Larval morphology of Rhantus Dejean, 1833 (Coleoptera: Dytiscidae: Colymbetinae): descriptions of 22 species and phylogenetic considerations
Bibliographic record
Abstract
Descriptions of larval instars of 22 species of Rhantus Dejean, 1833 are presented including a detailed chaetotaxic analysis of the cephalic capsule, head appendages, legs, last abdominal segment and urogomphi. A parsimony analysis including 25 Rhantus species (the 22 species described in this paper + 3 additional ones) from all major zoogeographic regions and representatives of other Colymbetini genera was conducted using the program TNT based on 43 informative larval characteristics. Jackknife values indicate strong support for the monophyly of members of the tribe Colymbetini (Colymbetinae), which is supported by eight synapomorphies. It is postulated that Rhantus is polyphyletic as Rhantus (Nartus) grapii (Gyllenhal, 1908) and R. monteithi Balke, Wewalka, Alarie & Ribera, 2007 occur as more closely related phylogenetically to other genera of the tribe Colymbetini than to the Rhantus species studied. We suggest that the Neotropical species R. orbignyi Balke, 1992, R. antarcticus nahueli Trémouilles, 1984, R. calidus (Fabricius, 1792) and R. validus Sharp, 1882 represent a distinct lineage within the Colymbetini. All these species diverge at the basis of the strict consensus trees prior to all other Colymbetini studied and are characterized by several unique larval character states. Larvae of Palearctic and Nearctic species of Rhantus were found to share similar character states, which is suggestive of a common phylogenetic origin.
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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 | 0.000 |
| 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) | 0.003 | 0.001 |
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".