Rediscovery and reexamination of a declared ' extinct' plant in South China: The species delimitation and conservation implications of Callicarpa oligantha (Lamiaceae)

Accurate species delimitation serves as a cornerstone for effective biodiversity conservation strategies, particularly for rare taxa where misclassification of taxa may lead to misallocation of limited resources. Callicarpa oligantha, one of only two plant species declared extinct in Guangdong Province, South China, was historically documented solely from its type specimen- - a single individual collected in 1917 at Luofushan (Loh Fau Mountain).

However, the morphological similarities with C. brevipes have long challenged the taxonomic status of C. oligantha. Following the rediscovery of the species at its type locality in 2024, we conducted an integrative taxonomic reassessment of C. oligantha and C. brevipes based on the newly collected materials using combined analyses of molecular phylogenetics and morphological comparisons. Both molecular and morphological evidence congruently support the conspecificity of C. oligantha and C. brevipes.

We therefore propose synonymizing C. oligantha under C. brevipes and recommend its exclusion from extinction lists. This study underscores the importance of robust taxonomic frameworks in preventing conservation misprioritization, and highlights the value of integrative, multidisciplinary approaches for establishing accurate biodiversity baselines prior to biological conservation action.