The introduction of alewives planktoneating fish into New En

The introduction of alewives (plankton-eating fish) into New England ponds resulted in a dramatic shift in the size frequency distribution of Daphnia because the fish consumed large individuals. The remaining Daphnia now reproduce at smaller sizes and often have long spines to protect them against predators. Is this an example of a bottleneck effect or selection? Defend your answer.

Solution

Yes, this is an example of bottleneck effect. According to bottleneck effect, when the size of a population is sharply reduced due to environmental effects or human activities, the genetic variation in remaining population will bereduced. This smaller genetic diversity passes on to the next generation. Consequently the ability to survive in new environment, changes. Although, generally the robustness of new generation decreases but sometimes depending upon the causes of the bottleneck, the new generations may have been the genetically fittest individuals. Hence this is an example of bottleneck effect.