Refer to the paragraph on dark-eyed junco birds. the ucsd campus male junco population tails are about 36% white, whereas the tails of males from nearby mountain populations are about 4045% white. the founding stock of ucsd birds was likely from the nearby mountain populations because some of those birds overwinter on the ucsd campus each year. population sizes on the ucsd campus have been reasonably large, and there are significant habitat differences between the ucsd campus and the mountain coniferous forests; ucsd campus has a more open environment (making birds more visible) and a lower junco density (decreasing intraspecific competition) than that in the mountain forests. given this information, which of the following evolutionary mechanisms do you think is most likely responsible for the difference between the ucsd and mountain populations?

a. gene flow
b. genetic drift
c. natural selection
d. mutation