The differentiation over the
relatively short distances in these studies was attributed to
the unique current patterns and ecological barriers of these
regions, small local populations or temporal variation.
Over longer distances, genetic differentiation and differences
in genetic diversity were detected among P. monodon
populations from eastern and western Australia (Brooker
et al. 2000), near Thailand (Supungul et al. 2000) and
between the Pacific and Indian Oceans (Duda & Palumbi
1999). Much of the differentiation in P. monodon has been
attributed to major historical biogeographical barriers
or to founder events of the recent ice ages; these patterns
of differentiation have remained despite any potential
for present-day gene flow (Benzie 2000). There does not
appear to be a strong relationship between penaeid life
history type (ranging from estuarine to oceanic) and the
amount of population structure (Benzie 2000).