The status of Sarcopoterium spinosum (Rosaceae) at the western periphery of its range: ecological constraints lead to conservation concerns

This paper considers the demography, ecology, and conservation perspectives of the western populations of the clonal dwarf-shrub Sarcopoterium spinosum (L.) Spach. While in the Middle East the species dominates large areas, westwards it is less common and many populations have become extinct since the late 19th century. We highlight the ecological limitations and their implications for the conservation of the species at the periphery of its range. In southern Italy we studied the demographic traits of two populations and the age spatial structure of a third. Ramet density and lifespan appear to be lower than in the Middle East. The floristic analysis of the stands studied and a climatic analysis over the whole range of S. spinosum provide a key for the interpretation of such differences. Given that summer drought stress decreases westwards, both the sprouting vigor and the ecological space available for S. spinosum become limited by increasing competition. This makes the populations more likely to become extinct in changing landscapes, as revealed by the decreasing extent of occurrence and area of occupancy due to habitat loss. Although S. spinosum is not at risk in the Middle East, at the western border of its range it qualifies as an endangered species.