The staggering diversity of life on Earth has long fascinated scientists and laypeople alike, prompting questions about how such extraordinary variety arose and why it is distributed so unevenly across different groups of organisms. Among the earliest and most memorable observations was made by the British evolutionary biologist JBS Haldane, who famously remarked that a divine creator seemed to have “an ordinate fondness for beetles.” This observation wasn’t just a witty comment but hinted at a fundamental biological reality: the branches of life’s tree are dramatically disproportionate, with some groups harboring millions of species while others contain only a handful.
Recent advances in evolutionary biology and computational analysis have now enabled scientists to quantify this unevenness on an unprecedented scale. A landmark study published in Frontiers in Ecology and Evolution offers compelling evidence that the known majority of Earth’s biodiversity is concentrated within a few specific groups that have undergone what are known as rapid radiations. These bursts of species diversification occurred over relatively short evolutionary periods, leading to a few “successful” clades dominating the global roster of life. This revelation provides critical insight into the tempo and mode of evolution that shapes the biosphere.
Led by Dr. John J. Wiens of the University of Arizona and Dr. Daniel Moen from the University of California Riverside, the research synthesized data from an extensive array of biological classifications, spanning kingdoms, phyla, classes, orders, and families. Their findings underscore a pervasive pattern: more than 80% of known species belong to a minority of clades characterized by exceptionally high diversification rates. This pattern repeats consistently across land plants, insects, vertebrates, and the animal kingdom as a whole, suggesting a universal evolutionary process underlying biodiversity.
To reach these conclusions, the research team employed rigorous statistical analyses of clade species richness, estimated clade ages, and diversification metrics—parameters that reflect how rapidly new species have evolved within each group. The dataset included over two million known species spanning 17 kingdoms and 2,545 families, making it one of the most comprehensive assessments of life’s diversity and evolutionary history to date. This unprecedented scale enabled the detection of robust patterns that smaller studies might have missed or misinterpreted.
Rapid radiations, as the researchers describe, are ecological and evolutionary phenomena wherein a lineage quickly proliferates into many distinct species, often following the exploitation of a new ecological niche. Classic examples include Darwin’s finches on the Galápagos Islands, which diversified after colonizing a previously unoccupied environment about 2.5 million years ago, and the evolutionary advent of powered flight, which catalyzed the extensive radiation of bats approximately 50 million years ago. These rapid bouts of diversification enable certain clades to dominate the tree of life, creating the uneven architecture that Haldane so astutely observed.
The analysis revealed that traits promoting adaptive versatility and ecological opportunity often accompany these rapid radiations. In plants, the emergence of multicellularity and the evolution of flowers paired with insect pollination revolutionized diversification rates within flowering plants. Among animal phyla, the invasion of terrestrial habitats and shifts toward plant-based diets within arthropods similarly spurred prolific speciation events. Fungi, too, showcased multicellularity as a key developmental leap, underscoring convergent evolutionary themes across distant branches of life.
Despite this landmark progress, there remains a significant caveat concerning bacterial species diversity. Bacteria represent one of the oldest and most abundant domains of life, with origins dating back approximately 3.5 billion years. Only about 10,000 bacterial species have been formally described, yet estimations of actual bacterial biodiversity range into the millions or even trillions, driven by newfound methodologies in metagenomics and environmental DNA sampling. This disparity implies that bacterial diversification rates appear much lower than those of multicellular organisms, but paradoxically, bacteria may harbor the vast majority of undiscovered species, representing a blind spot in biodiversity research.
The authors explicitly caution that their conclusions primarily apply to the currently known, described species pool. Should future studies confirm the massive uncharted diversity within bacteria and other microbial domains, the perceived pattern of rapid radiations dominating biodiversity might be significantly modified. This uncertainty highlights the challenges and dynamic nature of cataloging life, particularly microscopic life, on the planet and underscores the importance of integrating molecular and ecological data in future evolutionary studies.
The study’s implications extend beyond mere cataloging of species numbers. They highlight fundamental evolutionary principles about the drivers of diversification, the importance of ecological opportunity, and the role of key innovations that open new adaptive landscapes. Understanding these processes not only refines evolutionary theory but can also illuminate why some groups are more vulnerable to environmental changes, and others are poised for continued flourishing, crucial information in the context of rapid global biodiversity loss.
Moreover, the clarity brought by such comprehensive datasets provides a framework to explore additional questions in macroevolution and ecology: Are there predictable ecological or genetic factors that initiate rapid radiations? How do ecological limits and adaptive constraints eventually decelerate these bursts? Can understanding the mechanisms behind prolific clades guide conservation priorities by identifying lineages with the greatest evolutionary potential or vulnerability?
This research marks a pivotal step in elucidating the intricate architecture of life’s diversity. By unifying data across multiple taxa and hierarchical levels, Wiens and Moen have not only substantiated a classic biological hypothesis regarding unevenness in species richness but also provided a mechanistic lens through which to interpret evolutionary radiations. As methods and data improve, similar analyses could incorporate genomic information and more precise dating techniques, further enriching our grasp of how life diversifies and persists across deep time.
Ultimately, this work reaffirms that Earth’s biodiversity is sculpted by episodes of rapid evolutionary experimentation and expansion, outpacing slow, steady rates of speciation that mark less prolific clades. It also serves as a reminder of the vast unknown diversity still awaiting discovery, particularly among microbial life, whose invisible abundance may yet reshape our understanding of life’s evolutionary epic. Such insights propel the scientific community toward a more comprehensive, dynamic portrait of evolution, emphasizing not just the breadth of life’s branches but the speed at which some have grown to dominate the canopy of biological diversity.
Subject of Research: Not applicable
Article Title: Rapid Radiations Underlie Most of the Known Diversity of Life
News Publication Date: 20-Aug-2025
Web References:
- https://www.frontiersin.org/journals/ecology-and-evolution/articles/10.3389/fevo.2025.1596591/full
- http://dx.doi.org/10.3389/fevo.2025.1596591
References: As per the original article in Frontiers in Ecology and Evolution (DOI: 10.3389/fevo.2025.1596591)
Image Credits: Not provided
Keywords: Biodiversity, rapid radiation, species diversification, evolutionary biology, clades, species richness, macroevolution, adaptive radiation, ecological niches, beetles, flowering plants, bacteria
