What type of interaction often results in hybrid infertility?

Hybrid infertility arises from a postzygotic barrier, which is a mechanism that prevents the successful production of fertile offspring after fertilization has occurred. This phenomenon occurs when two different species mate and produce a hybrid zygote, but the resulting organism either fails to develop fully or is sterile. A classic example is the mule, a hybrid between a horse and a donkey, which is typically sterile due to chromosomal incompatibilities.

In the context of speciation, postzygotic barriers like hybrid infertility contribute significantly to the maintenance of species boundaries. By preventing hybrids from reproducing successfully, these barriers reinforce the separation and distinct identities of the parent species. This contrasts with other processes mentioned in the options, which do not directly relate to the inability of hybrids to reproduce. Sympatric speciation and prezygotic barriers focus on factors that lead to speciation and prevent fertilization from occurring in the first place, while convergent evolution describes the process where unrelated species independently evolve similar traits, which does not pertain to hybridization events at all.