Rotylenchus cretensis n. sp. and R. cypriensis Antoniou 1980 (Nematoda: Hoplolaimidae) recovered from the rhizosphere of olive at Crete (Greece) with a molecular phylogeny of the genus

Abstract

A new and a known species of Rotylenchus from Crete, each collected from the rhizosphere of olive, are described and illustrated based on morphological, morphometric and molecular studies. Rotylenchus cretensis n. sp. is characterised by having a truncate lip region with irregular longitudinal striation, lateral field areolated only in pharynx region, stylet length less than 41 μm, vulva located at 53–59 %, conoid-rounded to dorsally convex-conoid female tail with 7–11 annuli and specific D2-D3 of 28S, ITS, and partial 18S rRNA. Rotylenchus cretensis n. sp. appears to be similar to R. urmiaensis, having overlapping character ranges. Rotylenchus cretensis is also similar to R. striaticeps from which has got shorter stylet length (35.5–41.5 vs 39–50 μm), female tail shape (conoid-rounded to dorsally convex-conoid vs rounded), shorter spicules length (34–40 vs 41–50 μm), and phasmid position (varying from at level to three annuli posterior to the anus vs at level to seven annuli anterior to anus). Multivariate analysis of variance performed on R. cretensis n. sp., as well as two populations of R. striaticeps and R. urmiaensis from Iran on combined morphometric characters data set revealed a significant effect by species populations, indicating that closely morphological and morphometrically species differed significantly from each other. Additionally, analysis of variance showed that morphometric characters such as lip region width, distance from phasmid to tail tip (PHS) or a ratio can be used as key morphometric characters for species differentiation in this group. The results of phylogenetic analyses based on D2-D3 region, ITS of rRNA, and the partial 18S sequences confirmed the close molecular relationships between R. cretensis n. sp., R. urmiaensis and R. striaticeps, but clearly support the proposal of R. cretensis n. sp. as a new species. Also, the recognition of this cryptic species within Rotylenchus shows that the biodiversity of these nematodes is still not fully understood and requires further studies. Additionally, R. cypriensis is described and molecularly analysed for first time in Greece.