N Barton

..Thus, the influence of the complex pedigree of descendants on an individual's genetic contribution to the population can be summarized through a single number: its reproductive value...

..These arguments are illustrated by comparing the interaction between good and bad mutations at unlinked loci under the infinitesimal model...

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

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

..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...

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..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...

..In an elegant Perspective, Barton discusses two reports (Higgie et al. and Hendry et al.) showing that selection can cause reproductive isolation between two populations within a dozen or so generations...

..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...

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

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

..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 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...

..The hybrid zone may be approaching a state in which the gene pools are homogenized at all but the selected loci, not dissimilar from an early stage of sympatric divergence...

..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...

..It is clear that the rate of species-wide substitutions is typically far too low to generate appreciable selection for recombination. However, local sweeps within a subdivided population may be effective...

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

..A sharp threshold is only seen if survival in the 'wrong' niche is low; otherwise, strong isolation is impossible. Gene flow from divergent demes makes speciation much easier in parapatry than in sympatry...

..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...

..It is plausible that spatial and temporal fluctuations in selection generate much more fitness variance, and hence selection for recombination, than can be explained by uniformly deleterious mutations or species-wide selective sweeps...

..We find that selection for increased assortment is weak and that where increased assortment is costly, it does not invade...

..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...

..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...

..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...

..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...

..We show how the method can be modified for small mutation rates (4Nmicro --> 0). We outline how this method describes epistatic interactions as, for example, with stabilizing selection...

..An application to sequence data from an African population of Drosophila melanogaster shows that the bottleneck hypothesis is unlikely and that one or several selective sweeps probably occurred in the recent history of this population...

..5) are needed for significant conversion of higher-order components. We discuss alternative approaches to modeling multilocus epistasis and understanding its consequences...

..Instead, B. variegata-like individuals among the adults contributed disproportionately to the offspring cohort, consistent with their preference for the type of breeding habitat in which this study was conducted...

..We present numerical results that support our analytical approximations and discuss our results in connection to relevant data and alternative variance-maintaining mechanisms...

..Among the 40 isolated CA microsatellites, we noted a preponderance of compound and frequently interleaved CA-TA repeats as well as a striking polarity at the 5' end of the repeats...