Fig. 3

Basal passerine MHC class II β exon 2 sequences in the wider avian context. Bayesian phylogeny of MHC alleles from passerine and non-passerine families, rooted with Crocodylus niloticus. Asterisks denote major branches with posterior probabilities > 90 % and filled circles denote passerine species from the Corvida. Group A contains the majority of sequences from honeyeaters, pardalotes and fairy-wrens. Group B contains the remaining 18 sequences from these species, which comprise nine pseudoalleles and nine sequences with aspartic acid (D) or alanine (A) instead of glutamic acid (E) in the first position (see Additional file 4)