Population variability in space and time

One of the most ubiquitous phenomena of all natural populations is their va riability in numbers in space and time. However, there are notable differen ces among populations in the way the population size fluctuates. One of the major challenges in population and community ecology is to explain and und erstand this variety and to find possible underlying rules that might be mo dified from case-to-case. Population variability also has a spatial compone nt because fluctuations are often synchronized over relatively large distan ces. Recently, this has led to growing interest in how 'internal' (density- dependent) processes interact with 'external' factors such as environmental variability.