Phylogenetic relationships of Pristionchus species based on ribosomal protein genes. The phylogenetic trees of 18 Pristionchus species and Koerneria sp. were reconstructed from 10,971 bp of concatenated ribosomal protein CDS with the help of the PAUP*4.0b10 software . A. Maximum parsimony tree obtained by the heuristic search algorithm. Multistate characters were interpreted as polymorphisms, gaps asfifth state. The tree was rooted at midpoint. Robustness of the tree topology was evaluated by 1000 bootstrap replications. The support values are shown at the nodes. B. Neighbor-joining tree. The tree was reconstructed using the BIONJ algorithm  and HKY distances . The tree was rooted at midpoint. Numbers at nodes indicate bootstrap support values after 1000 replications. C. Maximum likelihood tree. The best substitution model, corresponding to the GTR+G+I model, was determined by Modeltest 3.7  and the phylogenetic relationships were reconstructed by the heuristic search algorithm. The tree was rooted at midpoint.