Breakdown in Postmating Isolation and the Collapse of a Species Pair through Hybridization
Bibliographic record
Abstract
Species that evolved through ecological speciation and that lack intrinsic genetic incompatibilities may nonetheless be maintained by extrinsic postmating isolating barriers that impose selection against hybrids. These species, however, may be vulnerable to a breakdown in postmating isolation. Here, we investigate a model system for ecological speciation: sympatric limnetic-benthic pairs of threespine sticklebacks. Recently, stickleback hybrid abundance in Enos Lake has increased. Given that ecological selection against hybrids was historically an important component of total reproductive isolation, we tested whether ecologically dependent postmating isolation is still functioning. We compared body shape, diet, growth, and survival in present-day Enos fish with trait data in the undisturbed Paxton Lake species pair and with historical Enos Lake data. In both Paxton and historical Enos data, we found a strong correlation between body shape and diet; however, in present-day Enos fish, this correlation was absent. Using fitness estimates based on growth rates and survival, we found no evidence of selection against intermediate morphologies. It appears that postmating isolation has broken down, allowing hybrids to persist and contributing to the collapse of the species pair.
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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 | 0.000 | 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".