The Bateman gradient is a popular explanation for why the strength of sexual selection is typically stronger on males than on females. Which one of the following figures is the correct representation of the Bateman gradient? In all figures, the dotted line represents males and the solid line females.
Show Hint
The Bateman gradient illustrates that sexual selection is usually stronger in males than in females, with males benefiting more from increasing their number of mates.
Step 1: Understanding the Bateman gradient.
The Bateman gradient refers to the relationship between the number of mates and the number of offspring produced, which typically shows a stronger increase for males than for females. This suggests that sexual selection, which drives increased mating success, generally has a greater effect on males.
Step 2: Explanation of the figures.
- (A) In figure A, males (represented by the dotted line) show a sharp increase in the number of offspring with an increasing number of mates, while females (represented by the solid line) show a much more modest increase, which is the classic representation of the Bateman gradient.
- (B) In figure B, the number of offspring increases for both males and females, but the gradient is similar for both sexes, which does not represent the Bateman gradient.
- (C) In figure C, the increase in offspring for females is too steep, which does not match the expected relationship for the Bateman gradient.
- (D) In figure D, the dotted line for males shows a flat slope, which is incorrect for the Bateman gradient, where we expect males to benefit more from multiple mates.
Step 3: Conclusion.
The correct answer is (A), as it accurately depicts the Bateman gradient with a steep slope for males and a relatively shallow slope for females.
