Phylogenetic distribution of the PARP family across eukaryotes. The topology of the schematic tree is based on recent evidence from single- and multi-gene phylogenetic analyses of eukaryotes or subgroups thereof. Some nodes, especially the deepest ones (e.g. monophyly of Excavates, Plantae or Chromalveolates + Rhizarians), remain controversial; these uncertainties do not affect the conclusions concerning the evolutionary history of the PARP family. Branch lengths do not reflect genetic distance. Presence or absence of PARP proteins are indicated by a red + or a blue -, respectively. For each species or group, PARP family members are listed with the clade numbers introduced in Figure 1. For an expanded phylogeny of the fungi, please see Figure 11. Accession numbers of the genes and details on the source of data for individual taxa is provided in Additional files 1 and 2. The six eukaryotic supergroups are indicated as follows: Amoebozoa, purple; Opisthokonta, red; Excavata, orange; Plantae, green; Rhizaria, black; Chromalveolates, blue. ND, no data; NA, not applicable; O, orphan PARPs, as discussed in the text; 3?, reflects the ambiguity of placement of the Tetrahymena proteins into this clade, as discussed in the text.