Phylogenetic clustering of individual PSA domains. Trees were inferred by Neighbor-Joining (NJ) from nucleotide distance matrix (TN93 model) calculated individually for all the indicated domains of the L. major Chr12 PSA genes. Individual LRR domains that were present in only a few genes were not analysed. For each domain, those genes that cluster together in the tree (with bootstrap values greater than 74%) are boxed with the same colour. Grey boxes indicate genes that do not cluster with any other genes. Absence of a box indicates that the corresponding domain is absent in the gene. N-ter: PSA N-terminal domain up to the first LRR repeat. LRRs are numbered from N-ter to C-ter according to the LRR alignment (see Additional file 9). ω : refers to the last (C-ter most) LRR of each gene; therefore, LRRω + (ω-1) corresponds to the sequence comprising the last and penultimate LRRs in each gene. (part.): partial; for example, 4 (part.) means portion of LRR 4. CGC-C2: the CGCx(23–26)CxxxxxC domain at the C-ter end of the LRR domain.