DOI: 10.5061/dryad.5qfttdzgb
title: Data from: An empirical test of Baker’s law: Dispersal favors increased rates of self-fertilization

description: Baker’s law is the observation that recently dispersed populations are
 more likely to be self-fertilizing than populations at the range core. The
 explanatory hypothesis is that dispersal favors self-fertilization due to
 reproductive assurance. Caenorhabditis elegans nematodes reproduce via
 either self-fertilization or outcrossing and frequently disperse in small
 numbers to new bacterial food sources. While C. elegans males facilitate
 outcrossing, males and outcrossing are rare in natural C. elegans
 populations. Here, we use experimental evolution to test if frequent
 dispersal selects for the invasion of self-fertilization into
 predominantly outcrossing populations. C. elegans dispersal often occurs
 in the dauer alternative life stage. Therefore, we tested the effects of
 dispersal on rates of self-fertilization in populations exposed to
 dauer-inducing conditions and populations maintained under standard lab
 conditions. Overall, we found that populations required to disperse to new
 food sources rapidly evolved substantially elevated rates of
 self-fertilization compared to populations that were not required to
 disperse in both dauer and non-dauer populations. Our results demonstrate
 that frequent dispersal can readily favor the evolution of increased
 selfing rates in C. elegans populations, regardless of life stage. These
 data provide a potential mechanism to explain the dearth of outcrossing in
 natural populations of C. elegans.
description: # Dispersal favors self-fertilization
 [https://doi.org/10.5061/dryad.5qfttdzgb](https://doi.org/10.5061/dryad.5qfttdzgb) ## Description of the data and file structure Data files are named after experiments described in manuscript.  **initial fecundity assays.xlsx:** Fecundity assays for signs of inbreeding depression described in the NEMATODE STRAINS AND REPRODUCTIVE MODE methods section. **patch dispersal assays.xlsx:** Assays for distribution of worms across bacterial patches as described in the DISPERSAL TREATMENTS methods section. **dispersal power analysis.xlsx:** beta values generated by power analysis for patch distribution assay as described in the DISPERSAL TREATMENTS methods section. **movement between patches.xlsx:** Assay for movement of worms between bacterial patches as described in the DISPERSAL TREATMENTS methods section.  **dispersal fecundity assays.xlsx:** Assays of the effect of dispersal and mating system on worm fecundity, as described in the FECUNDITY ASSAYS methods section. **dispersal selfing rates.xlsx:** Selfing rates calculated from male frequencies during evolution experiment described in the SELFING INVASION EVOLUTION EXPERIMENT methods section.  ### Files and variables #### File: initial\_fecundity\_assays.xlsx **Description:** Fecundity assays for signs of inbreeding depression described in the NEMATODE STRAINS AND REPRODUCTIVE MODE methods section. ##### Variables * Worm treatment: CF3 OC (CF3 WT herm outcrossed to CF3-30 male) or CF3 Self (CF3 WT allowed to self-fertilize)  * Replicate: Plate replicate number within treatment block * Reproductive mode: reproductive mode by P generation worm (outcrossing or selfing) * Offspring: Number of offspring produced by F1s, counted at 72 hours * Date: Date counted #### File: dispersal\_power\_analysis.xlsx **Description:** Beta values (portion of simulations with failed to reject the null hypothesis) generated by power analysis for patch distribution assay, as described in the DISPERSAL TREATMENTS methods section. Sheet 1 contains beta values generated by simulations for all worms; sheet 2 contains beta values generated by simulations for herm vs male worms.  ##### Variables * no of worms: number of worms found on bacterial patches * alt hypothesis: the portion of worms dispersed to the focal bacterial patch * beta: the generated beta value #### File: patch\_dispersal\_assays.xlsx **Description:** Assays for distribution of worms across bacterial patches as described in the DISPERSAL TREATMENTS methods section. Note that the data input for "bacterial patch" (as referred to in manuscript) was originally called "spot." ##### Variables * dispersal: dispersal treatment (dispersal or no dispersal) * dauer: dauer treatment (dauer or no dauer) * mating system: CF3 wt (mixed maters) or CF3-30 (obligate outcrossers) * plate: plate number (arbitrarily assigned) * spot: bacterial patch on plate (arbitrarily numbered) * worms plated: number of worms initially added to center of plate * herms: number of hermaphrodite/female worms found on each patch at 24 hours * males: number of male worms found on each patch at 24 hours (left blank on assays not using males) * total worms: total number of worms counted on each patch per plate at 24 hours, calculated by (herms + males) * plate total: all worms counted on each replicate plate at 24 hours, calculated by (spot 1 + spot 2 + spot 3 + spot 4) * plate expected: expected number of worms on patch if distributed evenly, calculated by (plate total*0.25) * portion on spot: portion of counted worms at 24 hours on each patch, calculated by (total worms / plate total) * portion plated on spot: portion of initially plated worms on each patch, calculated by (total worms / worms plated) * counter: initials of person counting worms (left blank for assays where information was not recorded) * date: date worms were counted (left blank for assays where information was not recorded) #### File: movement\_between\_patches.xlsx **Description:** Assay for movement of worms between bacterial patches as described in the DISPERSAL TREATMENTS methods section.  ##### Variables * Dispersal: dispersal treatment (dispersal or no dispersal) * Replicate: plate replicate number within treatment block * Total Plated: number of worms initially added to center of plate * Original Spot: number of worms counted on spot on which they were plated at end of assay * Alternate Spot: number of worms counted on other bacterial patch at end of assay (i.e., worms that moved to a new patch) * Total observed: the total number of worms counted at 24 hours, calculated by (Original Spot + Alternate Spot) * Percent Movement original: portion of plated worms that moved to a new patch, calculated by (Alternate Spot / Total Plated) * Percent Movement observed: portion of worms recovered at end of assay that had moved to a new patch, calculated by (Alternate Spot / Total observed) * Percent obs relative to total plated: a measurement of recovered worms compared to initially plated worms, calculated by (Total observed / Total Plated) #### File: dispersal\_fecundity\_assays.xlsx **Description:** Assays of the effect of dispersal and mating system on worm fecundity, as described in the FECUNDITY ASSAYS methods section. ##### Variables * dispersal: dispersal treatment (dispersal or no dispersal) * mating system: "Ob out" (CF3-30/obligate outcrossers) or "mixed mating" (CF3 WT) * rep: Plate replicate number within treatment block * \# worms plated: number of worms plated at start of assay * \# herm/female: number of worms estimated to be hermaphrodites/females based on mating system  * eggs 6 hr: number of eggs counted at 6 hours * eggs 8 hr: number of eggs counted at 8 hours * eggs 10 hr: number of eggs counted at 10 hours * eggs 12 hr: number of eggs counted at 12 hours * eggs 14 hr: number of eggs counted at 14 hours * eggs 20 hr: number of eggs counted at 20 hours * egg/egg-producing 14hr: eggs per egg-producing worm (herms/females only) at 14 hours * egg egg producing: eggs per egg-producing worm (herms/females only) at 20 hours * egg per worm: eggs per worm (herms/females and males) at 20 hours #### File: dispersal\_selfing\_rates.xlsx **Description:** Selfing rates calculated from male frequencies during evolution experiment described in the SELFING INVASION EVOLUTION EXPERIMENT methods section. Blank cells represent a lack of data for the population in question.  ##### Variables * Dauer: dauer treatment (dauer or no dauer) * Treatment: dispersal treatment (dispersal or no dispersal) * Replicate pop: replicate population number within each treatment * passage: passage at which male frequencies were counted * \# male: number of males  * \# herm: number of hermaphrodites * male freq: male frequency, calculated by (# male/(# male + # herm)) * outcrossing rate: rate of outcrossing within population, calculated from male frequency using nondisjunction rate to account for spontaneous male generation, or (male freq * (2-0.005)) * selfing rate: rate of self-fertilization calculated within population, calculated by (1 - outcrossing rate) ## Code/software All analyses were done in RStudio version 1.2.1335.