Host-associated genetic differentiation in Thrips tabaci (Insecta; Thysanoptera), as determined from mtDNA sequence data

Abstract

We tested for host-associated genetic differentiation in 22 populations of Thrips tabaci collected from tobacco and leek, respectively. Clustering analyses and haplotype networks based on sequence variation at a fragment of the mitochondrial cytochrome oxidase I gene yielded three major evolutionary lineages; two were clearly associated with leek and the third with tobacco. These genetic findings corroborated recent experimental observations on the heterogeneity of T. tabaci populations with regard to host-plant preference and their capacity to be vectors for tomato spotted wilt virus.Estimated divergence times suggested an ancient divergence of these lineages dating back to the Miocene 28-21 million years ago. F ST values between these lineages ranged between 0.824 and 0.954 (Po0.001 for all comparisons), and sequence divergences ranged between 4 and 11%. Given these findings and by the standards of genetic and ecological differentiation in other published species groups, T. tabaci must be considered a complex of cryptic (sub)species.

Dna Barcoding and Development of Species-Specific Markers for the Identification of Tea Mosquito Bugs (Miridae: Heteroptera) in India

“…viz. T. hawaiiensis and S. perseae along with previously reported cryptic species viz., T. palmi Glover et al 2010), T. tabaci (Brunner et al 2004), F. occidentalis (Rugman-Jones et al 2010), S. dorsalis Kadirvel et al 2013) based on the 'CO-I-10X barcoding Rule' proposed by Hebert et al 2004. All of them were supported by the calculated intra and inter specific genetic divergence (Table.…”

“…Morphological examination of Thrips to species level is restricted to adult specimens, as there are no adequate keys for identification of egg, larvae, or pupae (Kadirvel et al 2013). Thrips are notorious for eliciting taxonomic problems mainly because of minute size, polymorphism (Murai et al 2001), lack of solid morphological characters (Kadirvel et al 2013), co-existence of different species on the same host plant, high intraspecific variations observed in thrips populations (Mound 2011) and need for taxonomic expertise (Brunner et al 2004).…”

“…Furthermore, morphological examination of thrips to species requires adult specimens as there are no reliable keys for identification of immature stages, but even these are often difficult for a non-expert to use. In this regard, DNA barcoding can be an added advantage and an effective tool for molecular species identification (Brunner et al 2004;Glover et al 2010; Lee et al 2010), elucidation of biotypes or cryptic species, and host associated genetic differences (Shufran et al 2000;Brunner et al 2004) and species discovery in insects. Additionally, DNA barcoding could also be used in the identification of unknown thrips species that co-exist in a cropping system, since one particular Tospovirus disease may sometimes be vectored by more than one species of thrips (Wijkamp et al 1995;Kadirvel et al 2013;Amin et al 1981).…”

“…Classical taxonomy employing morphological characters cannot be used for all species of thrips in all life stages because of insufficient phenotypic variation (Brunner et al 2004). In addition, the presence of unusual morphological forms of species on different hosts, minute size, co-existence of different species on the same host, complex life cycles, color morphs, and parthenogenetic mode of reproduction, etc., add to the difficulties of precise identification.…”

“…In this connection, Hebert et al (2003a,b) proposed the concept of DNA barcoding, a powerful tool to identify all metazoan species employing a short standardized 658 bp fragment of the 5 end of the mitochondrial cytochrome oxidase-I (CO-I) gene. DNA barcoding can be employed as the most effective approach for molecular identification of species independent of life stages, sex and polymorphism , discriminating cryptic species (Glover et al 2010;Rebijith et al 2013), biotypes (Shufran et al 2000), haplotypes (Zhang et al 2011) and host and geographic associated genetic differences (Brunner et al 2004;Rebijith et al 2011). DNA barcoding can also play an important role in insect pest management program, where both selection and timing of the management practices can be affected by polymorphism and host adaptation/ suitability (Rebijith et al 2013;Brunner et al 2004).…”