Data for: Phenotypic adaptation to temperature in the mosquito vector, Aedes aegypti
Cite this dataset
Dennington, Nina et al. (2023). Data for: Phenotypic adaptation to temperature in the mosquito vector, Aedes aegypti [Dataset]. Dryad. https://doi.org/10.5061/dryad.z8w9ghxgc
Abstract
Most models exploring the effects of climate change on mosquito-borne disease ignore thermal adaptation. However, if local adaptation leads to changes in mosquito thermal responses, ‘one size fits all’ models could fail to capture current variation between populations and future adaptive responses to changes in temperature. Here we assess phenotypic adaptation to temperature in Aedes aegypti, the primary vector of dengue, Zika, and chikungunya viruses. First, to explore whether there is any difference in existing thermal response of mosquitoes between populations we used a thermal knockdown assay to examine five populations of Ae. aegypti collected from climatically diverse locations in Mexico, together with a longstanding laboratory strain. We identified significant phenotypic variation in thermal tolerance between populations. Next, to explore whether such variation can be generated by differences in temperature we conducted an experimental passage study by establishing six replicate lines from a single field-derived population of Ae. aegypti from Mexico, maintaining half at 27°C and the other half at 31°C. After 10 generations we found a significant difference in mosquito performance, with the lines maintained under elevated temperatures showing greater thermal tolerance. Moreover, these differences in thermal tolerance translated to shifts in the thermal performance curves for multiple life history traits, leading to differences in overall fitness. Together, these novel findings provide compelling evidence that Ae. aegypti populations can and do differ in thermal response, suggesting that simplified thermal performance models might be insufficient for predicting the effects of climate on vector-borne disease transmission.
README: Associated data for "Phenotypic adaptation to temperature in the mosquito vector, Aedes aegypti"
https://doi.org/10.5061/dryad.z8w9ghxgc
We used explored mosquito adaptation to temperature in the vector species Aedes aegypti through thermal knockdown of field mosquitoes and life history experiments of experimentally adapted mosquitoes. We used survival analysis and a Bayesian approach to analyze these data.
Description of the data and file structure
There are three types of files found in this set, excel/csv files containing raw data, R code and text files (containing models for Bayesian models). There are three sets of data containing field mosquito knockdown data, experimental passage mosquito knockdown data, and life history data for experimental passage mosquitoes. Both knockdown data sets correspond to R code labeled knockdown models. Selection experiment data correspond to models using a Bayesian approach. Models for mosquito development rate, egg-to-adult survival, and juvenile mortality rate models along with the fitness model are all contained in one R code. Each of these traits requires a .bug/.txt file which contains the model. Separately, we have the code for the hierarchical eggs per female per gonotrophic cycle code and the adult survival analysis code (and corresponding models).
This dataset includes three separate files:
"Mexico Knockdown Data.csv":
- Includes data from a thermal knockdown experiment using 5 populations of Aedes aegytpi from Mexico (Cabo San Lucas, Acapulco, Monterrey, Ciudad Juárez, and Jojutla) along with one laboratory adapted line of mosquitoes. This CSV file includes the replicate assay (6 total, 10 individuals in each), the population, the status (1=knocked down, 0= resisted knockdown), time to knockdown (amount of time until an individual was knocked down at 41°C), and Seconds (time to knockdown converted to seconds). This dataset corresponds to the R file "Dennington_GCB_ Knockdown models".
"Selection Experiment Knockdown Data.csv":
- Includes data from a thermal knockdown experiment using six lines of mosquitoes selected over 10 generations\, three at a control temperature of 27°C and three lines at an increased thermal pressure of 31°C. We compare these results to the population of mosquitoes from Monterrey\, Mexico before selection. This CSV file includes the replicate assay (6 total\, 10 individuals in each)\, the population (three selected at 27°C and three at 31°C)\, the status (1=knocked down\, 0= resisted knockdown)\, time to knockdown (amount of time until an individual was knocked down at 41°C)\, Seconds (time to knockdown converted to seconds) and Pressure (the selection pressure over 10 generations- N=no selection\, L=Selected at 27°C and H=Selected at 31°C). This dataset corresponds to the R file "Dennington_GCB_ Knockdown models".
"Dennington_SelectionExp_LarvalDevelopmentSurvival.csv":
Includes data from life history measurements including columns Population (the replicate lines at either 27°C or 31°C), Temp (Temperature at which the groups were reared), Rep (replicate measurements of each selected line), Pupae (number of pupae formed), Adults (number of adults eclosed), Larv_Surv (proportion of larvae that survived to adult from starting 200 larvae), Pupal death (number of pupae that formed but did not eclose), Time to pupa (days to pupation), Time to adult (days to adult), dev rate p (pupation rate= 1/ time to pupa), dev rate a (mosquito development rate= 1/time to adult), Pressure (the selection pressure over 10 generations- L=Selected at 27°C and H=Selected at 31°C), number attempted (total number of starting mosquitoes), and juvenileMU (juvenile mortality rate- approximation using the -(natural log of Larval survival)/ Time to adult). This dataset corresponds to the R file "Dennington_GCB_TPC Models. R".
"Dennington_ SelectionExp_Fecundity.csv":
Includes data from life history measures for fecundity including Population (the replicate lines at either 27°C or 31°C), Temp (Temperature at which the groups were reared), Rep (replicate measurements of each selected line), number (Individual within each experiemtal group), eggs (number of eggs for the first gonotrophic cycle), larvae (number of larvae that hatched), hatch_rate (number of larvae/number of eggs), date_fed (date of the first blood feed), date_first_lay (date of the first time eggs were layed), and cycle_length (amount of time in days between first blood feed to first egg lay). This dataset corresponds to the R file "Dennington_Fecundity Model.R".
"Dennington_SelectionExp_AdultSurvivalSummary.csv":
Includes data from life history measures for adult survival in a summary form. Columns are Population (the replicate lines at either 27°C or 31°C), Temp (Temperature at which the groups were reared), Rep (replicate measurements of each selected line), M (number of dead males), F (number of dead females), status (acknowledging that these individuals died), Day (day that we censored the experiment), Total (sum of dead individuals), Pressure (the selection pressure over 10 generations- L=Selected at 27°C and H=Selected at 31°C), NumberAdultsEclosed (number of individuals that made it to adulthood), and ProportionDead (total number that died over the total number that eclosed). This dataset corresponds to the R file "Adult Survival Anlysis (by LRJ).R".
"Dennington_SelectionExp_AdultSurvivalRaw.csv":
Includes data from life history measures for adult survival in a raw data form (counting how many individuals died on each day). Columns are Population (the replicate lines at either 27°C or 31°C), Temp (Temperature at which the groups were reared), Rep (replicate measurements of each selected line), Date (the date that the measurement was taken), Day (the day of the experiment, with day 1 being the first day), Dead_M (number of dead males, Dead_F (number of dead Females). This dataset corresponds to the R file "Adult Survival Anlysis (by LRJ).R".
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The files including the code to produce all models are:
"Dennington_GCB_ Knockdown models.R":
Includes analysis for thermal knockdown data using Kaplan-Meier survival curves with ggsurvplot (including both models in the main document and the supplementary documents).
"Dennington_Fecundity Model.R":
Analysis for eggs per female per first gonotrophic cycle model, with an interaction using Bayesian inference. This code uses "Dennington_SelectionExp_LarvalDevelopmentSurvival.csv" and "JAGS_Modelexample.bug" and "JAGS_quad_interaction.bug"
"Dennington_GCB_Code to get summary data for TPCs.R"
Example code to produce raw data plots (Figure 3). This code uses "Dennington_SelectionExp_Fecundity.csv".
"Dennington_GCB_TPC Models.R":
Code for for mosquito development rate, egg-to-adult survival, and juvenile mortality rate models along with fitness model. The fitness model integrates juvenile mortality rate, mosquito development rate, fecundity and adult survival models. This code requires "JAGS_model_briere.bug".
"Adult Survival Anlysis (by LRJ).R":
Code for adult survival analysis as used in the fitness model. This code uses the data set "Dennington_SelectionExp_AdultSurvivalRaw.csv" and "Dennington_SelectionExp_AdultSurvivalSummary.csv". This code requires "surv_gengamma_temp.txt".
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Sharing/Access information
All data and code were produced for the purpose of this manuscript.
Figure to produce the map in the supplemental material (SI figure 1) was adapted from published code by Valle-Jones D (2022). mxmaps: Create Maps of Mexico. https://www.diegovalle.net/mxmaps/, https://github.com/diegovalle/mxmaps).
Code/Software
This code was run on R/Rstudio Version 2023.06.1.
Methods
Mosquito Collection
Aedes aegypti mosquitoes were collected from the field using ovitraps in five different locations in Mexico (Cabo San Lucas, Acapulco, Monterrey, Ciudad Juárez, and Jojutla) and compared to a standard laboratory population (Rockefeller strain) maintained at Penn State University. The field locations were chosen to capture a gradient of the landscape and climate, driven primarily by variation in altitude. Populations were founded with sufficient viable eggs collected from multiple ovitraps across the cities to yield at least 100 adult mosquitoes in the F1 laboratory generation. Mosquitoes were reared for a generation (F2) in standard laboratory conditions (27°C, 80% humidity, 12:12hr photoperiod, 0.60 mg of bovine liver powder per 600 larvae and ad libitum access to 10% sugar solution for the adults) prior to experimentation to remove the influence of any maternal effects. Two populations, Jojutla and Juárez, were reared for an additional generation (F3) to ensure a large enough population for subsequent experiments.
Knockdown assays to estimate thermal tolerance
We followed methods developed recently by Ware-Gilmore et al. to examine the thermal tolerance of adult Ae. aegypti mosquitoes. These methods were adapted from numerous studies in Drosophila and were shown to be sufficiently sensitive to demonstrate the effects of infection with either dengue virus or the bacterial endosymbiont, Wolbachia, on thermal sensitivity. In brief, three-to-four-day-old female mosquitoes were placed into individual sealed 40mL glass vials. The vials were submerged into a tank filled with water at a regulated temperature of 41°C. Individuals were allowed two minutes to acclimate, after which they were monitored and the time to knockdown (immobility or death) was recorded. We monitored mosquitoes until all were knocked down. In the common garden experiment, we conducted six replicate runs of 10 mosquitoes giving a total of 60 mosquitoes per population. The passage experiment had 18 total replicates (6 per independent passaged line) of 10 mosquitoes for each temperature treatment.
Experimental passage
We used the F1 population of Ae. aegypti mosquitoes collected from Monterrey, Mexico, to establish six replicate lines, half of which were maintained at a standard insectary temperature of 27°C (80% humidity, 12:12hr photoperiod), which also approximates the overall mean temperature in Monterrey summer months, and the other half were maintained at an elevated temperature of 31°C (80% humidity, 12:12hr photoperiod) (SI Appendix, Fig. S1 and S2, Table S1). The elevated temperature of 31°C represents an increase of 4°C as might be expected under future climate warming. However, neither temperature simulates realistic environmental variation in the natural home environment and so both treatments were under some level of artificial selection to lab conditions.
Each replicate line was initiated with 600 first instar larvae. Larvae were added into 5.7 L containers containing 3 L of deionized water and 0.60mg of bovine liver powder (MP Biomedicals) and placed in controlled temperature incubators (3 replicate containers at 27°C and 3 containers at 31°C). Every other day we added 0.60 mg of bovine liver powder to each container until larvae began to pupate when we scaled the food to the number of remaining larvae. We removed pupae and placed them in a small cup (30 mL) with water from their original environment to allow for eclosion. Cups containing pupae were added to a large cage with ad libitum access to 10% sugar solution made with dextrose anhydrous and deionized water to sustain the adults as they emerged. We counted total pupae per container, along with the number of pupae that eclosed successfully. When the adult mosquitoes were of reproductive age (3-5 days after eclosion), any dead adult mosquitoes were counted. These measures were used to get an accurate count of surviving adult mosquitoes in each cage. To ensure balanced selection between lines and account for potential effects of genetic bottlenecks or drift that could result from different population sizes, adult mosquitoes were culled (3-5 days after eclosion) before blood feeding so that each line had the same number of mosquitoes. The lines were culled in pairs, for example replicate one at 27°C was paired with replicate one in 31°C, for all ten generations to ensure independence between replicates. Mosquitoes were culled with a 50:50 sex ratio to maintain possible differences in selection on sex. Once the adult cages were established, mosquitoes were fed a human blood meal every four days for 16 days using a standard membrane feeder. Eggs were collected every day and maintained on dry filter paper to prevent hatching. At the end of the 16-day egg laying period, the eggs were transferred to larval containers to initiate hatching, thus maintaining a uniform age structure. Mosquitoes were reared through to adult as described. We followed this protocol for ten generations (SI Appendix, Fig. S5).
At the end of the experimental period, we measured thermal tolerance for the six lines using the knockdown methods described above. In addition, to extend beyond this proxy variable and fully explore the effects of the passage treatments, egg-to-adult survival, mosquito development rate, mean adult survival, and fecundity were measured in mosquitoes reared in environmentally controlled incubators at 13°C, 17°C, 21°C, 25°C, 27°C, 29°C, 31°C, 33°C, 35°C, 37°C, each ± 0.2°C and 80%± 10% relative humidity. Eggs from the 6 passaged lines were hatched at 27°C. After 24 hours, 200 first instar larvae were put into 1.89 L containers with 1 L of deionized water and 0.20 mg of larvae bovine liver powder (MP Biomedicals) and placed in the respective incubator. We fed larvae 0.20 mg of liver powder every other day until pupation. Once larvae began to pupate, we scaled their food to the number of remaining larvae. We removed and counted living and dead pupae the day of pupation and placed them in a small cup (30 mL) with water from their original environment to allow for eclosion. Cups containing pupae were added to a small cage (17.5 cm3) with ad libitum access to 10% sugar solution made with dextrose anhydrous and deionized water. We then counted the number of adults that eclosed every day. After 95% of females emerged, we blood fed females who were then 3-5 days old. We used blood from de-identified human donors (BioIVT, Corp.) so IRB approval and human subjects’ approval was not needed. Immediately after blood-feeding, we counted the total number of blood-fed females and placed up to 10 individual females into separate containers (50 mL polypropylene centrifuge tubes) lined with filter paper that contained 7 mL deionized water to measure individual fecundity. We recorded the day that females in individual containers first laid eggs and let them lay eggs for three total days, after which we removed them from their containers. We extracted the water from the containers to let the filter paper dry in their respective incubators and then we counted the eggs. We counted and determined the sex of the number of adults that died every day. We censored this experiment 4 weeks after the first egg lay at each temperature (SI Appendix, Fig. S5).
Funding
National Science Foundation, Award: DEB-1518681, Ecology and Evolution of Infectious Diseases