摘要:

Littoraria filosa (Sowerby) is a member of theL. scabragroup, found amongst the foliage of mangrove trees in northern Australia. The colour of the shell is polymorphic, showing two discrete ground colours, either yellow or orange‐pink, with a variable degree of superimposed brown patterning. At a site on Magnetic Island, northern Queensland, colour frequencies of small snails were similar on different backgrounds. Amongst larger shells yellows were more frequent on Avicennia trees with abundant foliage, and browns on relatively bare trees, suggesting that visual selection for crypsis occurred. There was no evidence of substrate selection by the morphs. Yellow shells were cooler than brown shells, but differences in colour frequencies on sunny and shaded trees, and at different seasons, did not suggest climatic selection. By manipulating the colour frequencies of subpopulations of small snails isolated on individual trees, it was shown that the disappearance of yellow and brown shells was frequency‐dependent. This result is consistent with hypotheses of mimicry of background elements by the morphs and of apostatic selection by unknown predators. Only the latter can account for the persistence of the highly conspicuous pink morph at a low freque

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1987.tb00284.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

David Lack's theory of island biology was published in 1976. In this he stated that isolation was of little consequence as a barrier to bird dispersal. Lack's theory was singular for his lack of statistical support of his assertions. One reviewer indicated from his data that statistically significant isolation effects might be present. Here data for the Bahamas and Gulf of Guinea islands were examined. In both cases isolation from the mainland colonisation source was significantly inversely correlated with the number of breeding bird species on the islands.

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1987.tb00285.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Melanic polymorphism inB. betulariahas been extensively studied. Correlations between high melanic frequency and high levels of air pollution have been demonstrated. Kettlewell and others have shown that differential bird predation has an important effect on the maintenance of the polymorphism, and coefficients of visual selection have been obtained on the assumption that the moth habitually rests on tree trunks. Computer models based on these selective coefficients show that they are not sufficient accurately to explain observed melanic frequencies. Other non‐visual selective factors and weak frequency‐dependent selection have been invoked to improve fits. Analysis of the resting positions of moths recorded in the wild demonstrates that B. betularia does not usually rest in exposed positions on tree trunks, but rather rests on the underside of branches, on trunks in shaded positions just below major branch joints or on foliate twigs. The results of a pilot selection experiment, while agreeing qualitatively with Kettlewell's results, suggest that fitness estimates that assume trunk‐resting are quantitively incorrect. The error is greatest for melanic moths in rural areas. It is suggested that visual selective coefficients based on a true assessment of the resting behaviour of the moths may considerably improve the fit between computer predictions and observed phenotype frequency distribu

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1987.tb00286.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Two kinds of lemming have evolved genetic modifications of sex determination that result in surpluses of daughters. Female‐biased sex ratios can evolve when mating occurs between neighbouring individuals who are more related than if mating occurred randomly. Two proposed sources of such ‘viscous’ gene flow in lemmings arc cyclical changes in population density and mosaic habitat. Alternatively, perhaps cold climate favours winter aggregation and inhibits the dispersal of winter‐born offspring, which would Nature and mate with close relatives; dispersal and outbreeding would occur during the warm months. Thus the episodes of dispersal and inbreeding would be seasonal rather than density‐dependent and the supposition of discontinuous habitat is

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1987.tb00287.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

The analysis of various genetic components in the standard inbred laboratory strains of mice shows that several taxonomic units of the complex speciesMus musculushave contributed to their genetic background. These laboratory lines are often taken as archetypes of the mammalian genome and since their genealogy is known for around 80 years they have been used to estimate mutation rates and various other evolutionary parameters. The knowledge of their origins is important if one is to avoid erroneous interpretations. Do they possess haplotypes that could have existed in natural populations ofM. musculus domesticusor are they the fruit of artificial recombinations between divergent genomes? We discuss this in the light of various genetic systems.

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1987.tb00288.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1987.tb00289.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Sexual dimorphism in body length and proportion of overlap between the ranges of body length for males and females were estimated for 361 species of parasitoid wasps from 21 families. In most species, females are generally larger than males, though the range of male and female sizes overlap. Species in the family Ichneumonidae differ significantly from species in other families in three ways: (1) ichneumonids on average are larger, (2) in most species, females are generally smaller than males, and (3) on average, proportion overlap between the ranges of body length for males and females is greater. At present, there is a paucity of life history data on parasitoid wasp species for which size dimorphism is known. Thus it is not clear why ichneumonids differ from species in other families. Possible evolutionary explanations for variation in dimorphism among parasitoid wasp species are discussed.

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1987.tb00290.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Existing taxonomic schemes for the protists at the highest levels are confusing owing to insensitivity to evolutionary data, lack of stability, evolutionary misleading terminology and multiple, contradictory systems. We propose a system which circumvents these problems by recognizing the largest monophyletic groups possible, and creating a nomenclature for these by appending the suffix ‘protista’ onto an already recognizable prefix: for example, euglenoprotista, cilioprotista, chytridioprotista. This system provides a high degree of stability while also allowing for the further clustering of these groups and inclusion of their descendant groups, such as the plants, as more evolutionary data become availa

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1987.tb00291.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1987.tb00284a.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY