Distribution, hosts, 16S rDNA sequences and phylogenetic position of the Neotropical tick Amblyomma parvum (Acari: Ixodidae) S. NAVA * , M. P. J. SZABO ´ { , A. J. MANGOLD * and A. A. GUGLIELMONE * * Instituto Nacional de Tecnologı ´a Agropecuaria, Estacio ´n Experimental Agropecuaria Rafaela, CC 22, CP 2300 Rafaela, Santa Fe, Argentina { Faculdade de Medicina Veterinaria, Universidade Federal de Uberlandia, Avenida Para ´ 1720, Campus Umuarama — Bloco 2T, 38400-902 Uberlandia, Minas Gerais, Brazil Received 15 October 2007, Revised 30 November 2007, Accepted 3 December 2007 The hosts, distribution, intraspecific genetic variation and phylogenetic position of Amblyomma parvum (Acari: Ixodidae) have recently been re-assessed. Data on this tick’s hosts and distribution were obtained not only from existing literature but also from unpublished records. Sequences of the ticks’ mitochondrial 16S ribosomal DNA (rDNA) were used to evaluate genetic variation among specimens of A. parvum from different localities in Argentina and Brazil, and to explore the phylogenetic relationships between this tick and other Amblyomma species. Although several species of domestic and wild mammal act as hosts for adult A. parvum, most collected adults of this species have come from cattle and goats. Caviid rodents of the subfamily Caviinae appear to be the hosts for the immature stages. So far, A. parvum has been detected in 12 Neotropical biogeographical provinces (Chaco, Cerrado, Eastern Central America, Venezuelan Coast, Pantanal, Parana Forest, Caatinga, Chiapas, Venezuelan Llanos, Monte, Western Panamanian Isthmus, and Roraima) but the Chaco province has provided significantly more specimens than any other (P,0.0001). The 16S rDNA sequences showed just 0.0%–1.1% divergence among the Argentinean A. parvum investigated and no more than 0.2% divergence among the Brazilian specimens. The observed divergence between the Argentinean and Brazilian specimens was, however, greater (3.0%–3.7%). Although there is now molecular and morphological evidence to indicate that A. parvum, A. pseudoparvum, A. auricularium and A. pseudoconcolor are members of a natural group, previous subgeneric classifications do not reflect this grouping. The subgeneric status of these tick species therefore needs to be re-evaluated. The 16S-rDNA-based evaluation of divergence indicates that the gene flow between Argentinean and Brazilian ‘A. parvum’ is very limited and that the Argentinean ‘A. parvum’ may be a different species to the Brazilian. Amblyomma is the most represented tick genus of the Neotropics, with approximately 58 species (Guglielmone et al., 2003a; Labruna et al., 2005b). Amblyomma parvum is among the most widely distributed spe- cies, being found from southern Mexico to Argentina (Guglielmone et al., 2003a). Together, adult A. parvum, A. auricularium, A. pseudoconcolor and A. pseudoparvum form a group characterised by the presence of a spur on the trochanters (most noticeable on trochanter I) and by males with a complete marginal groove (Boero, 1957; Jones et al., 1972; Guglielmone et al., 1990). Although Santos Dias (1963, 1993) placed A. parvum, A. pseudoconcolor and A. pseudoparvum (and another five Neartic, Oriental or Australian Amblyomma species) in the subgenus Amerindia, and A. auricularium in the sub- genus Adenopleura, Camicas et al. (1998) subsequently placed A. parvum, A. pseudo- parvum and A. auricularium (and another Reprint requests to: S. Nava. E-mail: snava@rafaela.inta.gov.ar; fax: z54 34 92 440 114. Annals of Tropical Medicine & Parasitology, Vol. 102, No. 5, 409–425 (2008) # 2008 The Liverpool School of Tropical Medicine DOI: 10.1179/136485908X278883