Genetic population structure and range colonisation of Nezara viridula

Genetic variation in Nezara viridula (L.) sampled from 11 locations (Slovenia, Italy, Greece, France, Madeira, Guadeloupe, Galapagos, California, Brazil, Japan, and Botswana) was studied by sequencing 16S and 28S rDNA, cyt b and COI gene fragments and randomly amplified polymorphic DNA (RAPD) analysis. Sequencing revealed 11 distinct haplotypes clustering into three main lineages. Lineage C was limited to a single specimen from Botswana and lineage B to Japan, while lineage A haplotypes were found in the remaining Populations as well as in Japan. RAPD data were more variable but consistent with the structuring of mtDNA sequences. Sequence and RAPD results both support the African origin of N. viridula, followed by early dispersal to Asia and, more recently, by expansion to Europe and America. Japanese specimens with mtDNA lineage A haplotypes were revealed as Euro-Asian hybrids by RAPD analysis, suggesting a multiple colonisation of Japan. Invariant sequences of the 28S rDNA combined with other results do not support the hypothesis that cryptic (sibling) species exist within the populations investigated in this study.