Jumping plant-lice (Hemiptera, Psylloidea) associated with Diostea (Verbenaceae)

Five Russelliana species (Psyllidae, Aphalaroidinae) associated with plants of the small temperate South American genus Diostea spp. (Verbenaccae) are described and illustrated, the following four of which as new: Russelliana diosteae, R. marionae, R. sebastiani and R. theresae spp. n. A key is provided for the identification of the adults and last instar larvae. Three species are monophagous on D. juncea (R. bulbosa, diosteae and sebastiani) and two on Diostea scoparia (R. marionae and theresae); one species is restricted to Argentina (R. marionae), three occur only in Chile (R. diosteae, sebastiani and theresae) and one is known from both Argentina and Chile respectively (R. bulbosa). A cladistic analysis suggests that the species on Diostea juncea as well as those on D. scoparia form each monophyletic clades which, based on host association, may constitute sister taxa. The two species on D. scoparia have very restricted, vicariant distributions in Argentina and Chile respectively, the three species associated with D. juncea are partially sympatric and at least one of the species is more wide-spread. An evolutionary scenario is discussed.