“Life begats life, not only in terms of offspring, but also as each species, by its very presence, creates new conditions suitable for colonization by other species. A tree must be present before a resurrection fern can colonize its branches or before a northern parula warbler can forage for insects in its crown. Once the warbler is present, a black rat snake can eat its eggs and a mosquito or other parasite can drink its blood. As each new species arises in a natural community, it creates an opportunity, or niche, for other species to enter.”

from – Mountain Nature: A Seasonal Natural History of the Southern Appalachians
by Jennifer Frick-Ruppert, page 4.