Species Richness and Speciation Rates for all Terrestrial Animals Emerge from a Synthesis of Ecological Theories
Bibliographic record
Abstract
The total number of species on earth and the rate at which new species are created are fundamental questions for ecology, evolution and conservation. These questions have typically been approached separately, despite their obvious interconnection. In this study, we approach both questions in conjunction, for all terrestrial animals. To do this, we combine two previously unconnected bodies of theory: general ecosystem models and individual-based ecological neutral theory. General ecosystem models provide us with estimated numbers of individual organisms, separated by functional group and body size. Neutral theory, applied within a guild of functionally similar individuals, connects species richness, speciation rate, and number of individual organisms. In combination, for terrestrial endotherms where species numbers are known, they provide us with estimates for speciation rates as a function of body size and diet class. Extrapolating the same rates to guilds of ectotherms enables us to estimate the species richness of those groups, including species yet to be described. We find that speciation rates per species per million years decrease with increasing body size. Rates are also higher for carnivores compared to omnivores or herbivores of the same body size. Our estimate for the total number of terrestrial species of animals is in the range 1.03-2.92 million species, a value consistent with estimates from previous studies, despite having used a fundamentally new approach. Perhaps what is most remarkable about these results is that they have been obtained using only limited data from larger endotherms and their speciation rates, with the predictive process being based on mechanistic theory. This work illustrates the potential of a new approach to classic eco-evolutionary questions, while also adding weight to existing predictions. As we now face an era of dramatic biological change, new methods will be needed to mechanistically model global biodiversity at the species and individual organism level. This will be a huge challenge but the combination of general ecosystem models and neutral theory that we introduce here is a way to tractably achieve it.
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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 | 0.005 | 0.017 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.002 |
| Bibliometrics | 0.007 | 0.003 |
| Science and technology studies | 0.001 | 0.003 |
| Scholarly communication | 0.003 | 0.010 |
| Open science | 0.002 | 0.002 |
| Research integrity | 0.001 | 0.002 |
| Insufficient payload (model declined to judge) | 0.003 | 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".