Data from: The arduous path to obligate asexuality in Daphnia

Molinier, Cécile 1 2 ; Clément, Cassandra2; Calzan, Héloïse2; Lenormand, Thomas2; Haag, Christoph2

Published Nov 05, 2025 on Dryad. https://doi.org/10.5061/dryad.pzgmsbd1h

Data files

Nov 05, 2025 version files 3.22 MB

Likelihood_models.nb

3.20 MB
LOH_DATA.txt

8.59 KB
README.md

2.68 KB

Abstract

Evolutionary transitions to asexuality are often studied by comparing asexuals found in nature with closely related sexuals. Yet, asexuals sampled in nature may represent only the most successful lineages and therefore provide limited information about the average properties of newly emerging asexuals. These properties are crucial in determining the success of asexual lineages and hence the frequency with which transitions to asexual life cycles evolve. Here, we generate new asexual lineages of f Daphnia pulex through contagious asexuality, in which rare males from obligate asexual lineages transmit asexuality to new lineages by mating with sexual females. Unlike asexuals found in nature, most new lineages were capable of both sexual and asexual reproduction (facultative asexuality) and produced non-identical (i.e., non-clonal) daughters when reproducing asexually. They also showed reduced fertility compared to natural asexuals, especially when reproducing asexually, which is expected to reduce the success rate of sex-asex transitions in nature. Taken together, these results suggest that creating new asexual lineages by contagion is more complex than previously thought and may result in diverse, non-clonal offspring, on which subsequent selection can act. If general, such initial fitness valleys associated with sex-asex transitions may be key to resolving the evolutionary “paradox of sex”.

Dataset DOI: 10.5061/dryad.pzgmsbd1h

Description of the data and file structure

To obtain a quantitative estimate of the proportions of asexually produced F2s, mixed, and sexual F1s, as well as to test for a possible difference between male-producing (MP) vs. non-male producing (NMP) offspring, we used a likelihood model approach. This allowed us to combine the information from several technically difficult to obtain and therefore somewhat disparate data sets, but all from the main cross (TEX-114 x STM-2).

The models used data on fill rates in presence and absence of males (in NMP F1s and, for the estimation of the sterility rate also in MP F1s) and data on LOH (loss of heterozygosity) in F2s (asexual offspring of NMP F1s and all offspring of MP F1s), while accounting for differences in sample size (e.g., different numbers of diapause capsules checked for fill rates, different numbers of F2s genotyped, different number of variable loci). Sterility rate was accounted using fill rate data defined as empty diapause capsule, which we indeed found in one MP F1 and one NMP F1 lineage for which males were added. Considering the occurrence of mixed reproduction in the main cross, demonstrated by a substantial increase in fill rate upon male addition in MP and NMP F1 lineages (from 1.67% to 46.5%, Table S4 from) and supported by paternity tests (Table S5), it was pertinent to extend our analysis to the F2 level. We also jointly analysed LOH rates during asexual reproduction. All models can be found in the Mathematica file “Likelihood_models.nb” that needs the "LOH_DATA.txt" raw data file.

Files and variables

File: LOH_DATA.txt

Description:

Variables

Pheno: Phenotype of the individual: MP laboratory generated F1 male-producing, NMP laboratory generated F1 non-male producing, nat: natural obligate parthenogenic lineage, int: intercross between MP and NMP
Sample_clone: ID of the maternal lineage
Indiv_name: embryo ID
locus_total: total number of informative microsatellite loci
locus_homos: number of homozygous microsatellite loci
proportion_LOH_obs: proportion of loss of heterozygosity

File: Likelihood_models.nb

Description: Likelihood models

Code/software

We used Mathematica 13.2.1 (Wolfram Research 2017)

Access information

Other publicly accessible locations of the data:

Supplemental files of the article from Molinier C., Clément C., Calzan H., Lenormand T., Haag C. R. The arduous path to obligate asexuality in Daphnia, Proc. R. Soc. B, doi: 10.1098/rspb.2025.2307