SYSTEMATICS AND BIOLOGY OF THE APHALARA-EXILIS (WEBER AND MOHR) SPECIES ASSEMBLAGE (HEMIPTERA, PSYLLIDAE)

The species of an ill-defined assemblage centred around Aphalara exili s are revised. Two species, viz. A. siamensis and A. taiwanensis, are described as new and three species are synonymised (A. soosi with A. e xilis, A. kunashirensis with A. itadori, and A. augusta with A. fascia ta). A neotype is designated for Tettigonia exilis, a lectotype is des ignated for Aphalara rumicis Mally, and Aphalara ulicis is removed fro m synonymy with Aphalara calthae. The species are diagnosed, illustrat ed and keyed. The revision of types of A, polygoni, the type species o f Aphalara, showed that it had been misinterpreted and that it corresp onds to A. rumicicola Klimaszewski which is synonymised with it. A. po lygoni auct. nec Foerster is described as A. freji sp. n. A list is gi ven of the 37 currently recognised valid species of Aphalara with thei r distributions and host plants, and of 4 nomina dubia. A cladistic an alysis using PAUP yielded 5 most parsimonious trees suggesting that Ap halara contains six monophyletic species groups (the itadori (2 spp.), siamensis (1 sp.), exilis (7 spp.), rumicis (2 spp.), maculipennis (4 spp.) and calthae (21 spp.) groups). Biogeographical aspects are anal ysed in terms of area relationships (BPA), ancestral areas (methods of Bremer and Ronquist) and dispersal (cladistic subordinateness). Four species groups are restricted to the palaearctic, one to the nearctic and only one occurs in both. It is concluded that vicariance events ma y have occurred in the palaearctic but that the presence in the nearct ic is probably due to dispersal. The east palaearctic is likely to hav e been part of the ancestral area of Aphalara. Three of the species gr oups are monophagous on Polygonum, two on Rumex and one is polyphagous on Polygonaceae (Polygonum, Rumex), Brassicaceae, Caryophyllaceae, Pr imulaceae and Ranunculaceae. Polygonum is the likely ancestral host as sociation of Aphalara; Rumex has been colonised independently at least three times.