Population genetic structure and secondary endosymbionts of QBemisia tabaci(Hemiptera: Aleyrodidae) from Greece

Abstract

We investigated the molecular diversity of the major agricultural pest Bemisia tabaci and of its associated secondary endosymbionts in Greece. Analyzing mitochondrial DNA, we found that the Q1 (=Q west) is predominant. We used eight microsatellite polymorphic markers to study the genetic structure of 37 populations from mainland and insular Greece, collected on different host species from outdoor and protected crops as well as from non-cultivated plants. In some cases, gene flow was found to be low even between populations separated by just a few kilometres. Bayesian analysis identified two main genetic groups, the first encompassing populations from south Crete and the second composed of populations from north Crete, two other Aegean islands and mainland Greece. Genetic differentiation was not correlated with different host plant species or habitat, or greenhouse versus open environment populations. Gene flow significantly decreased with geographic distance, but no isolation by distance existed when only the samples from mainland Greece or only the samples from Crete were considered. The secondary symbionts Wolbachia and Hamiltonella were present at high frequencies while Arsenophonus, Cardinium and Rickettsia were absent from Greek populations. Multilocus sequence typing of Wolbachia identified two Wolbachia strains. These two strains were found together in most of the populations studied but never in the same host individual. Their role on the observed population structure is discussed.

Diversity and evolution of the Wolbachia endosymbionts of Bemisia (Hemiptera: Aleyrodidae) whiteflies

“…This is consistent with previous diversity studies on Bemisia and Trialeurodes whiteflies (Nirgianaki et al 2003; Sintupachee et al 2006; Gueguen et al 2010; Singh et al 2012; Tsagkarakou et al 2012). …”

Global Population Structure of a Worldwide Pest and Virus Vector: Genetic Diversity and Population History of the Bemisia tabaci Sibling Species Group

“…insecticide applications). In fact, estimates of allelic richness and heterozygosity were high in most populations of biotypes B and Q, indicating high levels of genetic diversity [50, 51]. Additionally, despite the relatively low structure observed in the clades containing the B biotype (and relatives), and the Western Mediterranean Spanish Q and Q-like relatives (Figs 3 and 6), we found substantial variation among individuals, especially within (Western) Q relatives, with all multilocus genotypes being unique and most of the variance partitioned among individuals.…”

“…Within the Q biotype there exists a large split in the Western and Eastern Mediterranean lineages that correspond to what are known as the Spanish-Q (Western) and the Israel-Q (Eastern) [24, 113, 114] or Q1 and Q2 subclades based on mtCOI haplotypes [46, 50, 51, 84, 92]. While they are both placed in the so-named Q clade (using the Spanish Q as the prototype), they clearly represent distinct and divergent lineages with little gene flow between them, a puzzling result, despite their occurrence in a zone where the Mediterranean Sea connects Spain and nearby islands, with the Middle East.…”

“…tabaci [38, 50, 52, 126, 131–133] suggests that impacts of symbionts are common phenomenon in this insect. Furthermore, the influence of endosymbionts might be even more profound if populations are infected with different bacterial strains or species, as was found by a number of studies in populations of the Western Q1 and Eastern Q2 across the Mediterranean [50, 51, 115]. Several lines of evidence suggest that maternally inherited endosymbionts can have huge effects on mtDNA evolution, by either decreasing inter-population genetic diversity (with a symbiont-induced, selective sweep and mtDNA hitchhiking along) or by increasing diversity following fixation of different symbiont strains in different populations (which would show high haplotype differentiation, despite ongoing nuclear gene flow which would remain unchanged) [34].…”

Variations in the identity and complexity of endosymbiont combinations in whitefly hosts

“…Overall, individuals were sampled from 20 host plants across 11 geographical locations that fall into 7 climatic zones and are classified into 13 distinct biotypes (Figure 1). The numbers of individuals sampled in the independent projects were: Project A: 330 (Tsagkarakou et al, 2012); Project B: 262 (Bing et al, 2013); Project C: 430 (Zchori-Fein's lab, unpublished); Project D: 237 (Gueguen et al, 2010); Project E: 393 (Thierry et al, 2011); and Project F: 378 (Gnankine et al, 2012). The biotype classifications of individuals from each project and the endosymbiont they harbor are provided at the Supplementary Material.…”