Plant chemistry for biodiversity conservation

Plant chemical compounds are crucial for ecosystem functioning and resilience 1 , yet the extent to which plant chemical diversity may disappear as threatened plants go extinct 2 remains largely unknown. Here, we show that only 5% of threatened plants are chemically studied and that 35% of these contain 3037 unique compounds not reported in other species. The remaining 95% of chemically neglected threatened species are concentrated in the Neotropical, Afrotropical, and Indomalayan phytogeographic realms. To accelerate research of chemically neglected threatened plants, we evaluate whether untargeted metabolomics on herbarium specimens can detect a significant fraction of compounds found in living botanical garden plants. We find that herbarium specimens contain 35–84% of compounds of living plants, including from all major plant biosynthetic pathways (e.g., alkaloids, terpenoids, flavonoids), regardless of collection date. Together, our findings introduce chemistry into conservation planning of species and ecosystems and position botanical gardens and herbaria as invaluable resources for unravelling plant chemical diversity at scale.