Taxonomic relationships of the subgenus Rhipistoma (Acari: Ixodidae: Haemaphysalis).
The possible evolution of the haemaphysalid subgenus Rhipistoma (Koch) (Acari: Ixodidae, Haemaphysalis) is postulated. H. hispanica and H. caucasica seem to be the most primitive species of the subgenus, closely related to a common ancestor, as can be deduced from the palpal outline and from the combination of spines and spurs on the coxae and palpi. However, H. adleri, H. asiatica, H. fossae, H. eupleres, and H. obtusa compose a group of phylogenetically more-advanced species, based on the development of complex palpal structures in the adults, but which have also retained some of the more primitive characteristics in the immature stages. An evolutionary line containing many species seems to have developed from the subgroup H. hispanica (bequaerti, cooleyi, hyracophila, calcarata, and houyi), as inferred from the morphological features of the palpi. The data from lemuris suggest a distant relationship with the H. asiatica group. H. bartelsi and H. koningsbergeri seem to have evolved from a common ancestor of the subgenus (or even from the subgroup hispanica) because they share primitive morphological characteristics. Also, H. heinrichi and H. indica may be considered as two modern members within the indica subgroup, from which H. canestrinii seems to have originated. The data from the canestrinii group suggest the existence of a relationship between the indica-heinrichi-canestrinii subgroup, spinulosa subgroup and leachi subgroup, because they share many morphological features. H. bartelsi and H. koningsbergeri would remain as two species of a primitive pathway from the common ancestor of the subgenus, evolving to the canestrinii subgroup. H. erinacei and its subspecies form a group with several primitive features, linking it to the subgenus Ornithophysalis. Also, H. pedetes and H. zumpti are two very similar species that appear to have evolved from an arinacei-like ancestor. It seems possible that the leachi and spinulosa subgroups have evolved from a complex of species included today in the spinulosa and canestrinii subgroups.
Estrada-Peña
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Facultad de Veterinaria, Departamento de Patología Animal, Unidad de Parasitología, Zaragoza, Spain.
D000818:Animals; D010802:Phylogeny; D013987:Ticks / Q000145:classification*