Vicariant Speciation of Curassows (Aves, Cracidae): A Hypothesis Based on Mitochondrial DNA Phylogeny
Bibliographic record
Abstract
Abstract The curassows comprise 14 species of sedentary Neotropical birds classified in four genera (Crax, Nothocrax, Mitu, and Pauxi) in the family Cracidae. Congeneric species have a striking pattern of allopatric distributions that might be attributable to vicariance, dispersal, or a combination of the two. To test those biogeographic hypotheses, a strongly supported phylogeny was needed, so that existing problems of taxonomic rank could be solved and a better understanding of the group's evolutionary history attained. We therefore estimated the phylogenetic relationships of all 14 species, on the basis of 6,929 sites of six different mitochondrial DNA regions, and reassessed the status of the four genera. Sequences from the ND4 gene favored a tree that was highly incongruent with the tree recovered using the other five gene regions. However, when the ND4 sequences were concatenated with the sequences of the other genes, the optimal phylogeny was unchanged from that derived for the other genes. That combined tree was divided into two well-supported clades: one containing the seven species of Crax and the other containing the monospecific genus Nothocrax, as sister to a clade of the Mitu and Pauxi species. Mitu and Pauxi are not reciprocally monophyletic, which appears to be attributable to a distant hybridization event and a transfer of Mitu mtDNA into P. unicornis. We estimated divergence times; the diversification of curassow seems to have occurred from the Middle Miocene to the end of the Pliocene (9.5 to 1.6 Ma). Vicariance—following marine transgressions, the rise of the Andes, and subsequent changes in river basins in South America—seems to be the major mode of isolation that favored allopatric speciation in the group.
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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".