Distinguishing species in Paramacrobiotus (Tardigrada, Macrobiotidae) via compensatory base change analysis of internal transcribed spacer 2 secondary structures

Morphologically almost identical organisms classified within Paramacrobiotus (Tardigrada) could be distinguished via an analysis of internal transcribed spacer 2 (ITS2) secondary structures. Sequences of five samples from four different continents were determined, annotated and their secondary structures predicted. A tree based on a combined sequence-structure alignment was reconstructed by Profile Neighbor-Joining. The topology obtained is consistent with a tree based on a distance matrix of compensatory base changes (CBCs) between all ITS2 sequence-structure pairs in the global multiple alignment. Recently it was shown that with 93% confidence a CBC can be used to distinguish species. Therefore the CBC analysis indicates that Paramacrobiotus consists of at least three sibling species distinguishable with molecular evidence.