MBE Advance Access published online on March 20, 2008
Molecular Biology and Evolution, doi:10.1093/molbev/msn065
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Research Article |
Evolutionary Patterns of MHC Class II B in Owls and their Implications for the Understanding of Avian MHC Evolution
,*
* Laboratory for Conservation Biology, Department of Ecology and Evolution, Biophore, University of Lausanne, CH-1015 Lausanne, Switzerland
Department of Ecology and Evolution, Biophore, University of Lausanne, CH-1015 Lausanne, Switzerland
Corresponding author: Reto Burri, Laboratory for Conservation Biology, Department of Ecology and Evolution, Biophore, University of Lausanne, CH-1015 Lausanne, Switzerland; Tel: ++41 (0)21 692 41 74, Fax ++41 (0)21 692 41 65, E-Mail: reto.burri{at}unil.ch.
Received for publication December 6, 2007. Revision received March 11, 2008. Accepted for publication March 14, 2008.
Owing to its special mode of evolution and central role in the adaptive immune system, the major histocompatibility complex (MHC) has become the focus of diverse disciplines such as immunology, evolutionary ecology and molecular evolution. MHC evolution has been studied extensively in diverse vertebrate lineages over the last few decades, and it has been suggested that birds differ from the established mammalian norm. Mammalian MHC genes evolve independently, and duplication history (i.e. orthology) can usually be traced back within lineages. In birds, this has been observed in only three pairs of closely related species. Here we report strong evidence for the persistence of orthology of MHC genes throughout an entire avian order. Phylogenetic reconstructions of MHC class II B genes in fourteen species of owls trace back orthology over tens of thousands of years in exon 3. Moreover, exon 2 sequences from several species show closer relationships than sequences within species, resembling trans-species evolution typically observed in mammals. Thus, while previous studies suggested that long-term evolutionary dynamics of the avian MHC was characterized by high rates of concerted evolution, resulting in rapid masking of orthology, our results question the generality of this conclusion. The owl MHC thus opens new perspectives for a more comprehensive understanding of avian MHC evolution.
Key Words: birds • gene duplication • major histocompatibility complex • molecular evolution • orthology • Strigiformes