Paleogene forest fragmentation and out‐of‐Africa dispersal explain radiation of the Paleotropical dung beetle tribe Epactoidini <i>trib. nov.</i> (Coleoptera: Scarabaeinae)
Bibliographic record
Abstract
Abstract Paleotropical clades with largely disjunct distributions are ideal models for biogeographic reconstructions. The dung beetle genera Grebennikovius Mlambo, Scholtz & Deschodt, Epactoides Olsouffief and Ochicanthon Vaz‐de‐Mello are distributed in Tanzania, Madagascar and Réunion, and the Oriental region, respectively. We combine morphology and molecular dataset to reconstruct the phylogenetic relationships between these taxa. Our analyses corroborate previous hypotheses of monophyly of the group, which is here described as new tribe Epactoidini trib. nov. Grebennikovius is recovered as sister to Epactoides , while Ochicanthon emerges as sister to them both. The disjunct distribution of our focal clade is unusual within the subfamily Scarabaeinae. Bayesian divergence time estimates and ancestral range reconstructions indicate an African origin of the crown group of the tribe Epactoidini trib. nov. in the early mid Eocene, ca. 46 Ma. The divergence between Epactoides and its sister is dated to 32.3 Ma, while the crown age for the genus Ochicanthon is dated to 27 Ma. We investigate the factors that may have shaped the current distribution of the tribe Epactoidini trib. nov . The formation of the Gomphotherium landbridge, along with favourable environmental conditions would have allowed dry‐intolerant organisms, such as Ochicanthon , to disperse out of Africa. Remarkable climatic stability of the Eastern Arc Mountains was critical for the retention of the monotypic genus Grebennikovius . We suggest two subsequent overwater dispersal events: the migration of the most recent common ancestor (MRCA) of Epactoides from Africa to Madagascar (32.3–29.5 Ma); the lately dispersal of the MRCA of the today's extinct Epactoides giganteus Rossini, Vaz‐de‐Mello & Montreuil to Réunion island from Madagascar (3.4 Ma). We suggest that the high potential of dispersal of Epactoidini trib. nov. dung beetles and the strict association to forest habitat might have triggered two major radiations, one in Madagascar and one in the Oriental Region.
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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 | 0.001 |
| 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 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.004 | 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".