An integrative approach to explore species limits in Laelaps mazzai Fonseca, 1939 (Mesostigmata, Laelapidae), a South American widespread mite parasitizing the cricetid Calomys Waterhouse, 1837.

Laelaps mazzai Fonseca, 1939 (Mesostigmata, Laelapidae) parasitizes several species of the widespread South American rodent genus Calomys Waterhouse, 1837. Morphological variation has been noticed within this laelapid but has yet to be analyzed. Since several other species of laelapids that initially were considered generalists have resulted in host-specific species, after further analyses, herein we explored, through morphology and genetics, the variation of this parasite across six species of Calomys, trying to establish if it constitutes a polymorphic species or a complex of cryptic host specific-species. An integrative approach was applied, including principal component and discriminant analyses of females and males and DNA sequences (nuclear region ITS and the COI gene). The obtained results indicate that female mites tend to differentiate only the sizes of their dorsal shield among host species but with extensive overlapping. At the same time the males lack metrical differentiation, and the genetic evidence failed to resolve specific-species clades. We conclude that L. mazzai is a single widespread mite with little genetic and phenotypic differentiation.