Wind, water currents, and animals often serve to aid dispersal of propagules. The amount and distribution of genetic variation within a population describes its genetic structure . Genetic variation serves as the basis of a population's capacity to respond to environmental change through natural selection. In most populations, individuals are genetically different and the genetic variability will permit some individuals to respond differently to environmental changes than other individuals. In clonal organisms or modular organisms, the distinction among individuals is muddled.
Aspens are a prime example.
An aspen grove often arises from a single zygote. Aspen individuals are natural clones. Each individual arising from a single zygote is a ramet , while the clump of individuals is a genet . Founder events - a small populations leaves a larger one and colonizes a new area. The small population very likely has only a fraction of the genetic variation found in the larger population.