MuD & PHuD

Since I posted a few evolution related items yesterday, I thought I'd point out this news item from the most recent issue of Science (subscription required):

New Migration Route Could Lead to New Species of Bird
[...]
On page 502, Stuart Bearhop, an animal ecologist at Queen's University Belfast, U.K., and his colleagues report that even though all the blackcaps gather each year at the same mating sites, they tend to reproduce with those from their particular wintering ground--a phenomenon called assortative mating. Moreover, the birds that stay north are reproducing more than those taking the southern route, which may improve the chances of the birds forming two species.
[...]
Assortative mating is a matter of timing, Bearhop says. The birds from Britain and Ireland have shorter migrations to their summer mating grounds in Germany and Austria and, prompted by the more dramatic changes in day length at their home locations as winter becomes spring, those more northern migrants leave about 2 weeks earlier than those wintering in Iberia. "Because [these birds] mate with whoever arrives first, they have tended to remain isolated from the later-arriving historical population," say Keith Hobson, an ecologist with the Canadian Wildlife Service in Saskatoon, Canada.
[...]
Still, Hobson and others question whether the north-based birds are becoming a new species. They argue, for example, that there is not yet enough information about the fate of hybrids between the two bird populations. Nonetheless, says Peter Marra of the National Zoological Park in Washington, D.C., "this study provides us with a scenario of how [separate migratory] patterns may evolve and should stimulate some good discussion among students of migration ecology."

It should be interesting to hear what happens to the 'hybrids' between these two populations as the years go by. I don't honestly expect that I'll actually witness a speciation event in my lifetime, but then again you never know.

Just for fun, here the title and abstract of the reserach paper refernced in the article above:

Assortative Mating as a Mechanism for Rapid Evolution of a Migratory Divide

Stuart Bearhop,1* Wolfgang Fiedler,2 Robert W. Furness,3 Stephen C. Votier,5 Susan Waldron,4 Jason Newton,6 Gabriel J. Bowen,7 Peter Berthold,2 Keith Farnsworth1

There have been numerous recent observations of changes in the behavior and dynamics of migratory bird populations, but the plasticity of the migratory trait and our inability to track small animals over large distances have hindered investigation of the mechanisms behind migratory change. We used habitat-specific stable isotope signatures to show that recently evolved allopatric wintering populations of European blackcaps Sylvia atricapilla pair assortatively on their sympatric breeding grounds. Birds wintering further north also produce larger clutches and fledge more young. These findings describe an important process in the evolution of migratory divides, new migration routes, and wintering quarters. Temporal segregation of breeding is a way in which subpopulations of vertebrates may become isolated in sympatry.

Wasn't that fun?
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