Despite speciation being a fundamental biological process crucial to creating biodiversity, we still lack a complete understanding of the mechanisms involved. Chromosome rearrangements are known to actively contribute to the divergence of some species, however, the mechanisms driving these genetic incompatibilities that lead to speciation have been much debated. Three mechanisms proposed to contribute to chromosomal speciation are being explored in this study. The first is known as underdominance, in which the hybrid offspring of two chromosomally diverse individuals are infertile as a result of meiotic missegregation. A second mechanism, recombination suppression, occurs when rearranged regions of chromosomes are suppressed from recombining at meiosis. The third mechanism explores the role of epigenetic incompatibilities in chromosomal speciation.
We are using a combination of cytogenetic, genomic and epigenetic techniques to determine the mechanisms and synergistic effects of genic and chromosomal variation in causing reproductive isolation in the chromosomally diverse rock-wallabies (Petrogale). We target four of the six parapatric northeast Queensland rock-wallabies which have recently diverged and have simple to complex chromosomal rearrangements. The first step in this study is to compare the gene order on chromosomes using fluorescence in situ hybridisation in order to fully characterise the chromosome rearrangements that have occurred across these species. The fine scale gene mapping has detected rearrangements not previously identified using lower resolution cytogenetic techniques. These mapping data will provide the backbone for the genomics and epigenetics aspects of this study.