Together, our results identify a relatively small number of genes that can be tested for speciation roles among D. melanogaster sibling species.
In order to understand speciation and its role in evolution, it is useful to know how much genetic change takes place during the course of species development.
It remains so today although just how important a role speciation plays in the evolutionary process is, nowadays, a matter of some dispute.
Historically, unresolved questions about the pace or patterns of change, mechanisms of speciation, or the role of mutations and mechanisms of gene flow indicate an active and vital scientific enterprise.
That is, if the process of speciation plays no role itself in causing change, then we do not expect that modern species at the end of paths through the tree with more speciation events will have diverged more from their common ancestor at the base of the tree.
A relatively unexplored area in ecological speciation is the role of gene expression.
With the current data available on the spiny-throated reed frogs, it seems possible that peripatric speciation plays a role in generating biodiversity within the forests and grasslands of the EABH.
We like to admit that open questions remain, such as the mechanisms of speciation or the role of sex in evolution as seen from a traditional perspective; but those questions are left at some distance from the fundamentals, and in that sense, traditional theory can be said to be complete.
Here we review two potential roles of gene expression in ecological speciation: (1) its indirect role in facilitating population persistence and (2) its direct role in contributing to genetically based reproductive isolation.
Diversified genitalia may play an essential role in speciation, whether acting at the onset of the lineage splitting process or after speciation to reinforce gene flow barriers between species (Coyne and Orr 2004; Eberhard 2010; Masly 2012).
