摘要:

It is difficult to imagine how warning colours evolve in unpalatable prey. Firstly, novel warningly coloured variants gain no protection from their colours, since predators have not previously encountered and learnt their colour patterns. This leads to a frequency‐dependent disadvantage of a rare variant within a species. Secondly, novel warningly coloured variants may be more conspicuous than non‐aposematic prey.Nevertheless, it is obvious that many palatable butterflies have bright colours used in intraspecific communication and in duping predators. Other palatable butterflies are already warningly coloured. Should such butterflies evolve unpalatability, perhaps because of a host‐plant shift, these bright colours would be preadapted to a warning role. Warning colours could then continue to evolve by enhancement of memorable characteristics of these patterns, or by mimicry.Even within lineages of warningly coloured, unpalatable butterflies, colour patterns have continued to evolve rapidly. This diversity of warning colour patterns could have evolved in a number of ways, including individual and kin selection, and by the shifting balance. Evidence for these mechanisms is discussed, as are the similarities between the evolution of warning colours and more general evolutionary processes, including sexual selection and speci

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1987.tb00435.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Eulophids attacking hosts with tentiform mines show a tendency to elongate the ovipositor. We interpret tentiform mines as a defence strategy against parasitoids in leaf mining insects.

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1987.tb00436.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Electrophoretic data from different populations of the teleostsSolea senegalensis, S. aegyptiacaandS. vulgariswere analysed using multivariate analysis. This confirmed thatSolea vulgarisis very different genetically and isolated from bothsenegalensisandaegyptiaca, and that the latter two forms are also well differentiated. The presence ofsenegalensisalleles in theaegyptiacapopulation of the Golfe‐du‐Lion, and reciprocally,aegyptiacaalleles in thesenegalensispopulation of the Gulf of Tunis, suggests that genetic exchange occurs between them. The association of these alleles (gametic disequilibria) and the existence of hybrid individuals show that these exchanges are an actual process rather than a consequence of ‘fossil’ gene flow. Furthermore, the genetic introgression seems to be asymmetrical in the two regions studied where they come into

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1987.tb00437.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Adult survival rates were estimated in field populations of domesticDrosophilaspecies by means of multiple capture‐recapture experiments. Micronized fluorescent dusts were used as marking agents and analysis used the Fisher‐Ford model: the assumptions of this model are justified using evidence from this study and the literature. Survival rates were commonly 0.45‐0.85 per day, suggesting that mean life expectancy for adult flies is from 1.3 to 6.2 days in natural populations. No consistent differences in survival between sexes or seasons were demonstrated. The implications of low natural survival rates are disc

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1987.tb00438.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Speciation induced by parasitic or mutualistic symbionts has been suggested for taxa ranging from plants to insects to monkeys. Previous models for symbiont‐induced speciation have been based upon hybrid inferiority and selection for reinforcement genes. Taken on their own, however, such models have severe theoretical limitations and little empirical support. Two conditions that may favour symbiont‐induced speciation are presented here: (1) interaction norms in which the outcomes of host/symbiont interactions differ between environments and (2) differential coadaptation of host and symbiont populations between environments or along an environmental gradient. Symbiont‐induced speciation can be considered as one form of ‘mixed‐process coevolution’: reciprocal evolution in which adaptation of a population of one species to a population of a second species (or coadaptation of the populations) causes the population of the second species to become reproductively isolated from other

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1987.tb00439.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

The small, typically estuarine fishAtherina boyeriRisso forms local populations which can differ greatly in their population biology and morphology; this species is viewed as being on the brink of speciation. This analysis of the reproductive strategy shows thatA. boyerican rapidly adapt its life history and morphology to environments ranging from freshwater to polyhaline coastal lagoons and oceanic waters. The optimum strategy is shown to be tied to temperate seasonality: the cold winters act to lengthen the life cycle, and result in cyclic switching of energy between reproduction, somatic growth and fat storage. The adaptability of the fish to a range of environmental characters is viewed as being due to natural selection acting to produce a genotype capable of a flexible phenotypic response. This flexibility is essential for survival in the highly variable inshore/brackish habitat. It is argued that such preadaptive plasticity, coupled with the potential for populations to become isolated, produces ideal conditions for speciation. The importance of the coastal, estuarine and lagoonal environment as a springboard for teleost evolution is discussed.

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1987.tb00440.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Two South African populations ofLittorina saxatiliswere examined by starch‐gel electrophoresis at 16 enzyme loci and compared with 13 populations of North Atlanticsaxatilisfrom both American and European coasts, and with six British populationsofthe closely related speciesLittorina arcana.The South African animals showed a severely reduced heterozygosity(H̄–0.052) compared with Atlantic populations ofsaxatilis (H̄= 0.181), and the mean genetic distance between the two areas was high(F̄= 0.203) compared with distances within the North Atlanticsaxatilispopulations(D =0.034). In fact, thesaxatilisfrom South Africa were genetically more distant from the North Atlantic samples ofL. saxatilisthan were thearcanafrom British shores. The reduced genetic heterozygosity and genetic divergence of the South African populations is attributed to founder effects following a postulated recent introduction

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1987.tb00441.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Some striped animals are camouflaged in their natural environment, whereas others are conspicuous. Mammals are known to have spatial frequency analysers in their visual mechanism, and it is suggested that the spatial characteristics of a striped pattern are different in camouflaged and conspicuous animals. Fourier analysis of the stripes of the zebra shows spatial frequencies in the pattern that are unlikely to be present so strongly in their natural background scene. A similar analysis of the camouflaging stripes of a tiger show that the distribution of spatial frequencies are similar to that in the background scene.

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1987.tb00442.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY