biostudies-literatureUnknownRockman MVNIGMS NIH HHSNIH HHSThe microscopic nematode <i>Caenorhabditis elegans</i> stands unrivaled as a model for developmental biology, neurobiology, and genetics, but fundamental aspects of its ecology, biogeography, and natural history remain unknown. Leveraging recent findings that place its center of diversity in the cool, high-elevation forests of Hawaii, we performed an intensive survey of the <i>Caenorhabditis</i> fauna of Pohnpei, a high island in Micronesia that is home to the largest patch of high-elevation forest between Hawaii and East Asia. We found nine species of <i>Caenorhabditis</i>, five of them new, but not <i>C. elegans</i>. Most species were limited to the hot lowlands but three spanned the elevational range and one was found only in the cloudforest. Using the distribution of <i>Caenorhabditis<bioRxiv : the preprint server for biology2025.09.22.677770https://www.ebi.ac.uk/biostudies/studies/S-EPMC12485960biostudies-literature<i>Caenorhabditis</i> diversity on Pohnpei, Micronesia, provides evidence that the Elegans Supergroup has its roots in the Americas and diversified in the Pacific en route to Asia.PMC12485960P40 OD010440R35 GM141906Nguyen THMHarmony Yomai VMTintori SCRockman MVfalse<i>Caenorhabditis</i> diversity on Pohnpei, Micronesia, provides evidence that the Elegans Supergroup has its roots in the Americas and diversified in the Pacific en route to Asia.The microscopic nematode <i>Caenorhabditis elegans</i> stands unrivaled as a model for developmental biology, neurobiology, and genetics, but fundamental aspects of its ecology, biogeography, and natural history remain unknown. Leveraging recent findings that place its center of diversity in the cool, high-elevation forests of Hawaii, we performed an intensive survey of the <i>Caenorhabditis</i> fauna of Pohnpei, a high island in Micronesia that is home to the largest patch of high-elevation forest between Hawaii and East Asia. We found nine species of <i>Caenorhabditis</i>, five of them new, but not <i>C. elegans</i>. Most species were limited to the hot lowlands but three spanned the elevational range and one was found only in the cloudforest. Using the distribution of <i>Caenorhabditis<2025-01-01T00:00:00Z2025 Sep2026-05-07T03:24:32.558Z2026-05-07T03:12:59.364ZS-EPMC124859604104029410.1101/2025.09.22.677770