  A phenomenon that strongly influences the demography of small introduced
populations and thereby potentially their genetic diversity is the Allee
effect, a reduction in population growth rates at small population sizes. We
take a stochastic modeling approach to investigate levels of genetic diversity
in populations that successfully overcame a strong demographic Allee effect, a
scenario in which populations smaller than a certain critical size are expected
to decline. Our results indicate that compared to successful populations
without Allee effect, successful Allee-effect populations tend to 1) derive
from larger founder population sizes and thus have a higher initial amount of
genetic variation, 2) spend fewer generations at small population sizes where
genetic drift is particularly strong, and 3) spend more time around the
critical population size and thus experience more drift there. Altogether, the
Allee effect can either increase or decrease genetic diversity, depending on
the average founder population size. In the case of multiple introduction
events, there is an additional increase in diversity because Allee-effect
populations tend to derive from a larger number of introduction events than
other populations. Finally, we show that given genetic data from sufficiently
many populations, we can statistically infer the critical population size.
