TABLE 3.

Definition of terminology used to describe simulations and core assignments

Term	Definition or explanation
True positives/true core	Taxa simulated to have core abundance and occupancy that were assigned core membership by one of the assignment methods.
False positives/false core	Taxa simulated to have non-core abundance and occupancy but assigned core membership by one of the assignment methods.
True negatives	Taxa simulated with non-core abundance and occupancy that were not assigned core membership.
Net assignment value	Absolute difference between true positives and false positives.
Core:non-core abundance ratio (π)	Ratio of mean abundances between simulated core taxa and simulated non-core taxa. A larger value indicates that the core is more abundant relative to non-core members. For example, π = 25 indicates that the simulated mean abundances of core taxa are 25× greater than the simulated mean abundance of non-core taxa.
Intensity parameter (θ)	Affects variation in π across replicates within a set of simulations. As the variance increases with a constant π, empty counts (e.g., 0’s) are introduced to the count matrix. By holding π constant within a set of simulations, the intensity parameter introduces variation in the occupancy of core and non-core taxa.