Valiente-Banuet A., Ezcurra E., Shade as a cause of the association between the cactus Neobuxbaumia tetetzo and the nurse plant Mimosa luisana in the Tehuacan Valley, Mexico, Journal of Ecology, 1991, 79(4):961-971, doi: 10.2307/2261091
The abstract describes an experiment on germination and survival of young Neobuxbaumia tetetzo under different light conditions and exclusion of seed and seedling consumers. The results associate the nurse effect with improved survival in shaded microsites. The abstract was consulted without the details of unavailable methods and tables.