Morphological distinction is one of the steps necessary for speciation to occur. What are the other two?

Genetic Separation / Geographic isolation

Explanation:

Morphological distinction (or phenotypic differentiation) can be defined as the diversification of a set of observable physical characteristics in a population, capable of differentiating certain species.

The genetic separation occurs when the division of a group of genes into two or more pools of genes separated over time and depending on several other situational factors.

Geographic isolation occurs due to the physical separation of subpopulations of a given species. The barriers that isolate these subpopulations can be, for example, a river that cuts through a plain, a valley that divides plateaus or a portion of the sea that separates islands and continents.