Phylogeny of hsp82 bdelloid rotifers (Mark Welch & Meselson 2000).  The ancient lineages A and B are nearly 50% divergent at 4-fold degenerate positions, implying a separation of 80-100 million years.  Both lineages are still present in genomes of P. roseola and M. quadricornifera, as would be expected if recombination were lost between alleles prior to speciation. Other nodes are attributed to duplication events (D) or to separations of taxa (S).  Dashed lines indicate lineages that should have originated at species separations but were not found and may have been lost or have been undetected.  Numbers at nodes are percentages of 1000 bootstrapped alignments (when over 50%) of 4-fold and 3-fold degenerate codon positions supporting each clade by maximum parsimony (above the line) or by neighbor-joining (below the line) using B. plicatilis AUS, a member of the sister-class Monogononta, as an outgroup.  The same tree topologies are found using neighbor-joining of synonymous site differences.  In all analyses, fewer than 10% of bootstrapped alignments resulted in trees which lacked an ancient A–B divergence.