Difference between haplotype diversity and genetic distance/population differentiation?

I'm take a marine mammal course for school and am reading a chapter about population genetic structure. In the first section of the chapter we were discussing a low number of haplotypes in certain populations, most likely due to a bottleneck event. In the next section we began discussing population differentiation (which is the same thing as genetic distance, right?). Well, if I understand this right, a haplotypes is basically a combination of alleles and wouldn't population differentiation result from different sets of alleles (or haplotypes)? So, my question is how these two are different? Wouldn't lots of population differentiation mean that there are many different haplotypes in that population and vice versa (low population differentiation = few haplotypes)?