New evidence on cryptic speciation in soil-inhabiting nematodes, with morphological and molecular characterisation of Xiphinema sangesarense n. sp. (Dorylaimida: Longidoridae) from north-central mountains of Iran

A new species of the dagger nematode, genus Xiphinema, was recovered from the rhizospheric soil samples collected from rangelands in Semnan province, north-central Iran, and described based upon both morphological and molecular data. Xiphinema sangesarense n. sp. is characterised by 3.7-4.8 mm long females having 136-154 μm long odontostyle, 74-87 μm long odontophore, two equally developed genital tracts with crystalloid bodies in the tubular part of the uterus, short dorsally convex, ventrally slightly convex tail with a mucron at the end, four juvenile developmental stages and males present, functional. The new species most closely resembles X. azarbaijanense and is regarded as its tentative cryptic form, but was separated from it by reproductive mode, and morphological and molecular differences. Compared to X. afratakhtehense, the second similar species, it could be separated based on morphological differences, especially characteristics of juveniles and molecular data. Furthermore, the new species has close morphology with five know species, namely: X. aequum, X. horvatovicae, X. illyricum, X. macedonicum and X. vuittenezi, in terms of morphological characteristics (mainly structure of uterus and similar female tail), and their differences are discussed. In phylogenetic analyses of the new species using several sequences of two partial large subunit (LSU) D2-D3, and internal transcribed spacer (ITS) sequences, the new species formed a clade with Xiphinema sp. in the LSU tree, and in the ITS tree it formed a clade with X. afratakhtehense. In the cytochrome c oxidase I (COI) gene tree, sequences of the new species occupied a placement inside the clade of several sequences of X. afratakhtehense.