Update on Ouratea cidiana Sastre (Ochnaceae), a microendemic species from the Amazon: enlightening the identity and conservation status

Ouratea cidiana (Ochnaceae) is a microendemic shrub species from the Brazilian Amazonia, occurring along the banks of the Trombetas River and restricted to the Cachoeira Porteira region, in western Pará State. Since the original collection nearly forty years ago, no additional records have been made, which is concerning given the continuous decline in habitat quality in the region. However, during the update of the red list of the flora of Pará, multiple herbarium collections were analyzed, and a focused field expedition, guided by research data, resulting in the rediscovery of the species at its type locality. Considering the ongoing reduction in the extent of occurrence and area of occupation, as well as declining of habitat quality and the populations subject to threat, we recommend that O. cidiana be classified as ‘Critically Endangered'. In this study, we report the rediscovery of O. cidiana and present an updated taxonomic treatment, including a emended description, illustrations, habitat information, distribution map, and a discussion of morphologically related species. Our results may support future taxonomic identification efforts and ecological actions aimed at conserving the species and the biodiversity of the Amazon region.