Phoretic association of Neoseius novus (Ouds., 1902) (Acari: Uropodina) with Nicrophorus spp. (Coleoptera: Silphidae): A case of sympatric speciation?

Abstract Phoresy, as a dispersal strategy, theoretically favors panmixis but sympatric speciation frequently occurs through increasing specificity towards a host. We detected such isolation in the uropodid mite, Neoseius noms, an associate of Necrophorus burying beetles. The mites phoretic on N. humator are significantly larger than those associated with N. vespillo and N. vespilloides, the two latter hosts being smaller than N. humator. Some biological features of the host may explain this separation but the pattern of dispersal may also play a role. The deutonymph of N. novus is monomorphic, thus, the risk of inbreeding between founders is not inconsiderable. Such mechanisms may lead to genetic drift and a progressive adaptation to a host. Our observations tend to verify this hypothesis: N. novus appears to be a stenoxenous species while many Uropodina exhibiting deutonymphal polymorphism (phoretic/resident) are euryxenous.