How evolution repeatedly builds complexity: a case study with <scp>C<sub>4</sub></scp> photosynthesis in <i>Blepharis</i> (Acanthaceae)
Bibliographic record
Abstract
Summary With over 60 parallel origins representing evolutionary replicates, C4 photosynthesis is well‐suited for studying complex trait evolution. However, lineages with diverse C3–C4 intermediate species are scarce, leaving uncertainty in models of C4 evolution. Phenotypic characterization of 28 living species of Blepharis (Acanthaceae) is presented, including photosynthetic gas exchange, enzyme activity assays, cell ultrastructure, and δ13C assays, the latter including 92 herbarium specimens from three species with phenotypic diversity. A well‐resolved transcriptome‐based phylogeny provides evolutionary context. C3, proto‐Kranz, C2, C4‐like, and C4 phenotypes occur in Blepharis sect. Acanthodium. The phylogeny supports a stepwise progression from C3 through C2 to C4 states and up to five distinct origins of the C4 cycle. Substantial intraspecific C2–C4 variation is demonstrated in Blepharis mitrata, Blepharis furcata, and Blepharis macra. Blepharis gazensis is a monospecific C4 lineage exhibiting an NADP malic enzyme C4 pathway with features of the NAD‐ME subtype, extending the ways in which the C4 cycle is known to function. Substantial photosynthetic diversity exists in Blepharis that rivals or exceeds the range of character states present in other C3 to C4 transitional lineages. This diversity in Blepharis represents a robust new model for studying convergent evolution of C4 photosynthesis and complex traits in general.
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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 | 0.003 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.003 | 0.002 |
| Scholarly communication | 0.002 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| 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".