Speciation: Islands vs Continents

If there is a topic that really excites a Museum evolutionary biologist, it's speciation: 
What drives speciation?
What affects rates of speciation?
Why are some groups of organisms more diverse than others? 
These are not easy questions at all.​.

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Mentors Lais Coelho and Brian Weeks along with their SRMP team, Jannatul and Josh, are tackling a classic idea that points to a link between dispersal ability and speciation rate in birds. Recent research has shown that for continental birds (e.g., those that live on the mainland), clades with higher dispersal abilities have lower speciation rates. Josh and Jannatul are stepping it up a notch. They are looking to compare speciation rates & dispersal ability among clades represented on both continents and remote (far-away) islands.

http://rspb.royalsocietypublishing.org/

Dispersal ability or vagility refers to an organism's ability to move around.  Low vagility = you can’t get far. High vagility = you are going places. Not all birds have the same capacity for long-distance flight. In fact you can predict vagility by the distance ratio to two feathers. This is exactly what Jannatul and Josh will be doing. ​

Their hypothesis is higher dispersal abilities on continents will inhibit rates of speciation while higher dispersal abilities on islands will stimulate rates of speciation. Why? Because continents present the opportunity for more continuous, suitable habitat (as opposed to thousands of miles of ocean). Great ability for movement keeps genes a flowing which prevents distant populations from diverging, a step along the path of speciation. Due to the continuity of continental habitats greater ability for movement is not necessary for range expansion, and therefore speciation, whereas on islands it is. 

The first step in this process is finding candidate birds (and islands) to test this hypothesis. To avoid an apples to oranges comparison, the team is scouring the literature for candidate bird clades that are well represented on BOTH islands and the mainland. So far, doves, flycatchers, and finches have made the list. Looking forward to an update once you start building those phylogenies and calculating speciation rates!