Genomic evidence of long-term asexuality at the northern range limit of the wetland plant, Decodon verticillatus (Lythraceae)
Bibliographic record
Abstract
For many plants, asexual, clonal reproduction appears to be the predominant form of reproduction at their geographic range edge, but how long clonal populations persist and their role in range dynamics are largely unknown. If asexuality enables well-adapted genotypes to persist, this may allow species to expand beyond their sexual niche. Under this scenario, genomic signatures of long-term asexuality should be detectable in range-edge populations. We investigated this hypothesis in the wetland plant, Decodon verticillatus (Lythraceae), which reproduces predominantly through clonal reproduction at its northern range limit. We assembled the transcriptome de novo, identified single nucleotide polymorphisms (SNPs), and compared patterns of genetic variation in sexual and asexual populations at and approaching the range limit. Asexual genotypes exhibited several signatures of long-term asexuality including higher heterozygosity, fewer unique homozygous SNPs (doubletons), and a breakdown of isolation by distance. They also tended to include more deleterious non-synonymous and radical amino acid altering mutations. However, the frequency of unique heterozygous SNPs (singletons) did not differ between sexual and asexual genotypes, and average genetic differentiation was unexpectedly higher among sexual than among asexual genotypes. Yet, overall, our results are consistent with the hypothesis that asexual reproduction enabled D. verticillatus to expand its range further north than would have been possible under sexual reproduction alone. Understanding the factors that influence range dynamics is becoming increasingly important to better anticipate the capacity of species to adapt and shift their ranges in response to anthropogenic environmental changes and to prioritize range-edge populations for conservation.
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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) | 0.000 | 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 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".