Population cytogenetics of the spiny-tailed goanna

Chromosomal rearrangements are often associated with local adaptation and
speciation because they suppress recombination, and as a result,
rearrangements have been implicated in disrupting geneflow. Although there
is strong evidence to suggest that chromosome rearrangements are a factor
in genetic isolation of divergent populations, the underlying mechanism
remains elusive. Here we applied an integrative cytogenetics and genomics
approach testing whether chromosomal rearrangements are the initial
process, or a consequence, of population divergence in the dwarf goanna,
Varanus acanthurus. Specifically, we tested whether chromosome
rearrangements are indicators of genetic barriers that can be used to
identify divergent populations by looking at geneflow within and between
populations with rearrangements. We found that geneflow was present
between individuals with chromosome rearrangements within populations, but
there was no geneflow between populations that had similar chromosome
rearrangements. Moreover, we identified a correlation between reduced
genetic variation in populations with a higher frequency of homozygous
submetacentric individuals. These findings suggest that chromosomal
rearrangements were widespread prior to divergence and because we found
populations with higher frequencies of submetacentric chromosomes were
associated with lower genetic diversity, this could indicate that
polymorphisms within populations are early indicators of genetic drift.