High Rate of Large-Scale Hemizygous Deletions in Asexually Propagating Daphnia: Implications for the Evolution of Sex
Bibliographic record
Abstract
The origin and maintenance of sex remains one of the most debated topics in evolutionary biology. Investigations of the molecular genetic consequences of asexuality, such as direct estimation of mutation and recombination rates in asexual lineages, are critical for explaining the prevalence of sex in nature. In this study, we use long-term mutation accumulation lines of asexually propagating Daphnia pulex and D. obtusa to examine the role of hemizygous deletion and ameiotic recombination (crossover and gene conversion) in the evolution of asexual taxa. Large-scale hemizygous deletions ranging from 2 to 30 kb are found to occur at a rate of 6.7 × 10(-5) locus(-1) generation(-1) in D. pulex, which is one order of magnitude higher than the rate of large-scale deletions in Saccharomyces cerevisiae and Drosophila melanogaster. A conservative estimate of gene conversion and crossing over in the apomictic germ line cells of Daphnia yields a rate of 3.3 × 10(-5) locus(-1) generation(-1). Our exceptionally high rate of large-scale segmental deletions suggests that the long-term survival of asexual Daphnia lineages is likely compromised by a high deleterious mutation pressure and that selection against deleterious mutations may play an important role in the evolution and maintenance of sex.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".