Complex sentence: Haldane's rule applies to the vast majority of heterogametic organisms examined, including when two species, where secondary contact in an area of sympatry results in incomplete reproductive isolation, form hybrids after allopatric speciation has occurred.
Split into simpler sentences: Haldane's rule applies to the vast majority of heterogametic organisms. This includes the case where two species make secondary contact in an area of sympatry and form hybrids after allopatric speciation has occurred.