Phylogenetic relationships among species of Stilestrongylus Freitas, Lent and Almeida, 1937 (Trichostrongyloidea : Heligmonellidae : Nippostrongylinae), parasites of myomorph rodents (Rodentia : Muridae) in the neotropics

The phylogenetic relationships of 14 species of Stilestrongylus were analyz ed using the comparative morphology of 21 characters. We obtained 2 shortes t trees of 50 steps, with a consistency index of 0.540 and 25 apomorphic ch aracter states. Ingroup monophyly was supported on these trees by 2 and 3 s ynapomorphies, respectively, and the ingroup was defined by the following c haracters: greater number of ventral ridges relative to the number of ridge s dorsally, asymmetric bursa, and externo-dorsal rays differing in size. Si ster-group relationships among Stilestrongylus and the other genera designa ted as outgroups are relatively consistent with those postulated by Durette -Desset's in a classification of the Nippostrongylinae. The ancestor of the species groups comprising Hassalstrongylus, Guerrerostrongylus, and Stiles trongylus originated and diversified in murids in the Neotropical region. S pecies of Hassalstrongylus occur in rodents between southeastern North Amer ica and the eastern part of South America (Brazil and Argentina), whereas s pecies of Guerrerostrongylus and Stilestrongylus diversified exclusively in rodents in the Neotropics.