In most ecosystems in which abundance has been calculated, most often only a small number of species are abundant, while a large number are pretty rare.[1] These abundant species are often generalists, with many rare species being specialists.[4] High density of a species in multiple localities will usually lead to it being relatively abundant over all in an ecosystem.[4] Therefore, high local abundance can be directly linked to high regional distribution. Species with high abundance are likely to have more offspring, and these offspring in turn are more likely to colonize a new sector of the ecosystem then a species which is less abundant. Thus begins a positive feedback loop leading to a species distribution in which a few "core species" are wide spread, and the other species are restricted and scarce known as satellite species.[2]