Rediscovery of the greater chestnut weevil highlights the power of digital platforms in biodiversity research and conservation

The 20^th-century collapse of the American chestnut (Castanea dentata)-once a dominant tree in eastern North American forests, decimated by introduced plant pathogens Cryphonectria parasitica and Phytophthora cinnamomi-was long thought to have driven its specialist seed predator, the greater chestnut weevil (Curculio caryatrypes), to extinction-a textbook case of coextinction.¹^,²^,³^,⁴^,⁵^,⁶^,⁷^,⁸^,⁹^,¹⁰^,¹¹^,¹²^,¹³^,¹⁴ By the early 21st century, the weevil had not been observed in over two decades and was widely presumed extinct. Here, we report its rediscovery through community science observations posted to iNaturalist from pathogen-resistant hybrid chestnut plantings and the closely related native Allegheny chinquapin in the eastern United States. Genomic analyses and field surveys confirmed the beetles' identity and documented active reproduction, demonstrating the resilience of host-specialist insects in refugial habitats and underscoring the transformative role of digital community science in biodiversity 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.¹⁵^,¹⁶^,¹⁷ 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. The platform has documented many of the chestnut's 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.¹⁵^,¹⁶^,¹⁷.