  Many natural patterns, such as the distributions of blood particles in a
blood sample, proteins on cell surfaces, biological populations in their
habitat, galaxies in the universe, the sequence of human genes, and the fitness
in evolutionary computing, have been found to follow power law. Taylor's power
law (Taylor 1961: Nature, 189:732-) is well recognized as one of the
fundamental models in population ecology. A fundamental property of biological
populations, which Taylor's power law reveals, is the near universal
heterogeneity of population abundance distribution in habitat. Obviously, the
heterogeneity also exists at the community level, where not only the
distributions of population abundances but also the proportions of the species
composition in the community are often heterogeneous. Nevertheless, existing
community diversity indexes such as Shannon index and Simpson index can only
measure "local" or "static" diversity in the sense that they are computed for
each habitat at a specific time point, and the indexes alone do not reflect the
diversity changes. In this note, I propose to extend the application scope of
Taylor's power law to the studies of human microbial communities, specifically,
the community heterogeneity at both population and community levels. I further
suggested that population dispersion models such as Taylor (1980: Nature, 286,
53-), which is known to generate population distribution patterns consistent
with the power law, should also be very useful for analyzing the distribution
patterns of human microbes within the human body. Overall, I hope that the
approach to human microbial community with the power law offers an example that
ecological theories can play an important role in the emerging medical ecology,
which aims at studying the ecology of human microbiome and its implications to
human diseases and health, as well as in personalized medicine.
