Effective Population Size

Effective Population Size (EPS) is a population genetics metric that describes the number of individuals in an idealized population needed to maintain the same genetic diversity as an actual population being studied. In cannabis breeding contexts, EPS helps breeders understand how much genetic variation persists within a cultivar line or seed batch after multiple generations of selection. A low EPS relative to census size indicates genetic bottlenecks—periods where fewer plants contributed to the next generation, reducing allelic diversity. Tracking EPS is relevant when preserving heirloom genetics or establishing stable breeding populations, as it flags whether a line risks losing trait variation through unintentional selection pressure or small founding populations.

Breeders use EPS calculations to assess risk of inbreeding depression and loss of adaptive potential in closed populations. Understanding EPS informs decisions about population size, outcrossing strategies, and germplasm banking to maintain long-term breeding options.