Final answer:
Reproductive isolation can happen in both allopatric and sympatric speciation, not just sympatric. Speciation requires some form of reproductive barrier, regardless of whether a geographic barrier is present.
Step-by-step explanation:
The statement that reproductive isolation only occurs in sympatric speciation is false. Speciation, the creation of new species, can occur both through allopatric speciation, which involves geographic separation, and sympatric speciation, which occurs without geographic barriers. Reproductive isolation is an essential factor in both scenarios and can arise from various mechanisms, including behavioral differences, temporal isolation such as different mating seasons, or even chromosomal changes like polyploidy. Examples of sympatric speciation include the case of the East African cichlid fish, in which mate selection based on coloration leads to reproductive isolation even though there is no physical barrier between the groups.