How important are columnar cacti as sources of water and nutrients for desert consumers?
Succulent CAM plants, such as columnar cacti, are important physiognomic elements of many arid lands. Although, these plans are often ecologically important because they provide abundant resources in the form of nectar and fruit, their contribution to the energy, nutrient and water budgets of consumes has not been quantified. We describe an isotopic approach that allows quantifying the ecological importance of CAM succulents. We first briefly review our work on the interaction between saguaros, an archetypical CAM succulent, and the desert doves that feed on its fruit. We then describe the potential importance of saguaro fruit as a function of its abundance, macronutrient composition, and seasonal availability. We argue that the resources provided by saguaros do much to satisfy the energy and water requirements of the birds that reside in hot subtropical deserts during the summer. We then describe the carbon isotope composition of saguaros and of the plant community in which they are i
