Spatial associations between two globose cacti and two dominant mimosoid bushes in a tropical semiarid enclave

Abstract

Spatial relationships between two globose cacti (Mammillaria mammillaris (L) Karsten and Melocactus schatzlii Till & Gruber) and two dominant mimosoid shrubs (Acacia farnesiana (Willd.) L. and Prosopis julifora DC.) were evaluated in two habitats (cactus thicket and thornscrub) of a Venezuelan semi-desert mountain valley. Globose cacti and shrubs are spatially associated, mainly in the cactus thicket, suggesting that cacti probably benefit from shrubs for their recruitment (sensu nurse plant syndrome). The presence of cacti in open areas, however, suggests that the need of a nurse plant for establishment of both globose cacti may be highly facultative. This is the first assessment reporting a positive globose cactusshrub spatial association from the Andes of northern South America. By confirming that mimosoid shrubs can influence thespatial distributions of globose cacti, this observational approach provides a foundation for future research and essential information to increase our knowledge on the role of mimosoid bushes as nurse plants in the tropical Andes.