S.W. Europe, N.W. Africa, S.W. Asia
"The drupes of Ilex aquifolium contain up to four pyrenes, but brood size reduction by both pyrene number reduction and/or seed abortion producing blank pyrenes affected 2/3 of fruit production.... The pyrenes were heavily predated by rodents that discard the fibrous coat and consume the seed. The examination of pyrene remains after predation by rodents showed that they opened most of the seeded pyrenes and left most of the blank pyrenes intact. However, the rodents opened some blank pyrenes, which may increase the handling time and might be interpreted as an escape from predation. Larger fruits invest proportionately less in pulp and more in pyrenes, especially in pyrene fibrous coat. In the same way, heavier seeds had proportionately heavier fibrous coats; hence, larger fruits invested proportionately more in defence than in dispersal. There is a significant degree of phenotypic variability in fruit traits that might affect both dispersal and predation; however, frugivorous birds probably do not exert selective pressures on fruit traits because they consume the entire crop." 
"As in other spinescent plants, the production of prickly leaves in Ilex L. is a plastic defensive response induced by mammalian browsing, which may subsequently reduce herbivory." 
"Holly was considered sacred by the ancient Romans. Holly was used to honor Saturn, god of agriculture, during the Saturnalia festival held during the winter solstice. The Romans gave one another holly wreaths, carried it in processions and adorned images of Saturn with it. During the early years of Christianity in Rome, many Christians continued to decorate their homes with holly to avoid detection and persecution by Roman authorities. Gradually, holly became a symbol of Christmas as Christianity became the dominant religion of the empire." 
"American holly (Ilex opaca) and English holly (Ilex aquifolium) are prized for their glossy, green leaves and red, berry-like fruit. Sprigs of both hollies are often used in wreaths, centerpieces and other Christmas decorations." 
 Obeso, J. R. (1998). Patterns of variation in Ilex aquifolium fruit traits related to fruit consumption by birds and seed predation by rodents. Ecoscience, 5(4), 463-469.
 Herrera, C. M., & Bazaga, P. (2013). Epigenetic correlates of plant phenotypic plasticity: DNA methylation differs between prickly and nonprickly leaves in heterophyllous Ilex aquifolium (Aquifoliaceae) trees. Botanical Journal of the Linnean Society, 171(3), 441-452.
 Jauron, Richard, & Wallace, Greg (2017). Yard and Garden: Planting and Growing Holly Varieties in Iowa. Iowa State University Extension and Outreach News. Retrieved from https://www.extension.iastate.edu/news/yard-and-garden-planting-and-growing-holly-varieties-iowa