Autosomal suppression and fitness costs of an old driving X chromosome in <i>Drosophila testacea</i>
Bibliographic record
Abstract
Abstract Driving X chromosomes (X D s) bias their own transmission through males by killing Y‐bearing gametes. These chromosomes can in theory spread rapidly in populations and cause extinction, but many are found as balanced polymorphisms or as “cryptic” X D s shut down by drive suppressors. The relative likelihood of these outcomes and the evolutionary pathways through which they come about are not well understood. An X D was recently discovered in the mycophagous fly, Drosophila testacea , presenting the opportunity to compare this X D with the well‐studied X D of its sister species, Drosophila neotestacea . Comparing features of independently evolved X D s in young sister species is a promising avenue towards understanding how X D s and their counteracting forces change over time. In contrast to the X D of D. neotestacea , we find that the X D of D. testacea is old, with its origin predating the radiation of three species: D. testacea , D. neotestacea and their shared sister species, Drosophila orientacea . Motivated by the suggestion that older X D s should be more deleterious to carriers, we assessed the effect of the X D on both male and female fertility. Unlike what is known from D. neotestacea , we found a strong fitness cost in females homozygous for the X D in D. testacea : a large proportion of homozygous females failed to produce offspring after being housed with males for several days. Our male fertility experiments show that although X D male fertility is lower under sperm‐depleting conditions, X D males have comparable fertility to males carrying a standard X chromosome under a free‐mating regime, which may better approximate conditions in wild populations of D. testacea . Lastly, we demonstrate the presence of autosomal suppression of X chromosome drive. Our results provide support for a model of X D evolution where the dynamics of young X D s are governed by fitness consequences in males, whereas in older X D systems, both suppression and fitness consequences in females likely supersede male fitness costs.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| 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) | 0.000 | 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 teacher head, 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".