YeeWen Low (刘 逸 汶)

Miniaturization is widespread among vertebrates, yet its genomic basis remains poorly understood. 🔓 pnas.org/doi/10.1073/pnas.26… In Cypriniformes, the most species-rich order of freshwater fishes, miniaturization has evolved repeatedly, producing two distinct forms: proportioned dwarfs, which closely resemble smaller versions of larger relatives, and progenetic miniatures, which retain larval traits due to developmental truncation into adulthood. By reconstructing the evolutionary history of miniaturization and performing comparative genomic analyses, the authors in this study show that progenetic miniatures, but not proportioned dwarfs, exhibit consistent genome size reductions. Independently evolved progenetic lineages share convergent genomic signatures, including repeat loss and genome-wide intron shortening. Their findings demonstrate that progenetic miniaturization is driven by predictable structural genomic changes, revealing a fundamental link between genome architecture and developmental truncation in vertebrates. 𝗥𝗲𝘀𝗲𝗮𝗿𝗰𝗵 𝗧𝗶𝘁𝗹𝗲 Convergent genome streamlining accompanies independent miniaturization in the world’s smallest fishes 𝗖𝗶𝘁𝗮𝘁𝗶𝗼𝗻 H. Sudasinghe, M. Matschiner, R. Britz, K.W. Conway, H.H. Tan, W. Salzburger,C.L. Peichel, & L. Rüber, Convergent genome streamlining accompanies independent miniaturization in the world’s smallest fishes, Proc. Natl. Acad. Sci. U.S.A. 123 (42) e2614605123, doi.org/10.1073/pnas.2614605… (2026). 𝗔𝗯𝘀𝘁𝗿𝗮𝗰𝘁 Miniaturization, the reduction of adult body size to an extreme degree, has evolved repeatedly across vertebrates. Yet its genomic underpinnings remain poorly understood. Cypriniformes, the most species-rich order of freshwater fishes, contains multiple miniaturized lineages that have evolved via contrasting developmental processes. Proportioned dwarfs are tiny-bodied but otherwise morphologically similar to larger relatives, while progenetic miniatures exhibit developmental truncation and retain larval-like anatomical features into adulthood. Using a new time-calibrated phylogeny of 309 cypriniform species and comparative genomic analyses of 33 high-quality genome assemblies, we investigated the evolutionary history and genomic correlates of miniaturization across this order. Ancestral state reconstruction revealed multiple independent origins of both miniature types, with reversals to the nonminiature state rarely recovered and miniature origins nonrandomly distributed across the phylogeny. The origins of the two types of miniatures differed in their timing. Progenetic miniatures arose predominantly in the Eocene whereas proportioned dwarfs arose mainly within the Miocene period. Genome size variation across Cypriniformes has been overwhelmingly driven by polyploidy. However, progenetic miniatures showed a directionally consistent, though nonsignificant, trend toward genome size reduction. Comparative genomic analyses revealed that all three independently evolved progenetic miniature lineages share convergent signatures of repeat loss alongside genome-wide intron shortening, patterns absent in proportioned dwarfs. Our study provides the broadest evidence to date that progenetic miniaturization, despite independent origins, is underpinned by predictable structural genomic changes, revealing a fundamental link between developmental truncation and genome architecture in vertebrates. 𝗣𝗵𝗼𝘁𝗼 𝗖𝗿𝗲𝗱𝗶𝘁 Time-calibrated phylogeny of Cypriniformes inferred from a dataset of combined first and second codon positions of BUSCO loci and ultraconserved elements (UCEs; 120 loci, 55,332 bp) under a relaxed clock model in BEAST 2. Branches are colored by family and node bars represent 95% HPD intervals in million years (Ma). Labeled nodes indicate fossil calibration points. Inset shows the same phylogeny collapsed to the family level. Fish illustrations by Nadeela Hirimuthugoda. nadeela.weebly.com/illustrat… © 2026 the Author(s). Published by PNAS. An open access article, distributed under the terms of the Creative Commons Attribution 4.0 International (CC-BY-4.0) licence. creativecommons.org/licenses… #FreshwaterFishes #BodySize #ComparativeGenomic #Miniaturization #Macroevolution #Cypriniformes #Ichthyology #Biodiversity #AquariumHobby #Fishkeeping #Aquarist #TropicalFish #FishTank #Paedocypris #Danionella #Sundadanio #Fangfangia