International Journal of Tropical Insect Science page 1 of 14 doi:10.1017/S1742758416000126 © icipe 2016 Resolving the taxonomic status of Frankliniella schultzei (Thysanoptera: Thripidae) colour forms in Kenya – a morphological-, biological-, molecular- and ecological-based approach M. W. Gikonyo 1,2 , S. Niassy 1 , G. B. Moritz 3 , F. M. Khamis 1 , E. Magiri 2 and S. Subramanian 1 ∗ 1 Plant Health Division, International Centre of Insect Physiology and Ecology (icipe), Nairobi, Kenya; 2 Department of Biochemistry, Jomo Kenyatta University of Agriculture and Technology, Juja, Kenya; 3 Faculty of Natural Sciences I, Institute of Biology, Martin Luther University Halle-Wittenberg, Halle (Saale), Germany (Accepted 8 January 2016) Abstract. Frankliniella schultzei Trybom is a polyphagous pest and vector of tospoviruses worldwide. It occurs in dark and pale colour forms that are morphologically similar but differ in vector competency and geographic spread. In Kenya and other tropical regions, mixed populations of both colour forms are observed in similar habitats, so are considered as one species. To ascertain the taxonomic status of the two colour forms, they were characterized using morphological, molecular, biological and ecological approaches. Morphological characterization revealed differences between the colour forms on eight features and they separated into distinct clusters through principal component analysis. Restriction fragment length polymorphism of the internal transcribed spacer region (ITS- RFLP) analysis revealed differences between the two colour forms and was confirmed by differences in ITS2 sequences. Virgin pale females had female offspring (thelytoky), while virgin dark females had male offspring (arrhenotoky). Interbreeding of dark males with pale females resulted in pale females, indicating absence of interbreeding between the two colour forms. Laboratory colonies of pale forms lacked males and further analysis of F. schultzei males from Ipomoea setosa flowers in the field indicated the presence of dark males and the absence of pale males. Field surveys in Kenya indicated differences in distribution and host plant preferences among the colour forms. Lack of interbreeding, distinct host preferences and distribution, and morphological and molecular differences indicate that the two colour forms of F. schultzei could be different species. The results highlight the need for combining morphological, biological, molecular and ecological characteristics for resolving taxonomic status of closely related insects. Key words: Common blossom thrips, colour forms, ITS-RFLP, ITS2, parthenogenesis, interbreeding, morphometry Introduction Frankliniella schultzei Trybom (Thysanoptera: Thripidae), known as the common blossom thrips ∗ E-mail: ssubramania@icipe.org (CBT), is a key crop pest causing worldwide economic loss (Kakkar et al., 2014). The pest causes direct damage during feeding and oviposition, and indirect damage as a vector of tospoviruses (Sakimura, 1969). Frankliniella schultzei is one of the