Write abstract here .
Despite half a century spent scrutinizing levels of naturally occuring polymorphism and, more recently, levels of between species divergence at the molecular level, we know embarrassingly little about which forces explain these patterns ( See a recent review (Leffler ) for an overview of the “old riddle”) although some recent analyses on large comprattive dataset suggest that some life history traits may have a pervasive effect on the amount of neutral nucleotide diversity at a very large phylogenetic scale. What do we know from previous studies is that :
. Mutation rate vary substantially throughout the genome and between species divergence for presumaly neutrally evolving regions/sites can reveal that variation;
The amount of drift experienced by a particular locus may also vary due to selection at linked sites. There is mounting evidence that this phenomenon is quite widespread although the quantitative effect of either positive and/or negative selection at linked sites h