How to Explain Genetic Differences in Isolated Cicada Populations

What mechanism is the most likely cause of the dramatic gene differences in isolated cicada populations?

A. Bottleneck effect
B. Disruptive selection
C. Migration
D. Gene flow

Answer: A. Bottleneck Effect

Let's break it down:

When a landslide isolates a portion of the cicada population, a small population size may occur suddenly. This situation can lead to the bottleneck effect, where the genetic variation within the population is altered. As a result, the new generations of cicadas exhibit dramatic gene differences from the previous generations.

Disruptive selection is unlikely to happen in this scenario because the same traits or phenotypes are present in both split populations of cicadas, and the landslide itself does not favor specific genes over others.

Similarly, migration or gene flow is not relevant in this specific case, as the populations are isolated and cannot mate with each other, affecting the gene flow between them.

Therefore, the most likely cause of the significant gene differences in isolated cicada populations is the bottleneck effect, resulting from the sudden reduction in population size due to the landslide.