摘要:

Chaflinches have differentiated within the last million years on the Canary Islands and the Azores. All island populations differ more from mainland relatives than from each other. The characteristics of island birds are large body size, short wings, long legs and beaks, and blue dorsal colour. Beak depth and width have increased on the Azores but not on the Canaries. As a consequence the Azores chaffinch has evolved more in the direction of the Canary IslandF. teydeathan have Canary Island chaflinches. Character displacement may have occurred on the Canaries. Most of the evolutionary shifts are not predicted from a knowledge of clinal variation on the mainland. Populations have differentiated more on the Canaries than on die Azores, but are less variable regardless of whether ecologically restricted (byteydea)or not. Similarly, within the Azores archipelago the most differentiated populations are die least variable. On the Azores, but not on the Canaries, differentiation increases with isolation, whereas wimin‐population variation decreases with isolation and increases with elevation. A model for diese patterns is proposed in terms of gene flow between populations, which reduces differentiation but enhances variation, and directional selection and random genetic processes which have the opposite effect

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1979.tb00042.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

A survey of the freshwater crustacean fauna of the island of Rhum (Inner Hebrides) revealed at least 68 species. Information is provided on die distribution and ecology of these, and individual preferences are noted. These preferences lead to assemblages found in habitats whose ecological attributes can be related to geological, edaphic and chemical features of the environment.While species diversity on the island as a whole is perhaps greater than might have been anticipated, that of individual water bodies tends to be low, the maximum number ol species in any one water body being 2 7.The fauna includes a sizeable element of species that favour acidic waters of various kinds or oligotropliic/dystrophic lakes and pools of low ionic content, and includes a number of northern or burco‐Alpine species. The origin of this isolated fauna is briefly considere

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1979.tb00043.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

The uses of biochemical genetics as an aid to taxonomy are discussed briefly. A survey is made of published data to establish expected levels of genetic similarity or identity between conspecific populations, between congeneric species and between species of different genera. Existing measures of genetic similarity, identity or distance are discussed and some of the difficulties involved in their use in taxonomy are outlined. A new measure of genetic similarity is proposed specifically designed for use in making interspecific comparisons for taxonomic purposes. This measure offers considerable advantages in ease of calculation and also greatly simplifies the estimation of sampling errors. An empirical comparison is made, using published data, of the measures and confidence limits obtained by the proposed memod against published measures of genetic variation between species.

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1979.tb00044.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

I propose that the relative productivity of an organism in its community importantly influences the kinds of predator defences that are most effective relative to their costs. Two classes of defence mechanisms are distinguished: those that give some energy to the predator(tribute defences)and those that do not(non‐tribute defences).The pattern of distribution of these two types of defences both geographically and among different taxonomic groups of organisms support the hypothesis that the productivity of a species relative to others in its community is an important determinant of the type ol defence a species adopt

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1979.tb00045.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1979.tb00046.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY