The genetic and demographic consequences of hybridization in small plant populations
Bibliographic record
Abstract
Hybridization is widely believed to be a homogenizing force and a source of genotypic novelty. However, its role in causing the local extinction of small plant populations is not well understood. I assessed the magnitude and direction of hybridization between small populations of red mulberry (' Morus rubra' L.) and its more abundant congener, white mulberry (' Morus alba' L.) in Canada and measured its effect on conspecific mating and establishment. Molecular analysis using nuclear markers (Randomly Amplified Polymorphic DNA) showed that hybrid frequency was relatively high (53.7%). Most hybrids (67%) had proportionately more white than red mulberry markers in their nuclear genome and the degree of white-bias increased with increasing population frequency of white mulberry. Furthermore, 68% of hybrids had the same chloroplast genome as white mulberry. These results indicate that introgression is bidirectional but asymmetrical and is related, in part, to the relative frequency of parental taxa. Hybridization also affected conspecific mating in red mulberry, where experimental removal of whites and hybrids increased the relative siring fertility of red mulberry by 14%, but there was no change in seed set. This indicates that ovules of red mulberry are discounted by heterospecific pollen, most of which is generated by hybrid plants. Moreover, pollen production in red mulberry was lower (2.7% to 10.3% of the total) than the mean of white and hybrid mulberry combined. Collectively, these results suggest that red mulberry is experiencing a mating disadvantage associated with low abundance. The effect on seed production is exacerbated at establishment, where reciprocal transplants of red mulberry were not ecologically differentiated and were consistently less fit than white and hybrid mulberry in all environments. Common garden experiments revealed that variation in offspring fitness was determined largely by the identity of the maternal parent; specifically, progeny with white mothers had the highest fitness. These results indicate that red mulberry is at a strong establishment disadvantage. Given that hybridization with white and hybrid mulberry has a negative effect on the formation and establishment of red mulberry, it is likely that asymmetrical gene flow will lead to the genetic assimilation of red mulberry in southern Ontario.
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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 | 0.001 | 0.002 |
| 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 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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".