Synonymy between two spider mite species, Tetranychus kanzawai and T-hydrangeae (Acari : Tetranychidae), shown by ribosomal ITS2 sequences and cross-breeding experiments

Amplification of the second internal transcribed spacer (ITS2) of ribosomal DNA was used to compare seven samples of the Tetranychus kanzawai Kishida- T. hydrangeae Pritchard & Baker mite complex from five different countries : Australia, the Congo, Indonesia, Japan and the USA. No morphological diff erences were detected between these mites and their ITS2 sequences displaye d strong similarity except for a small nucleotide divergence of 0.2% in spe cimens from Australia and Indonesia. Reciprocal crosses and backcrosses bet ween mites assumed to be T. kanzawai and T. hydrangeae respectively showed reproductive compatibility. Fertile hybrid females were obtained in all cas es, indicating conspecificity of the mites tested. It is concluded that T. hydrangeae is a synonym of T. kanzawai. The evidence suggests that T. kanza wai originated in South-east Asia and probably spread throughout the world on Hydrangea spp. cuttings.