What prevents speciation from occurring in sympatric populations?

Within the Northeast Pacific, two types of killer whales (Orcinus orca) are found. Resident killer whales feed mostly on salmon, while the transient population feeds mostly on marine mammals. While these populations spend a lot of time in the same waters, they do not interbreed, likely because they use different systems of calls to communicate. Some scientists believe that these two populations of orca are undergoing speciation. What type of speciation is occurring, and what type of reproductive barrier do you suspect is reinforcing the speciation?

Polyploidy creates individuals or gametes with novel numbers of chromosomes. To mate, these individuals must mate with other organisms that are also polyploid. Would this lead to polyploidy being more common in animals or plants, and why?

What is the difference between autopolyploids and allopolyploids?