Validation of the taxon Ixodes aragaoi Fonseca (Acari: Ixodidae) based on morphological and molecular data

Abstract

The species Ixodes aragaoi Fonseca was described as Ixodes ricinus aragaoi, and later placed in synonymy with Ixodesaffinis. However, this synonymy was rejected and the subspecies was elevated to species, and named as I. aragaoi. Someresearchers did not consider the validity of I. aragaoi and maintained the synonymy proposed until 1998 when I. aragaoiwas revalidated, and it was suggested that Ixodes pararicinus could be a synonym. The aim of this study was to confirmthe taxonomic validity of I. aragaoi by means of redescription of adults and molecular analysis. Morphological studieswere performed by optical and scanning electron microscopy; types of I. aragaoi were compared with those of I. pararicinusfrom Argentina, and also with material of I. pararicinus from Uruguay and I. affinis from the United States. Mitochondrial16S rDNA sequences were obtained for determining phylogenetic relationships based on maximumparsimony. Morphological and molecular differences between I. aragaoi, I. pararicinus from Argentina, and I. affinis confirmthe validity of the first each of these species. The morphological similarities of I. pararicinus from Uruguay with I.aragaoi, and the small distance of nucleotide sequences between them, confirm that the Uruguayan ticks are in fact I. aragaoiand expand the geographical distribution of this species. Based on the specimens of Ixodes examined in the presentstudy, from the same locality of the types of I. ricinus rochensis in Uruguay, we agree with the synonymy of this subspecieswith I. aragaoi as previously reported. Finally, our analyses indicate that both I. aragaoi and Ixodes fuscipes, anotherSouth American tick species, belong to the I. ricinus complex, currently composed of 19 species.