Research Interests: Evolutionary Biology, Genetics, Microbiology, Genomics, Comparative Genomics, and 15 moreBiology, Medicine, Comparative, Animals, Gene Order, Genome, Biological evolution, Arthropods, PLoS Genetics, Host Pathogen Interactions, Cytoplasmic Incompatibility, Cytoplasm, Biosynthetic Pathways, Incompatibility, and bacteroidetes
Parasitoid wasps in the genus Encarsia are commonly used as biological pest control agents of whiteflies and armored scale insects in greenhouses or the field. They are also hosts of the bacterial endosymbiont Cardinium hertigii, which... more
Parasitoid wasps in the genus Encarsia are commonly used as biological pest control agents of whiteflies and armored scale insects in greenhouses or the field. They are also hosts of the bacterial endosymbiont Cardinium hertigii, which can cause reproductive manipulation phenotypes, including parthenogenesis, feminization, and cytoplasmic incompatibility (the last is mainly studied in Encarsia suzannae). Despite their biological and economic importance, there are no published Encarsia genomes and only one public transcriptome. Here, we applied a mapping-and-removal approach to eliminate known contaminants from previously-obtained Illumina sequencing data. We generated de novo transcriptome assemblies for both female and male E. suzannae which contain 45,986 and 54,762 final coding sequences, respectively. Benchmarking Single-Copy Orthologs results indicate both assemblies are highly complete. Preliminary analyses revealed the presence of homologs of sex-determination genes character...
Research Interests:
A laboratory selected strain of Heliothis virescens demonstrating a 400-fold resistance to permethrin exhibited no differences in penetration and only a slight enhancement of metabolism when compared with a susceptible strain. Synergism... more
A laboratory selected strain of Heliothis virescens demonstrating a 400-fold resistance to permethrin exhibited no differences in penetration and only a slight enhancement of metabolism when compared with a susceptible strain. Synergism with piperonyl butoxide and DEF produced similar synergist ratios for the resistant and susceptible strains, but the resistant strain showed a much larger synergist difference. Thin layer chromatography of extracts from larvae dosed with 14C-labelled permethrin demonstrated a small increase in metabolism of the cis-isomer by the resistant strain, but no differences in metabolism of the trans-isomer. The synergism study and the 14C-labelled permethrin experiment both indicate that there is a small increase in metabolism of permethrin in the resistant strain, but not enough to account for the greatly increased LD50 value. Cross-resistance to DDT indicated that target site insensitivity may play a major role in resistance to pyrethroids in this strain
Research Interests:
For each cage of each generation, we randomly selected 24 females among those stored in ethanol at the end of each generation by pipetting without observation. The number of parental species and hybrid progeny per cage per generation as... more
For each cage of each generation, we randomly selected 24 females among those stored in ethanol at the end of each generation by pipetting without observation. The number of parental species and hybrid progeny per cage per generation as identified by the High Resolution Melting assay is presented here
Research Interests:
These are the estimates of Rickettsia titer relative to actin titer among the 4 Rickettsia-infected treatments. (Fig. 5
Research Interests:
Minute parasitoid wasps in the genus Encarsia are commonly used as biological pest control agents of whiteflies and armored scale insects in greenhouses or in the field. They are also a key host of the bacterial endosymbiont Cardinium... more
Minute parasitoid wasps in the genus Encarsia are commonly used as biological pest control agents of whiteflies and armored scale insects in greenhouses or in the field. They are also a key host of the bacterial endosymbiont Cardinium hertigii which can cause a suite of reproductive manipulation phenotypes, including parthenogenesis, feminization, and cytoplasmic incompatibility; the last being most thoroughly studied in Encarsia suzannae. Despite their biological and economic importance, there are currently no published Encarsia genomes and only one public transcriptome. In this study, we applied a mapping-and-removal approach to eliminate known contaminants from previously-obtained Illumina sequencing data. We generated de novo transcriptome assemblies for both female and male E. suzannae which contain 45,986 and 54,762 final coding sequences, respectively. Benchmarking Single-Copy Orthologs (BUSCO) results indicate both assemblies are highly complete. Preliminary analyses reveale...
Research Interests:
Data from laboratory crossing experiments, organized by bloc
Research Interests:
Terrestrial arthropods, including insects, commonly harbor maternally inherited intracellular symbionts that confer benefits to the host or manipulate host reproduction to favor infected female progeny. These symbionts may be especially... more
Terrestrial arthropods, including insects, commonly harbor maternally inherited intracellular symbionts that confer benefits to the host or manipulate host reproduction to favor infected female progeny. These symbionts may be especially vulnerable to thermal stress, potentially leading to destabilization of the symbiosis and imposing costs to the host. For example, increased temperatures can reduce the density of a common reproductive manipulator, Wolbachia, and the strength of its crossing incompatibility (cytoplasmic incompatibility, or CI) phenotype. Another manipulative symbiont, Cardinium hertigii, infects ~ 6-10% of Arthropods, and also can induce CI, but there is little homology between the molecular mechanisms of CI induced by Cardinium and Wolbachia. Here we investigated whether temperature disrupts the CI phenotype of Cardinium in a parasitic wasp host, Encarsia suzannae. We examined the effects of both warm (32°C day/ 29°C night) and cool (20°C day/ 17°C night) temperatures on Cardinium CI and found that both types of temperature stress modified aspects of this symbiosis. Warm temperatures reduced symbiont density, pupal developmental time, vertical transmission rate, and the strength of both CI modification and rescue. Cool temperatures also reduced symbiont density, however this resulted in stronger CI, likely due to cool temperatures prolonging the host pupal stage. The opposing effects of cool and warm-mediated reductions in symbiont density on the resulting CI phenotype indicates that CI strength may be independent of density in this system. Temperature stress also modified the CI phenotype only if it occurred during the pupal stage, highlighting the likely importance of this stage for CI induction in this symbiosis
Research Interests:
These are the sex ratio data used for figure 4. Refer to the manuscript text for descriptions of treatments etc
Research Interests:
We compared fecundity of 3 longstanding laboratory colonies (1st exp) and of 2 longstanding lab colonies and colonies recently established from field collected individuals (2nd exp). Female wasps were individually paired for 24 h in small... more
We compared fecundity of 3 longstanding laboratory colonies (1st exp) and of 2 longstanding lab colonies and colonies recently established from field collected individuals (2nd exp). Female wasps were individually paired for 24 h in small vials with a conspecific male. Females were then placed individually in arenas with leaf disks bearing about 80 whitefly nymphs. The leaf disks rested on a layer of agar in ventilated 35 mm agar Petri dishes. Females were transferred to new whitefly-infested arenas every other day until day eight. At day 4, we provided females with the opportunity to mate again to avoid the risk of sperm depletion by introducing a male into the arena for 24h. Arenas were kept at 27°C, 16L:8D, and 65% RH. After females were removed on day 8, arenas were incubated for approximately 10 more days. At the end of this period, we recorded the number of progeny pupae, a proxy for adult emergence, as a measure of fecundity
Page 1. Inheritance of Resistance to Permethrin by the Tobacco Budworm, Heliothis Virescens (F): Implications for Resistance Management Theo F. Watson and Suzanne E. Kelly Abstract A laboratory selected permethrin resistant strain of... more
Page 1. Inheritance of Resistance to Permethrin by the Tobacco Budworm, Heliothis Virescens (F): Implications for Resistance Management Theo F. Watson and Suzanne E. Kelly Abstract A laboratory selected permethrin resistant strain of tobacco budworm. Heliothis virescens (F), was crossed with a susceptible strain to determine the nature of
inheritance of the resistance. Crossing of these highly resistant and highly susceptible
strains showed susceptibility to permethrin to be autosomal and incompletely dominant.
Backcrosses of F1 progeny with resistant males indicated either that more than one gene
is responsible for the resistance in this strain, or that the strain was not homozygous for
resistance. It is likely that more than one locus is influencing permethrin resistance.
The crosses and backcrosses performed provided relevant information for resistance
management in the field.
inheritance of the resistance. Crossing of these highly resistant and highly susceptible
strains showed susceptibility to permethrin to be autosomal and incompletely dominant.
Backcrosses of F1 progeny with resistant males indicated either that more than one gene
is responsible for the resistance in this strain, or that the strain was not homozygous for
resistance. It is likely that more than one locus is influencing permethrin resistance.
The crosses and backcrosses performed provided relevant information for resistance
management in the field.
Research Interests:
Many intracellular microbial symbionts of arthropods are strictly vertically transmitted and manipulate their host’s reproduction in ways that enhance their own transmission. Rare horizontal transmission events are nonetheless necessary... more
Many intracellular microbial symbionts of arthropods are strictly vertically transmitted and manipulate their host’s reproduction in ways that enhance their own transmission. Rare horizontal transmission events are nonetheless necessary for symbiont spread to novel host lineages. Horizontal transmission has been mostly inferred from phylogenetic studies but the mechanisms of spread are still largely a mystery. Here, we investigated transmission of two distantly related bacterial symbionts – Rickettsia and Hamiltonella – from their host, the sweet potato whitefly, Bemisia tabaci, to three species of whitefly parasitoids: Eretmocerus emiratus, Eretmocerus eremicus and Encarsia pergandiella. We also examined the potential for vertical transmission of these whitefly symbionts between parasitoid generations. Using florescence in situ hybridization (FISH) and transmission electron microscopy we found that Rickettsia invades Eretmocerus larvae during development in a Rickettsia-infected ho...
Research Interests: Engineering, Physics, Chemistry, Biology, Transmission Electron Microscopy, and 15 moreMedicine, Multidisciplinary, Female, Animals, Polymerase Chain Reaction, Trophic Level, Enterobacteriaceae, Endosymbionts, Hemiptera, PLoS one, Sweet Potato, Digestive Tract, Bemisia tabaci, Haemolymph, and Rickettsia
Cytoplasmic incompatibility (CI) is a common form of reproductive sabotage caused by maternally inherited bacterial symbionts of arthropods. CI is a two-step manipulation: first, the symbiont modifies sperm in male hosts which results in... more
Cytoplasmic incompatibility (CI) is a common form of reproductive sabotage caused by maternally inherited bacterial symbionts of arthropods. CI is a two-step manipulation: first, the symbiont modifies sperm in male hosts which results in the death of fertilized, uninfected embryos. Second, when females are infected with a compatible strain, the symbiont reverses sperm modification in the fertilized egg, allowing offspring of infected females to survive and spread the symbiont to high frequencies in a population. Although CI plays a role in arthropod evolution, the mechanism of CI is unknown for many symbionts. Cardinium hertigii is a common CI-inducing symbiont of arthropods, including parasitoid wasps like Encarsia partenopea. This wasp harbors two Cardinium strains, cEina2 and cEina3, and exhibits strong CI. The strains infect wasps at different densities, with the cEina3 present at a lower density than cEina2, and it was previously not known which strain caused CI. By differentially curing wasps of cEina3, we found that this low-density symbiont is responsible for CI and modifies males during their pupal stage. cEina2 does not modify host reproduction and may spread by 'hitchhiking' with cEina3 CI or by conferring an unknown benefit. The cEina3 strain also shows a unique localization pattern in male reproductive tissues. Instead of infecting sperm like other CI-inducing symbionts, cEina3 cells are found in somatic cells at the testis base and around the seminal vesicle. This may allow the low-density cEina3 to efficiently modify host males and suggests that cEina3 uses a different modification strategy than sperm-infecting CI symbionts.
Research Interests:
A new heritable bacterial association can bring a fresh set of molecular capabilities, providing an insect host with an almost instantaneous genome extension. Increasingly acknowledged as agents of rapid evolution, inherited microbes... more
A new heritable bacterial association can bring a fresh set of molecular capabilities, providing an insect host with an almost instantaneous genome extension. Increasingly acknowledged as agents of rapid evolution, inherited microbes remain underappreciated players in pest management programs. A Rickettsia bacterium was tracked sweeping through populations of an invasive whitefly provi-sionally described as the BB ^ or BMEAM1 ^ of the Bemisia tabaci species complex, in the southwestern USA. In this pop-ulation, Rickettsia provides strong fitness benefits and distorts whitefly sex ratios under laboratory conditions. In contrast, whiteflies in Israel show few apparent fitness benefits from Rickettsia under laboratory conditions, only slightly decreas-ing development time. A survey of B. tabaci B samples re-vealed the distribution of Rickettsia across the cotton-growing regions of Israel and the USA. Thirteen sites from Israel and 22 sites from the USA were sampled. Across the USA, Ric...
Terrestrial arthropods are commonly infected with maternally inherited bacterial symbionts that cause cytoplasmic incompatibility (CI). In CI, the outcome of crosses between symbiont-infected males and uninfected females is reproductive... more
Terrestrial arthropods are commonly infected with maternally inherited bacterial symbionts that cause cytoplasmic incompatibility (CI). In CI, the outcome of crosses between symbiont-infected males and uninfected females is reproductive failure, increasing the relative fitness of infected females and leading to spread of the symbiont in the host population. CI symbionts have profound impacts on host genetic structure and ecology and may lead to speciation and the rapid evolution of sex determination systems. Cardinium hertigii, a member of the Bacteroidetes and symbiont of the parasitic wasp Encarsia pergandiella, is the only known bacterium other than the Alphaproteobacteria Wolbachia to cause CI. Here we report the genome sequence of Cardinium hertigii cEper1. Comparison with the genomes of CI–inducing Wolbachia pipientis strains wMel, wRi, and wPip provides a unique opportunity to pinpoint shared proteins mediating host cell interaction, including some candidate proteins for CI t...
Research Interests:
Many beneficial symbioses between bacteria and their terrestrial arthropod hosts are vertically transmitted from mother to offspring, ensuring the progeny acquire necessary partners. Unusually, in several families of coreoid and lygeoid... more
Many beneficial symbioses between bacteria and their terrestrial arthropod hosts are vertically transmitted from mother to offspring, ensuring the progeny acquire necessary partners. Unusually, in several families of coreoid and lygeoid bugs (Hemiptera), nymphs must instead ingest the beneficial symbiont, Burkholderia ( sensu lato ), from the environment early in development. We studied the effects of Burkholderia on development of two species of leaf-footed bug (Coreidae) in the genus Leptoglossus, L. zonatus and L. phyllopus. We found no evidence for vertical transmission of the symbiont, but found stark differences in performance between symbiotic and aposymbiotic individuals. Symbiotic nymphs grew more rapidly, were approximately four times more likely to survive to adulthood than aposymbiotic bugs, and were two times larger. These findings suggest that Burkholderia is an obligate symbiont for Leptoglossus species. We also tested for variation in fitness effects conferred by fou...
Research Interests:
Theory predicts that intraguild consumers such as predators or parasitoids may displace more specialized heterospecific competitors and thereby actually increase the population densities of a shared host or prey. We tested this idea with... more
Theory predicts that intraguild consumers such as predators or parasitoids may displace more specialized heterospecific competitors and thereby actually increase the population densities of a shared host or prey. We tested this idea with a native primary parasitoid, Eretmocerus eremicus, and an exotic autoparasitoid Encarsia sophia, both at- tacking the sweetpotato whitefly Bemisia tabaci. Autoparasitoids are intraguild consumers that attack and kill both the immature stages of hemipteran hosts, such as whiteflies, and heterospecific and conspecific parasitoids. In population cages on cotton plants in the field in 1997 and 1998, we introduced whiteflies and then parasitoids in a replacement design with constant total numbers of parasitoids, as follows: (1) control (whiteflies only), (2) E. eremicus only, (3) E. sophia only, and (4) both E. eremicus and E. sophia. Destructive samples of plants were taken 2, 4, and 6 wk after wasp releases, and immature whitefly and wasp stages were c...
Research Interests:
Populations of pink bollworm. Pectinophora gossypiella (Saunders), from Yuma, Casa Grande, Marana and Safford were compared with that of a susceptible laboratory (USDA) strain relative to their susceptibility to permethrin. A limited... more
Populations of pink bollworm. Pectinophora gossypiella (Saunders), from Yuma, Casa Grande, Marana and Safford were compared with that of a susceptible laboratory (USDA) strain relative to their susceptibility to permethrin. A limited comparison was made with azinphosmethyl. All field strains were significantly more tolerant to permethrin than was the USDA susceptible strain. A comparison of the USDA and Yuma strains using azinphosmethyl indicated no difference in susceptibility between the laboratory and field strains.
Research Interests:
In 1991 four Insect Pest Management studies were conducted to help understand the pink bollworm and aid in its control. The first two were replicated cage studies where cages were placed over the soil and insect emergence from the soil... more
In 1991 four Insect Pest Management studies were conducted to help understand the pink bollworm and aid in its control. The first two were replicated cage studies where cages were placed over the soil and insect emergence from the soil wasmonitored several times a week from January to mid-summer. The first had pink bollworm (pbw) infested bolls buried at 0, 2, 4 and 8 inches under the soil. The second had four plow down dates and sub -treatments of one or no irrigations. Perhaps due to the cold winter, few pink bollworm moths emerged in either study. In the buried infested boll study, no bolls buried at 8 inches produced pink bollworm moths in the spring and few emerged from either 4 or 2 inches. Of the bolls left on the surface, there was emergence from only some of the replications. Less than I% of all of the potential moths
Field populations of tobacco budworm. Heliothis virescens (F.). have been monitored annually since 1977 with topical applications of synthetic pyrethroid insecticides (primarily permethrin) and methyl parathion to detect changes in... more
Field populations of tobacco budworm. Heliothis virescens (F.). have been monitored annually since 1977 with topical applications of synthetic pyrethroid insecticides (primarily permethrin) and methyl parathion to detect changes in insecticide susceptibility. These data showed that LD50's fluctuated somewhat from year to year with permethrin. but with one possible exception. the fluctuations were not sufficient to change levels of expected control in the field. Field populations continue to show susceptibility to permethrin even though one Maricopa County population showed an increase in the LDs0 to 12.4 in 1988. Field populations continue to show resistance to methyl parathion and susceptibility to permethrin.
Cotton tvas sprayed with permethrin, chiordimeform and the permethrin-chlordimeform combination to determine residual efficacy against resistant (R) and susceptible (S) populations of tobacco budworm (TBW) and reciprocal crosses of the... more
Cotton tvas sprayed with permethrin, chiordimeform and the permethrin-chlordimeform combination to determine residual efficacy against resistant (R) and susceptible (S) populations of tobacco budworm (TBW) and reciprocal crosses of the two populations. Permethrin alone gave excellent results against susceptible tobacco budworm for the entire 7 -day test period. However, against the resistant strain the highest level of mortality achieved was 40% on the 1 -day post -treatment residue; results with the S:R and R: S ( 8) crosses were generally intermediate. Chlordimeform gave poor and erratic kill unrelated to the residue period regardless of the strain of TBW. The combination resulted in mortality similar to that of permethrin alone with the cusceptible strain hut generally greater than that with permethrin alone against the re.sistafrtr strain. The combination resulted in high mortality in the crosses, particularly the R. S (ce: 8) cross. Introduction The tobacco budworm, Heliothis v...
Research Interests:
Arthropods harbor heritable intracellular symbionts that may manipulate host reproduction to favor symbiont transmission. In cytoplasmic incompatibility (CI), the symbiont sabotages the reproduction of infected males such that high levels... more
Arthropods harbor heritable intracellular symbionts that may manipulate host reproduction to favor symbiont transmission. In cytoplasmic incompatibility (CI), the symbiont sabotages the reproduction of infected males such that high levels of offspring mortality result when they mate with uninfected females. In crosses with infected males and infected females, however (the “rescue” cross), normal numbers of offspring are produced. A common CI-inducing symbiont,Cardinium hertigii, causes variable levels of CI mortality in the parasitoid wasp,Encarsia suzannae.Previous work correlated CI-induced mortality with male development time in this system, although the timing ofCardiniumCI-induction and the relationship between development time and CI mortality was not well understood. Here, using a combination of crosses, manipulation of development time, and fluorescence microscopy, we identify the localization and the timing of the CI-induction step in theCardinium-E. suzannaesystem. Antibio...
Research Interests:
Background Cardinium is an intracellular bacterial symbiont in the phylum Bacteroidetes that is found in many different species of arthropods and some nematodes. This symbiont is known to be able to induce three reproductive manipulation... more
Background Cardinium is an intracellular bacterial symbiont in the phylum Bacteroidetes that is found in many different species of arthropods and some nematodes. This symbiont is known to be able to induce three reproductive manipulation phenotypes, including cytoplasmic incompatibility. Placing individual strains of Cardinium within a larger evolutionary context has been challenging because only two, relatively slowly evolving genes, 16S rRNA gene and Gyrase B, have been used to generate phylogenetic trees, and consequently, the relationship of different strains has been elucidated in only its roughest form. Results We developed a Multi Locus Sequence Typing (MLST) system that provides researchers with three new genes in addition to Gyrase B for inferring phylogenies and delineating Cardinium strains. From our Cardinium phylogeny, we confirmed the presence of a new group D, a Cardinium clade that resides in the arachnid order harvestmen (Opiliones). Many Cardinium clades appear to ...
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Cytoplasmic incompatibility (CI) is an intriguing, widespread, symbiont-induced reproductive failure that decreases offspring production of arthropods through crossing incompatibility of infected males with uninfected females or with... more
Cytoplasmic incompatibility (CI) is an intriguing, widespread, symbiont-induced reproductive failure that decreases offspring production of arthropods through crossing incompatibility of infected males with uninfected females or with females infected with a distinct symbiont genotype. For years, the molecular mechanism of CI remained unknown. Recent genomic, proteomic, biochemical, and cell biological studies have contributed to understanding of CI in the alphaproteobacterium Wolbachia and implicate genes associated with the WO prophage. Besides a recently discovered additional lineage of alphaproteobacterial symbionts only moderately related to Wolbachia, Cardinium (Bacteroidetes) is the only other symbiont known to cause CI, and genomic evidence suggests that it has very little homology with Wolbachia and evolved this phenotype independently. Here, we present the first transcriptomic study of the CI Cardinium strain cEper1, in its natural host, Encarsia suzannae, to detect importa...
When allopatric species with incomplete prezygotic isolation come into secondary contact, the outcome of their interaction is not easily predicted. The parasitoid wasp Encarsia suzannae (iES), infected by Cardinium inducing cytoplasmic... more
When allopatric species with incomplete prezygotic isolation come into secondary contact, the outcome of their interaction is not easily predicted. The parasitoid wasp Encarsia suzannae (iES), infected by Cardinium inducing cytoplasmic incompatibility (CI), and its sibling species E. gennaroi (EG), not infected by bacterial endosymbionts, may have diverged because of the complementary action of CI and asymmetric hybrid incompatibilities. Whereas postzygotic isolation is now complete because of sterility of F1 hybrid progeny, prezygotic isolation is still incipient. We set up laboratory population cage experiments to evaluate the outcome of the interaction between ES and EG in two pairwise combinations: iES vs EG and cured ES (cES, where Cardinium was removed with antibiotics) vs EG. We also built a theoretical model aimed at exploring the role of life-history differences and asymmetric mating on competitive outcomes. In three of four cages in each treatment, ES dominated the interaction. We found evidence for reproductive interference, driven by asymmetric mating preferences, that gave a competitive edge to ES, the species that better discriminated against heterospecifics. However, we did not find the fecundity cost previously shown to be associated with Cardinium infection in iES. The model largely supported the experimental results. The finding of only a slight competitive edge of ES over EG in population cages suggests that in a more heterogeneous environment the species could coexist. This is supported by evidence that the two species coexist in sympatry, where preliminary data suggest reproductive character displacement may have reinforced postzygotic isolation.
Research Interests:
Cytoplasmic incompatibility (CI) is a conditional sterility in numerous arthropods that is caused by inherited, intracellular bacteria such as Wolbachia Matings between males carrying CI-inducing Wolbachia and uninfected females, or... more
Cytoplasmic incompatibility (CI) is a conditional sterility in numerous arthropods that is caused by inherited, intracellular bacteria such as Wolbachia Matings between males carrying CI-inducing Wolbachia and uninfected females, or between males and females infected with different Wolbachia strains, result in progeny that die during very early embryogenesis. Multiple studies in diploid (Drosophila) and haplodiploid (Nasonia) insects have shown that CI-Wolbachia cause a failure of the paternally derived chromatin from resolving into distinct chromosomes. This leads to the formation of chromatin bridges and other mitotic defects as early as the first mitotic division, and to early mitotic arrest. It is currently unknown if CI-inducing symbionts other than Wolbachia affect similar cellular processes. Here, we investigated CI caused by an unrelated bacterium, Cardinium, which naturally infects a parasitic wasp, Encarsia suzannae CI crosses in this host-symbiont system resulted in early...
Research Interests:
The potential importance of cytoplasmic incompatibility (CI) - inducing bacterial symbionts in speciation of their arthropod hosts has been debated. Theoretical advances have led to a consensus that a role is plausible when CI is combined... more
The potential importance of cytoplasmic incompatibility (CI) - inducing bacterial symbionts in speciation of their arthropod hosts has been debated. Theoretical advances have led to a consensus that a role is plausible when CI is combined with other isolating barriers. However, the insect model systems Nasonia and Drosophila are the only two experimental examples documented. Here we analyzed the components of reproductive isolation between the parasitoid wasp Encarsia suzannae, which is infected by the CI-inducing symbiont Cardinium, and its uninfected sibling species Encarsia gennaroi. Laboratory crosses demonstrated that: 1) sexual isolation is incomplete; 2) hybrid offspring production is greatly reduced in the interspecific CI cross; 3) viable hybrids may be produced by curing E. suzannae males of Cardinium with antibiotics; 4) hybrid offspring production in the reciprocal cross is greatly reduced by hybrid inviability due to genetic incompatibilities; 5) hybrid sterility is nea...
Research Interests: Evolutionary Biology, Speciation, Gene Flow, Reproduction, Molecular Evolution, and 14 moreSymbiosis, Evolution, Hymenoptera, Mitochondrial DNA, Wasps, Animals, Male, Flavobacterium, Molecular Phylogenetics and Evolution, Wolbachia, Reproductive Isolation, Chalcidoidea, Cytoplasmic Incompatibility, and Cardinium
Research Interests:
... Hoddle et al., 1998] ). Almost all Encarsia species have an unusual life history, which is characterized by obligate sex-specific differences in host use ( [Walter, 1983] and [Hunter and Woolley, 2001] ). Whereas female Encarsia ...
Research Interests:
Research Interests:
Inherited bacterial symbionts are common in arthropods and can have strong effects on the biology of their hosts. These effects are often mediated by host ecology. The Rickettsia symbiont can provide strong fitness benefits to its insect... more
Inherited bacterial symbionts are common in arthropods and can have strong effects on the biology of their hosts. These effects are often mediated by host ecology. The Rickettsia symbiont can provide strong fitness benefits to its insect host, Bemisia tabaci, under laboratory and field conditions. However, the frequency of the symbiont is heterogeneous among field collection sites across the USA, suggesting that the benefits of the symbiont are contingent on additional factors. In two whitefly genetic lines collected from the same location, we tested the effect of Rickettsia on whitefly survival after heat shock, on whitefly competitiveness at different temperatures, and on whitefly competitiveness at different starting frequencies of Rickettsia. Rickettsia did not provide protection against heat shock nor affect the competitiveness of whiteflies at different temperatures or starting frequencies. However, there was a strong interaction between Rickettsia infection and whitefly genet...
Research Interests:
Research Interests:
Insect endosymbionts are important drivers of ecological interactions, and may influence an organism’s invasiveness and pest status. A recent study revealed a rapid spread of the endosymbiont Rickettsia among sweetpotato whitefly (Bemisia... more
Insect endosymbionts are important drivers of ecological interactions, and may influence an organism’s invasiveness and pest status. A recent study revealed a rapid spread of the endosymbiont Rickettsia among sweetpotato whitefly (Bemisia tabaci, B biotype) populations in the southwestern USA in the early 2000s. While laboratory assays indicated that Rickettsia infection was associated with an increase in whitefly performance, pest managers in the field observed no clear increases in pest characteristics of whiteflies following Rickettsia invasion. To understand whether Rickettsia infection increases growth rates in the field, an experiment was designed to examine population growth and competitive interactions in Rickettsia infected and uninfected whiteflies over a cotton field season. We measured population growth rates and plant growth and nutrition in cages containing either Rickettsia-infected or uninfected whiteflies, as well as changes in Rickettsia infection frequency in popu...
Theory suggests that maternally-inherited endosymbionts can promote their spread and persistence in host populations by enhancing the production of daughters by infected hosts, either by improving overall host fitness, or through... more
Theory suggests that maternally-inherited endosymbionts can promote their spread and persistence in host populations by enhancing the production of daughters by infected hosts, either by improving overall host fitness, or through reproductive manipulation to favor production of daughters. In the doubly-infected parasitoid Encarsia inaron, we have found that Wolbachia manipulates host reproduction, but Cardinium does not. We therefore investigated the fitness costs and/or benefits of infection by each bacterium in this parasitoid, as a potential explanation for persistence of Cardinium in the population. We differentially cured E. inaron of Wolbachia, Cardinium, or both, introgressed the infected lines with the fully cured line to create a similar genetic backround, and evaluated several fitness parameters. We found that wasps infected with Cardinium (either alone or in combination with Wolbachia) had lower initial eggloads than wasps without Cardinium, but that wasps bearing Cardini...
Inherited intracellular bacterial symbionts are strong agents of evolutionary change in host populations. Rickettsia, a lineage of bacteria in the Alphaproteobacteria, has been known primarily as an arthropod-vectored pathogen of humans.... more
Inherited intracellular bacterial symbionts are strong agents of evolutionary change in host populations. Rickettsia, a lineage of bacteria in the Alphaproteobacteria, has been known primarily as an arthropod-vectored pathogen of humans. More recently these bacteria have been found to be common vertically transmitted secondary (facultative) symbionts of arthropods and other invertebrates. Here we report the rapid spread of a Rickettsia in the Rickettsia bellii clade in the whitefly Bemisia tabaci (Biotype B) in the Southwestern United States. Alcohol preserved samples of whiteflies from several sites in Arizona, New Mexico and California collected in 2000, 2003 and 2006 were used to determine the frequency of the infection at these three time-points. Across all sites, the frequency of infection rose from 3% in 2000 to 51% in 2003, to 97% in 2006. The rapid spread of the infection suggests one of three possibilities under investigation: horizontal transfer of the bacterium, strong fi...
Encarsia pergandiella (Hymenoptera: Aphelinidae) is an important parasitoid of whiteflies distributed in a number of geographically differentiated populations that differ in reproductive mode and endosymbiotic bacteria infection. Whereas... more
Encarsia pergandiella (Hymenoptera: Aphelinidae) is an important parasitoid of whiteflies distributed in a number of geographically differentiated populations that differ in reproductive mode and endosymbiotic bacteria infection. Whereas E. pergandiella from California appears uninfected, the endosymbiotic bacterium Cardinium causes thelytoky in a population from Brazil, and cytoplasmic incompatibility (CI) in a sexual population of from Texas. E. pergandiella from California and Texas have subtle but consistent morphological differences, and show partial to complete reproductive isolation from each other, in spite of genetic distinctiveness suggesting that the two populations are distinct species. The aim of this work was to evaluate the role of CI-inducing bacteria and genic incompatibilities in the reproductive isolation and competitive interactions of these parasitoid populations. The level of reproductive compatibility between Cardinium-infected and uninfected E. pergandiella w...