Abstract
The most prevalent dagger nematode recovered from rhizospheric soil samples of forest trees in the Afrātakhteh region of Golestan province (Iran) was Xiphinema afratakhtehnsis sp. nov. and it is described and illustrated with integrative approaches using both morphological and molecular criteria. It belongs to the morphospecies group 6 of the intragenic historical grouping of Xiphinema non-americanum species. The new species is characterized by females with 3.3–4.9 mm sized body, lip region separated from the rest of body by a depression, anteriorly expanded, 16–18 μm wide, vulva located at 47.2–58.5%, odontostyle 155–173 μm and odontophore 89–107 μm long, female genital system composed of two equally developed branches, the tubular part of each having spines, short symmetrically rounded female tail to symmetrically rounded with a small mucro-like projection at the end in a few females, rare males (n = 1 out of 74 females) with 83 μm long dorylaimoid spicules and four juvenile developmental stages. The third-stage juveniles (J3) have a characteristic tail shape (short, symmetrically conical with a club-shaped long mucro) demarcating the species, and being typologically useful for its separation from closely similar species (except X. cohni, with currently no data on its juvenile stages) viz. X. adenohystherum, X. iranicum, X. mazandaranense, X. nuragicum, X. pyrenaicum, X. robbinsi, X. sphaerocephalum and X. zagrosense. Molecular phylogenetic studies using genomic (partial large subunit and internal transcribed spacer 1 ribosomal RNA genes: D2-D3 and ITS1 rDNA) and mitochondrial cytochrome c oxidase subunit I gene (COI mtDNA) revealed the new species forming a unique lineage in all reconstructed trees using Bayesian inference (BI) and maximum likelihood (ML) methods. The sequenced isolates of the new species formed a monophyletic group in the D2-D3 tree. The sequenced isolates of the new species for their COI mtDNA formed four subclades in COI mtDNA phylogeny, and four haplotypes in corresponding analysis.
Highlights
The dagger nematode genus Xiphinema was established in 1913 by Cobb [1] with the monotypic designation of X. americanum Cobb, 1913 [1]
Adults and juvenile paratypes extracted from soil samples collected from the same locality as the holotype; mounted in pure glycerin and deposited in the following nematode collections: five paratype females, two paratype juveniles from each stage and populations of other localities deposited at the Nematode Collection of the Faculty of Agriculture, Tarbiat Modares University, Tehran, in the Afrātakhteh region of Golestan province (Iran); five paratype females and two paratype juveniles from each stage were deposited at USDA Nematode Collection, Beltsville, MD; eight paratype females and other paratype juveniles at WANECO collection, Wageningen, The Netherlands; and several voucher specimens at Ghent University Museum, Zoology Collections, Ghent, Belgium, Nematode Collection of the Faculty of Agriculture, Tarbiat Modares University, Tehran, Iran and USDA Nematode Collection, Beltsville, MD
Xiphinema afratakhtehnsis sp. nov. is a parthenogenetic species characterized by medium sized females 3.3–4.9 mm long, anteriorly wide-expanded lip region 16–18 μm wide, 155–173 μm long odontostyle, 89–107 μm long odontophore, vulva located at 47.2– 58.5%, two developed female genital tracts having discernible spines in fresh and permanent mounts, symmetrically rounded short tail sometimes with a small bulge at the end in few females, rare male, and four juvenile developmental stages, J1-J4, with J3 having a characteristic tail morphology, helping discriminate it from eight out of nine morphologically close species
Summary
The dagger nematode genus Xiphinema was established in 1913 by Cobb [1] with the monotypic designation of X. americanum Cobb, 1913 [1]. From 1996 (after publication of the second supplement key) to the present, 54 extra species were added to the genus and five previously synonymized species (their synonymization was accepted by Coomans et al [16]) have been revalidated using molecular phylogenetic studies [17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55] (S1 Table)
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