Breeding system diversification and evolution in American<i>Poa</i>supersect.<i>Homalopoa</i>(Poaceae: Poeae: Poinae)
Bibliographic record
Abstract
BACKGROUND AND AIMS: Poa subgenus Poa supersect. Homalopoa has diversified extensively in the Americas. Over half of the species in the supersection are diclinous; most of these are from the New World, while a few are from South-East Asia. Diclinism in Homalopoa can be divided into three main types: gynomonoecism, gynodioecism and dioecism. Here the sampling of species of New World Homalopoa is expanded to date its origin and diversification in North and South America and examine the evolution and origin of the breeding system diversity. METHODS: A total of 124 specimens were included in the matrix, of which 89 are species of Poa supersect. Homalopoa sections Acutifoliae, Anthochloa, Brizoides, Dasypoa, Dioicopoa, Dissanthelium, Homalopoa sensu lato (s.l.), Madropoa and Tovarochloa, and the informal Punapoa group. Bayesian and parsimony analyses were conducted on the data sets based on four markers: the nuclear ribosomal internal tanscribed spacer (ITS) and external transcribed spacer (ETS), and plastid trnT-L and trnL-F. Dating analyses were performed on a reduced Poa matrix and enlarged Poaceae outgroup to utilize fossils as calibration points. A relaxed Bayesian molecular clock method was used. KEY RESULTS: Hermaphroditism appears to be pleisiomorphic in the monophyletic Poa supersect. Homalopoa, which is suggested to have originated in Eurasia 8·4-4·2 million years ago (Mya). The ancestor of Poa supersect. Homalopoa radiated throughout the New World in the Late Miocene-Early Pliocene, with major lineages originating during the Pliocene to Pleistocene (5-2 Mya). Breeding systems are linked to geographic areas, showing an evolutionary pattern associated with different habitats. At least three major pathways from hermaphroditism to diclinism are inferred in New World Homalopoa: two leading to dioecism, one via gynodioecism in South America and another directly from hermaphroditism in North America, a result that needs to be checked with a broader sampling of diclinous species in North America. A third pathway leads from hermaphroditism to gynomonoecism in Andean species of South America, with strictly pistillate species evolving in the highest altitudes. CONCLUSIONS: Divergence dating provides a temporal context to the evolution of breeding systems in New World Poa supersect. Homalopoa The results are consistent with the infrageneric classification in part; monophyletic sections are confirmed, it is proposed to reclassify species of sect. Acutifoliae, Dasypoa and Homalopoa s.l. and it is acknowledged that revision of the infrageneric taxonomy of the gynomonoecious species is needed.
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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".