摘要:

European populations of the common dog‐whelk,Nucella lapillus(L.), usually show a neat and precise pattern of shell shape variation with the exposure of their habitat to wave action. Whilst this is the case along much of the west coast of Scotland, there are a number of instances where unusually elongated shells occur, somewhat reminiscent of the form described for the Severn Estuary. There are no obvious environmental or geographical correlates to explain the occurrence of these forms and a genetical interpretation is sough

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1982.tb02025.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Two sphecid wasps,Sceliphron asiaticum(L.) andS. fistularium(Dahlbom), which build mud nests and capture spider prey, had overlapping but distinctly different distributions in Trinidad.Sceliphron asiaticumwas associated with drier (50° mortality of the females between emergence and starting to nest. The regulation of numbers of these wasps in relation to that ofS. assimile(Dahlbom) in Jamaica is dis

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1982.tb02026.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

The recently developed techniques of leaf demography are compared with those of the plastochron index. Data derived from the plastochron index that are relevant to leaf demography can be found in morphological and physiological literature. These are presented and show the usefulness of both concepts in the measurement and description of plant growth, productivity and morphology.

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1982.tb02027.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

In Darwin's and Fisher's theory of sexual selection, females prefer ornamented males; the evolution of larger ornaments is limited by increased mortality, lor example through predation. An adornment of given size should often raise mortality more in low than in high quality phenotypes. Possible consequences for the evolution and optimal size of ornaments are here examined with mathematical models.Fisher suggested that an ormamem may evolve if it initially improves male survival. Female preference then spreads for adorned males. Their consequent mating advantage furthers propagation of the preferred trail. An alternative, the ‘handicap mechanism’, suggests that only those males best able to survive can do so with a large, handicapping ornament. Choosing adorned males, females might therefore bear offspring with high general survivorship, but sons also inherit the handicapping ornament. When it reduces survival more in low than in high quality phenotypes, the handicap mechanism (in conjunction with the Fisherian mating advantage) becomes powerful with lower heritability of fitness than previously supposed. It still requires that fitness has some heritability, for which there is indirect evidence, but field measurements are lacking.In Darwin's and Fisher's theory, both mating advantage and mortality disadvantage increase with ornament size, and balance at its optimal development. If a given adornment reduces survival most in low quality phenotypes, the optimum increases with phenotypic quality. Ornament size then may provide a measure of fitness, and can be used in mate choice. A male can usually not gain fitness by developing larger adornments than other males of the same quality.Ornaments can probably also evoke through direct competition between males, without female preferences for adorned males. Field experiments are needed to clarify this and other aspects of sexual selection.Sexual ornaments form part of the reproductive effort. Certain predictions from life‐history theory should therefore apply. One is that ornaments will increase in size over the first few reproductive seasons; this is the case in many sp

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1982.tb02028.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Populations of the flounder,Platichthys flesus, were screened for electrophoretically detectable protein variation at up to 37 loci. Atlantic and North Sea populations (subspeciesflesus) were genetically very similar to one another (I>0.99) but different from Adriatic (subspeciesitalicus) and Black Sea (subspeciesluscus) populations. The values for genetic identity between subspecies were around 0.9. Diagnostic loci enabled specimensof flesus, italicusandluscusto be differentiated from one another. Samplesof flesusshowed two to three times the heterozygosity levels ofitalicusorluscus, consistent with the greater population size offlesus. Morphological comparisons enabled populations to be categorized to subspecies.Platichthys flesus italicusandluscusare valid subspecies: the terms are not synonyms. The genetic distance data provide an estimate of divergence time of the three subspecies at about 2 My ago, an estimate that seems reasonable in the light of present knowledge concerning the recent geological histories of the Mediterranean and Black Sea basins.

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1982.tb02029.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY