Morphological and Molecular Diversity among Pin Nematodes of the Genus Paratylenchus (Nematoda: Paratylenchidae) from Florida and Other Localities and Molecular Phylogeny of the Genus.

Abstract

Pin nematodes (Paratylenchus spp.) are root parasites found worldwide. They have different life cycles and feeding habits and can damage a wide range of plants. A remarkable diversity of pin nematode species was found in soil samples from Florida and other states of the USA, Canada, and Spain. Using integrative taxonomy, two new species (Paratylenchus hawaiiensis sp. n. and P. roboris sp. n.), six valid species (Paratylenchulus acti, P. aquaticus, P. goldeni, P. paralatescens, P. minutus (=P. shenzhenensis syn. n.), and P. straeleni), and two undescribed species were identified from Florida; P. goldeni, P. hamatus, P. hamicaudatus, P. holdemani, and P. pedrami were found in California, P. minutus in Hawaii, P. goldeni in Oregon and Washington, and one new species, Paratylenchus borealis sp. n., in Alaska. Outside the USA, Paratylenchus projectus was detected in samples from Canada and Spain as well as P. holdemani and Paratylenchus sp. from Spain. The pin nematode species from Belgium and Russia identified in former studies as Paratylenchus sp. F was herein described as a new species with the name of P. borealis sp. n., using a population from Alaska. Previously reported molecular type A of P. aquaticus from Hawaii was reclassified as P. hawaiiensis sp. n., using a population from Florida. Paratylenchus roboris sp. n. from Florida has obese sedentary females with a stylet 63-71 µm long. The results of the molecular analysis of P. shenzhenensis from Florida and China indicated that it was conspecific with P. minutus from Hawaii and considered here as its junior synonym. New 26 D2-D3 expansion segments of 28S rRNA, 17 ITS rRNA, and 20 COI gene sequences were obtained in this study. Phylogenetic relationships of Paratylenchus are reconstructed using the D2-D3 of 28S rRNA, ITS rRNA, and COI gene sequences. Congruence of molecular and morphological evolution and species identification problems are discussed. Obese females were found in two major clades of Paratylenchus. The problem of reference materials is discussed, and it is proposed to make more efforts to collect topotype materials of known Paratylenchus species for molecular study.