Molecular evidence for fragmentation among populations of <i>Taxus wallichiana</i> var. <i>mairei</i>, a highly endangered conifer in China
Bibliographic record
Abstract
Taxus wallichiana var. mairei (Lemée & Léveillé) L. K. Fu & Nan Li is a highly endangered conifer in China. It is dioecious and wind pollinated, with seed dispersal by animals. Extant natural populations on mainland China and Taiwan are highly scattered, largely as a result of habitat loss and overexploitation. Intersimple sequence repeat (ISSR) markers were employed to assess the genetic structure among 464 individuals from 17 populations across the variety’s distribution range in the Sino–Japanese and Malesian floristic subkingdoms. ISSRs revealed a high genetic diversity (percentage of polymorphic loci = 98.4%, Nei’s gene diversity = 0.3467, Shannon’s information index = 0.5152) at the species level and high differentiation among populations (coefficient of gene differentiation = 0.4066; θB = 0.4376). Gene flow among populations was found to be limited to the mainland populations. A UPGMA (unweighted pair group method with arithmetic mean) dendrogram suggests that the population in Taiwan is genetically the most isolated, while among the mainland populations a trend of an east–west split is suggested. This finding is supported by the analysis of molecular variance. The pattern of genetic variation suggests that the extant distribution of T. wallichiana var. mairei is the result of the fragmentation of a historically more continuous distribution. Conservation measures for this highly endangered plant are discussed, and an integrated approach to increase plant density and connectivity among the remaining populations is suggested.
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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 | 0.001 |
| Science and technology studies | 0.001 | 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".