Perturbation expansions of multilocus fixation probabilities for frequency-dependent selection with applications to the Hill-Robertson effect and to the joint evolution of helping and punishment.

Natural populations are of finite size and organisms carry multilocus genotypes. There are, nevertheless, few results on multilocus models when both random genetic drift and natural selection affect the evolutionary dynamics. In this paper we describe a formalism to calculate systematic perturbation expansions of moments of allelic states around neutrality in populations of constant size. This allows us to evaluate multilocus fixation probabilities (long-term limits of the moments) under arbitrary strength of selection and gene action. We show that such fixation probabilities can be expressed in terms of selection coefficients weighted by mean first passages times of ancestral gene lineages within a single ancestor. These passage times extend the coalescence times that weight selection coefficients in one-locus perturbation formulas for fixation probabilities. We then apply these results to investigate the Hill-Robertson effect and the coevolution of helping and punishment. Finally, we discuss limitations and strengths of the perturbation approach. In particular, it provides accurate approximations for fixation probabilities for weak selection regimes only (Ns < or = 1), but it provides generally good prediction for the direction of selection under frequency-dependent selection.

[W. J.] Brunnel [250 cmc], Fred Dove [750 cmc], [Geoffrey] Hill [550 cmc], sur Triumph [concurrents de la course motocycliste Paris-Nice] : [photographie de presse] / [Agence Rol]

Référence bibliographique : Rol, 57951

¿Cuando los deseos no lo son todo? Hacienda Pública en Bolivia, 1882-2007

El presente trabajo pretende un análisid de la intervención estatal en Bolivia a través de la hacienda pública. El trabajo supone un avance respecto a anteriores estudios por dos motivos. Por un lado, porque presenta un horizonte temporal de análisis mucho más amplio: se inicia en el último cuarto de siglo XIX y llega hasta la actualidad. Por otro lado, porque presenta evidencia cuantitativa totalmente inédita: una estimación de los ingresos y gastos fiscales del Estado Central desagregados de acuerdo a parámetros internacionales.