Imagine a large population of flowering plants that lives on a large expanse of western
prairie. The plants in this population interbreed only amongst themselves and can
therefore be classified as members of a single species. Letâ€™s also assume that a diverse
community of insects, consisting of about equal proportions of moths and bees, pollinates
the flowers. Suppose that over geological time, a mountain range divides this population
into two distinct sub-populations. At some point the mountains become so tall that
pollenating insects can no longer travel from one side of the range to the other, thus
establishing an effective barrier to gene flow between our sub-populations. Because of
the â€œrain shadowâ€ effect, the habitat on the western side of the range is cool and wet,
while the eastern side is hot and dry. The difference in climate also affects the
communities of pollinators upon which the plants depend for reproduction. On the
eastern side they consist mostly of nocturnal long-tongued moths and on the western side
diurnal bees. Finally, letâ€™s assume that there is substantial
for ecologically important traits such as drought tolerance, flower shape and color, and seed
1. Given the habitat characteristics on the western side of the range, what type of
adaptive evolutionary changes might you expect to see in traits such as flower color, time
of flowering, drought and temperature tolerance, and seed germination?
2. Given the habitat characteristics on the eastern side of the range, what type of adaptive
evolutionary changes might you expect to see in traits such as flower color, time of
flowering, drought and temperature tolerance, and seed germination?
3. Suppose that over time the two sub-populations of plants diverge substantially with
respect to flowering time (day vs. night). How might this result in reproductive isolation
between the sub-populations?
All questions must be answered