Sunday, 18 April 2010

Azorean Gull

Discussion thread here:
Been reading up on 'Atlantic Gull' populations recently. Dorit Liebers et al (2001, 2004- see link below) have carried out genetic studies and made some interesting discoveries. Atlantic Gulls and Lesser Black-backed Gulls are traditionally considered to be close relatives but their genes tell a different story. Atlantic Gulls were derived from an ancient population of gulls (green circle on map) which became isolated in the North Atlantic about 250,000 years ago (during an ice age) and Lesser Black-backed Gulls were derived from a population at the same time that were isolated in central Asia (cream circle on map). So they are not closely related.

Interestingly, the first 'Yellow-legged Gulls' to evolve were on the Atlantic islands/coast and these Atlantic Gulls colonized the Mediterranean. A first colonization event led to the evolution of Armenian Gull and later colonization led to the evolution of Yellow-legged Gull. Most interesting of all is a genetic north/south divide in Atlantic Gulls. The birds on Madeira and mainland Morocco are different to the birds of the Azores and Iberian Atlantic coasts. It also appears that it was the Azores and Iberian Atlantic gulls that colonized the Mediterranean to give rise to Yellow-legged and Armenian Gull while the southern Atlantic Gulls appear to have been sedentary.

It has taken me about three weeks to get my head round that so I may have misunderstood it. Comments very welcome.

Atlantic Gull photo collection here:
For Dorit Lieber's et al article see here:


Darryl said...

Perhaps I'm getting this wrong but, given that the paper is based on cytochrome b, don't the following conclusions rather undermine things a little:

"The current mitochondrial genetic make-up of the herring gull [...] shows clear signs of past hybridization between birds derived from different [...] ancestral refugia, although no definite geographical scenario can be reconstructed for this reticulation"; and that, "Such polyphyletic representation in the haplotype network [...] provides a striking illustration of how discrepancies may arise between a gene tree and the taxon phylogeny. The fact that some species, apparently owing to past gene-flow episodes, contain highly divergent haplotypes suggests that mitochondrial lineage sorting may have quite different and unpredictable outcomes."

Presumably Liebers et al. are now using nuclear markers and a much more extensive sampling regime?

Peter Alfrey said...

Wouldn't we expect a rather disordered/random haplotype network in a hybrid population and some kind of order where the divergence has been as a result of isolation and evolution.
The paper says something about using the hypervariable control region 1 (HVR-1)as the best way of studying gull evolution- because the evolution is very recent.
Pierre will know about all this.