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Publications (398)
Moth sex pheromones are a classical model for studying sexual selection. Females typically produce a species-specific pheromone blend that attracts males. Revealing the enzymes involved in the interspecific variation in blend composition is key for understanding the evolution of these sexual communication systems. The nature of the enzymes involved...
The maize weevil, Sitophilus zeamais , is a worldwide pest that disproportionately affects subsistence farmers in developing countries. Damage from this pest threatens food security in these communities as widely available and effective control methods are lacking. With advances over the last decade in the development of genetic pest management tec...
The importance of mosquitoes in human pathogen transmission has motivated major research efforts into mosquito biology in pursuit of more effective vector control measures. Aedes aegypti is a particular concern in tropical urban areas, where it is the primary vector of numerous flaviviruses, including the yellow fever, Zika, and dengue viruses. Wit...
The maize weevil, Sitophilus zeamais, is a worldwide pest that disproportionately affects subsistence farmers in developing countries. Damage from this pest threatens food security in these communities as widely available and effective control methods are lacking. With advances over the last decade in the development of genetic pest management tech...
Moth sex pheromones are a classical model for studying sexual selection. Females produce a species-specific pheromone blend that attracts males. Revealing the enzymes involved in the interspecific variation in blend composition is key for understanding the evolution of these sexual communication systems. The nature of the enzymes involved in the va...
The importance of mosquitoes in human pathogen transmission has motivated major research efforts into mosquito biology in pursuit of more effective vector control measures. Aedes aegypti is a particular concern in tropical urban areas, where it is the primary vector of numerous flaviviruses, including the yellow fever, Zika, and dengue viruses. Wit...
This study describes the evolution of knockdown resistance (kdr) haplotypes in Aedes aegypti in response to pyrethroid insecticide use over the course of 18 years in Iquitos, Peru. Based on the duration and intensiveness of sampling (~10,000 samples), this is the most thorough study of kdr population genetics in Ae. aegypti to date within a city. W...
Introduction
One genetic approach to insect pest management aims to suppress or locally eliminate a species through large, repeated releases of genetically engineered strains that render female offspring unviable. Strains with this female‐killing characteristic have been developed either with all molecular components in a single construct or in two...
This study describes the evolution of knockdown resistance (kdr) haplotypes in Aedes aegypti in response to pyrethroid insecticide use over the course of 18 years in Iquitos, Peru. Based on the duration and intensiveness of sampling (~10,000 samples), this is the most thorough study of kdr population genetics in Ae. aegypti to date within a city. W...
Introduced rodent populations pose significant threats worldwide, with particularly severe impacts on islands. Advancements in genome editing have motivated interest in synthetic gene drives that could potentially provide efficient and localized suppression of invasive rodent populations. Application of such technologies will require rigorous popul...
Gene drive organisms (GDOs), whose genomes have been genetically engineered to spread a desired allele through a population, have the potential to transform the way societies address a wide range of daunting public health and environmental challenges. The development, testing, and release of GDOs, however, are complex and often controversial. A key...
The spread of synthetic gene drives is often discussed in the context of panmictic populations connected by gene flow and described with simple deterministic models. Under such assumptions, an entire species could be altered by releasing a single individual carrying an invasive gene drive, such as a standard homing drive. While this remains a theor...
The spread of synthetic gene drives is often discussed in the context of panmictic populations connected by gene flow and described with simple deterministic models. Under such assumptions, an entire species could be altered by releasing a single individual carrying an invasive gene drive, such as a standard homing drive. While this remains a theor...
Many novel genetic approaches are under development to combat insect pests, which continue to impose substantial burdens in the forms of transmission of vector-borne disease and the reduction of agricultural yields. One category of genetic pest management aims to suppress or locally eliminate a species through large, repeated releases of fertile ma...
Selfish genetic elements have been found in the genomes of many species, yet our understanding of their evolutionary dynamics is only partially understood. A number of distinct selfish Medea elements are naturally present in many populations of the red flour beetle (Tribolium castaneum). Although these Medea elements are predicted by models to incr...
Selfish genetic elements (SGEs) are DNA sequences that are transmitted to viable offspring in greater than Mendelian frequencies. Medea SGEs occur naturally in some populations of red flour beetle (Tribolium castaneum) and are expected to increase in frequency within populations and spread among populations. The large‐scale U.S. distributions of Me...
Invasive species pose a major threat to biodiversity on islands. While successes have been achieved using traditional removal methods, such as toxicants aimed at rodents, these approaches have limitations and various off-target effects on island ecosystems. Gene drive technologies designed to eliminate a population provide an alternative approach,...
Optimism regarding potential epidemiological and conservation applications of modern gene drives is tempered by concern about the possibility of unintended spread of engineered organisms beyond the target population. In response, several novel gene drive approaches have been proposed that can, under certain conditions, locally alter characteristics...
Invasive rodents have signifi cant negative impacts on island biodiversity. All but the smallest of rodent eradications currently rely on island-wide rodenticide applications. Although signifi cant advances have been made in mitigating unintended impacts, rodent eradication on inhabited islands remains extremely challenging. Current tools restrict...
Invasive species pose a major threat to biodiversity on islands. While successes have been achieved using traditional removal methods, such as toxicants aimed at rodents, these approaches have limitations and various off-target effects on island ecosystems. Gene drive technologies designed to suppress a population provide an alternative approach, b...
Optimism regarding potential epidemiological and conservation applications of modern gene drives is tempered by concern about the potential unintended spread of engineered organisms beyond the target population. In response, several novel gene drive approaches have been proposed that can, under certain conditions, locally alter characteristics of a...
Background
Aedes aegypti is a primary vector of dengue, chikungunya, Zika, and urban yellow fever viruses. Indoor, ultra low volume (ULV) space spraying with pyrethroid insecticides is the main approach used for Ae. aegypti emergency control in many countries. Given the widespread use of this method, the lack of large-scale experiments or detailed...
Histogram of AA/HSE at baseline (C1).
Rows show treatment sector. X-axis is sqrt-scaled. The majority of house surveys find no adults.
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Model results, as in Fig 4.
All models include fixed effects of sector and circuit, with a separate model for each year. (A) Counts: negative binomial GLM (NB-GLM). (B) Proportions: logistic GLM (L-GLM). Note that Breteau Index (BI) = 100*PC/HSE. See also S2–S10 Tables.
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Observation counts by circuit.
Weeks: Week number from experiment start. Houses: number of unique houses surveyed. Surveys: total surveys (either adult, or combined adults and immature). Full surveys: surveys where both adult and immatures were surveyed. Buffer, Spray: surveys in buffer and spray sector, respectively.
(PDF)
All supporting tables and figures.
(PDF)
Maps of experimental areas, showing satellite imagery.
Note the scale differs between experiments. See also Fig 1.
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Comparison between spray status (whether house was sprayed prior to survey).
Ratio of AA/HSE in houses that were either sprayed or not sprayed prior to surveying (no prior spray/prior spray). Bold p-values: In L-2014, houses without prior spraying yielded significantly more adults than houses with prior spraying. In S-2013, most houses were sprayed...
Effect of prior spray on AA/HSE.
A single model (NB-GLM) includes both experiment year and spray status as predictors. Group: significance groups (Tukey HSD) compare among all rows. Only house surveys in the spray sector during experimental spraying are included (i.e., S-2013 C2 and L-2014 C6). Not all sprayed houses were subsequently surveyed. The...
Proportion nulliparous Aedes aegypti females (PrNF).
(A) S-2013. (B) L-2014. Model estimates by circuit and treatment sector. Horizontal line separates treatment sectors, significance groups (Tukey HSD) compare among all rows. See S5 Fig.
(PDF)
Time series of survey results, aggregated by week.
X-axis shows week start date. Color and line-type shows treatment sector (orange triangle: spray sector). Point size shows number of surveyed houses. Vertical lines show approximately spray dates: dashed, experimental spraying (spray sector only); dotted, citywide spraying (February 2014, all secto...
Maps of spray events (red) by spray cycle (rows).
(A) S-2013. (B) L-2014. During L-2014, in addition to experimental spraying, 3 cycles of emergency citywide spraying were conducted. Note the map scale differs between A and B. See also Fig 1.
(PDF)
Comparison between sectors (within time).
Ratio of AA/HSE in spray sector relative to buffer sector (spray/buffer). Bold p-values: significant difference between sectors. In both years, the spray sector starts with more adults per house, and spraying reduces AA/HSE relative to buffer sectors. As in S3 Table, the effects of spraying are more pronoun...
Comparison between times (within spray sector).
Ratio of AA/HSE relative to baseline (C1, spray sector only). Bold p-values: significant difference from baseline circuit. In both years, spraying reduces AA/HSE relative to baseline (C1). The effects of spraying are most pronounced in S-2013, but are short-lived in both years. See also Fig 4A.
(PDF)
Proportion of Aedes aegypti adult-infected houses (PrIH).
(A) S-2013. (B) L-2014. Model estimates by circuit and treatment sector. Horizontal line separates treatment sectors, significance groups (Tukey HSD) compare among all rows. See Fig 4B for model description.
(PDF)
Proportion Aedes aegypti positive containers (PrPC).
(A) S-2013. (B) L-2014. Model estimates by circuit and treatment sector. Horizontal line separates treatment sectors, significance groups (Tukey HSD) compare among all rows. No container surveys were conducted during spraying See also S5 Fig.
(PDF)
Summary of spray coverage in S-2013 (A) and L-2014 (B). In both years, most houses were sprayed in at least 5 out of 6 spray cycles, while a small number of houses were never sprayed. In L-2014, experimental spray coverage was much higher than emergency (citywide) spray coverage.
(PDF)
Boxplot of control cage house means: 25 adults per cage, 4 cages per house, approximately 5 houses per spray cycle.
Insects were from a laboratory colony (one colony per year).
(PDF)
Maps showing survey locations by circuit (panel) and week with circuit (color).
(A) S-2013. (B) L-2014.
(PDF)
Aedes aegypti adults per house (AA/HSE).
(A) S-2013. (B) L-2014. Model estimates by circuit and treatment sector. Horizontal line separates treatment sectors; significance groups (Tukey HSD) compare among all rows. See Fig 4A for model description.
(PDF)
Aedes aegypti positive containers per house (PC/HSE).
(A) S-2013. (B) L-2014. Note that Breteau Index (BI) = 100*PC/HSE. Model estimates by circuit and treatment sector. Horizontal line separates treatment sectors, significance groups (Tukey HSD) compare among all rows. See S5 Fig.
(PDF)
Intraspecific variation in ecologically important traits is a cornerstone of Darwin's theory of evolution by natural selection. The evolution and maintenance of this variation depends on genetic architecture, which in turn determines responses to natural selection. Some models suggest that traits with complex architectures are less likely to respon...
Background
Aedes aegypti is a primary vector of dengue, chikungunya, Zika, and urban yellow fever viruses. Indoor, ultra low volume (ULV) space spraying with pyrethroid insecticides is the main approach used for Ae. aegypti emergency control in many countries. Given the widespread use of this method, the lack of large-scale experiments or detailed...
A gene drive biases inheritance of a gene so that it increases in frequency within a population even when the gene confers no fitness benefit. There has been renewed interest in environmental releases of engineered gene drives due to recent proof of principle experiments with the CRISPR-Cas9 system as a drive mechanism. Release of modified organism...
Recent advances in research on gene drives have produced genetic constructs that could theoretically spread a desired gene (payload) into all populations of a species, with a single release in one place. This attribute has advantages, but also comes with risks and ethical concerns. There has been a call for research on gene drive systems that are s...
Recent advances in research on gene drives have produced genetic constructs that could theoretically spread a desired gene (payload) into all populations of a species, with a single release in one place. This attribute has advantages, but also comes with risks and ethical concerns. There has been a call for research on gene drive systems that are s...
A gene drive biases inheritance of a gene so that it increases in frequency within a population even when the gene confers no fitness benefit. There has been renewed interest in environmental releases of engineered gene drives due to recent proof of principle experiments with the CRISPR-Cas9 system as a drive mechanism. Release of modified organism...
The success of control programs for mosquito-borne diseases can be enhanced by crucial information provided by models of the mosquito populations. Models, however, can differ in their structure, complexity, and biological assumptions, and these differences impact their predictions. Unfortunately, it is typically difficult to determine why two compl...
Fall armyworm, Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae), is a target species of transgenic corn (Zea mays L.) that expresses single and pyramided Bacillus thuringiensis (Bt) toxin. In 2014, S. frugiperda were collected from a light trap in North Carolina, and a total of 212 F1/F2 isofemale lines of S. frugiperda were screened for...
Adaptation of pest species to laboratory conditions and selection for resistance to toxins in the laboratory are expected to cause inbreeding and genetic bottlenecks that reduce genetic variation. Heliothis virescens, a major cotton pest, has been colonized in the laboratory many times, and a few laboratory colonies have been selected for Bacillus...
Many vector-borne diseases lack effective vaccines and medications, and the limitations of traditional vector control have inspired novel approaches based on using genetic engineering to manipulate vector populations and thereby reduce transmission. Yet both the short- and long-term epidemiological effects of these transgenic strategies are highly...
Equilibria for the host-vector-pathogen system in the main text in the absence of control.
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Approximating explicit population-genetic models for the spread of a transgenic, anti-pathogen construct using a phenomenological description G(t) of change in mean vector competence.
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Comparing resultant epidemiological dynamics using a phenomenological description of the decline G(t) in vector competence against dynamics predicted by an explicit model of the spread of an anti-pathogen construct (Wolbachia).
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The long-term effect of integrating transgenic population replacement with clinical interventions when relative vector competence cannot be lowered beyond a fixed threshold.
(PDF)
Adaptation of pest species to laboratory conditions and selection for resistance to toxins in the laboratory are expected to cause inbreeding and genetic bottlenecks that reduce genetic variation. Heliothis virescens, a major cotton pest, has been colonized in the laboratory many times, and a few laboratory colonies have been selected for Bt resist...
Heliothine pests such as the tobacco budworm, Heliothis virescens (F.), pose a significant threat to production of a variety of crops and ornamental plants and are models for developmental and physiological studies. The efforts to develop new control measures for H. virescens, as well as its use as a relevant biological model, are hampered by a lac...
Recently, the Vaccines to Vaccinate (v2V) initiative was reconfigured into the Partnership for Dengue Control (PDC), a multi-sponsored and independent initiative. This redirection is consistent with the growing consensus among the dengue-prevention community that no single intervention will be sufficient to control dengue disease. The PDC's expecta...
Background
Transgenic cotton that expresses a gene derived from the bacterium Bacillus thuringiensis (Bt) has been deployed for combating cotton bollworm in China since 1997. As a follow-up on research started in 2002 the quantitative shifts in larval Cry1Ac resistance of field Helicoverpa armigera populations were monitored from 2009–2013 using bi...
Heliothis virescens is an historically important pest of cotton. For nearly two decades, H. virescens populations have been successfully managed by transgenic cotton cultivars that express Bt toxin. Yet H. virescens infestations persist in other cropping systems. This suggests that Bt cotton cultivars impose strong selection pressure on H. virescen...
Recently, genetic strategies aimed at controlling populations of disease-vectoring mosquitoes have received considerable attention as alternatives to traditional measures. Theoretical studies have shown that female-killing (FK), antipathogen (AP), and reduce and replace (R&R) strategies can each decrease the number competent vectors. In this study,...
Background:
Introgressing anti-pathogen constructs into wild vector populations could reduce disease transmission. It is generally assumed that such introgression would require linking an anti-pathogen gene with a selfish genetic element or similar technologies. Yet none of the proposed transgenic anti-pathogen gene-drive mechanisms are likely to...
Evolutionary diversification of sexual communication systems in moths is perplexing because signal and response are under stabilizing selection in many species, and this is expected to constrain evolutionary change. In the moth Heliothis virescens, we consistently found high phenotypic variability in the female sex pheromone blend within each of fo...
