Morphological and molecular characterisation of the Saratov population of the European dagger nematode, Xiphinema diversicaudatum (Nematoda: Dorylaimida), with notes on phylogeography of the species

Abstract

Plesiotype specimens of the European dagger nematode, Xiphinema diversicaudatum, were collected in Saratov, Russia, and morphologically, morphometrically and molecularly characterised. PCR with specific primer was developed for rapid diagnostics of this species. Phylogenetic relationships of X. diversicaudatum with other Xiphinema species, as inferred from the analyses of the D2-D3 expansion segments of 28S rRNA, ITS rRNA and coxI mtDNA gene sequences, are also provided. The study revealed that the clade X. diversicaudatum, together with X. bakeri (North America) and X. chengi (Asia), is related to Xiphinema species from the Mediterranean region and likely originated from a common ancestor inhabiting this area. The phylogenetic reconstructions with coxI mtDNA were used to describe the pattern of present genetic diversity of X. diversicaudatum and infer its biogeographical history in Europe. Haplotype diversity of X. diversicaudatum populations from Central Europe was significantly higher than those from south-eastern Europe, central, south-eastern and southern European Russia. It has been hypothesised that, during the Last Glacial Maximum, X. diversicaudatum populations probably persisted in refuge areas in the Carpathian mountains or the Alps, the species subsequently expanding from these areas and colonising other regions in Europe.