Divergence among generalist herbivores: the Frankliniella schultzei species complex in Australia (Thysanoptera: Thripidae)
Understanding and interpreting the host plant interactions of “generalist” herbivorous insects requires that species limits are accurately defined, as such taxa frequently harbour cryptic species with restricted host use. We tested for the presence of cryptic species across different host plant species in Australian Frankliniella schultzei using a combination of gene sequencing and newly developed microsatellite markers. We detect deep divergence between three colour morphs (black, brown and yellow) but no discordance between mitochondrial and nuclear genes in areas of sympatry, indicating the presence of at least three species in Australia (and potentially six globally). Microsatellite markers were developed for the brown species but could not be amplified in the black or yellow species because the divergence between them is too great. When applied to six populations across Queensland and New South Wales the microsatellites showed high levels of gene flow across thrips collected from Gossypium hirsutum (cotton), Hibiscus rosa-sinensis and Malvaviscus arboreus, and over distances of at least 950 km, indicating considerable movement by these insects and no host-associated genetic differentiation in the brown species. Significantly, the divergence between the three species in Australia was not associated with any noticeable host specialisation. The substantial overlap in geographical distribution and host plant range raises questions about the process of speciation in generalist insects. Our results provide the basis from which detailed quantification of relative host use can be conducted for each species within the F. schultzei complex; this next step is crucial to fully understanding the host plant relationships of each and, thus, the basis of their speciation.
KeywordsFrankliniella schultzei Thrips Cryptic species Virus transmission Host plant relationships Species complex Sex ratio
The authors acknowledge the Cruiser fund (Under the grant “Invasion ecology of thrips in relation to seedling cotton”) granted for financial support towards this project. We would like to thank Sharon Van Brunschot, Dean Brookes, Justin Cappadonna and Murray Sharman for collecting specimens. We are also very grateful to Mark Schutze for lodging the specimens in the Queensland Primary Industries Insect Collection.
- Bhatti J, Alavi J, zur Strassen R, Telmadarraiy Z (2009) Thysanoptera in Iran 1938–2007. An overview. Part 1. Thrips 7–8:1–373Google Scholar
- Meglécz E, Pech N, Gilles A et al (2014) QDD version 3.1: a user-friendly computer program for microsatellite selection and primer design revisited: experimental validation of variables determining genotyping success rate. Mol Ecol Resour 14:1302–1313. doi: 10.1111/1755-0998.12271 CrossRefPubMedGoogle Scholar
- Mound LA (1968) A review of R. S. Bagnall’s Thysanoptera collections. Bullet Br Mus suppl 11:1–181 (Natural History) (Ent.) Google Scholar
- Mound LA, Tree DJ, Paris D (2015) OzThrips—Thysanoptera in Australia. http://www.ozthrips.org/. Accessed 2015–2016
- Paterson H (1991) The recognition of cryptic species among economically important insects. In: Zalucki MP (ed) Heliothis, research methods and prospects. Springer, New York, pp 1–10Google Scholar
- Rambaut A, Drummond AJ (2017) Tracer v1.4. http://tree.bio.ed.ac.uk/software/tracer/
- Sakimura K (1969) A comment on the color forms of Frankliniella schultzei (Thysanoptera: Thripidae) in relation to transmission of the tomato-spotted wilt virus. Pac Insects 11:761–762Google Scholar
- Silva R (2015) Invasion ecology of thrips in relation to seedling cotton. Unpublished PhD thesis. The University of Queensland, Brisbane. doi:10.14264/uql.2015.853, pp 227Google Scholar
- Toon A, Daglish G, Ridley A et al (2016) Random mating between two widely divergent mitochondrial lineages of Cryptolestes ferrugineus (Coleoptera: Laemophloeidae): A test of species limits in a Phosphine-resistant stored product pest. J Econ Entomol 109:2221–2228. doi: 10.1093/jee/tow178 CrossRefPubMedGoogle Scholar