Diversity vs. Heterogeneity: New Insights from Animal Gut Microbiome Scaling

Diversity and heterogeneity are two related but distinct ideas that describe biological communities. As part of his recent heterogeneity research through the Bullard Fellowship at Harvard Forest, Dr. Zhanshan (Sam) Ma collaborated with Aaron Ellison, Harvard Forest Associate, to examine the differences between these two phenomena by studying animal gut microbiomes (AGMs). Recently published in Oikos, the study found that while diversity refers to the number and variety of microbes in a system, heterogeneity describes how those communities differ between hosts. They estimated a global pool of 640,000 microbial species, but only a very tiny portion exists in any one animal. They also discovered that an animal's evolutionary relationships with other species play a bigger role in shaping these differences than its diet.

The study also showed that diversity and heterogeneity may change over different timescales. Diversity is influenced by short-term changes, like how species move or grow, while heterogeneity is shaped by long-term processes, such as evolution and animal behavior. These findings highlight the importance of understanding diversity and heterogeneity as separate but connected concepts. By doing so, scientists can better study ecosystems and apply these ideas to other natural and human systems.