Centaurea pumilio (Asteraceae): Conservation Status, Threats and Population Size of a Critically Endangered Species in Italy

This paper presents a comprehensive study of the size and conservation status of the only Italian population of Centaurea pumilio (Asteraceae) and the threats to its survival. The population is located on a short stretch of sandy shoreline along the Ionian coast of Puglia, near Torre S. Giovanni (Ugento, Lecce). It was estimated in the 1990s to number about 500 plants, but in recent years a significant reduction, bringing the population to fewer than 100 individuals, has been observed. This study involved a census of the individuals (differentiating young plants from adult and reproductive ones) conducted with a precision GPS tool, phytosociological analysis and high-definition orthophoto image acquisition using a drone. Concerning the latter, to evaluate anthropic pressure from tourism, data were acquired in spring 2023 and autumn 2024 and compared using GIS geoprocessing, showing a significant increase in the area occupied by footpaths. GIS analysis also revealed that the survival of C. pumilio is strongly linked to the intensity of the walking routes, which have fragmented the population into small and isolated clusters. On the basis of all the collected data, the current conservation status of the species in Italy was assessed as critically endangered. Finally, our study provides a series of suggestions to improve the conservation status of the species and strategies to reduce the risk of extinction in Italy.