Abstract
During the past twenty years, a number of molecular analyses have been performed to determine the evolutionary relationships of Onchocercidae, a family of filarial nematodes encompassing several species of medical or veterinary importance. However, opportunities for broad taxonomic sampling have been scarce, and analyses were based mainly on 12S rDNA and coxI gene sequences. While being suitable for species differentiation, these mitochondrial genes cannot be used to infer phylogenetic hypotheses at higher taxonomic levels. In the present study, 48 species, representing seven of eight subfamilies within the Onchocercidae, were sampled and sequences of seven gene loci (nuclear and mitochondrial) analysed, resulting in the hitherto largest molecular phylogenetic investigation into this family. Although our data support the current hypothesis that the Oswaldofilariinae, Waltonellinae and Icosiellinae subfamilies separated early from the remaining onchocercids, Setariinae was recovered as a well separated clade. Dirofilaria, Loxodontofilaria and Onchocerca constituted a strongly supported clade despite belonging to different subfamilies (Onchocercinae and Dirofilariinae). Finally, the separation between Splendidofilariinae, Dirofilariinae and Onchocercinae will have to be reconsidered.
Highlights
The Onchocercidae (Spirurida), commonly referred to as filariae, are a family of parasitic nematodes characterised by a wide host-range in squamates, crocodilians, amphibians, mammals and birds [1]
As several filarial species are agents of human and veterinary diseases [2,3,4], the Onchocercidae have been the subject of numerous studies
Nematode specimens and DNA samples were deposited in the National Nematode collection of the Muséum National d’Histoire Naturelle (MNHN), Paris, France; accession numbers are recorded in Tables 1 and S1
Summary
The Onchocercidae (Spirurida), commonly referred to as filariae, are a family of parasitic nematodes characterised by a wide host-range in squamates, crocodilians, amphibians, mammals and birds [1]. The family is divided into eight subfamilies, including 88 genera [5,6,7,8]. They are nematodes with an evolved life cycle, involving blood- or skin-inhabiting first-stage larvae transmitted by haematophagous arthropods vectors [1,9]. A pronounced regression of morphological features and a number of convergences resulting from a parasitic life style, as well as the absence of fossilised material, make it difficult to produce phylogenetic hypotheses for this family [10]. In numerous morphological and biological studies an attempt has been made to elucidate the evolution of the Onchocercidae [1,10]. First drawn up by Wehr in 1935 [11], the classification of the family has been reconstructed several times [12,13], with the most comprehensive analysis being that of Anderson and Bain in 1976 [6]
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