Evolution under the multilocus Levene model without epistasis.
Evolution under the multilocus Levene model is investigated. The linkage map is arbitrary, but epistasis is absent. The geometric-mean fitness, w(rho), depends only on the vector of gene frequencies, rho; it is nondecreasing, and the single-generation change is zero only on the set, Lambda, of gametic frequencies at gene-frequency equilibrium. The internal gene-frequency equilibria are the stationary points of w(rho). If the equilibrium points rho of rho(t) (where t denotes time in generations) are isolated, as is generic, then rho(t) converges as t-->infinity to some rho. Generically, rho(t) converges to a local maximum of w(rho). Write the vector of gametic frequencies, p, as (rho,d)(T), where d represents the vector of linkage disequilibria. If rho is a local maximum of w(rho), then the equilibrium point (rho,0)(T) is asymptotically stable. If either there are only two loci or there is no dominance, then d(t)-->0 globally as t-->infinity. In the second case, w(rho) has a unique maximum rho and (rho,0)(T) is globally asymptotically stable. If underdominance and overdominance are excluded, and if at each locus, the degree of dominance is deme independent for every pair of alleles, then the following results also hold. There exists exactly one stable gene-frequency equilibrium (point or manifold), and it is globally attracting. If an internal gene-frequency equilibrium exists, it is globally asymptotically stable. On Lambda, (i) the number of demes, Gamma, is a generic upper bound on the number of alleles present per locus; and (ii) if every locus is diallelic, generically at most Gamma-1 loci can segregate. Finally, if migration and selection are completely arbitrary except that the latter is uniform (i.e., deme independent), then every uniform selection equilibrium is a migration-selection equilibrium and generically has the same stability as under pure selection.
Nagylaki
Thomas
T
Department of Ecology and Evolution, The University of Chicago, 1101 East 57th Street, Chicago, IL 60637, USA. nagylaki@uchicago.edu
D005075:Biological Evolution; D002874:Chromosome Mapping; D004843:Epistasis, Genetic; D015810:Linkage Disequilibrium; D008957:Models, Genetic