Distribution of Scirtothrips dorsalis (Thysanoptera: Thripidae) cryptic species complex in the United States and reproductive host assessment of its dominant member.

Chilli thrips, Scirtothrips dorsalis Hood, is a cryptic species complex of at least 9 species, 2 of which (South Asia 1 and East Asia 1) have been confirmed damaging >50 plant taxa in the United States. To develop a knowledge-based management program for this pest in the United States, the objectives of the study were to (i) survey for S. dorsalis species complex in the suspected regions and (ii) assess the reproductive hosts of the predominant member available. Thrips samples received from collaborators were subjected to morpholo-molecular characterization. Of the 101 thrips populations received across the United States between 2015 and 2021, 71 populations were confirmed as S. dorsalis, with ~25% further identified as East Asia 1, compared with ~41% identified as South Asia 1, suggesting the latter species is more prevalent in the US. East Asia 1 was primarily found in samples collected from Hydrangea sp. (95%) in Massachusetts, New York, and Pennsylvania, indicating geographic range expansion in the Northeast and successful overwintering in areas with hard freezes. While assessing the host range of South Asia 1 (dominant species), 62 plant taxa were evaluated under greenhouse conditions. Among these, 40 feeding and reproductive hosts were confirmed in Florida. We also found 18 new reproductive hosts and 3 feeding hosts of S. dorsalis, which were not previously reported in the literature. The results provide insight into the increasing host range and expanded geographical distribution of S. dorsalis species and will enable the development of a species-specific monitoring and management program.

Pragmatic Applications and Universality of DNA Barcoding for Substantial Organisms at Species Level: A Review to Explore a Way Forward.

DNA barcodes are regarded as hereditary succession codes that serve as a recognition marker to address several queries relating to the identification, classification, community ecology, and evolution of certain functional traits in organisms. The mitochondrial cytochrome c oxidase 1 (CO1) gene as a DNA barcode is highly efficient for discriminating vertebrate and invertebrate animal species. Similarly, different specific markers are used for other organisms, including ribulose bisphosphate carboxylase (rbcL), maturase kinase (matK), transfer RNA-H and photosystem II D1-ApbsArabidopsis thaliana (trnH-psbA), and internal transcribed spacer (ITS) for plant species; 16S ribosomal RNA (16S rRNA), elongation factor Tu gene (Tuf gene), and chaperonin for bacterial strains; and nuclear ITS for fungal strains. Nevertheless, the taxon coverage of reference sequences is far from complete for genus or species-level identification. Applying the next-generation sequencing approach to the parallel acquisition of DNA barcode sequences could greatly expand the potential for library preparation or accurate identification in biodiversity research. Overall, this review articulates on the DNA barcoding technology as applied to different organisms, its universality, applicability, and innovative approach to handling DNA-based species identification.

Parasitoid-mediated horizontal transmission of Rickettsia between whiteflies.

Intracellular bacterial endosymbionts of arthropods are mainly transmitted vertically from mother to offspring, but phylogenetically distant insect hosts often harbor identical endosymbionts, indicating that horizontal transmission from one species to another occurs in nature. Here, we investigated the parasitoid Encarsia formosa-mediated horizontal transmission of the endosymbiont Rickettsia between different populations of whitefly Bemisia tabaci MEAM1. Rickettsia was successfully transmitted from the positive MEAM1 nymphs (R +) into E. formosa and retained at least for 48 h in E. formosa adults. Fluorescence in situ hybridization (FISH) visualization results revealed that the ovipositors, mouthparts, and digestive tract of parasitoid adults get contaminated with Rickettsia. Random non-lethal probing of Rickettisia-negative (R- ) MEAM1 nymphs by these Rickettsia-carrying E. formosa resulted in newly infected MEAM1 nymphs, and the vertical transmission of Rickettsia within the recipient females can remain at least up to F3 generation. Further phylogenetic analyses revealed that Rickettsia had high fidelity during the horizontal transmission in whiteflies and parasitoids. Our findings may help to explain why Rickettsia bacteria are so abundant in arthropods and suggest that, in some insect species that shared the same parasitoids, Rickettsia may be maintained in populations by horizontal transmission.

Parasitoid vectors a plant pathogen, potentially diminishing the benefits it confers as a biological control agent.

Huanglongbing (HLB) is a destructive disease of citrus primarily transmitted by the Asian citrus psyllid (ACP). Biocontrol of ACP is an environmentally sustainable alternative to chemicals. However, the risk of parasitoid rational application in ACP biocontrol has never been evaluated. Here we show, the dominant parasitoid of ACP, Tamarixia radiata, can acquire the HLB pathogen Candidatus Liberibacter asiaticus (CLas) and transmit it horizontally when probing ACP nymphs. If these ACP nymphs survive the probing, develop to adults and move to healthy plants, CLas can be transmitted to citrus leaves during feeding. We illustrate the formerly unrecognized risk that a parasitoid can potentially serve as a phoretic vector of the pathogen transmitted by its host, thus potentially diminishing some of the benefits it confers via biocontrol. Our findings present a significant caution to the strategy of using parasitoids in orchards with different infection status of insect-vectored pathogens.

Taxonomic and identification review of adventive Fiorinia Targioni Tozzetti (Hemiptera, Coccomorpha, Diaspididae) of the United States.

This work provides general descriptions, illustrations, molecular diagnostic data, taxonomic keys, slide mounting recommendations, and Florida distribution records for Fiorinia Targioni Tozzetti species occurring in the USA. Species treated are F.externa Ferris, F.fioriniae (Targioni Tozzetti), F.japonica Kuwana, F.pinicola Maskell, F.phantasma Cockerell & Robinson, F.proboscidaria Green, and F.theae Green. New descriptions of second-instar males and females of all seven species in addition to first-instar nymphs and adult females of F.phantasma and F.proboscidaria are presented. Taxonomic keys to second-instar males and females are developed for the first time and previously available taxonomic keys to first-instar nymphs and adult females are improved. DNA sequences were used to further evaluate the monophyly of Fiorinia and provide additional diagnostic tools for Fiorinia species. Multigene phylogenetic analyses, COI barcoding methods, and examination of type material indicate that F.yongxingensis Liu, Cai & Feng, 2020, syn. nov. is a junior synonym of F.phantasma. A morphological survey of the genus demonstrates, for the first time, the utility of second-instar males for diagnostics. This study will help inform regulatory and pest management decisions by facilitating morphological and molecular identification of adventive Fiorinia species occurring in the USA.

Antagonistic interaction between male-killing and cytoplasmic incompatibility induced by Cardinium and Wolbachia in the whitefly, Bemisia tabaci.

Cardinium and Wolbachia are maternally inherited bacterial symbionts of arthropods that can manipulate host reproduction by increasing the fitness of infected females. Here, we report that Cardinium and Wolbachia coinfection induced male-killing and cytoplasmic incompatibility (CI) when they coexisted in a cryptic species of whitefly, Bemisia tabaci Asia II7. Cardinium and Wolbachia symbionts were either singly or simultaneously localized in the bacteriocytes placed in the abdomen of B. tabaci nymphs and adults. Cardinium-Wolbachia coinfection induced male-killing and resulted in a higher female sex ratio in the intraspecific amphigenetic progeny of Asia II7 ICWH and ICWL lines; interestingly, male-killing induction was enhanced with increased Cardinium titer. Moreover, single infection of Wolbachia induced partial CI in the Asia II7 IW line and resulted in reduced fecundity, higher embryonic mortality, and lower female sex ratio. The uninfected Asia II7 IU line had significantly higher fecundity, lower embryonic and nymphal mortalities, and a lower level of CI than both the Wolbachia-infected Asia II7 IW line and the Cardinium-Wolbachia-coinfected Asia II7 ICWH line. Our findings indicate that Cardinium-Wolbachia coinfection induced male-killing, which may have had antagonistic effects on Wolbachia-induced CI in the Asia II7 whiteflies. For the first time, our study revealed that B. tabaci Asia II7 reproduction is co-manipulated by Cardinium and Wolbachia endosymbionts.

A single-pair method to screen Rickettsia-infected and uninfected whitefly Bemisia tabaci populations.

Bacterial endosymbionts such as Rickettsia and Wolbachia play prominent roles in the development and behaviour of their insect hosts, such as whiteflies, aphids, psyllids and mealybugs. Accumulating studies have emphasized the importance of establishing experimental insect populations that are either lacking or bearing certain species of endosymbionts, because they are the basis in which to reveal the biological role of individual symbionts. In this study, using Rickettsia as an example, we explored a "single-pair screening" method to establish Rickettsia infected and uninfected populations of whitefly Bemisia tabaci MEAM1 for further experimental use. The original host population had a relatively low infection rate of Rickettsia (< 35%). When B. tabaci adults newly emerged, unmated males and females were randomly selected, and released into a leaf cage that covered a healthy plant leaf in order to oviposit F1 generation eggs. Following 6 days of oviposition, the parents were recaptured and used for PCR detection. The F1 progeny, for which parents were either Rickettsia positive or negative, were used to produce the F2 generation, and similarly in turn for the F3, F4 and F5 generations respectively; if the infection status of Rickettsia was consistent in the F1 to F5 generations, then the populations can be used as Rickettsia positive or negative lines for further experiments. In addition, our phylogenetic analyses revealed that Rickettsia has high fidelity during the maternal transmission in different generations.

Compatibility and Efficacy of the Parasitoid Eretmocerus hayati and the Entomopathogenic Fungus Cordyceps javanica for Biological Control of Whitefly Bemisia tabaci.

Biological control is an effective method for whitefly management compared to the potential problems caused by chemical control, including environmental pollution and the development of resistance. Combined use of insect parasitoids and entomopathogenic fungi has shown high efficiency in Bemisia tabaci control. Here, we assessed the impacts of an entomopathogenic fungus, Cordyceps javanica, on the parasitism rate of a dominant whitefly parasitoid, Eretmocerus hayati, and for the first time also compared their separate and combined potential in the suppression of B. tabaci under semi-field conditions. Six conidial concentrations of C. javanica (1 × 103, 1 × 104, 1 × 105, 1 × 106, 1 × 107 and 1 × 108 conidia/mL) were used to assess its pathogenicity to the pupae and adults of E. hayati. Results showed that the mortality of E. hayati increased with higher concentrations of C. javanica, but these higher concentrations of fungus had low pathogenicity to both the E. hayati pupae (2.00-28.00% mortality) and adults (2.67-34.00% mortality) relative to their pathogenicity to B. tabaci nymphs (33.33-92.68%). Bioassay results indicated that C. javanica was harmless (LC50 = 3.91 × 1010) and slightly harmful (LC50 = 5.56 × 109) to the pupae and adults of E. hayati respectively on the basis of IOBC criteria, and that E. hayati could parasitize all nymphal instars of B. tabaci that were pretreated with C. javanica, with its rate of parasitism being highest on second-instar nymphs (62.03%). Interestingly, the parasitoids from second and third-instar B. tabaci nymphs infected with C. javanica had progeny with increased longevity and developmental periods. Moreover, experimental data from 15 day semi-field studies indicate that combined application of C. javanica and E. hayati suppresses B. tabaci with higher efficiency than individual applications of both agents. Therefore, combined applications of C. javanica (1 × 108 conidia/mL) and E. hayati is a more effective and compatible biological control strategy for management of B. tabaci than using either of them individually.

Infection dynamics of endosymbionts reveal three novel localization patterns of Rickettsia during the development of whitefly Bemisia tabaci.

The whitefly Bemisia tabaci (Hemiptera: Aleyrodidae) is a severe agricultural pest that harbors at least seven endosymbionts. Many important aspects of the symbiosis mechanism between these bacterial endosymbionts and their hosts are poorly understood, such as endosymbiont proliferation dynamics, spatial distribution and titer regulation during host development. In this study, infection by bacterial endosymbionts in the whitefly B. tabaci Middle East-Asia Minor-1 (MEAM1, formerly B biotype) South China population, their infection titers in various stages of whitefly host development and their spatial localization were investigated. Results revealed that the MEAM1 B. tabaci harbors the primary symbiont Portiera and secondary symbionts Rickettsia and Hamiltonella. The titers of these three endosymbionts increased with the development of their B. tabaci host. Significant proliferation of Portiera and Hamiltonella mainly occurred during the second to fourth instar nymphal stages, while Rickettsia proliferated mainly during adult eclosion. Fluorescence in situ hybridization analysis of B. tabaci adults revealed three novel infection patterns of Rickettsia: assemblage in the bacteriocytes that scattered through the entire abdomen of the female host, localization in wax glands and localization in the colleterial gland. These novel infection patterns may help to uncover the function of Rickettsia in its insect hosts.

Monitoring the Attack Incidences and Damage Caused by the Almond Bark Beetle, Scolytus amygdali, in Almond Orchards.

The almond bark beetle, Scolytus amygdali Geurin-Meneville, is responsible for significant loss of fruit production in almond orchards throughout the world. Here, we studied the damage and the incidences of S. amygdali attack on two different scales: (1) at the level of a single tree; and (2) in an entire orchard. Our results revealed no differences in attack level among four orientations (east, west, south and north sides) for the whole tree. However, the bark that was facing west side in the direction of the prevailing wind was found to be the most suitable for females to initiate attack in Stratum S2. Attack distribution remains the same among different strata (strata is vertical divisions of the tree from the ground to the uppermost twigs with ~40 cm intervals). More than 50% of attack was observed in the trunk of the tree and upper strata. However, multiplication rate (number of emerged adults/maternal gallery) varies significantly between strata. In addition, we studied attack intensity (holes produced by beetle per tree) comparing it to tree morphology (flowers, leaves and circumferences) and gum deposit. Our results revealed a positive correlation between attack intensity and gum deposits, and a negative correlation between attack intensity and tree morphology. This revealed that gum on the tree was an indicator for attack intensity. A positive correlation between attack intensity and the circumference of the tree revealed that older trees were more susceptible to S. amygdali attack. These results, while preliminary, aim to help in the monitoring of S. amygdali populations before deciding to apply any control measures.

Plant-mediated horizontal transmission of Rickettsia endosymbiont between different whitefly species.

A growing number of studies have revealed the presence of closely related endosymbionts in phylogenetically distant arthropods, indicating horizontal transmission of these bacteria. Here we investigated the interspecific horizontal transmission of Rickettsia between two globally invasive whitefly species, Bemisia tabaci MEAM1 and B. tabaci MED, via cotton plants. We found both scattered and confined distribution patterns of Rickettsia in these whiteflies. After entering cotton leaves, Rickettsia was restricted to the leaf phloem vessels and could be taken up by both species of the Rickettsia-free whitefly adults, but only the scattered pattern was observed in the recipient whiteflies. Both the relative quantity of Rickettsia and the efficiency of transmitting Rickettsia into cotton leaves were significantly higher in MEAM1 females than in MED females. The retention time of Rickettsia transmitted from MEAM1 into cotton leaves was at least 5 days longer than that of MED. Phylogenetic analysis based on 16S rRNA and gltA genes confirmed that the Rickettsia extracted from the donor MEAM1, the cotton leaves, the recipient MEAM1 and the recipient MED were all identical. We conclude that cotton plants can mediate horizontal transmission of Rickettsia between different insect species, and that the transmission dynamics of Rickettsia vary with different host whitefly species.

Plantmediated horizontal transmission of Wolbachia between whiteflies.

Maternal transmission is the main transmission pathway of facultative bacterial endosymbionts, but phylogenetically distant insect hosts harbor closely related endosymbionts, suggesting that horizontal transmission occurs in nature. Here we report the first case of plant-mediated horizontal transmission of Wolbachia between infected and uninfected Bemisia tabaci AsiaII7 whiteflies. After infected whiteflies fed on cotton leaves, Wolbachia was visualized, both in the phloem vessels and in some novel 'reservoir' spherules along the phloem by fluorescence in situ hybridization using Wolbachia-specific 16S rRNA probes and transmission electron microscopy. Wolbachia persisted in the plant leaves for at least 50 days. When the Wolbachia-free whiteflies fed on the infected plant leaves, the majority of them became infected with the symbiont and vertically transmitted it to their progeny. Multilocus sequence typing and sequencing of the wsp (Wolbachia surface protein) gene confirmed that the sequence type of Wolbachia in the donor whiteflies, cotton phloem and the recipient whiteflies are all identical (sequence type 388). These results were replicated using cowpea and cucumber plants, suggesting that horizontal transmission is also possible through other plant species. Our findings may help explain why Wolbachia bacteria are so abundant in arthropods, and suggest that in some species, Wolbachia may be maintained in populations by horizontal transmission.

Evidence for common horizontal transmission of Wolbachia among butterflies and moths.

BACKGROUND: Wolbachia is one of the most widespread bacteria on Earth. Previous research on Wolbachia-host interactions indicates that the bacterium is typically transferred vertically, from mother to offspring, through the egg cytoplasm. Although horizontal transmission of Wolbachia from one species to another is reported to be common in arthropods, limited direct ecological evidence is available. In this study, we examine horizontal transmission of Wolbachia using a multilocus sequence typing (MLST) strains dataset and used Wolbachia and Lepidoptera genomes to search for evidence for lateral gene transfer (LGT) in Lepidoptera, one of the most diverse cosmopolitan insect orders. We constructed a phylogeny of arthropod-associated MLST Wolbachia strains and calibrated the age of Wolbachia strains associated with lepidopteran species. RESULTS: Our results reveal inter-specific, inter-generic, inter-familial, and inter-ordinal horizontal transmission of Wolbachia strains, without discernible geographic patterns. We found at least seven probable cases of horizontal transmission among 31 species within Lepidoptera and between Lepidoptera and other arthropod hosts. The divergence time analysis revealed that Wolbachia is recently (22.6-4.7 mya, 95 % HPD) introduced in Lepidoptera. Analysis of nine Lepidoptera genomes (Bombyx mori, Danaus plexippus, Heliconius melpomene, Manduca sexta, Melitaea cinxia, Papilio glaucus, P. polytes, P. xuthus and Plutella xylostella) yielded one possible instance of Wolbachia LGT. CONCLUSIONS: Our results provide evidence of high incidence of identical and multiple strains of Wolbachia among butterflies and moths, adding Lepidoptera to the growing body of evidence for common horizontal transmission of Wolbachia. This study demonstrates interesting dynamics of this remarkable and influential microorganism.

Genetic Record for a Recent Invasion of Phenacoccus solenopsis (Hemiptera: Pseudococcidae) in Asia.

The cotton mealybug Phenacoccus solenopsis Tinsley is an emerging invasive insect pest. Since its first report as a pest in the United States in 1991, it has invaded and colonized more than 23 countries over the past century. It was first recorded from Pakistan in 2006 and from China in 2008. In this study, we performed field surveys from 2010 to 2012 and obtained mtCOI sequences from specimens across China and Pakistan, then compared them with already available mtCOI sequences from additional Asian and North American countries. Our genetic analysis provides evidence that P. solenopsis should be classified into two groups, one of which is found only in the United States, and the other found only in Asia. The Asian group contains nine unique haplotypes, two of which have invaded and spread across China, Pakistan, India, and Vietnam over the last 4-6 yr. Our genetic analysis also indicates that P. solenopsis has a close relationship with the parasitoid wasp Aenasius bambawalei Hayat, providing preliminary evidence of a congruent spread of this mealybug and its parasitoids across China.

Wolbachia in butterflies and moths: geographic structure in infection frequency.

INTRODUCTION: Butterflies and moths (Lepidoptera) constitute one of the most diverse insect orders, and play an important role in ecosystem function. However, little is known in terms of their bacterial communities. Wolbachia, perhaps the most common and widespread intracellular bacterium on Earth, can manipulate the physiology and reproduction of its hosts, and is transmitted vertically from mother to offspring, or sometimes horizontally between species. While its role in some hosts has been studied extensively, its incidence across Lepidoptera is poorly understood. A recent analysis using a beta-binomial model to infer the between-species distribution of prevalence estimated that approximately 40 % of arthropod species are infected with Wolbachia, but particular taxonomic groups and ecological niches seem to display substantially higher or lower incidences. In this study, we took an initial step and applied a similar, maximum likelihood approach to 300 species of Lepidoptera (7604 individuals from 660 populations) belonging to 17 families and 10 superfamilies, and sampled from 36 countries, representing all continents excluding Antarctica. RESULTS: Approximately a quarter to a third of individuals appear to be infected with Wolbachia, and around 80 % of Lepidoptera species are infected at a non-negligible frequency. This incidence estimate is very high compared to arthropods in general. Wolbachia infection in Lepidoptera is shown to vary between families, but there is no evidence for closely related groups to show similar infection levels. True butterflies (Papilionoidea) are overrepresented in our data, however, our estimates show this group can be taken as a representative for the other major lepidopteran superfamilies. We also show substantial variation in infection level according to geography - closer locations tend to show similar infection levels. We further show that variation in geography is due to a latitudinal gradient in Wolbachia infection, with lower frequencies towards higher latitudes. CONCLUSIONS: Our comprehensive survey of Wolbachia infection in Lepidoptera suggests that infection incidence is very high, and provides evidence that climate and geography are strong predictors of infection frequency.

The incidence of bacterial endosymbionts in terrestrial arthropods.

Intracellular endosymbiotic bacteria are found in many terrestrial arthropods and have a profound influence on host biology. A basic question about these symbionts is why they infect the hosts that they do, but estimating symbiont incidence (the proportion of potential host species that are actually infected) is complicated by dynamic or low prevalence infections. We develop a maximum-likelihood approach to estimating incidence, and testing hypotheses about its variation. We apply our method to a database of screens for bacterial symbionts, containing more than 3600 distinct arthropod species and more than 150 000 individual arthropods. After accounting for sampling bias, we estimate that 52% (CIs: 48-57) of arthropod species are infected with Wolbachia, 24% (CIs: 20-42) with Rickettsia and 13% (CIs: 13-55) with Cardinium. We then show that these differences stem from the significantly reduced incidence of Rickettsia and Cardinium in most hexapod orders, which might be explained by evolutionary differences in the arthropod immune response. Finally, we test the prediction that symbiont incidence should be higher in speciose host clades. But while some groups do show a trend for more infection in species-rich families, the correlations are generally weak and inconsistent. These results argue against a major role for parasitic symbionts in driving arthropod diversification.

The intracellular bacterium Wolbachia uses parasitoid wasps as phoretic vectors for efficient horizontal transmission.

Facultative bacterial endosymbionts are associated with many arthropods and are primarily transmitted vertically from mother to offspring. However, phylogenetic affiliations suggest that horizontal transmission must also occur. Such horizontal transfer can have important biological and agricultural consequences when endosymbionts increase host fitness. So far horizontal transmission is considered rare and has been difficult to document. Here, we use fluorescence in situ hybridization (FISH) and multi locus sequence typing (MLST) to reveal a potentially common pathway of horizontal transmission of endosymbionts via parasitoids of insects. We illustrate that the mouthparts and ovipositors of an aphelinid parasitoid become contaminated with Wolbachia when this wasp feeds on or probes Wolbachia-infected Bemisia tabaci AsiaII7, and non-lethal probing of uninfected B. tabaci AsiaII7 nymphs by parasitoids carrying Wolbachia resulted in newly and stably infected B. tabaci matrilines. After they were exposed to infected whitefly, the parasitoids were able to transmit Wolbachia efficiently for the following 48 h. Whitefly infected with Wolbachia by parasitoids had increased survival and reduced development times. Overall, our study provides evidence for the horizontal transmission of Wolbachia between insect hosts by parasitic wasps, and the enhanced survival and reproductive abilities of insect hosts may adversely affect biological control programs.

Host suitability comparison between the MEAM1 and AsiaII 1 cryptic species of Bemisia tabaci in cotton-growing zones of Pakistan.

BACKGROUND: Bemisia tabaci is a cryptic species complex. In Pakistan, members of the complex, MEAM1 and AsiaII 1, are the predominant species infesting cotton. The biology of the two on cotton, collard, cucumber and tomato was studied. RESULTS: In all cases there were significant interactions between species and host. MEAM1 developmental periods did not differ significantly across hosts, whereas AsiaII 1 developed more slowly on vegetables than on cotton. MEAM1 survival was highest on tomato (53.5 ± 1.1%), while AsiaII 1 survived best on cotton (67.3 ± 11.6%). MEAM1 longevity and fecundity were highest on tomato (14.7 ± 1.7 days and 82.4 ± 9.9 eggs), while AsiaII 1 longevity and fecundity were highest on cotton (23.7 ± 2.5 days and 135.2 ± 13.6 eggs). The MEAM1 intrinsic rates of increase (r(m)) on cotton and vegetable were similar (0.08-0.10), whereas the AsiaII 1 r(m) on cotton (0.15) was higher than on vegetables (0.11-0.13). The biology of MEAM1 from Pakistan was compared with published studies; it had a consistently slower rate of development, lower percentage survival, lower adult longevity, longer generation time, lower net reproductive rate and lower r(m). CONCLUSIONS: MEAM1 performed similarly across all hosts, whereas AsiaII 1 performed better on cotton. The comparison between the Pakistani MEAM1 with published studies suggests that the invasive MEAM1 may have higher performance.

Evidence for horizontal transmission of secondary endosymbionts in the Bemisia tabaci cryptic species complex.

Bemisia tabaci (Hemiptera: Aleyrodidae) is a globally distributed pest composed of at least 34 morphologically indistinguishable cryptic species. At least seven species of endosymbiont have been found infecting some or all members of the complex. The origin(s) of the associations between specific endosymbionts and their whitefly hosts is unknown. Infection is normally vertical, but horizontal transmission does occur and is one way for new infections to be introduced into individuals. The relationships between the different members of the cryptic species complex and the endosymbionts have not been well explored. In this study, the phylogenies of different cryptic species of the host with those of their endosymbionts were compared. Of particular interest was whether there was evidence for both coevolution and horizontal transmission. Congruence was observed for the primary endosymbiont, Portiera aleyrodidarum, and partial incongruence in the case of two secondary endosymbionts, Arsenophonus and Cardinium and incongruence for a third, Wolbachia. The patterns observed for the primary endosymbiont supported cospeciation with the host while the patterns for the secondary endosymbionts, and especially Wolbachia showed evidence of host shifts and extinctions through horizontal transmission rather than cospeciation. Of particular note is the observation of several very recent host shift events in China between exotic invader and indigenous members of the complex. These shifts were from indigenous members of the complex to the invader as well as from the invader to indigenous relatives.

Inactivation of Wolbachia reveals its biological roles in whitefly host.

BACKGROUND: The whitefly Bemisia tabaci is cryptic species complex composed of numerous species. Individual species from the complex harbor a diversity of bacterial endosymbionts including Wolbachia. However, while Wolbachia is known to have a number of different roles, its role in B. tabaci is unclear. Here, the antibiotic rifampicin is used to selectively eliminate Wolbachia from B. tabaci so as to enable its roles in whitefly development and reproduction to be explored. The indirect effects of Wolbachia elimination on the biology of Encarsia bimaculata, a dominant parasitoid of B. tabaci in South China, were also investigated. METHODOLOGY/PRINCIPAL FINDING: qRT-PCR and FISH were used to show that after 48 h exposure to 1.0 mg/ml rifampicin, Wolbachia was completely inactivated from B. tabaci Mediterranean (MED) without any significant impact on either the primary symbiont, Portiera aleyrodidarum or any of the other secondary endosymbionts present. For B. tabaci MED, Wolbachia was shown to be associated with decreased juvenile development time, increased likelihood that nymphs completed development, increased adult life span and increased percentage of female progeny. Inactivation was associated with a significant decrease in the body size of the 4(th) instar which leads us to speculate as to whether Wolbachia may have a nutrient supplementation role. The reduction in nymph body size has consequences for its parasitoid, E. bimaculata. The elimination of Wolbachia lead to a marked increase in the proportion of parasitoid eggs that completed their development, but the reduced size of the whitefly host was also associated with a significant reduction in the size of the emerging parasitoid adult and this was in turn associated with a marked reduction in adult parasitoid longevity. CONCLUSIONS/SIGNIFICANCE: Wolbachia increases the fitness of the whitefly host and provides some protection against parasitization. These observations add to our understanding of the roles played by bacterial endosymbionts.