Molecular phylogeny of Malenchus and Filenchus (Nematoda: Tylenchidae)

Abstract

The family Tylenchidae is phylogenetically important to understanding early‐branching Tylenchomorpha and to assess soil ecosystems. In this study, we focus on Malenchus and Filenchus as representatives of the Tylenchidae. Samples collected worldwide result in 58 new sequences, and light microscopy and transmission electron microscopy provide details on morphological features. For the first time, comprehensive morphological data are evaluated in the context of a molecular framework, thus highlighting the phylogenetic and evolutionary complexity of this structurally minimalistic group. Results show that the genus Filenchus is polyphyletic in both the 18S and 28S rDNA phylogeny, while Malenchus is polyphyletic and monophyletic in the 28S rDNA and the 18S rDNA, respectively. Ultrastructural study demonstrates specific aspects of lateral cuticular incisures, cuticular layering and the amphideal fovea are surprisingly congruent with the obtained molecular phylogenies, while classical characteristics such as cuticle annulations are evolutionary highly plastic and mosaic in distribution. The study also reveals the shortage of D2/D3 domain in 28S rDNA as a phylogenetic marker for early‐branching Tylenchomorpha.

Redefinition of Genus Malenchus Andra’ssy, 1968 (Tylenchomorpha: Tylenchidae) with Additional Data on Ecology

“…However, a recent study shows that annulations can vary from prominent and folded to rather faint (Qing et al, 2017). These variations can be explained by different combinations of annuli width (a in Fig.…”

“…After mounting on stubs samples were coated with gold and observed with a JSM-840 EM (JEOL, Tokyo, Japan) at 12 kV. For transmission electron microscope (TEM), specimens were fixed, ultra-thin sections were cut and sections were stained as detailed by Qing et al (2017). Sections were observed with a JEOL JEM 1010.…”

“…Body behind vulva usually tapers markedly so that width at anus is about half of that at vulva, but an elongated-cylindrical shape similar to that of other genera in Tylenchidae is also possible (e.g., Malenchus sp. C163 nested within Malenchus clade [Qing et al, 2017] but with elongatedcylindrical shape behind vulva).…”

“…The only genus review was made more than 30 years ago based on a limited number of morphological details (Andr assy, 1981). Recently, molecular methods have revealed a phylogenetic position for the genus Malenchus (Yaghoubi et al, 2015;Qing et al, 2016Qing et al, , 2017, but the need for a review is growing. In this present study, we examined type or paratype of 12 species together with 10 populations worldwide.…”

“…In this present study, we examined type or paratype of 12 species together with 10 populations worldwide. We do not intend to establish new nor to synonymize current taxon but rather to summarize morphological variations and analyze the results in a phylogenical context, as most of the taxonomically important characters are generally absent or incomplete in the original description (Qing et al, 2017).…”