摘要:

To determine the effectiveness of montane barriers to gene flow of the two‐striped grasshopper,Melanoplus bivittatus, collections were made at four sites at the corners of a square location, each bisected by one of five Colorado mountains (total: five locations, 18 sites). The premise of this design is that samples from opposite sides of an effective barrier should have more genotypic differences than samples from the same side. Genotypic differences were measured for each grasshopper as 18 morphological measurements and six enzyme loci. Dissimilarities in morphology or enzyme loci were expressed as significant estimates of Mahalanobis squared distance (respectively, D2or G2) between two sample sites.The presence of foothills had no influence on the number of significant G2(age and sex classes combined) or significant D2(age and sex classes separated). For samples near the foothills, adult females had more significant D2than adult males. For samples near the two higher mountains, adult males had more significant D2for site samples from opposite sides. A combination of gene flow and selection is the most plausible explanation for most of these result

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1988.tb01965.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

An experiment on life‐history evolution is described in which replicated populations of the CladoceranDaphnia magna, made up of a standard mixture of clones, were subjected to two contrasting culling regimes, involving removal of small or large individuals. After approximately 150 days of culling, analysis of the life histories showed that genetic differences had emerged between culling regimes. Clones selected by culling small sized individuals grew rapidly through small size classes, whereas those selected by culling large sizes grew slowly through small size classes, with the result that the age at which they became vulnerable to harvesting was delayed. In addition, there was some redistribution of reproduction towards size classes that were not culled. This evolution is consistent with a major decline observed in the yield from populations in which large individuals were culled. We argue that changes of this general kind are likely to take place in exploited populations and that serious consideration should be given to evolutionary aspects of the management of such population

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1988.tb01966.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Enzyme variability at 28 presumptive gene loci was studied, by standard starch gel electrophoresis, in 30 populations belonging to the five recognized species of the landsnailSolatopupafrom its entire NW Mediterranean range.Six genetically differentiated groups can be identified among the 30 populations sampled. These are distinguished by two to 19 diagnostic loci, different levels of genetic variability and populations genetics. They are also significantly different as far as theDvalues are considered. There is no evidence of gene flow among them. Genetically inferred groups correspond in four cases to morphologically distinguished species. In contrast,S. similis, as identified by morphological features, is likely to be a complex of at least two cryptic species.Populations and species ofSolatopupaare characterized by: high fixation of alternative alleles both within and between species; medium‐lo‐low levels of genie variation; heterozygote deficiency; sharp genetic differentiation among population within species; restricted gene flow; and high genetic distances. Genetic variability is partly associated with climatic factors related to moisture.Both deterministic and stochastic processes may play a part in the genetic differentiation ofSolatopupasnails. Founder events seem to be the main factor affecting the genetic structure of populations and perhaps also speciation.Solatopupapopulations display many attributes of populations that may be expected to undergo speciation events involving reorganization of the whole genome after a founder ev

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1988.tb01967.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

A faunal list of oribatid mites collected from the summit of the Cheviot, Northumberland, is given, together with notes on the taxonomy and distribution of several of the species. Special attention is paid to the Arctic‐alpine and European‐alpine species and the list provides further support for the view that the upland areas of Britain are characterized by a common group of oribatid species. It is suggested that these species may be cold hardy or cold tolerant with relatively high supercooling points, enabling them to survive the winter at these higher altitu

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1988.tb01968.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

In recent years several different kinds of sexual selection models have been developed, and tail ornaments in birds have frequently been used as an example of a sexually selected character where the models might apply. However, very little is known about intra‐ and interpopulation variation in ornament size. We have studied the elongated tail ornaments in four species of whydahsVidua, the forktailed flycatcherTyrannus savanaand the Asian paradise flycatcherTerpsiphone paradisi.Ornaments were relatively longer in males with the longest tarsi (‘heterogony’ with positive allometry). Also, tail lengths were remarkably variable within each geographical area, the coefficient of variation (average = 11%) being three times as high as for body size characters. Models, with female preference of ornaments bearing no relation to male viability, usually generate lines of neutral equilibria. Thus, they predict extraordinary variation in ornaments between populations. However, elongated tail ornaments did not show higher geographical variation than the body size characters, suggesting that there is no line of equilibria for these orna

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1988.tb01969.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY