3: Inferring demographic change during invasion and its
quantifying its impact on invasion success
In the simplest model of a successful invasion, some small fraction of a
native population is transported to a new environment where a viable
population forms and increases in size over time. This leads to a
demographic bottleneck (a decrease in population size followed by an
increase), which can have wide-ranging implications for both practical
and theoretical aspects of invasion genetics (see Box 2). From a
pragmatic perspective, the extreme demographic dynamics of colonization
can be used to reconstruct invasion events in time. From a biological
perspective, invasion geneticists are tasked with explaining how so many
invasive species form viable populations, let alone dominate foreign
ecosystems, in the face of a population bottleneck that reduces genetic
diversity and increases the risk of inbreeding depression (Estoup et
al., 2016). We discuss these two perspectives separately.