Abstract
In this paper, we explore possible conflict between morphological and molecular interpretations of phylogenetic relationships within the well-known peritrichous genus
Zoothamnium
. On the basis of morphological evidence, for a long time this genus has been believed to be a well-defined monophyletic taxon. Nonetheless,
Zoothamnium
exhibits higher genetic diversity than the gross morphology of its species. Here, we used all available genetic information for the small subunit of ribosomal RNA (SSU rRNA) and internal transcribed spacer region (ITS1-5.8S-ITS2) for this genus to reconstruct phylogenies for four datasets (SSU rRNA, ITS1, ITS2, and ITS1-5.8S-ITS2) and a combined dataset (SSU rRNA+ITS1-5.8SITS2) using different phylogenetic methods and with consideration of the secondary structure of the genes. Confidence in phylogenetic tree selection was assessed with the approximately unbiased test. The molecular results showed both that
Zoothamnium
is more likely to be polyphyletic, and morphologically similar genera
Zoothamnopsis
and
Myoschiston
were always nested among
Zoothamnium
species. Accordingly, as with some other groups of ciliates, to understand more fully the correct phylogeny of
Zoothamnium
there remains a need for additional data from both morphological and molecular studies, covering additional
Zoothamnium
spp. and members of closely related genera (e.g.
Zoothamnopsis, Myoschiston
, and
Epistylis
).