Amblyomma parvum Aragão, 1908 (Acari: Ixodidae): Phylogeography and systematic considerations

Abstract

The geographical distribution of Amblyomma parvum Aragão 1908 in the New World is disjunct, withtwo main clusters separated from each other by the Amazon basin. The main objectives of this studywere to further investigate the systematic relationships within A. parvum, to determine whether or notpopulations from different geographical areas might represent cryptic species, and to reconstruct the phy-logeographical evolutionary history of the species. The genetic diversity of A. parvum collected throughoutits distributional range was analyzed by using 6 molecular markers: 5 mitochondrial [the small and thelarge ribosomal subunits 12rDNA and 16SrDNA, the cytochrome oxidase I (COI) and II (COII) and thecontrol region or d-loop (DL)], and one nuclear (ITS2, Inter transcribed spacer 2). Phylogenetic trees wereinferred by using maximum parsimony and Bayesian analyses. In addition, node dating was attemptedfor the main lineages identified phylogenetically. Although mitochondrial and nuclear topologies werenot totally congruent, they all identified at least two main supported clusters, a Central American lineage,and a Brazilian-Argentinian lineage. Clade support and divergence values strongly suggest that the twolineages correspond to different taxonomic entities. Node dating placed the split between the CentralAmerican and the Brazilian-Argentinian lineages at approximately 5.8?4.9 Mya, just after the progres-sive replacement of the dry areas that occupied the northern part of South America by the Amazon Basinin the early-mid Miocene. This event might be the cause of fragmentation and putative speciation withinthe ancestral relatively xerophilic A. parvum population.