Q24.2-3CC - Campbell Biology

Question

Is allopatric speciation more likely to occur on an island close to the mainland or on a more isolated island of the same size? Explain your prediction.

Step-by-Step Solution

Answer

Allotropic speciation is more likely to occur in an isolated island. The island close to the mainland would allow gene flow which prevents the formation of new species. 

Step 1: Speciation

The formation of two or more species due to linage splitting is called speciation. Ecological conditions such as natural disasters, mountain formation, migration, and genetic drift can split the group of organisms from the parental population. Speciation causes evolution.

Step 2: Allotropic Speciation

The physical separation in an ancestral population forms two or more descendants, and such a speciation process is called allotropic speciation. The physical barriers include a change in habitat, volcanoes, changes of landscape, formation of mountains or water resources.

 

The group isolated from the main population might undergo genetic divergence due to the selection pressure.

Step 3: Influence of the gene flow on allotropic speciation

When separated population inhabits near the main population, breeding between the two populations allows gene flow. It decreases the formation of entirely new species. Geographical separation causes habitat isolation which prevents gene flow and causes speciation to occur. 

 

Thus, when an island is near to mainland, the species present in both the lands are more likely to breed. It does not cause allotropic speciation. An isolated island allows allotropic speciation.