Question

three populations of wildflowers become isolated from one another due to habitat loss. flower color in this species ranges from white to yellow to orange, with yellow considered to be the intermediate phenotype. prior to isolation, these populations had enough gene flow that each population was a mix of the three phenotypes. a botanist studying the populations observed that after 5 years of isolation, each population had distinct differences in the dominant phenotype. the study results comparing the first year and fifth year after isolation are in the table below. which type of selection did each population experience? drag the correct label to the population number.

table (chart) with columns: population 1, population 2, population 3; rows: white flowers, yellow flowers, orange flowers; years: year 1, year 5. data:
population 1: white (year 1: .32, year 5: .49); yellow (year 1: .29, year 5: .11); orange (year 1: .39, year 5: .40)
population 2: white (year 1: .26, year 5: .12); yellow (year 1: .34, year 5: .80); orange (year 1: .40, year 5: .08)
population 3: white (year 1: .33, year 5: .07); yellow (year 1: .45, year 5: .23); orange (year 1: .22, year 5: .73)

options: stabilizing selection, directional selection, disruptive selection (drag-and-drop labels)

Explanation:

• Population 1: White (0.32→0.49) and orange (0.39→0.40) stay stable, yellow (0.29→0.11) decreases. This reduces variation around intermediate? No, wait—stabilizing selects against extremes, but here white and orange (extremes?) are stable/increasing, yellow (intermediate) decreases. Wait, no—wait, stabilizing selection favors intermediate (yellow). But Population 1: yellow drops, white and orange (extremes) are stable or white increases. Wait, maybe I mixed up. Wait, disruptive selection favors both extremes, stabilizing favors intermediate, directional favors one extreme. Let's recheck:

• Population 1: Year 1: white=0.32, yellow=0.29, orange=0.39. Year 5: white=0.49, yellow=0.11, orange=0.40. So white (one extreme) and orange (other extreme) are increasing/stable, yellow (intermediate) decreasing. This is disruptive selection (favors both extremes, selects against intermediate).

• Population 2: Year 1: white=0.26, yellow=0.34, orange=0.40. Year 5: white=0.12, yellow=0.80, orange=0.08. Yellow (intermediate) increases, both extremes (white, orange) decrease. This is stabilizing selection (favors intermediate, selects against extremes).

• Population 3: Year 1: white=0.33, yellow=0.45, orange=0.22. Year 5: white=0.07, yellow=0.23, orange=0.73. Orange (one extreme) increases, white (other extreme) and yellow (intermediate) decrease. This is directional selection (favors one extreme, orange here).

Wait, let's confirm the selection types:

• Stabilizing Selection: Favors intermediate phenotype, reduces variation (extremes selected against). So Population 2: yellow (intermediate) goes from 0.34 to 0.80, while white (0.26→0.12) and orange (0.40→0.08) decrease. So intermediate is favored—stabilizing.

• Directional Selection: Favors one extreme, shifts phenotype distribution. Population 3: orange (extreme) goes from 0.22 to 0.73, white (0.33→0.07) and yellow (0.45→0.23) decrease. So favors orange—directional.

• Disruptive Selection: Favors both extremes, selects against intermediate. Population 1: white (0.32→0.49) and orange (0.39→0.40) increase/stable, yellow (0.29→0.11) decreases. So both extremes (white and orange) are favored, intermediate (yellow) selected against—disruptive.

So:

• Population 1: Disruptive Selection

• Population 2: Stabilizing Selection

• Population 3: Directional Selection

Answer:

• Population 1: disruptive selection
• Population 2: stabilizing selection
• Population 3: directional selection