Introduced populations of organisms typically have
reduced diversity compared to those that are native. It is,
therefore, unusual that introduced populations of the fungal
tree pathogen Diplodia pinea have been shown to have high
levels of genetic diversity, even surpassing diversity in some
native regions. This is thought to be due to multiple
introductions over time or the existence of a cryptic and
yet undiscovered sexual cycle. In this study, we consider
whether populations of D. pinea in Southern Hemisphere
countries have similar patterns of diversity, share some level
of genetic identity and how they might be influenced by
sexual recombination. A total of 173 isolates from Argentina,
Australia, Ethiopia and South Africa were characterized
using 12 microsatellite markers. The results show that all
these populations have high gene and genotype diversities,
with the Australian population having the lowest diversity.
Very few private alleles were found, suggesting that isolates
from different countries might share a source of introduction.
However, based on allele distribution and frequency, each of
the populations appeared to be evolving independently. The
results showed that in all but the Australian population,
alleles are randomly associated, suggesting that widespread
sexual recombination has influenced population structure.