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Adaptation and reproductive isolation, the engines of biological diversity, are still elusive when discussing the genetic bases of speciation. Namely, the number of genes and magnitude of selection acting positively or negatively on genomic traits implicated in speciation is contentious. Here, we describe the first steps of an ongoing research program aimed at understanding the genetic bases of population divergence and reproductive isolation in the lake whitefish ( Coregonus clupeaformis). A preliminary linkage map originating from a hybrid cross between dwarf and normal ecotypes is presented, whereby some of the segregating AFLP markers were found to be conserved among natural populations. Maximum-likelihood was used to estimate hybrid indices from non-diagnostic markers at 998 AFLP loci. This allowed identification of the most likely candidate loci that have been under the influence of selection during the natural hybridisation of whitefish originating from different glacial races. As some of these loci could be identified on the linkage map, the possibility that selection of traits in natural populations may eventually be correlated to specific chromosomal regions was demonstrated. The future prospects and potential of these approaches to elucidate the genetic bases of adaptation and reproductive isolation among sympatric ecotypes of lake whitefish is discussed. [ABSTRACT FROM AUTHOR]

Genetic research in fishes is poised to contribute a vast amount of information on the structural organization and function of vertebrate genomes. Recent advances in molecular biology have made possible the widescale characterization of genomes in all living organisms. This includes defining chromosomes at the cytological level down to their linear composition at individual nucleotide base pairs. Pioneering gene mapping studies into the genomes of fishes will only serve as the starting point for more detailed studies into the function of these genomes. Future research directed at understanding the mechanisms of gene actions and interactions will benefit all areas of biology, including ecology, ethology, evolution, and physiology. Gene mapping data from brown trout and rainbow trout are used to exemplify how basic information on gene transmission in a species may help to localize centromeres onto a genetic map and identify chromosomal regions possessing a high degree of segregation distortion. Genetic maps may also be used to identify differences in recombination levels among individuals and between the sexes when multiple mapping families are utilized in studies. Observations of this type are the antecedents to more complex biological investigations on the genetic architecture underlying these phenomena. [ABSTRACT FROM AUTHOR]