Species Conservation Dependence on a Reliable Taxonomy as Emphasized by the Extinction Risk Assessment of Grindelia atlantica (Asteraceae: Astereae)

Accurate taxonomy is fundamental for assessing extinction risks and implementing conservation strategies. We evaluated the extinction risk of Grindelia atlantica (Asteraceae), endemic to southern Brazil, using the IUCN criteria, and comparing three scenarios of taxonomic accuracy and data availability. Herbaria records and field surveys confirmed the historical existence of five records and currently only two remaining, isolated populations, totaling 633 individuals (513 in Pelotas and Rio Grande; 120 in Jaguarão). Habitat loss and invasive species are the primary threats. Analyses resulted in an Extent of Occurrence of 9681 km2 and an Area of Occupancy of 48 km2. These findings, coupled with significant population decline, justify the classification as Critically Endangered. The results emphasize the critical role of reliable taxonomy in conservation biology. They demonstrate the impact of a few errors on extinction risk assessments, which can unfold in the misallocation of resources or insufficient protection. This is critical, particularly for endemic species like G. atlantica in the threatened Pampas, one of Brazil’s most degraded biomes and the least represented in preserves. The creation of a conservation unit is proposed as an urgent measure to ensure the survival of this species and its habitat, benefiting other endemic and rare threatened animal and plant species.