Low levels of mitochondrial DNA and symbiont diversity in the worldwide agricultural pest, the greenhouse whitefly Trialeurodes vaporariorum (Hemiptera: Aleyrodidae).

Trialeurodes vaporariorum, the greenhouse whitefly, is a cosmopolitan agricultural pest. Little is known about the genetic diversity of T. vaporariorum and the bacterial symbionts associated with this species. Here, we undertook a large phylogeographic study by investigating both the mitochondrial (mt) diversity and the infection status of 38 T. vaporariorum collections from 18 countries around the world. Genetic diversity of T. vaporariorum was studied by analyzing sequence data from the mt cytochrome oxidase I, cytochrome b, and NADH dehydrogenase subunit 5 genes. Maximum-likelihood (ML) phylogeny reconstruction delineated 2 clades characterized by limited sequence divergence: one clade comprised samples only from the Northern hemisphere whereas the other comprised samples from a broader geographical range. The presence of secondary symbionts was determined by PCR using primers specific for Hamiltonella, Rickettsia, Arsenophonus, Cardinium, Wolbachia, and Fritschea. Most individuals examined harbored at least one secondary endosymbiont, and Arsenophonus was detected in almost all male and female individuals. Wolbachia was present at a much lower frequency, and Cardinium was detected in only a few individuals from Greece. Rickettsia, Hamiltonella, and Fritschea were not found. Additionally, we set out to further analyze Arsenophonus diversity by multilocus sequence typing analysis; however, the Arsenophonus sequences did not exhibit any polymorphism. Our results revealed remarkably low diversity in both mtDNA and symbionts in this worldwide agricultural pest, contrasting sharply with that of the ecologically similar Bemisia tabaci.

Agroecosystems shape population genetic structure of the greenhouse whitefly in Northern and Southern Europe.

BACKGROUND: To predict further invasions of pests it is important to understand what factors contribute to the genetic structure of their populations. Cosmopolitan pest species are ideal for studying how different agroecosystems affect population genetic structure within a species at different climatic extremes. We undertook the first population genetic study of the greenhouse whitefly (Trialeurodes vaporariorum), a cosmopolitan invasive herbivore, and examined the genetic structure of this species in Northern and Southern Europe. In Finland, cold temperatures limit whiteflies to greenhouses and prevent them from overwintering in nature, and in Greece, milder temperatures allow whiteflies to inhabit both fields and greenhouses year round, providing a greater potential for connectivity among populations. Using nine microsatellite markers, we genotyped 1274 T. vaporariorum females collected from 18 greenhouses in Finland and eight greenhouses as well as eight fields in Greece. RESULTS: Populations from Finland were less diverse than those from Greece, suggesting that Greek populations are larger and subjected to fewer bottlenecks. Moreover, there was significant population genetic structure in both countries that was explained by different factors. Habitat (field vs. greenhouse) together with longitude explained genetic structure in Greece, whereas in Finland, genetic structure was explained by host plant species. Furthermore, there was no temporal genetic structure among populations in Finland, suggesting that year-round populations are able to persist in greenhouses. CONCLUSIONS: Taken together our results show that greenhouse agroecosystems can limit gene flow among populations in both climate zones. Fragmented populations in greenhouses could allow for efficient pest management. However, pest persistence in both climate zones, coupled with increasing opportunities for naturalization in temperate latitudes due to climate change, highlight challenges for the management of cosmopolitan pests in Northern and Southern Europe.

Variation in mortality among populations is higher for pymetrozine than for imidacloprid and spiromesifen in Trialeurodes vaporariorum in greenhouses in Finland.

BACKGROUND: Insecticide resistance in Trialeurodes vaporariorum W. is unknown in the species' northern distribution range where it inhabits mainly commercial greenhouses. Resistance development in whiteflies feeding on year-round crops in greenhouses is possible owing to the use of chemical treatments to back up biocontrol. The authors tested the response levels to spiromesifen, pymetrozine and imidacloprid in whiteflies collected from seven greenhouses within a 35 km radius in western Finland. RESULTS: All except one (PR) population had LC50 values below the recommended concentrations for the tested compounds. However, some populations showed reduced susceptibility to pymetrozine in comparison with the reference susceptible population. Resistance ratios to pymetrozine were highly variable (resistance ratio 0.5-39.7), even among closely located greenhouses, and higher than those for imidacloprid (resistance ratio 1.05-10.5) and spiromesifen (resistance ratio 0.8-11.5). LC50 values and application frequencies of pymetrozine correlated positively among the sampled populations. CONCLUSION: High variation in resistance levels to pymetrozine among populations within natural whitefly dispersal limits reflects variation in the usage of this compound among individual greenhouse crop producers. Thus, resistance management is recommended at the individual greenhouse crop producer level, even in a dense production cluster. © 2014 Society of Chemical Industry.

Permanent genetic resources added to molecular ecology resources database 1 October 2012-30 November 2012.

This article documents the addition of 153 microsatellite marker loci to the Molecular Ecology Resources Database. Loci were developed for the following species: Brassica oleracea, Brycon amazonicus, Dimorphandra wilsonii, Eupallasella percnurus, Helleborus foetidus, Ipomoea purpurea, Phrynops geoffroanus, Prochilodus argenteus, Pyura sp., Sylvia atricapilla, Teratosphaeria suttonii, Trialeurodes vaporariorum and Trypanosoma brucei. These loci were cross-tested on the following species: Dimorphandra coccicinea, Dimorphandra cuprea, Dimorphandra gardneriana, Dimorphandra jorgei, Dimorphandra macrostachya, Dimorphandra mollis, Dimorphandra parviflora and Dimorphandra pennigera.