N H Barton

..Linkage disequilibria can generate a substantial increase in genetic variance, which is concentrated at sharp gradients in trait means...

..Both methods perform well when tested against simulations with two or four loci...

..Although we demonstrate that low rates of F1 hybridization can lead to substantial introgression, the progress of hybridization and introgression appears to be unpredictable over the short timescales...

..Selection for a modifier that increases recombination is highest when linkage among loci is tight, when beneficial alleles rise from low to high frequency, and when the population size is small...

..Although our analyses clarify the conditions under which drift is expected to increase V(A), we question the evolutionary importance of such increases...

..Moreover, because adaptation is via substitutions of small effect, Fisher's model does not generate the strong effects of single chromosome regions often observed in species crosses...

..This allows the stability of symmetrical solutions to be determined. We apply the method to stabilizing and disruptive selection in a single deme and to selection against heterozygotes in a linear cline...

..Various processes that can cause such an effect have been studied theoretically. It has, however, so far proved hard to discriminate among them empirically...

..This analogy with statistical thermodynamics brings together previous ideas in a general framework, and justifies a maximum entropy approximation to the dynamics of quantitative traits...

..For beta > 1, gene number is systematically overestimated and, conversely, when beta < 1, it is underestimated...

..There is a smooth transition between a system in which a set of loci effectively act independently of each other and one in which they act as a single nonrecombining unit...

..Thus, in a two-dimensional population, barriers to gene flow can be detected through their effect on the spatial pattern of genetic marker alleles...

..We also reconsider experimental data collected on Chlamydomonas moewussi using two of the three methods. Finally, we suggest how the test could be applied to diploid species...

..Although this is consistent with "hybridisation" between the diverging human and chimp lineages, such observations can be explained more simply by the null model of allopatric speciation...

..Moreover, small fluctuations in allele frequency due to random drift can greatly reduce any such effects. This will make it difficult to detect the action of selection from neutral variation alone...

..However, it seems unlikely that such sweeps can be sufficiently frequent to increase significantly the drift of neutral alleles...

..A full age-structured model can also be applied to the data from both types of experiment. For the invasion method, this gives fitness estimates close to those from the discrete generation model...