Why some parasites are widespread and abundant while others are local and rare?
Abundances and distributions of species are usually associated. This implies that as a species declines in abundance so does the number of sites it occupies. Conversely, when there is an increase in a species' range size, it is usually followed by an increase in population size (Gaston etal. ). This ecological phenomenon, also known as the abundance-occupancy relationship (AOR), is well documented