Local Adaptation of Male Sexual Fitness in Drosophila melanogaster
Data files
Jun 18, 2025 version files 30.88 KB
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dryad_Data_population.csv
5.69 KB
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dryad_Data_replicate.csv
11.47 KB
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R_code_for_dryad.R
7.68 KB
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README.md
6.04 KB
Abstract
Mate competition gives rise to sexual selection, and healthier, more vigorous males are likely to be superior competitors. Because most genes are likely to impact an individual’s vigor, sexual selection should act across much of the genome to favor the same alleles as natural selection, thereby promoting adaptation. On the other side of the coin, adaptation to an environment should enhance male sexual fitness in that environment because it is likely to increase the overall vigor of individuals within a population. Surprisingly, there are few tests of this latter prediction, and results are mixed. Taking advantage of a long-term evolution experiment involving replicate populations of Drosophila melanogaster, we performed a reciprocal transplant in which populations evolved in one of two alternative larval environments were reared in each of these two environments. Larval survival was quantified as an index of non-sexual fitness reflective of adaptation to their local larval environment, and the sexual fitness of the males that ecolosed was then compared via a comprehensive measure that included pre- and post-copulatory reproductive success in a competitive assay performed under conditions that closely mirrored those to which the populations had been evolving. Body size (adult dry weight) and development time (egg-to-adult eclosion) were also recorded for males and females that eclosed from the reciprocal transplant. The results add support to the idea that local adaptation to the abiotic environment enhances male sexual fitness.
Dataset DOI: 10.5061/dryad.6djh9w1dw
Description of the data and file structure
Data from a reciprocal transplant of 20 replicate experimental populations, 10 adapted to each of two larval rearing environments (termed adaptation sets), one involving a novel cornstarch larval medium and a 2 h heat shock at 37 C to 3-day old larvae, and the second supplementing the standard cornmeal-based larval medium with 5% salt and a constant 28 C throughout larval development (termed ‘corn’ and ‘salt’ larval adaptation sets respectively, for brevity). To promote continued adaptation to these novel larval environments, after six generations, the heat shock was increased to 4 h in the corn set, and the salt was increased to 6% in the salt set. Within each larval adaptation set, the 10 replicate populations were split equally between two adult mating environments such that mate competition occurred each generation in either small and structurally simple standard Drosophila culture vials, or larger (1.65 L) containers with multiple food patches and added structural complexity from two pipe cleaners protruding from the lid into the interior (‘simple’ vs. ‘complex’ mating environments, respectively).
Reciprocal transplant: For each experimental population in each rearing environment, multiple vials of 100 larvae were set up, allowing the number of adults that eclosed to be used as a measure of non-sexual fitness (i.e., larval survival) reflecting the extent of local adaptation to that rearing environment. Adult males were then competed against bw competitor males for mating with bw females, allowing the sexual fitness (i.e., reproductive success) of the experimental males to be compared when these males developed in the two rearing environments. The reciprocal transplant was performed in four blocks (B1-B4).
Files and variables
File: dryad_Data_population.csv
Description: A single value of larval survival, development time, and adult dry weight was collected for each population when reared in each environment. The sexual fitness of experimental males was estimated by counting the adult offspring that eclosed from the competitive sexual fitness assay after phenotyping them by eye color (bw vs. wt). In this data file, the total number of each was summed across the five replicates for a given population and rearing environment and the sexual fitness of the experimental males in that rearing environment was then calculated as the number of wt offspring divided by the total number of offspring, yielding a single value for each population in each rearing environment.
Replicate-level data for the sexual fitness assay are given in the separate data file: dryad_Data_replicate.csv
Variables
- population: combination of adaptation set (corn vs. salt), mating environment (simple vs. complex, denoted 's' and 'c' respectively), and population replicate number (1-5) within that combination of adaptation set and mating environment.
- rearing_env: larval environment the population was reared during the reciprocal transplant
- adapt_set: larval environment in which the population evolved
- mating_env: mating environment in which the population evolved and was tested
- block: experimental block
- larvae_in: number of larvae for that population in that rearing environment during the reciprocal transplant. A varying number of vials of 100 larvae each were set up for each population in each rearing environment.
- female_adults_out: number of females that eclosed
- male_adults_out: number of males that eclosed
- adults_out: total number of adults that eclosed (females + males)
- larvae_died: number of larvae that failed to eclose (i.e. larvae_in - adults_out)
- female_larval_survival: female_adults_out / (larvae_in / 2)
- male_larval_survival: male_adults_out / (larvae_in / 2)
- larval_survival: adults_out/larvae_in
- n_wt_offspring: number of wt offspring eclosed in sexual fitness assay
- n_bw_offspring: number of bw offspring eclosed in sexual fitness assay
- focal_sire: n_wt_offspring/(n_wt_offspring + n_bw_offspring)
- mean_emergence_day_male: mean emergence day of male offspring
- mean_emergence_day_female: mean emergence day of male offspring
- Male_mass_mg: mean mass of male offspring in mg
- Female_mass_mg: mean mass of male offspring in mg
File: dryad_Data_replicate.csv
Description: For the sexual fitness assay during the reciprocal transplant, five replicates were created for each combination of population × rearing environment, each consisting of 10 focal males together in a single vial or container with 25 bw males and 35 bw females. This file reports these data separately by replicate instead of being pooled across replicates.
Variables
- population: combination of adaptation set (corn vs. salt), mating environment (simple vs. complex, denoted 's' and 'c' respectively), and population replicate number (1-5) within that combination of adaptation set and mating environment.
- replicate: replicate number (1-5)
- rearing_env: larval environment the population was reared during the reciprocal transplant
- adapt_set: larval environment in which the population evolved
- mating_env: mating environment in which the population evolved and was tested
- block: experimental block
- n_focal_males_survived: number of experimental males that survived the 6-day interaction phase during the sexual fitness assay
- n_competitor_males_survived: number of competitor (bw) males that survived the 6-day interaction phase during the sexual fitness assay
- n_wt_offspring: number of wt offspring eclosed in sexual fitness assay
- n_bw_offspring: number of bw offspring eclosed in sexual fitness assay
- focal_sire: n_wt_offspring/(n_wt_offspring + n_bw_offspring)
Code/software
File: R_code_for_dryad.R
R code for data analysis.
R version 4.2.3.
Packages are listed in the R script.