Speciation
Speciation is the process that leads to the evolution of new species.
Traditionally, the emphasis has been on the geographical mode of speciation, i.e. if the speciating populations are geographically isolated from one another or not. Now, speciation is a sprawling field of research spanning population genomics, ecological adaptation, epigenetics and development and sexual selection.
One key question scientists are beginning to discuss is the genetic architecture of reproductive isolation. Which genes cause reproductive isolation; are there many or just one? Why do they cause reproductive isolation? Do the speciation genes diverge due to adaptation or drift? Advances in technology have made it possible to isolate particular genes and causes for reproductive isolation, but we are still struggling to see the bigger pattern.
There is also an ecological side of speciation: Is each speciation process unique, or are there common features of several speciation events? Can a certain gene or ecological or geographical situation repeatedly cause speciation? Is it a by-product of other evolutionary processes such as selection or drift?
My approach has been to look at the molecular variation and biogeographical history of several closely related species complexes. I have found two things:
1. Depending on which method you use to discover species you may get different results. Therefore you should approach a particular speciation event as an hypothesis that has to be tested and proven.
2. Seemingly similar species can have very different biogeographical patterns. I believe that the structure of the molecular variation depends a lot on the ecology of a certain species, and the biogeographical history of the habitat and its inhabitants.
Learn more about speciation:
Species and gene-flow
http://www.botany.ubc.ca/people/whitton/2001-RundleJEvolBiol.pdf
Ecological speciation
The problem of defining species
http://en.wikipedia.org/wiki/Species_problem