DOI: 10.5061/dryad.6djh9w1dw
title: Local Adaptation of Male Sexual Fitness in Drosophila melanogaster

description: 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.
description: # Local adaptation of male sexual fitness in *Drosophila melanogaster*
 Dataset DOI: [10.5061/dryad.6djh9w1dw](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.