A class of functions describing the Allee effect and local catastrophe
s in population dynamics is introduced and the behaviour of the result
ing one-dimensional discrete dynamical system is investigated in detai
l. The main topic of the paper is a treatment of the two-dimensional s
ystem arising when an Allee function is coupled with a function descri
bing the population decay in a so-called sink. New types of bifurcatio
n phenomena are discovered and explained. The relevance of the results
for metapopulation dynamics is discussed.