Molecular and morphological support for the synonymy of Nephrostomum and Patagifer: discovery of new species and broad geographic connections.

Abstract

In this study, DNA was sequenced from adults of Patagifer Dietz, 1909 and Nephrostomum Dietz, 1909 (Digenea: Echinostomatidae) collected from avian definitive hosts in Nearctic, Neotropic, Palearctic and Afrotropic regions. Phylogenetic analyses of entire mitochondrial genomes, nuclear rDNA operons, and partial 28S, ITS2, cox1, and nad1 all indicate that Nephrostomum is synonymous with Patagifer, which is given priority, and that head-collar characters formerly used to separate these genera represent traits that vary among closely related congeneric species. Low interspecific divergence in partial 28S (0-0.41 %) in Patagifer has contributed to misidentifications, while mitochondrial markers provided greater resolution and revealed greater species diversity. Six species were included in the present study: P. ramosum, P. bilobus, P. vioscai, P. limai, an unidentified species known only from cercariae, and a new species with distinctive head collar morphology, from Theristicus caerulescens in Argentina. In both P. ramosum and P. bilobus, mitochondrial markers show intercontinental distributions that can be plausibly linked to historical transatlantic expansions of their Old-World avian hosts.