imagine a large population of flowering plants that lives on a large expanse of western prairie the plants in this population interbreed only among themselves and can therefore be classified as members of a single species let s also assume that a dive

Scenario

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

genetic variation

for ecologically important traits such as drought tolerance, flower shape and color, and seed

germination.

Questions

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