The prevalence of genome replacement in unisexual salamanders of the genus Ambystoma (Amphibia, Caudata) revealed by nuclear gene genealogy.
Bibliographic record
Abstract
BACKGROUND: Unisexual salamanders of the genus Ambystoma exemplify the most ancient lineage of unisexual vertebrates and demonstrate an extremely flexible reproductive system. Unisexual Ambystoma interact with and incorporate genomes from two to four sexual species (A. laterale, A. jeffersonianum,A. texanum, and A. tigrinum), to generate more than 20 genome compositions or biotypes. Unisexual ploidy levels range from diploid to pentaploid, but all contain at least one A. laterale (L) genome. Replacement of nuclear genomes might be responsible for the evolutionary longevity of unisexual Ambystoma but direct evidence for the prevalence of genome replacement in natural populations is absent. Two major puzzling questions have remained unanswered over the last few decades: 1) is genome replacement a common reproductive method in various unisexual populations and, 2) is there an ancient "L" genome that persists in various unisexual genome compositions. RESULTS: We examined 194 unisexual and 89 A. laterale specimens from 97 localities throughout their range and constructed a genealogy of the "L" genomes using a nuclear DNA marker (L-G1C12) to answer the above questions. Six L-G1C12 haplotypes (A-F) were shared by individuals in various A. laterale and unisexual populations. The general geographical distribution of the haplotypes in unisexual populations conformed to those found in A. laterale, indicating that "L" genomes in unisexuals are obtained from sympatric or nearby populations of A. laterale. CONCLUSION: Our data demonstrate that genome replacement frequently occurs in unisexual Ambystoma across their range, and support previous speculations that genome replacement is an important reproductive mechanism that can enhance their evolutionary longevity. Our results show that there is no ancient "L" genome in the unisexual lineages, and no particular "L" genome is favored in any unisexual individual. The presence of an "L" genome in all unisexuals implies that it is important to the maintenance of unisexuals. Nuclear gene genealogy is a powerful tool to examine the historical interaction between sperm-dependent unisexuals and their sexual sperm donors. This methodology could be applicable to many other unisexual lineages to improve our understanding of their reproduction and their ability to persist.
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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 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 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".