Resolving the taxonomic status of Frankliniella schultzei (Thysanoptera: Thripidae) colour forms in Kenya – a morphological-, biological-, molecular- and ecological-based approach

Abstract

Frankliniella schultzeiTrybom 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 ofF. schultzeimales fromIpomoea setosaflowers 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 ofF. schultzeicould be different species. The results highlight the need for combining morphological, biological, molecular and ecological characteristics for resolving taxonomic status of closely related insects.

The economically important thrips from Malaysia, with a key to species (Thysanoptera, Thripinae)

“…Recognition : This species apparently exists as two very different colour forms, with the body either brown or yellow. According Gikonyo et al (2017) from the field surveys in Kenya indicate that the two colour forms of F.schultzei could be different species, of which, both showed distinct host preferences, lack of interbreeding and molecular differences. In general, F.schultzei is distinguished by the lack of ctenidia on abdominal tergite V, the position of ocellar setae pair III between the posterior ocelli, and the absence from the posterior margin of tergite VIII of a comb of microtrichia.…”

Frontiers Approaches to the Diagnosis of Thrips (Thysanoptera): How Effective Are the Molecular and Electronic Detection Platforms?

“…However, pale F. schultzei is the major tospovirus vector in field crops of North Queensland, Australia, where both sexes occur (personal communication, LA Mound). Barriers to interbreeding between the color morphs appear to exist [ 97 ]. In addition to these two color morphs, a brown color morph of F. schultzei has been reported from Australia [ 98 ].…”

Multiple invasions of a generalist herbivore—Secondary contact between two divergent lineages of Nezara viridula Linnaeus in Australia

“…Climatic tolerances might be one important component of speciation for host-plant generalists more broadly (Brunner & Frey, 2010;Gikonyo et al, 2017;Hereward et al, 2017). In Australia, N. viridula from eastern regions experience much cooler conditions and more variable photoperiods than those in the north-western region (Table S8) in Australia.…”

“…Some invasive insects, once seen as one generalist species, have been found to represent a complex of cryptic species, with each one relatively more specialized in its host use (Dumas et al, 2015; Malka et al, 2018; Rafter, Hereward, & Walter, 2013). But genetic analysis has also revealed cryptic species complexes comprised of different generalist species (Gikonyo et al, 2017; Hereward, Hutchinson, McCulloch, Silva, & Walter, 2017; Vyskočilová, Seal, & Colvin, 2019). All of this implies that close attention should be paid when divergent evolutionary lineages have already been documented in a particular species.…”