Turnera stipularis (family Turneraceae) is an erect shrub up to 2 m tall with small, yellow flowers arranged in the axils of its branches. The species was described 140 years ago and until now was known from only eight subpopulations, along river banks in the Cerrado of Maranhão state in north-east Brazil. Only one of these populations occurs in a protected area (the Chapada das Mesas National Park). The conservation status of T. stipularis has not yet been assessed for the IUCN Red List, but our preliminary assessment suggests it should be categorized as Endangered under criterion B (geographical distribution) as its area of occupancy is < 20 km2, it is known from < 10 localities and the quality of its habitat is declining (Maranhão is on the western edge of the Cerrado in the Arc of Deforestation).
In December 2022, during a herbarium review of the Turneraceae species from Maranhão, we discovered a new record of T. stipularis, from the state of Pará, c. 700 km from the previously known populations in Maranhão. This new record expands the distribution of this species to Amazonia. Inclusion of the new record in our preliminary assessment, based only on criterion B, indicates the species would be assessed as Near Threatened rather than as Endangered. However, this new population occurs in the municipality of Altamira, near the Belo Monte Hydroelectric Power Plant, an area of conflicts involving illegal mining and environmental degradation. Thus the new record does not necessarily indicate an improved conservation status, but rather indicates threats additional to those the species is subject to in the Cerrado of Maranhão.
Existence of a previously unknown population of T. stipularis in Amazonia offers a greater chance of conserving the species, as the great distance to the previously known populations implies additional genetic variability. Although we now know T. stipularis has a wider distribution, the species is still threatened, demonstrating that geographical distribution cannot be the only tool used to assess conservation status, as it can mask critical local threats. This new record also reinforces the importance of herbarium collections for documenting the distribution of species and supporting conservation action.
We thank the Brazilian National Council for Scientific and Technological Development (CNPq) for financial support (Universal, 402943/2021-0) and a research grant awarded to LR (PCI, 305110/2022-5), and the CAPES Foundation (financial code 001) for a scholarship to MJCdS.
Turnera stipularis, from the state of Maranhão, with inset showing the flower (photos: Alessandro W. Ferreira).
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