Most known species evolved during 'explosions' of diversity, shows first analysis across 'tree of life'
The Tree of Life
Gustav Klimt, 1909
Analysing enormous datasets covering more than 2 million described species across multiple taxonomic levels, the team found that "over 80% of all known biodiversity is packed into the clades with the fastest diversification rates". This pattern holds true for animals, plants, insects, vertebrates, and even across kingdoms, showing that biodiversity is not spread evenly but arises overwhelmingly from rapid radiations and occurs at all taxonomic levels. The message is clear: most of life’s diversity comes from bursts of speciation linked to ecological opportunity and innovation, not from slow, uniform accumulation over time. The results reveal a universal pattern across the tree of life, confirming that natural selection acting on changing environments and new niches drives the extraordinary richness we see today. For creationists, this is more bad news. Their model of static “kinds” appearing fully formed cannot explain why biodiversity clusters so strongly in rapidly radiating groups, or why it forms the nested hierarchies that evolution predicts. The evidence instead shows life as a continuous, dynamic process of descent with modification from common ancestors—exactly as Darwin envisaged, and the exact opposite of “special creation.”
Major Radiations in the History of Life.Having flatly denied evolution for a couple of generation or so, creationists have recently conceded that species do indeed evolve and did so at unprecedented rates following the genocidal flood, but only within each 'kind'. This concession was introduced to counter the indefensibly absurd notion that a wooden boat could be large enough to contain the requisite number of representatives of every extant and extinct species.
- The Cambrian Explosion (~541–520 million years ago)
- Perhaps the most famous radiation in Earth’s history.
- Rapid diversification of most major animal phyla, including arthropods, molluscs, chordates, and echinoderms.
- Gave rise to the basic body plans still seen today.
- Ordovician Radiation (~485–443 mya)
- A massive increase in marine biodiversity, especially among brachiopods, molluscs, corals, and trilobites.
- Sometimes called the “Great Ordovician Biodiversification Event.”
- Devonian Radiation of Fishes (~419–359 mya)
- Explosive diversification of jawed fishes (placoderms, lobe-finned fishes, ray-finned fishes, early sharks).
- Set the stage for the first vertebrates to invade land.
- Terrestrial Plant Radiation (~470–360 mya)
- Diversification of early land plants, from moss-like forms to vascular plants, ferns, seed plants, and eventually forests.
- Triggered sweeping ecological changes and paved the way for terrestrial animals.
- Radiation of Insects (~400 mya onward, with major boosts ~325–300 mya)
- Insects diversified rapidly, becoming the most species-rich animal group.
- The evolution of flight (around 325 mya) was a major innovation.
- Mesozoic Reptile Radiations (~250–65 mya)
- After the Permian extinction, reptiles diversified into dinosaurs, pterosaurs, ichthyosaurs, plesiosaurs, and early crocodilians.
- Each group occupied new ecological niches in land, air, and sea.
- Angiosperm (Flowering Plant) Radiation (~140–100 mya)
- Rapid diversification of flowering plants, which now make up ~90% of all plant species.
- Co-evolution with pollinators (insects, birds, bats) spurred further adaptive radiation.
- Cenozoic Mammal and Bird Radiations (~66 mya onward)
- Following the end-Cretaceous extinction, mammals and birds rapidly diversified into vacated niches.
- Produced today’s major mammalian lineages (primates, rodents, cetaceans, bats, ungulates) and bird orders.
- African Cichlid Fish Radiations (~10–2 mya, ongoing)
- Lakes such as Victoria, Malawi, and Tanganyika saw explosive diversification into hundreds of closely related cichlid species.
- A classic modern example of adaptive radiation, driven by ecological opportunity, sexual selection, and rapid speciation.
There is no biblical justification for the claim of a period of rapid speciation following the supposed genocidal flood. It is just another of those creationists, 'It must be true, because we need it to be', arguments that are increasingly having to be invented to retain the delusion in the face of increasing evidence of its implausibility.
However, as this study shows, these rapid bursts of diversification include diversification across taxons - what creationists define as 'macro-evolution', so, if creationists are tempted to offer that as a get out of jail free ploy, they will need to explain why they've now abandoned the distinction between 'micro-' and 'macro-evolution', that they so recently plucked out of thin air.
Most known species evolved during 'explosions’ of diversity, shows first analysis across ‘tree of life’
Biologists in the US have shown for the first time that global biodiversity is concentrated within a few disproportionately large groups with exceptional rates of evolutionary diversification. This result suggests that rapid radiations, including adaptive radiations, have generated the majority of life on Earth.
The British evolutionary biologist JBS Haldane is said to have quipped that any divine being evidently had ‘an ordinate fondness for beetles’. This bon mot conveyed an important truth: the ‘tree of life’ – the family tree of all species, living or extinct – is very uneven. In places, it resembles a dense thicket of short twigs; elsewhere it has only sparse but long branches. A few groups tend to predominate: as Haldane pointed out, more than 40% of extant insects are beetles, while 60% of birds are passerines, and more than 85% of plants are flowering plants.
But is such a concentration of species within a few exceptionally large groups a universal phenomenon of life on Earth? This question, important for our understanding of evolution and ecology, has long been the subject of controversy among biologists. But until recently, it was difficult to answer due to our poor knowledge of the number of species in existence, their evolutionary relationships, and the age of each group. But now, scientists in the US finally have provided an answer, published in Frontiers in Ecology and Evolution.
Here we show for the first time that most living species do indeed belong to a limited number of rapid radiations: that is, they form groups with many species which evolved in a relatively short period of time. Specifically, if we look among the kingdoms of life, among animal phyla, and among plant phyla, we find in each case that more than 80% of known species belong to the minority of groups with exceptionally high rates of species diversification.
Professor John J. Wiens, lead author
Department of Ecology and Evolutionary Biology
University of Arizona, Tucson, AZ, USA.
Wiens and his coauthor Dr Daniel Moen, an assistant professor at the University of California Riverside, here analyzed the distribution of species richness and diversification rates across ‘clades’ – groups of species that each evolved from a single ancestor, such as phyla, classes, or families.
Out on a limb
They did this for land plants, insects, vertebrates, for all animals, and for all species across life. They analyzed data on each clade’s species richness, age, and estimated diversification rate: that is, the accumulation of new species over time.
They focused on 10 phyla, 140 orders, and 678 families of land plants, jointly spanning more than 300,000 species; 31 orders and 870 families of insects, encompassing more than one million known species; 12 classes of vertebrates, encompassing more than 66,000 species; and 28 phyla and 1,710 families of animals with more than 1.5 million species. Finally, they analyzed 17 kingdoms and 2,545 families across all of life, including more than 2 million species.
The results were clear and consistent: irrespective of hierarchical level or group of organisms, the majority of extant species proved to be restricted to a few disproportionately large clades with higher-than-average diversification rates.
‘Rapid radiations’ of species are thought to occur when a new ecological niche opens up: for example, when a flock of grassquit birds dispersed from Central America to the virgin territory of the Galápagos Islands approximately 2.5 million years ago to diversify into the famous Darwin’s finches; or when an evolutionary innovation like powered flight prompted the radiation of bats 50 million years ago.
Seeing the forest for the trees
Our results imply that most of life's diversity is explained by such relatively rapid radiations. We also suggest key traits that might explain these rapid radiations, based on our results and results of earlier studies. These traits include multicellularity in plants, animals, and fungi across the kingdoms of life; the invasion of land and the adoption of a plant-based diet in arthropods among animal phyla; and the emergence of flowers and insect pollination in flowering plants among plant phyla.
Professor John J. Wiens.
However, one ‘known unknown’ remains: the distribution of species within the kingdom bacteria. Approximately 10,000 species of bacteria are known to science, but current estimates for the true number range from millions to trillions. However, the origin of bacteria dates back to 3.5 billion years ago, and so the overall diversification rate among them is actually quite low.
If actual bacterial richness really is much higher than described richness for other groups, then a clade with low diversification rates [namely bacteria] would contain the majority of species across life – this would be in stark contrast to our results. Therefore, we caution that our results apply primarily to known species diversity
The authors.
Publication:
Abstract
Rapid radiations, including adaptive radiations, are of considerable interest to evolutionary biologists, in large part because they are thought to underlie much of the species diversity of life. Yet, this fundamental idea has only been tested at a limited scale, within frogs. Here, we test this idea across living organisms and within many of the largest clades (e.g. animals, plants). Specifically, we quantify how much of Earth’s species richness is contained within rapid radiations (clades with high net diversification rates). We find that among the major clades of living organisms and among land plant phyla and animal phyla, >80% of known species richness is contained within the few clades in the upper 90th percentile for diversification rates in each group. Thus, these exceptionally rapid radiations contain most of Earth’s extant species diversity. Patterns were broadly similar using smaller clades (orders, families) and in insects and vertebrates, with the majority of species generally contained within clades in the upper 75th percentile. Results were also similar using large-scale clades defined by their ages instead of taxonomic ranks. Overall, these results show for the first time that most of the known species richness of life is explained by rapid radiations. Moreover, phenotypic evidence from previous studies suggests that some of the most species-rich rapid radiations across life, animals, and plants may also qualify as adaptive radiations.
1 Introduction
Adaptive radiation has become a central topic in modern evolutionary biology. Adaptive radiations are generally thought to involve rapid diversification of species (i.e. high rates of speciation minus extinction) accompanied by the evolution of ecologically relevant phenotypes (Schluter, 2000; Gillespie et al., 2020; Moen et al., 2021). One reason that adaptive radiations are of such great interest is that they are thought to underlie much of the species diversity and phenotypic diversity of life (Simpson, 1953; Schluter, 2000; Glor, 2010; Givnish, 2015). After all, if the idea of adaptive radiation applied to only a few exceptional clades with limited species diversity (e.g. African rift-lake cichlids, Caribbean anoles, Galápagos finches, sticklebacks), then it is unclear why adaptive radiation should be a broadly important topic in the field. However, with the exception of a recent study in frogs (Morinaga et al., 2023), no studies have explicitly quantified how much of Earth’s overall species richness is contained in clades resembling adaptive radiations.
The study in frogs (Morinaga et al., 2023) developed a framework for addressing how much species diversity and phenotypic diversity is explained by clades with different dynamics of diversification and phenotypic evolution (following Moen et al., 2021). Thus, they classified clades as resembling adaptive radiations (those with rapid phenotypic change and rapid species diversification), non-adaptive radiations (those with rapid species diversification but unexceptional rates of phenotypic change), adaptive non-radiations (with rapid phenotypic change but unexceptional diversification rates), and non-adaptive, non-radiations (with relatively slow rates of phenotypic change and species diversification). They found that in frogs ~75% of both species richness and phenotypic diversity was contained in clades resembling adaptive radiations, with above-average rates of diversification and phenotypic change. Here and throughout, we refer to diversification rates as the rate of speciation minus the rate of extinction, or the rate of species accumulation over time. For brevity, we use “diversification rate” instead of “net diversification rate”.
Here, we apply this general framework (Moen et al., 2021; Morinaga et al., 2023) to ask: how much of life’s current species diversity evolved from relatively rapid radiations? It would be very difficult to estimate comparable species-level rates of phenotypic change for hundreds of species in every major clade across life. Therefore, without phenotypic data and rates, one cannot distinguish adaptive radiations from non-adaptive radiations, adaptive non-radiations, and non-adaptive non-radiations. Nevertheless, we can quantify how much of life’s species richness is contained within relatively rapid radiations (i.e. clades with high diversification rates) as opposed to non-radiations (i.e. clades with lower diversification rates).
Some previous analyses have found that variation in species richness of named clades of comparable rank (e.g. families, phyla) is strongly related to the diversification rates of these clades (Scholl and Wiens, 2016). However, this relationship alone says nothing about what proportion of species belong to rapidly diversifying clades as opposed to clades with more moderate diversification rates. For example, in both of the hypothetical examples in Figure 1, diversification rates and species richness are very strongly related (Example A: r2 = 0.98, P=0.002; Example B: r2 = 0.93, P=0.008; details in Figure 1, Supplementary Table S1). But in Example A, the most rapidly diversifying clade contains only 30% of the group’s species richness, whereas in Example B, the most rapidly diversifying clade contains 80%. Overall, the contribution of rapid radiations to life’s species diversity remains unknown, and is not addressed by the relationship between diversification rates and species richness. Figure 1Two factors now facilitate addressing this question. First, several recent studies have analyzed patterns of diversification rates and richness across all of life, and among major clades of land plants, animals, insects, and vertebrates (see Methods for details). Thus, many of the building blocks needed to address this question are now available. Second, recent studies have also shown that the clade-based estimator of diversification rates used in these studies (Magallón and Sanderson, 2001) yields estimates that are strongly related to true diversification rates in simulations (r2~0.7), including simulations in which speciation and extinction rates vary within clades over time and among subclades (Meyer and Wiens, 2018; Meyer et al., 2018.1). Empirical analyses of randomly selected clades across life (Yu and Wiens, 2024; see also Supplementary Dataset S1, Supplementary Table S2) show that these clade-based estimates (Magallón and Sanderson, 2001) generally are strongly related (r2~0.8) to estimates from a new Bayesian species-based method (ClaDS; Maliet et al., 2019; Maliet and Morlon, 2022). These two lines of evidence suggest that these clade-based estimates are accurate and a reasonable proxy for estimates from this Bayesian species-level method. These clade-based estimators can estimate diversification rates given only the age and species richness of each clade (Magallón and Sanderson, 2001). Therefore, a well-sampled, fully-resolved, time-calibrated, species-level phylogeny is not necessary to estimate diversification rates within each clade using this clade-based approach, unlike ClaDS and many other estimators based on species-level branch lengths. By using this clade-based estimator, we can conduct analyses across all of life and within many major groups that lack a comprehensive species-level phylogeny (i.e. most of them).Figure 1
Example A shows five clades with species counts of 30, 25, 20, 15, and 10, respectively. Example B combines these into Clade 1 with 80 species and smaller clades with 9, 5, 4, and 2 species. Clade 1 in both examples is blue, with others in orange.
Two hypothetical examples, illustrating how the proportion of species in a group that are contained in the most rapidly diversifying clade(s) can vary. In Example A, the most rapidly diversifying clade (Clade 1) includes only 30% of the group’s overall richness. In Example B, the most rapidly diversifying clade (Clade 1) contains 80%. Our hypothesis is that, within a given taxonomic group, the majority of species will belong to the most rapidly diversifying clade (Clade 1), as in Example B This hypothesis follows from the idea that rapid radiations (such as adaptive radiations) contain most of the diversity of life. The alternative hypothesis is that species richness will be more evenly distributed among clades (Example A), such that only a minority of species are in the most rapidly diversifying clade (Clade 1). Importantly, the proportion of species in a clade that are contained within the most rapidly diversifying clade can be independent of the relationship between diversification rates and species richness among clades. Thus both of these examples show a strong relationship between species richness and diversification rates among clades (Example A: r2 = 0.98, P=0.002; Example B: r2 = 0.93, P=0.008), regardless of whether the most rapidly diversifying clade contains a minority (Example A) or majority (Example B) of the group’s overall species richness. For these examples, we assumed that all clades were 50 million years old and estimated diversification rates using the stem-group MS estimator with ϵ=0.5 (values in Supplementary Table S1).
In this study we quantify how much of life’s species richness is contained within relatively rapid radiations. We do this across living organisms and within some of the most species-rich groups, including land plants, animals, insects, and vertebrates. For each of these five groups, we compile data on diversification rates and species richness for named clades. We then determine what proportion of the richness of each group is contained within clades with above-average diversification rates (following Morinaga et al., 2023), and those with diversification rates in the upper 75th, 90th, and 95th percentiles. These new analyses allow us to address the long-standing question of whether most of the diversity of life is contained within rapid radiations.
Creationists sometimes claim that all this diversity arose through a burst of “warp-speed evolution” after Noah’s flood, but only within fixed “kinds.” The problem is obvious: no one ever noticed this miraculous period of super-evolution, it left no trace in the historical or fossil record, and — conveniently — it seems to have stopped just before science began documenting the natural world.
The notion is, of course, entirely ad hoc and non-biblical, plucked from thin air to make the myth seem slightly more plausible. If Noah and his immediate descendants had really witnessed the miraculous proliferation of multiple new species in each generation, springing forth without intermediates, we would surely expect them to have recorded it in their “history.” Yet the testimony of these silent witnesses is that it never happened.
By contrast, the evidence shows that diversification is real, measurable, and still happening—just not at the breakneck pace creationists imagine. Wiens and Moen’s study makes it plain: life’s rich variety comes from repeated, natural bursts of speciation over deep time, not a one-off creation myth patched up with imaginary hyper-evolution.
In the end, evolution doesn’t need miracles to explain biodiversity — but creationism needs miracles to explain away evolution.
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