I was reading the paper "A survey of methods and tools to detect recent and strong positive selection" (2017) and came across this:
Upon fixation of the beneficial mutation, elevated levels of LD emerge on each side of the selected site, whereas a decreased LD level is observed between sites found on different sides of the selected site. The high LD levels on the different sides of the selected locus are due to the fact that a single recombination event allows existing polymorphisms on the same side of the sweep to escape the sweep. On the other hand, polymorphisms that reside on different sides of the selected locus need a minimum of two recombination events in order to escape the sweep. Given that recombination events are independent, the level of LD between SNPs that are located on different sides of the positively selected mutation decreases.
I am having trouble understanding how this works. If I am understanding this correctly, if you took two sites on the left side of the beneficial mutation during a selective sweep, you would see high LD between them. The same goes for taking two sites on the right side of the beneficial mutation. (Provided they are close enough to the mutation site of course.) However, if you took one site 300 bp to the left of the mutation, and another 300 bp to the right of it, you may not see the same rise in LD. I am not sure why this would be the case: wouldn't the entire region linked to the beneficial mutation, regardless of which side of the mutation it occurs to, be co-inherited and thus display similar high LD across the board, provided it is overall close enough to the site of beneficial mutation?