During nematode surveys in southern Spain and Italy 14 populations of Xiphinema species tentatively identified as Xiphinema americanum-group were detected. Morphological and morphometrical studies identified three new species and six known Xiphinema americanumgroup species, viz.: Xiphinema parabrevicolle n. sp., Xiphinema parapachydermum n. sp., Xiphinema paratenuicutis n. sp., Xiphinema duriense, Xiphinema incertum, Xiphinema opisthohysterum, Xiphinema pachtaicum, Xiphinema rivesi, and Xiphinema santos. The Xiphinema americanum-group is the most difficult Xiphinema species group for diagnosis since the morphology is very conservative and morphometric characters often overlap. This group includes vectors of several important plant pathogenic viruses that cause significant damage to a wide range of agricultural crops. Molecular characterisation of these species using D2-D3 expansion regions of 28S rRNA, 18S rRNA, ITS1-rRNA and the protein-coding mitochondrial gene, cytochrome oxidase c subunit 1 was carried out and maximum likelihood and Bayesian inference analysis were used to reconstruct phylogenetic relationships among these species and with other Xiphinema americanum-group species.

P. (2010). Molecular analysis and comparative morphology to resolve a complex of cryptic Xiphinema species. -Zoologica Scripta, 39, 483-498.During nematode surveys in cultivated and natural environments in southern Spain nine populations of parthenogenic Xiphinema species tentatively identified as Xiphinema cf. pyrenaicum and one population morphologically close to Xiphinema turcicum were detected. Surveys in southern France also identified one population resembling X. pyrenaicum. We developed a comparative study among these related Xiphinema species, including topotypes of two species of this group previously synonymized, viz. Xiphinema hispanum and Xiphinema sphaerocephalum, by considering morphological and morphometrical features together with molecular data from nuclear ribosomal RNA genes (D2-D3 expansion segments of 28S, ITS1, and partial 18S). Morphological and morphometrical results identified eight of the Spanish populations as Xiphinema nuragicum (previously synonymized with X. pyrenaicum) whereas the ninth population was identified as Xiphinema adenohystherum (also synonymized with X. pyrenaicum). The species X. adenohystherum, X. nuragicum, X. pyrenaicum, and X. sphaerocephalum were shown to be morphologically almost indistinguishable but clearly separated by phylogenetic analyses, thus constituting a complex of cryptic species. Consequently, X. adenohystherum, X. nuragicum, and X. sphaerocephalum were re-established as valid species. Similarly, X. hispanum (morphologically similar to X. aceri) was also shown as a valid species. Xiphinema turcicum, morphologically related to X. pyrenaicum complex by its rounded tail, uterus with a pseudo-Z-differentiation and small spines, was phylogenetically distant to these species based on D2-D3 expansion segments of 28S and ITS1, which suggests a morphological convergence in their evolution.

The phylum Nematoda includes the genus Longidorus, a remarkable group of invertebrates that are polyphagous root‐ectoparasites of many plants including various agricultural crops and trees. Damage is caused by direct feeding on root cells as well as by transmitting nepoviruses. Species discrimination in Longidorus is complicated by phenotypic plasticity (intraspecific variability and minor interspecific differences) leading to potential misidentification. We conducted nematode surveys in cultivated and natural environments in southern Spain that detected 11 species of Longidorus. We developed a comparative study amongst these related species by considering morphological and morphometric features together with molecular data from nuclear ribosomal RNA genes [D2‐D3 expansion segments of large ribosomal subunit (28S), internal transcribed spacer 1 (ITS1), and partial small ribosomal subunit (18S)]. The results of our molecular and phylogenetic analyses confirmed the morphological hypotheses and allowed the delimitation and discrimination of three new species of the genus, described herein as Longidorus baeticus sp. nov., Longidorus oleae sp. nov., and Longidorus andalusicus sp. nov., and eight known species (Longidorus alvegus, Longidorus crataegi, Longidorus fasciatus, Longidorus intermedius, Longidorus iuglandis, Longidorus magnus, Longidorus rubi, and Longidorus vineacola). Phylogenetic analyses of Longidorus spp. based on the three molecular markers resulted in a general consensus of these species grouping, as lineages were maintained for the majority of species (i.e. species with a conoid‐rounded lip region, amphidial fovea asymmetrically bilobed, female tail bluntly rounded), but not in some others (i.e. positions of L. crataegi, L. intermedius, and L. rubi were quite variable). To date, this is the most complete phylogenetic analysis for Longidorus and Paralongidorus species, with the highest number of species included. No correspondence between phylogenetic trees and morphological characters was found for ribosomal markers, with the exception of amphidial shape. Thus, polyphasic identification, based on integration of molecular analysis with morphology, is a tool beyond doubt in Longidorus identification. © 2013 The Linnean Society of London