A population of dark-eyed junco birds became established near the California coastline, many miles from the junco's normal habitat in the mixed-coniferous temperate forests in the mountains. Juncos have white outer tail feathers that the males display during aggressive interactions and during courtship displays. Males with more white in their tail are more likely to win aggressive interactions, and females prefer to mate with males with more white in their tails.
The coastal male junco population tails were, on average, 36% white; whereas the tails of males from the mountain populations averaged 40-45% white. Which of the following factors is the most likely original cause of the difference between the populations if the trait is inherited?
A) mutations in the coastal population
B) gene flow between populations
C) a bottleneck effect in the coastal population
D) a founder effect in the coastal population

Question

Quizplus · Accepted Answer

The most likely original cause of the difference in tail coloration between the coastal and mountain junco populations is the founder effect. This occurs when a new population is established by a small number of individuals from a larger population, leading to reduced genetic variation and potentially different traits in the new population compared to the original one.

A Population of Dark-Eyed Junco Birds Became Established near the California