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

Matthias Herrmann,Kohta Yoshida,Christian Rödelsperger,Natsumi Kanzaki,Christian Weiler,Ralf J Sommer

doi:10.21307/jofnem-2019-024

Abstract

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.

Highlights

The genus Pristionchus (Kreis, 1932) with the model organism P. pacificus has emerged as an important group of nematodes to study various aspects of macroevolution, including comparative developmental biology, phenotypic plasticity, evolutionary ecology, and comparative genomics (Sommer et al, 1996; Sommer, 2015)
P. paulseni sp. n. was isolated from Taiwan and represents the gonochoristic sister species of P. fissidentatus
The general morphology, e.g., body shape and gonadal structures, is described first as common characters, and the distinctive characters are described for each species

Summary

Introduction

The genus Pristionchus (Kreis, 1932) with the model organism P. pacificus has emerged as an important group of nematodes to study various aspects of macroevolution, including comparative developmental biology, phenotypic plasticity, evolutionary ecology, and comparative genomics (Sommer et al, 1996; Sommer, 2015). N. was isolated from Taiwan and represents the gonochoristic sister species of P. fissidentatus This species exhibits a mouth dimorphism found in many Pristionchus species, suggesting that mouth-form plasticity is an ancestral character in the genus. N. and P. fissidentatus form a new species group of the genus that represents the sister group to all described beetle-associated Pristionchus species. In order to characterize both species, morphology, morphometrics, mating experiments and genome-wide transcriptome sequencing are used

Methods

Results

Conclusion