Two new Species of Pristionchus (Nematoda: Diplogastridae) include the Gonochoristic Sister Species of P. fissidentatus.

The genus Pristionchus (Kreis, 1932) consists of more than 30 soil nematode species that are often found in association with scarab beetles. Three major radiations have resulted in the "maupasi species group" in America, the "pacificus species group" in Asia, and the "lheritieri species group," which contains species from Europe and Asia. Phylogenetic analysis indicates that a group of three species, including the gonochorists P. elegans and P. bucculentus and the hermaphrodite P. fissidentatus, is basal to the above-mentioned radiations. Two novel species are described here: Pristionchus paulseni sp. n. from Taiwan and P. yamagatae sp. n. from Japan by means of morphology, morphometrics and genome-wide transcriptome sequence analysis. Previous phylotranscriptomic analysis of the complete Pristionchus genus recognized P. paulseni sp. n. as the sister species of P. fissidentatus, and thus its importance for macro-evolutionary studies. Specifically, the gonochorist P. paulseni sp. n. and the hermaphrodite P. fissidentatus form a species pair that is the sister group to all other described Pristionchus species. P. paulseni sp. n. has two distinct mouth forms, supporting the notion that the mouth dimorphism is ancestral in the genus Pristionchus.The genus Pristionchus (Kreis, 1932) consists of more than 30 soil nematode species that are often found in association with scarab beetles. Three major radiations have resulted in the "maupasi species group" in America, the "pacificus species group" in Asia, and the "lheritieri species group," which contains species from Europe and Asia. Phylogenetic analysis indicates that a group of three species, including the gonochorists P. elegans and P. bucculentus and the hermaphrodite P. fissidentatus, is basal to the above-mentioned radiations. Two novel species are described here: Pristionchus paulseni sp. n. from Taiwan and P. yamagatae sp. n. from Japan by means of morphology, morphometrics and genome-wide transcriptome sequence analysis. Previous phylotranscriptomic analysis of the complete Pristionchus genus recognized P. paulseni sp. n. as the sister species of P. fissidentatus, and thus its importance for macro-evolutionary studies. Specifically, the gonochorist P. paulseni sp. n. and the hermaphrodite P. fissidentatus form a species pair that is the sister group to all other described Pristionchus species. P. paulseni sp. n. has two distinct mouth forms, supporting the notion that the mouth dimorphism is ancestral in the genus Pristionchus.

Nine new Pristionchus (Nematoda: Diplogastridae) species from China.

The model organism Pristionchus pacificus and the genus Pristionchus, Kreis, 1932 have been intensively studied in the last decade with contemporary work focusing on the development, evolution, ecology, behavior, neurobiology, and genomics of this group of organisms. In particular, mechanistic studies on the development and evolution of mouth-form plasticity, predation and associated self-recognition processes enabled unique insight into life history strategies and the evolution of novelty. These studies include a comparative research agenda making use of the 39 available species of Pristionchus, all of which can be studied in living cultures. Sampling efforts revealed that Asia represents a biodiversity hotspot for Pristionchus worms. However, previous samplings have a bias towards northern and island areas, largely for logistic reasons. Here, we report on two extensive sampling trips to the Yunnan and Shaanxi provinces in Mainland China. We report the isolation of nine new Pristionchus species by morphology, morphometrics, mating experiments and genome-wide sequence analysis.