摘要:

The evolution of resistance to insecticides has become a serious problem world‐wide. It is important to identify patterns of insecticide use whereby insecticides can be used in integrated pest management programmes to help control insect numbers, but in such a manner that the evolution of resistance to insecticides will be retarded. The principal mechanisms of insecticide action and of resistance to these are reviewed. Some generalizations that can be made about the evolution of resistance are examined. In general, to control resistance it appears better to use an intense dose of non‐persistent pesticides over a circumscribed area. Some features of the problem where population genetics and evolutionary theory might contribute to controlling resistance are discus

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1986.tb01728.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

Three species of epiphyticDischidiahave been investigated in terms of their relationship to ants on trees. Two species,D. parvifoliaandD. astephana, are associated with ants and trees in montane areas. A clear association has been found between ants of the genusCrematogasterand the treeLeptospermum flavescens.This relationship is complex and probably both organisms benefit from the association. The ants live in tunnels in the wood of the major branches and the trunk, and the entire tree is occupied by one ant colony. Trees occupied by ants are maintained by the ants substantially clear of epiphytes other than the two species ofDischidia.The potential benefits to the tree and to the ants of this association are noted. The roots ofD. astephanaandD. parvifoliapenetrate into the cavities of these ant nests and presumably gain nutrients from waste in the ant nests. BothDischidiaspecies are effectively scavenging upon the waste material from the ant‐tree association. The leathery dome‐shaped leaves ofD. astephanaare not vital to the development of the scavenging habit asD. parvifoliahas lens‐shaped leaves, but may offer some advantage toD. astephanaby the uptake of nutrients from waste deposited by the ants under the dome‐shaped leaves by interception of stem flow and by uptake of gaseous waste. Ants do not nest under these leaves. Seeds of these species ofDischidiaare taken by ants into the central woody area of the ant nest where they germinate. BothLeptospermumandDischidiacan be visualized as showing adaptations to a nutient‐deficient tropical montane environment. These adaptations are discussed as is the need for reassessment in this genus of the term ‘ant‐plant’, and the need for wider recognition of the 1ant‐tree’ relationship betweenCrematoga

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1986.tb01729.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

A principal components analysis was performed on 20 measurements of the ectopterygoids of 85 colubroid snakes. This sample encompassed all the shape variation previously recognized in the ectopterygoid of colubroids. Simple proportions which correlate with the first two principal component axes are: relative ectopterygoid length with the first and five measures of absolute or relative head shape with the second. Using these simple proportions colubroid ectopterygoids can be sorted into four shape classes each concordant with a taxonomic grouping: relatively long with broad notched head—Crotalinac; relatively long with narrow, flat head—Viperinae; relatively short with broad, notched head—Colubridae; and relatively short with narrow, flat head—Elapidae. This concordance has an error of about 1000. We propose that these shape classes reflect phylogenetically old and conservative functional differences in the palatomaxillary complexes of the four taxonomic groupings. Other aspects of ectopterygoid shape are described and provisional character state phylogenies for some aspects of the ectopterygoid are presented. Finally, the bearing of our data on the systematics of aparallactines, micrurines, sea snakes,Azemiopsand certain other genera are di

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1986.tb01730.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

The evolution of a population of organisms will be dependent upon the ecological circumstances in which it lives. It has been suggested that organisms in constant environments will be subject to natural selection acting to influence their equilibrium population density, but in organisms in temporally variable environments natural selection will act more on differences in rates of increase in population size. These two types of selection have been calledr‐ andK‐selection. A quantitative relationship between the optimum genotype of an organism and environmental variability is calculated, and shown to depend upon the trade‐off between evolutionarily possible values of

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1986.tb01731.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

Silene latifolia(white campion) is widespread in W Eurasia and shows clinal variation in seed morphology. Two extensive parapatric races, within which seed morphology changes gradually with geographic distance, are separated by a transition zone where the morphological gradient is steeper. A sample of seeds from across the species' native range was scored for morphological characters and analysed using detrended correspondence analysis ordination and multiple regression, in order to simplify mapping of the variation pattern and to investigate statistical relationships with climatic variables. The transition zone, as defined by ordination scores, follows the convolutions of the 0d̀C isotherm for January mean temperature along its entire length from N Europe to the Middle East. January temperature proved to be a highly significant predictor of seed morphology even after the removal of simple spatial trends. Although the origins of comparable large‐scale clines have often been interpreted in historical terms, the result reported here supports a role for climatic selection in maintaining the existing variation patte

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1986.tb01732.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

Colour in theEphippiger ephippigercomplex varies with the geographical distribution and with rearing density. In the W European subspeciesE. e. vitium, wild insects from northern and eastern parts of the range tend to have green tergites with relatively inconspicuous banding, whereas those from S France have conspicuously pale banded dark‐green or brown tergites. These forms represent the ends of a continuum and there is no zone of distinction. However, the E Pyrenean subspecies,E. e. cunii, lacks the broad banding of its neighbouringE. e. vitium.The tergites of laboratory cultured insects of these stocks when reared in isolation are distinctly green but when reared together become progressively brown. The darkness of the brown is density dependant, so that at high densities the tergites may become almost black. These colour changes are irreversible. Adult insects also become darker with sexual maturity and after contact on mating. Wild‐caughtE. e. ephippigerfrom Italy and Yugoslavia have green tergites without obvious banding. Colour changes have not been found or induced in this subspecies. The significance of the colour change is considered and although firm data are wanting, circumstantial evidence suggests a deliberate shift to an aposematic or pseudoaposematic colour patt

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1986.tb01733.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY