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Traditionally, evolution has been perceived as a journey toward greater complexity and the acquisition of new genes. However, insights from the genomic era reveal that gene loss and simplification occur more frequently than previously recognized, potentially enhancing biological adaptations that aid survival. This concept, which flips the common wisdom on its head—suggesting that in genetic terms, “less is more”—introduces an intriguing new perspective. It points to the phenomenon of significant gene deletions accompanied by extensive gene duplications, illustrating a scenario where organisms evolve by losing unnecessary elements while retaining or replicating crucial ones.
The conclusions drawn from this research are detailed in an article published in the journal Molecular Biology and Evolution. A collaborative effort led by researchers from the University of Barcelona’s Genetics Section, involving teams from the Okinawa Institute of Science and Technology (OIST), discusses new evolutionary patterns and highlights the extensive capacity for genetic adaptation prompted by both substantial gene loss and subsequent duplication.
Less, but more: a new evolutionary scenario
Despite advancements in understanding gene loss, many questions remain regarding its role in species diversification and the genesis of innovative evolutionary traits. Cristian Cañestro, the study’s lead author, emphasizes that gene loss is prevalent across the biological spectrum and acts as a significant evolutionary force that fosters genetic variability and biological adaptation—a concept historically dubbed the “less is more” hypothesis.
Expanding on this idea, the current research proposes a novel framework termed “less, but more,” which underscores the critical influence of gene loss in driving evolution.
This study, part of Gaspar Sánchez-Serna’s doctoral research, specifically investigates the genome of Oikopleura dioica, a marine zooplankton belonging to the tunicate family, which is closely related to the lineage of vertebrates. Using this organism as a model, the research team traced the evolutionary shifts within fibroblast growth factor (FGF) gene families—essentially important for developmental processes in various organisms.
“Our results indicate that gene loss has led to a drastic reduction of FGF gene families from eight to merely two, specifically the Fgf9/16/20 and Fgf11/12/13/14 families. Notably, these remaining subfamilies have then undergone duplication, resulting in a total of ten functional genes within appendicularians,” Sánchez-Serna reports. He further notes that the Fgf9/16/20 and Fgf11/12/13/14 subfamilies likely represent a core set that retains fundamental secretory and intracellular functions, shedding light on the evolutionary trajectories of the FGF system.
From sessile life to active swimming
The findings yield fresh insights into the evolution of FGF gene subfamilies within chordates, marking significant gene losses and duplications that occurred early in the appendicularian lineage after its separation from ascidians. These genetic alterations have played a pivotal role in creating distinct morphological features among various species of free-living tunicates, including O. dioica.
“Our research proposes a compelling hypothesis that links FGF gene modifications—both losses and duplications—to broad developmental transformations. These are not mere changes; they represent evolutionary milestones that facilitated the transition from a sessile, ascidian-like existence to the dynamic, free-swimming lifestyle characteristic of appendicularians,” Sánchez-Serna explains.
The study also notes variances in the FGF gene structures of O. dioica across different global regions, providing initial molecular evidence of how these rapidly evolving populations may be on the verge of becoming cryptic species—organisms that, despite similar morphological and genomic characteristics, have historically been classified under the same species umbrella.
The “less, but more” evolutionary model elucidates how, paradoxically, losses in genetic material can pave the way for newer evolutionary innovations, suggesting that such losses may be essential in fostering the emergence of new adaptations.
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