Genetic divergence in the absence of strong ecological differences between coexisting white and common Atlantic marine sticklebacks
Bibliographic record
Abstract
Abstract Identifying taxa in the earliest phases of speciation is critical for understanding how reproductive isolation arises. In Nova Scotia, Canada, “white” threespine sticklebacks co-occur with common marine sticklebacks but differ in nuptial coloration, nesting behavior, and parental care, raising the possibility that they represent a nascent species. We combined population genomics, morphometrics, and stable isotope analysis to test whether white sticklebacks represent a distinct lineage and whether they have diverged along ecological axes as in other stickleback populations. Genotyping-by-sequencing revealed that male and female white sticklebacks form a genetic cluster distinct from sympatric common sticklebacks with evidence of ongoing gene flow yet with very low overall genomic divergence (F ST ≈ 0.01). Genetic differences were distributed across many loci rather than localized to a single genomic region. Morphological and isotopic analyses revealed no differences in most classic ecological traits (body shape, armor, gill rakers, or trophic niche). Instead, whites are smaller-bodied, paler, and exhibit shorter spines, reduced testes size, and smaller but more numerous eggs compared to common sticklebacks. These results indicate that white sticklebacks are genetically distinct from the common Atlantic threespine stickleback but have not diverged conspicuously in their ecology, suggesting that their differentiation is driven by reproductive and sexual traits rather than trophic specialization. The white stickleback thus represents a promising new system for investigating the interplay of sexual selection, reproductive strategy, and gene flow in the early stages of speciation.
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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 | 0.001 | 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".