems essential for survival.5. It is to be expected that the physiological interferon response, although amenable to experimental verification, may be difficult to detect. On the basis that interferon is normally absent from serum, it is suggested that most of the released immune‐type interferon is either bound by cells surrounding the site of its synthesis or catabolized locally.6. It is postulated that the progressive decline of the physiological interferon response with increasing age may represent one of the factors favouring the insurgence of autoimmune diseases and tumours in the process of ageing. It is also suggested that the involution of the thymus may in part be due to intrathymic production of interferon induced by proteases released fro

ISSN:1464-7931    

DOI:10.1111/j.1469-185X.1981.tb00343.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY