In ecological studies, what does a lognormal distribution typically indicate?

A lognormal distribution in ecological studies is characterized by a concentration of species abundance, where there are few species that are very rare and a few that are very common. This pattern suggests that most species have intermediate abundance levels, which is typical in many ecological communities.

This type of distribution arises because many ecological factors, such as resource availability and environmental variability, can act multiplicatively on species populations, leading to the emergence of such patterns. In contrast to an even distribution of species or an equal number of individuals per species, a lognormal distribution highlights the common ecological phenomenon where a small number of species dominate in number, while the majority remain less abundant. Additionally, it does not imply a direct correlation between species size and abundance; rather, size may influence abundance but is not a determining factor in the lognormal distribution itself.