Systematic relationships in the soft ticks (Acari: Ixodida: Argasidae)

Abstract. A phylogenetic analysis of relationships at the generic to subgeneric level is carried out for the family Argasidae. The analysis is based on a total of eighty-three characters drawn from larval and adult body and leg morphology, Haller's organ morphology, development and behaviour. These characters are polarized by comparison with representatives of the families Ixodidae and Nuttalliellidae (both suborder Ixodida), and the suborders Holothyrida and Mesostigmata. A total of two equally most parsimonious trees was generated after successive approximations character weighting. Although the support for some lineages in these trees is not very strong, they provide a substantially better overall fit to the data than any of the hypotheses derived from existing classifications of the family. The classification of the Argasidae is revised to reflect the results of the phylogenetic analysis, and compared to existing classifications employed by Eastern European (‘Soviet’) and American authors. The subfamily Argasinae sens.n. contains one genus, Argas sens.n., with five subgenera, A.(Argas) sens.n. [including A.(Persicargas)syn.n.], A.(Secretargas), A.(Ogadenus), A.(Proknekalia)comb.n. and A.(Alveonasus)comb.n. The latter two subgenera (latter three in the Soviet classification) are transferred from the Ornithodorinae, where they were classified as subgenera of Ornithodoros (American school) or Alveonasus (Soviet school). The Ornithodorinae sens.n. consists of three genera, Ornithodoros sens.n., Otobius sens.n. and Carios stat.n. [raised from Argas (Carios)]. The genus Ornithodoros includes the previously recognized subgenera Ornithodoros (Pavlovskyella), O.(Ornamentum) and Argas (Microargas), all syn.n., while Otobius is expanded to include Ornithodoros sparnuscomb.n. The genus Carios contains nearly all bat-associated argasids, including the previously recognized genera Antricola and Nothoaspis, and subgenera Argas (Chiropterargas), Ornithodoros (Alectorobius), O.(Reticulinasus) and O.(Subparmatus), all syn.n. The available evidence does not allow recognition of subgenera in the genera Ornithodoros, Otobius or Carios. Summary A phylogenetic analysis of relationships in the Argasidae based on a wide variety of characters drawn from all life stages generated two highly similar and relatively well corroborated hypotheses of relationships. These hypotheses provide a much better fit to the data than phylogenies derived from existing, traditional classifications, and are used as the basis for a revision of the classification within the Argasidae. Although this classification has its weaknesses, e.g. the relatively poor support for Ornithodoros, Carios and Argas (Secretargas), it is considered superior to traditional classifications not only because of the superior fit to the data, but also because it recognizes only monophyletic taxa. In addition, by abandoning the more or less typological approach traditional in argasid systematics in favour of a lineage approach, it allows the explicit recognition of affinities for all taxa, including unusual forms such as Argas (Alveonasus) cooleyi, Ornithodoros transversus, O.elongatus, Otobius megnini, O.lagophilus, O.sparnus, Carios rudis and C.reddelli.