The most common type of distribution pattern(s) in nature is(are)

The given blank can be filled with cluster.

Explanation:

The most general pattern of distribution in nature is clustered. This is because the resources are distributed intermittently in the environment. Thus, if the resources are rare, or because of the social element, the individuals would cluster together in the region where these factors become auspicious.  

The least common kind of distribution pattern is termed as the random distribution, and it is evident in homogenous surroundings that are very rare. The other kind of pattern known as regular distribution is the outcome for direct social associations amongst the individuals within the population, or for a resource.