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Recent taxonomic (Drosopoulos & Asche 1991; Abdul-Nour & Lahoud 1995; Drosopoulos & Remane 2000), ecological (Drosopoulos 2003), genetic (Loukas & Drosopoulos 1993), molecular (Maryańska-Nadachowska et al. 2008a) and caryological (Maryańska-Nadachowska et al. 2008b) studies in the whole Mediterranean revealed that dorsal colour polymorphism in the spittlebug Philaenus spumarius is more complicated than reported earlier (Halkka 1962; Thompson 1973; Stewart & Lees 1988). These studies warranted that in addition to two then recognized species, the Holarctic P. spumarius and the Mediterranean P. signatus six more species occur in the Mediterranean. Only after clearing up the taxonomy of the genus it was possible to investigate the colour polymorphism of each species. In previous reports it had been concluded that the two species then known P. spumarius and P. signatus, both considered polyphagous, had an equal number of parallel colour morphs (Halkka & Lallukka 1969; Halkka & Halkka 1990). The analysis of all these data gathered for the eight species known now, comes in conflict with previous contradictory theories and conclusions (Quartau & Borges 1967; Whittaker 1968; Lees & Stewart 1987; Boucelham et al. 1988; Halkka & Halkka 1990; Stewart & Lees 1996) on colour polymorphism in general and evidently suggests 1. speciation in Philaenus originated in the Mediterranean, 2. its polymorphism probably preceded speciation also in the Mediterranean as polymorphism is common in other genera occurring in that region (e.g. Mesoptyelus). and 3. the expression of polymorphism is developed separately in each species by visual selection (predator pressure) which takes place during the long period (6-8 months) of obligatory aestivation of the adults on various shrubs or trees and not during larval development. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. |
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