Causes of heterozygosity excess: The case of Mexican populations of Populus tremuloides
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Bibliographic record
Abstract
The presence of heterozygous individuals in a population is crucial for maintaining genetic diversity, which can positively affect fitness and adaptability to environmental changes. While inbreeding generally reduces the proportion of heterozygous individuals in a population, polyploidy tends to increase the proportion. North American Populus tremuloides is one of the most widely distributed and ecologically important tree species in the Northern Hemisphere. However, genetic variation in Mexican populations of P. tremuloides , including the genetic signatures of their adaptation to a variety of environments, remains largely uncharacterized. The aim of this study was to analyze how inbreeding coefficient ( F IS ) and ploidy are associated with clonal richness, population cover, climate and soil traits in 91 marginal to small, isolated populations of this tree species throughout its entire distribution in Mexico. Genetic variables were determined using 36,810 filtered SNPs derived from genome re-sequencing. We found that F IS was approximately between 0 and –1, indicating an extreme heterozygosity excess. One key contributor to the observed extreme heterozygosity excess was asexual reproduction, although ploidy levels cannot explain this excess. Analysis of all neutral SNPs showed that asexual reproduction was positively correlated with observed heterozygosity ( H o ) but negatively correlated with expected heterozygosity ( H e ). Analysis of outlier SNPs also showed that asexual reproduction was positively correlated with H o and negatively correlated with H e , although this latter correlation was not significant. These findings support the presence of a Meselson effect. • The presence of heterozygous individuals in a P. tremuloides population is crucial for maintaining genetic diversity. • In Mexican P. tremuloides populations, polyploidy tends to increase the proportion of heterozygous individuals. • Asexual reproduction in these populations leads to extremely negative inbreeding coefficients. • Observed heterozygosity for neutral and outlier SNPs was positively correlated with clonal proliferation. • Our findings suggest a Meselson effect is counteracting the effects of inbreeding in small and isolated populations.
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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 | 0.000 |
| 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 it