MIGRATION PATTERNS AND THE DEVELOPMENT OF MULTILOCUS ASSOCIATIONS IN A SELFING ANNUAL, TRITICUM DICOCCOIDES.

Migration patterns in wild emmer wheat, Triticum dicoccoides, were inferred from single-locus and multilocus genetic distributions based primarily on expectations derived from single-locus and multilocus cline theory. Populations from five collections displayed a large amount of multilocus structuring, as indicated by high values of gametic-phase disequilibrium between pairs of loci and by high values of multilocus associations. Analyses of the distributions of individual alleles, however, indicated that alleles had apparent independent centers of origin and that at least some independent dispersal within regions occupied by ecotypes or races of wild emmer had occurred. The distribution of the degrees of multilocus association suggests that there has been a net migration of the northern or Qazrin race south and west into the pocket occupied by the Yehudiyya race. The results suggest that ecotypic differentiation may be independent and may antedate electrophoretically determined differentiation in these populations. There is no convincing evidence that the multilocus associations represent coadapted complexes; rather they appear to involve associations of mutant alleles that have been accentuated and preserved by low recombination rates and gene-flow barriers within previously differentiated ecotypes.