Two distinct DNA polymerase B families in Caenorhabditis polintons. a) A phylogenetic tree (left) was constructed by applying a ML-based method (IQ-TREE) to a multiple sequence alignment of pPolB proteins from Polintons of 19 nematode species. The genetic architectures of these elements are shown on the right. These Polintons were chosen for initial sequence alignment based on uninterrupted DNA polymerase and other Polinton protein coding regions. Bootstrap supporting values are shown on the top position of tree branches. Abbreviations for inferred polinton components are as follows: PRO for adenovirus-like maturation protease, puORF for Polinton-uncharacterized ORF, ATPase for a packaging ATPase, MCP and mCP for major and minor capsid proteins, INT for a retroviral-like-element integrase, and TIR for terminal inverted repeat. "Uncharacterized" are novel (potentially either spurious or functional) ORFs that have not been previously described in other Polintons. Labels in parentheses denote unique identifiers (UIs) for each Polinton (see supplementary table S1, Supplementary Material online). b) A dot plot and a background box plot show percent (%) amino acid identities between each Polinton protein found in 49 C. briggsae Polintons.