How would homologous recombination and mutations affect speciation?
Recombination occurs when homologous DNA sequences pair with each other and cross over, essentially swapping genetic material. Now, say that this crossover junction is in the middle of a gene, and we have some genetic differences in the top half and some in the bottom that distinguish the two alleles. If recombination occurs in the middle of the gene, then a new combination of alleles is created that didn't exist before. This new version of the chromosome can now be passed on as a single unit via sexual reproduction. 

I left out a lot of details obviously, but this is the basic idea. The reason why recombination adds to genetic diversity and can lead to speciation is because it is essentially mixing and matching existing combinations to create new alleles.