Morphostatic Speciation within the Dagger Nematode Xiphinema hispanum-Complex Species (Nematoda: Longidoridae)

The more we search, the more we find: discovering and expanding the biodiversity in the ring nematode genus Xenocriconemella De Grisse and Loof, 1965 (Nematoda: Criconematidae)

The ring nematode genus Xenocriconemella De Grisse and Loof, 1965 comprises only one nominal species, Xenocriconemella macrodora (Taylor, 1936) De Grisse and Loof, 1965. The initial objective of the present study was to investigate the morphological-morphometric and molecular diversity of 28 X. macrodora populations in the Iberian Peninsula associated with tree forests (mainly Quercus spp.). However, a detailed integrative taxonomic analysis (morphological-morphometric and molecular data) from each population and analysis of this data using principal component analysis (PCA) for morphometric data (including these 28 populations and other 25 X. macrodora populations around the world) and molecular and phylogenetic species delimitation methods revealed that X. macrodora forms a species complex. This species complex is composed by species that are morphometricly and morphologically similar, but clearly different at the molecular level. Three new species are described applying integrative taxonomy, namely as Xenocriconemella iberica sp. nov., Xenocriconemella paraiberica sp. nov. and Xenocriconemella pradense sp. nov. However, the molecular diversity of this species in USA and Italy confirmed that additional species are likely present in this species complex, and the diversity of this group may be higher than expected. The study of X. macrodora topotypes can clarify the position of this species using molecular markers under an integrative approach.

First Report of Aphelenchoides Bicaudatus (Imamura, 1931) Filipjev and Schuurmans Stekhoven, 1941 Associated with Grass in South Africa

Aphelenchoides bicaudatus associated with grass in South Africa was identified morphologically and molecularly. This population is characterized by a body length of 409 - 529 μm, a stylet length of 9.5 - 13 μm, a post-vulval uterine sac of 45 - 50 μm, and the characteristic tail bifurcated at the end with one prong longer than the other. Molecular analyses based on the 18S and ITS rDNA data confirmed the primary morphological identification of the A. bicaudatus species. The obtained phylogenetic trees revealed a close positioning of the South African population to other representatives of A. bicaudatus with the maximum (1.00) posterior probability value. Principal component analysis (PCA) also indicated a variation within the populations of A. bicaudatus. This is the first report of A. bicaudatus from South Africa.

A New Interactive Web-Based Polytomous Key for Species Identification of Pin Nematodes of the Genus Paratylenchus Micoletzky, 1922 (Nematoda: Paratylenchinae) with the Use of Ribosomal and Mitochondrial Genes

Pin nematodes of the genus Paratylenchus comprise 140 species. This group of nematodes is characterized by a quite homogeneous morphology and cosmopolitan distribution and is prevalent in cultivated and natural soil ecosystems. The present study describes the first interactive and illustrated web-assisted polytomous identification key for the genus Paratylenchus. The updated Paratylenchus species polytomous key was based on a wide list of 24 diagnostic characters generated for the 140 species comprising this genus. Here we developed a web-assisted method to achieve an easy and accurate Paratylenchus species characterization that will greatly improve the identification of these plant-parasitic nematodes for many diagnostic laboratories and researchers. However, this identification needs to be completed with the use of molecular markers available for the species due to the existence of species complexes studied in former researches. This idea is pointed in the polytomous key in the specific species complexes up-to-know. In some cases, the presence in the soil as survival stage of few individuals in the fourth-stage juvenile (J4) required the use of molecular markers for species identification. We suggest the use of at least a fragment of mitochondrial COI gene for species identification or the combination of nuclear D2-D3 regions of the 28S rRNA and the COI to complement each marker. However, for some species complexes, the use of the D2-D3 regions alone has not enough resolution to separate the putative species inside the species complex. Web-based polytomous key was constructed using the free software Xper3, for computers and mobile devices (smartphones, tablets, and pocket PCS).

Remarkable Cryptic Diversity of Paratylenchus spp. (Nematoda: Tylenchulidae) in Spain

In previous studies, fifteen species of Paratylenchus, commonly known as pin nematodes, have been reported in Spain. These plant-parasitic nematodes are ectoparasites with a wide host range and global distribution. In this research, 27 populations from twelve Paratylenchus species from 18 municipalities in Spain were studied using morphological, morphometrical and molecular data. This integrative taxonomic approach allowed the identification of twelve species, four of them were considered new undescribed species and eight were already known described. The new species described here are P. caravaquenus sp. nov., P. indalus sp. nov., P. pedrami sp. nov. and P. zurgenerus sp. nov. As for the already known described species, five were considered as first reports for the country, specifically P.enigmaticus, P. hamatus, P. holdemani, P. israelensis, and P. veruculatus, while P. baldaccii, P. goodeyi and P. tenuicaudatus had already been recorded in Spain. This study provides detail morphological and molecular data, including the D2-D3 expansion segments of 28S rRNA, ITS rRNA, and partial mitochondrial COI regions for the identification of different Paratylenchus species found in Spain. These results confirm the extraordinary cryptic diversity in Spain and with examples of morphostatic speciation within the genus Paratylenchus.