What role do different isolation mechanisms play in speciation. What form of selection has a decisive role in speciation?

An important factor in evolution is isolation, which leads to the divergence of characters within the same species and prevents the crossing of individuals. Isolation can be geographical, ethological (behavioral) and environmental. The following speciation methods are distinguished.
Geographical speciation – new forms of organisms arise as a result of a break in the range and spatial isolation. In each isolated population, gene pool changes due to gene drift and selection. Next comes reproductive isolation, which leads to the formation of new species.
The reasons for the breakdown of the range can be mountain processes, glaciers, river formation and other geological processes. For example, different types of larch, pine, Australian parrots formed as a result of rupture of the range.
Ecological speciation is a method of speciation in which new forms occupy different ecological niches (spatial) within the same range. Isolation occurs due to the mismatch of time and place of crossing, animal behavior, adaptation to different pollination methods in plants, consumption of different foods, etc. For example, species of Sevan trout have different spawning places, different types of Buttercups are adapted to life in different conditions.
The decisive role in the processes of speciation belongs to natural selection.

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