摘要:

The Israeli land snail,Xeropicta vestalis, offers a particularly clear example of gene regulation in relation to natural selection, in that within each population the appropriate phenotype is generated only at the correct part of the animals life cycle, and a contrasting phenotype develops when the forces of natural selection change. In the mountains of Jerusalem, where the winter is cold, the shells are dark. Westwards, towards the coastal plain where the winter is warmer, the shells gradually become paler. As dark shells absorb more radiation than pale ones, this clinal variation in morph frequencies can be explained in thermal terms. (Banded shells are also more cryptic than non‐banded shells, so that in the mountains visual selection by predators may be an additional force which favours dark shells.)Xeropicta vestalisis an annual, semelparous species: the snails hatch in winter, become mature within one year, reproduce, and then die. In the coastal plain the snails are active throughout most of the year, and they have a long period in which to grow to reach adult size. In the mountains and hills, on the other hand, the snails are active for only a very short period. They spend most of their lives as small snails, in a state of aestivation.Xeropicta vestalismust be dark in mountains because when it finally awakens, it must very rapidly and hastily reach reproduction size. A dark shell, by speeding up temperature‐dependent processes in this critical stage, assists the snail to mature rapidly.Shell darkness varies with age: in the mountains and hills the shells are moderately dark when they hatch, but become darker whilst growing in early winter. In the coastal plain also, the snails are moderately dark when they hatch; but here they become paler, whilst growing in winter and spring. In both cases, each snail is darker in the colder months and paler in the hot ones.A strategy of gene regulation of shell colour is thus favoured when the subsequent forces of the environment are very contrasting in their direction, very severe—yet also very predic

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1981.tb01651.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Along the coastal plain of Israel, shell darkness of the polymorphic land snailXeropicta vestalisis positively related to the extent of perennial vegetation. It is not related to rain, temperature, geographic position or darkness of the ground.White shells reflect more radiation than dark ones do, and therefore in Israel's coastal plain, where solar radiation is very strong, they are favoured. Perennial vegetation, where it occurs, shields the snails from the sun by absorbing radiation, so that snails amongst them can afford to be darker, and thus more cryptic. Hence, the more perennial vegetation in the habitat, the darker the shells.Also during the Pleistocene, when temperatures were 5–10°C lower than today, the shells of the coastal plain were as pale as recent ones are. The distribution of a snail‐predator,Gerbillus allenbyi, which is restricted to sandy biotopes where perennial bushes occur, and which was absent from Israel during the Pleistocene, could perhaps explain the distribution ofX. vestalismorphs, both today and in the

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1981.tb01652.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

The anatomical illustrations for the scientific papers of Edward Phelps Allis, one of the foremost comparative anatomists and evolutionary morphologists in the early twentieth century, have been discovered at the Museum of Comparative Zoology, Harvard University. The discovered work includes many unpublished illustrations, large numbers of color drawings of serial sections of primitive actinopterygian fishes, and complete series of figures for several papers (rough copies, final drawings and proofs), clearly showing the progress of the investigations. A summary of the published and unpublished material is provided. All illustrations have been deposited in the archives of the Museum of Comparative Zoology Library.

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1981.tb01653.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Microdistribution and habitat selection were investigated in a populationof Drosophila subobscuranear Leeds, Yorkshire. Microdistribution was examined along a transect running through a deciduous woodland. Two main types of habitat were recognized, those with dry soil and a closed canopy of mature trees (dry and dark) and those with wet soil and an open canopy of mature trees (wet and light). Flies were much more frequent, judged by their attendance at baited traps, in the dry/dark habitat. Flies taken from both habitat types, marked with different coloured fluorescent dust and released at a point mid‐way between the original habitats, tended to return to their area of initial captur

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1981.tb01654.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

In order to clarify the taxonomy and the interrelationships among Asiatic cultivated rice,Oryza sativa, and its related wild species (O. rufipogon, O. nivaraand O. barthii), 41 morphological characters were examined. Numerical taxonomic methods were used to analyse the data and to illustrate species relationships.Distinctive differences among the materials studied suggest the retention ofO. rufipogoon, O. nivaraand O. sativaas three distinct species. The origin ofO. sativafromO. nivarathrough domestication is discussed. An annual wild taxon from Australia, which had been classified as a form ofO. nivara, is shown to be distinct from typicalO. nivnraand is raised to specific rank. This species has been namedO. meridionalisNg.

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1981.tb01655.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

In the two‐year period, 1972–73, 6445 Ichneumonidae of 455 species were caught in a Malaise trap operated in a suburban garden in Leicester, England. An additional 74 species were trapped in 1974. The collection includes a number of species new to the British list. The flight season of ichneumonids extended from March to November or December, with peak abundance and diversity in August. Size of trap samples fluctuated erratically, depending on air temperature. No species was particularly common and many were rare, 141 being taken once only in the two‐year period. The commoner species were present throughout the season, supporting the suggestion that ichneumonids are niche‐specific rather than host‐specific. Parasites of aphidophagous Neuroptera and Syrphidae, of spiders, of micro‐Lepidoptera, and of Diptera found in decaying plant material were especially abundant, as is characteristic of the British fauna as a whole. Adult ichneumonids are mobile, and it is assumed that the Malaise trap was sampling an area far larger than the garden in which it was sited, although suburban gardens are a particularly favourable habitat for ichneumonids. Twenty‐two species of Serphidae were captured in the Malaise trap during 1972–74, five of them

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1981.tb01656.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Fifteen functionally significant aspects of skull morphology were measured on skulls of 36 additional species of carnivores to complete a survey of skull shape in modern fissiped (land) carnivores that includes most of the living genera. The measurements were transformed to dimensionless variables based on the residuals from allometric equations, and were analysed singly and in a 10 variable principal components analysis. An initial study of 62 species of viverrids, canids, mustelids and felids had shown those families to be distinguished from each other by the functionally significant measurements. However, among the additional 36 species, some procyonids, ursids and mustelids display a range of diversity of skull morphology that overlaps that of the other families and diminishes the potential value of the measurements as taxonomic characters. Intraspecific variation is presented for 12 species, and is low enough to allow use of some features as species level diagnostic characters. The lack of correlation between diet and functionally significant aspects of skull morphology among omnivorous carnivores, and the absence of certain skull shapes among carnivores are discussed.

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1981.tb01657.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1981.tb01658.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY