Rediscovery of the greater chestnut weevil highlights the growing power of digital tools in biodiversity science

The collapse of the American chestnut (Castanea dentata) was long thought to have driven its specialist seed predator, the greater chestnut weevil (Curculio caryatrypes), to extinction—a textbook case of coextinction. Here we report its rediscovery through recent community science observations posted to iNaturalist from pathogen-resistant hybrid chestnut plantings and native Allegheny chinquapin—a close relative of American chestnut—in the eastern United States. Genomic analyses and field surveys confirmed the beetles’ identity and documented active reproduction. This finding demonstrates the resilience of host-specialist insects in refugial habitats and underscores the transformative role of digital biodiversity platforms in research and conservation. Platforms such as iNaturalist integrate crowd-sourced observations, AI-assisted species identification, and expert validation to enable scalable, near-real-time biodiversity monitoring. iNaturalist now hosts more than 250 million observations from nearly 4 million users, including over 159 million research-grade records spanning more than 500,000 species. In the chestnut’s historical range, the platform has documented most known insect associates, including species considered rare, declining, or of conservation concern. Rediscoveries like that of C. caryatrypes—once dependent on specialized fieldwork—now emerge through global participatory networks that expand taxonomic reach, bridge geographic and temporal data gaps, and inform conservation action. This case illustrates how digital tools are reshaping biodiversity science amid the accelerating extinction crisis.