Phylogeny of salmonine fishes based on growth hormone introns: Atlantic (Salmo) and Pacific (Oncorhynchus) salmon are not sister taxa

Though salmonid fishes are a well-studied group, phylogenetic questions rem ain, especially with respect to genus-level relationships. These questions were addressed with duplicate growth hormone (GrH) introns. Intron sequence s from each duplicate gene yielded phylogenetic trees that were not signifi cantly different from each other in topology. Statistical tests supported v alidity of the controversial monotypic genus Parahucho, monophyly of Oncorh ynchus, and inclusion of Acantholingua ohridana within Salmo. Surprisingly, GH1 intron C (GH1C) did not support the widely accepted hypothesis that On corhynchus (Pacific salmon and trout) and Salmo (Atlantic salmon and trout) are sibling genera; GH2C was ambiguous at this node. Previously published data were also examined for support of Salmo and Oncorhynchus as sister tax a and only morphology showed significant support. If not sister taxa, the i ndependent evolution of anadromy - the migration to sea and return to fresh water for spawning - is most parsimonious. While there was incongruence wit h and among published data sets, the GH1C intron phylogeny was the best hyp othesis, based on currently available molecular data. (C) 1999 Academic Pre ss.