Abstract
Many hypotrich genera, including
Trachelostyla
, are taxonomically challenging and in a need of integrative revision. Using morphological data, molecular phylogenetic analyses, and internal transcribed spacer 2 (ITS2) secondary structures, we attempt to cast more light on species relationships within the genus
Trachelostyla
. The present multifaceted approach reveals that (1) a large-sized species with numerous macronuclear nodules, isolated from sandy littoral sediments in southern China, is new to science and is endowed here with a name,
T. multinucleata
spec. nov.; (2) two other Chinese populations previously identified as
T. pediculiformis
represent undescribed species; and (3) multigene phylogeny is more robust than single-gene trees, recovering the monophyly of the genus
Trachelostyla
with high bootstrap frequency. Additionally, ITS2 secondary structures and the presence of compensatory base changes in helices A and B indicate the presence of four distinct taxa within the molecularly studied members of the genus
Trachelostyla
. Molecular data are more suitable for delimitation of
Trachelostyla
species than morphological characters as interspecific pairwise genetic distances of small subunit (18S) rDNA, ITS1-5.8S-ITS2, and large subunit (28S) rDNA sequences do not overlap, whereas ranges of multiple morphometric features might transcend species boundaries.