Scenario 1 When you think of the American Southwest, you probably think of cacti, both big and small. If you were to
visit the American Southwest today, you might be disappointed with the lack of variation among cactus
species, especially right off the major highways. In 1926, Route 66 was the nation's first major highway to
allow visitors to visit the Southwest. Like many tourists, these visitors wanted to take home a memento of
their travels. Many people would pull over and begin looking for their own living souvenir. Since many of the
tourists did not have the necessary tools to extract a spiny cactus out of the soil, they usually had to make a
conscious decision about what type of cactus they should dig up. The cacti with too many spines were seen
as too difficult to dig out, and the visitors likely didn't have gloves to protect their hands. The cacti with too
few spines were seen as homely and were often overlooked. Therefore, the tourists found a cactus that was
between these two extremes. Over the last century, the phenotypic variation within these small cacti has
changed (at least in areas accessible by these highways).