Evolution of multiple paralogous adenosine kinase genes in the moss genus Hygroamblystegium: phylogenetic implications.

Maximum likelihood analyses of DNA sequences from two chloroplast regions, trnL-trnF and atpB-rbcL, and the internal transcribed spacers of 18S-5.8S-26S rRNA gene array, were performed to resolve species relationships within the moss genus Hygroamblystegium. Constraining morphospecies to monophyly resulted in significantly less likely trees for H. tenax, but not for the other species. The lack of support for most clades and the partial incongruence among topologies necessitated the use of another independent, more variable region, namely the adenosine kinase gene (adk). Sequences for adk were polymorphic but were present as multiple copies within individuals, making parology a problem for phylogenetic analyses. Adk evolution was reconstructed using a reconciled gene tree approach in which duplications and losses were minimized in the context of an estimate of the species tree derived from the analysis of the cp and nrDNA sequence data. Additional resolution of the species tree was then obtained by searching for reconstructions that further reduced adk duplications and losses. All the traditionally recognized morphospecies appeared to be polyphyletic in the resulting tree. Together with previous data from different molecular markers, the results support the interpretation that Hygroamblystegium represents a recent radiation in which molecular and morphological evolution have been uncoupled.