Revealing the history of sheep domestication using retrovirus integrations.

The domestication of livestock represented a crucial step in human history. By using endogenous retroviruses as genetic markers, we found that sheep differentiated on the basis of their "retrotype" and morphological traits dispersed across Eurasia and Africa via separate migratory episodes. Relicts of the first migrations include the Mouflon, as well as breeds previously recognized as "primitive" on the basis of their morphology, such as the Orkney, Soay, and the Nordic short-tailed sheep now confined to the periphery of northwest Europe. A later migratory episode, involving sheep with improved production traits, shaped the great majority of present-day breeds. The ability to differentiate genetically primitive sheep from more modern breeds provides valuable insights into the history of sheep domestication.

Challenges and prospects of population genetic studies in terns (Charadriiformes, Aves)

Little information is available about the population structure of communally nesting terns (Sternidae) and skimmers (Rynchopidae) throughout the world. In order to fill this gap, a survey of molecular markers was carried out for six species of terns (Anous stolidus, Sterna hirundinacea, S. fuscata, S. superciliaris, Thalasseus maximus and Phaetusa simplex) and one species of skimmer (Rynchops niger). First, we describe the results of the construction of genomic DNA libraries and document problems encountered during this procedure. Secondly, we tested the cross-amplification of 18 microsatellite loci previously described for related species (the number of polymorphic loci ranged from three to seven). Thirdly, we tested the usefulness of mtDNA (control region, ND2, Cytochrome b and ATPase 6/8) for phylogeographic studies in this group of birds. The occurrence of nuclear copies of the mitochondrial control region is reported. Nucleotide divergence in the mtDNA genes analyzed ranged from 0.0 to 0.006. Despite the difficulties associated with the selection of variable markers in this group of seabirds, we were able to select polymorphic markers for each species tested and we anticipate these results will help the development of genetic studies concerning important biological questions in terns.