DNA barcode assessment of Xanthium section Xanthium cockle burrs in Australia
Bibliographic record
Abstract
Abstract Xanthium cockle burrs are invasive weeds in many countries, affecting local ecosystems and agriculture. All Xanthium in Australia are naturalised weeds from multiple overseas sources, but their taxonomic identities are contentious. In particular, species identities of four burr varieties or “complexes” under Xanthium section Xanthium in Australia are unclear. These complexes, commonly referred to as “Noogoora”, “Californian”, “Hunter”, and “South American” burr, are regarded as either varieties of a single species (Xanthium strumarium) or four separate species in the section. To genetically determine the species identities of these complexes in Australia, we compared their chloroplast DNA barcodes to reference sequences of vouchered Xanthium species reported by Tomasello (2018). We barcoded 173 plants from 26 sites consisting of single complex burrs and 175 plants from sites containing mixed burr complexes. Single complex sites contained either of two DNA barcode clades. One clade consisting of Noogoora and Californian burrs matched reference sequences of X. chinense. The second clade consisting of Hunter and South American burrs matched X. orientale. Genetic exchange between these two species in Australia was partially evident at some sites containing sympatric complexes or putative hybrids. Reference X. strumarium sequences were unmatched to the DNA barcodes of specimens sampled in Australia, and subsequently, we advise against future claims to a historical presence of this species in Australia. Our findings are significant for taxonomic treatment of Xanthium species in Australia and for consideration of source-specific biological controls of these weeds.
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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 | 0.001 |
| 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 | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.001 | 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".