Use the following information to answer the question below.
In 1983, a population of dark-eyed junco birds became established on the campus of the University of California, San Diego (UCSD), which is located 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. Females have less white in their tails than do males and display it less often. (Pamela J. Yeh. 2004. Rapid evolution of a sexually selected trait following population establishment in a novel habitat. Evolution 58[1]:166-74.)
Refer to the paragraph on dark-eyed junco birds. The UCSD campus male junco population tails were, on average, 36 percent white, whereas the tails of males from nearby mountain populations averaged 40-45 percent white. If this observed trait difference were due to a difference in the original colonizing population, it would most likely be due to ________.
A) mutations in the UCSD population
B) sexual selection
C) gene flow between populations
D) a genetic bottleneck
E) a founder effect

Question

Quizplus · Accepted Answer

The observed trait difference between the UCSD population and the nearby mountain populations is most likely due to a founder effect because the UCSD population was established from a small group of individuals that were not representative of the larger mountain population. This led to a reduced genetic variation in the UCSD population, which may have led to the observed lower average percentage of white in their tails.

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