Reciprocal and homologous crosses were carried out using pairs or groups of twenty males and females for three biotypes of the whitefly Bemisia tabaci complex. Crosses were undertaken for the A biotype-Arizona (AzA), the B biotype-Africa (AzB), and the monophagous, Jatropha (Jat) biotype-Puerto Rico. The maternal haplotype pedigree of parents and selected offspring (F₁, F₂) was determined using the mitochondria cytochome oxidase I sequence. All reciprocal crosses yielded viable female offspring, indicating reproductively compatibility, except for AzB♀ x AzA♂, or AzB♀ x Jat♂ crosses, which yielded females unidirectionally. As an unidirectional pattern was reminiscent of cytoplasmic-mediated incompatibility (CI), the possibility was investigated that the phenotype might be caused by CI-bacteria, instead of a germ line barrier. Using the 16S rRNA sequence three prospective CI-bacterial species were identified in whitefly colonies. A Cardinium spp. (Bacteroidetes) was present in the A biotype (isolates AzA, CulA, RivA, SalA), whereas the B biotype (isolates AzB, FlB1, FlB2) was infected with Rickettsia bellii (Proteobacteria), and a Wolbachia spp. (Proteobacteria) was associated with the Jat biotype. The unidirectional incompatible phenotypes were consistent with CI-bacterial infection of AzA (Cardinium) and Jat (Wolbachia), but no such association was apparent for B biotype-Rickettsia infections. The bidirectional compatibility for Jat x AzA suggested a CI-bacteria-mediated reciprocal rescue. However, that Wolbachia-infected Jat♀ and Cardinium-infected AzA♂ crosses yielded fewer females, compared to AzA-Cardinium♀ and Jat- Wolbachia♂ crosses, suggested that Cardinium could better counter Wolbachia-induced female mortality than Wolbachia. This suggested the possibility that these phylogenetically divergent bacteria might utilize similar CI-mechanisms. In this study, the suspect CI-bacteria were strongly associated with complete or partial obstruction of gene flow in certain crosses, and with sex bias in the AzA x Jat crosses. This is the first evidence that female offspring can be produced between phylogeographically divergent, and polyphagous and monophagous B. tabaci, for which gene flow barriers are widely reported, suggesting that hybridization is utilized as a means of diversification in B. tabaci. The inability to rid colonies of CI-bacteria has necessitated introgression experiments to investigate direct CI-causality over CI-association.

Strains of the well-studied plant pathogen Pseudomonas syringae show large differences in their ability to colonize plants epiphytically and to inflict damage to hosts. Additionally, P. syringae can infect some sap-sucking insects and at least one P. syringae strain is highly virulent to insects, causing death to most individuals within as few as 4 days and growing to high population densities within insect hosts. The likelihood of agricultural pest insects coming into contact with transient populations of P. syringae while feeding on plants is high, yet the ecological implications of these interactions are currently not well understood as virulence has not been tested across a wide range of strains. To investigate virulence differences across strains we exposed the sweet potato whitefly, Bemisia tabaci, and the pea aphid, Acyrthosiphon pisum, both of which are cosmopolitan agricultural pests, to 12 P. syringae strains. We used oral inoculations with bacteria suspended in artificial diet in order to assay virulence while controlling for other variables such as differences in epiphytic growth ability. Generally, patterns of pathogenicity remain consistent across the two species of hemipteran insects, with bacterial strains from phylogroup II, or genomospecies 1, causing the highest rate of mortality with up to 86% of individuals dead after 72 h post infection. The rate of mortality is highly variable across strains, some significantly different from negative control treatments and others showing no discernable difference. Interestingly, one of the most pathogenic strains to both aphids and whiteflies (Cit7) is thought to be nonpathogenic on plants. We also found Cit7 to establish the highest epiphytic population after 48 h on fava beans. Between the nine P. syringae strains tested for epiphytic ability there is also much variation, but epiphytic ability was positively correlated with pathogenicity to insects, suggesting that the two traits may be linked and that strains likely to be found on plants may often be entomopathogenic. Our study highlights that there may be a use for epiphytic bacteria in the biological control of insect crop pests. It also suggests that interactions with epiphytic bacteria could be evolutionary and ecological drivers for hemipteran insects.

1. Plant quality (bottom-up effects) and natural enemies (top-down effects) affect herbivore performance. Furthermore, plant quality can also influence the impact of natural enemies. 2. Lower plant quality through reduced irrigation increased the abundance of the cryptic species from the Bemisia tabaci complex [hereafter B. tabaci Middle East Asia Minor 1 (MEAM1)], but not its natural enemies on cotton. It was therefore predicted that lower plant quality would diminish the impact of natural enemies in regulating this herbivore. 3. Over three cotton seasons, plant quality was manipulated via differential irrigation and natural enemy abundance with insecticides. Life tables were used to evaluate the impact of these factors on mortality of immature B. tabaci (MEAM1) over nine generations. 4. Mortality of B. tabaci (MEAM1) was consistently affected by natural enemies but not by plant quality. This pattern was driven by high levels of sucking predation, which was the primary (key) factor associated with changes in immature mortality across all irrigation and natural enemy treatments. Dislodgement (chewing predation and weather) and parasitism contributed as key factors in some cases. Analyses also showed that elimination of sucking predation and dislodgement would have the greatest effect on overall mortality. 5. The top-down effects of natural enemies had dominant effects on populations of B. tabaci (MEAM1) relative to the bottom-up effects of plant quality. Effects were primarily due to native generalist arthropod predators and not more host-specific aphelinid parasitoids. The findings of this study demonstrate the important role of arthropod predators in population suppression and validate the importance of conservation biological control in this system for effective pest control.

Submitted by Sandra Pereira (srpereira@ufrrj.br) on 2016-07-29T14:10:25Z No. of bitstreams: 1 2011 - Thiago Dias Trindade.pdf: 25311327 bytes, checksum: 31c6d8973abf784dba92673fcd0bdfbd (MD5) / Made available in DSpace on 2016-07-29T14:10:25Z (GMT). No. of bitstreams: 1 2011 - Thiago Dias Trindade.pdf: 25311327 bytes, checksum: 31c6d8973abf784dba92673fcd0bdfbd (MD5) Previous issue date: 2011-07-28 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior - CAPES. / The objective of this study was to aleurodic?neos in Rio de Janeiro the State - Brazil and their hosts in environments as diverse as agriculture, urban trees, gardens and Atlantic forest, seeking to contribute to an inventory of the representatives of this subfamily in this unit of the Federation. Samples were collected randomly in the leaves of the host, and looked up the slides incorporated into the Entomological Collection Angelo Moreira da Costa Lima. Aleurodic?neos were collected in 33 municipalities of the State of Rio de Janeiro, pointing to 11 genera and 23 species. We examined 896 slides of material collected on fifty-eight host plants. The botanical family Myrtaceae had the highest number of hosts aleurodic?neos. The whitefly Paraleyrodes bondari had the highest geographical distribution, affecting all regions of the state, as well as larger number of municipalities (18%). Have been reported for the first time in the state Aleurodicus magnificus species, A. trinidadensis, Aleuronudus induratus, Bakerius attenuatus, Ceraleurodicus varus. Aleurodicus trinidadensis is reported for the first time in Brazil. / O objetivo deste trabalho foi conhecer os aleurodic?neos no Estado do Rio de Janeiro - Brasil, bem como seus hospedeiros, em ambientes diversos como culturas agr?colas, arboriza??o urbana, jardins e mata atl?ntica, buscando contribuir para um invent?rio dos representantes desta subfam?lia nesta unidade da Federa??o. As coletas foram realizadas de forma aleat?ria nas folhas dos hospedeiros, bem como consultaram-se as l?minas incorporadas ? Cole??o Entomol?gica Angelo Moreira da Costa Lima. Coletaram-se aleurodic?neos em 33 munic?pios do Estado do Rio de Janeiro, assinalando-se 11 g?neros e 23 esp?cies. Foram examinadas 896 l?minas de material coletado em cinq?enta e oito plantas hospedeiras. A Fam?lia bot?nica Myrtaceae apresentou o maior n?mero de hospedeiros de aleurodic?neos. A mosca branca Paraleyrodes bondari apresentou a maior distribui??o geogr?fica, atingindo a todas as regi?es do estado, bem como maior n?mero de munic?pios (18%). Foram assinaladas pela primeira vez no estado as esp?cies Aleurodicus magnificus, A. trinidadensis, Aleuronudus induratus, Bakerius attenuatus, Ceraleurodicus varus. A presen?a de Aleurodicus trinidadensis ? in?dita para o Brasil.