A transcriptome-based resolution for a key taxonomic controversy in Cupressaceae
Bibliographic record
Abstract
Background and Aims: Rapid evolutionary divergence and reticulate evolution may result in phylogenetic relationships that are difficult to resolve using small nucleotide sequence data sets. Next-generation sequencing methods can generate larger data sets that are better suited to solving these puzzles. One major and long-standing controversy in conifers concerns generic relationships within the subfamily Cupressoideae (105 species, approx. 1/6 of all conifers) of Cupressaceae, in particular the relationship between Juniperus, Cupressus and the Hesperocyparis-Callitropsis-Xanthocyparis (HCX) clade. Here we attempt to resolve this question using transcriptome-derived data. Methods: Transcriptome sequences of 20 species from Cupressoideae were collected. Using MarkerMiner, single-copy nuclear (SCN) genes were extracted. These were applied to estimate phylogenies based on concatenated data, species trees and a phylogenetic network. We further examined the effect of alternative backbone topologies on downstream analyses, including biogeographic inference and dating analysis. Results: Based on the 73 SCN genes (>200 000 bp total alignment length) we considered, all tree-building methods lent strong support for the relationship (HCX, (Juniperus, Cupressus)); however, strongly supported conflicts among individual gene trees were also detected. Molecular dating suggests that these three lineages shared a most recent common ancestor approx. 60 million years ago (Mya), and that Juniperus and Cupressus diverged about 56 Mya. Ancestral area reconstructions (AARs) suggest an Asian origin for the entire clade, with subsequent dispersal to North America, Europe and Africa. Conclusions: Our analysis of SCN genes resolves a controversial phylogenetic relationship in the Cupressoideae, a major clade of conifers, and suggests that rapid evolutionary divergence and incomplete lineage sorting probably acted together as the source for conflicting phylogenetic inferences between gene trees and between our robust results and recently published studies. Our updated backbone topology has not substantially altered molecular dating estimates relative to previous studies; however, application of the latest AAR approaches has yielded a clearer picture of the biogeographic history of Cupressoideae.
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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 | 0.000 |
| 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 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".