Trinidad Guppy

Trinidad guppies are the subject of David Reznick's famous 1990 experiments demonstrating rapid evolution of energy allocation strategies based on predation environment. In high-predation streams (pike cichlid eats adults), guppies mature early (60 days), reproduce young, and produce many small offspring with 60% reproduction, 30% growth, 10% maintenance allocation. In low-predation streams (killifish eats juveniles only), guppies mature late (90 days), produce fewer large offspring with 30% reproduction, 50% growth, 20% maintenance allocation. Transplanted guppies evolved to match new environment within 5-10 generations (18 months), proving allocation strategy is not fixed but evolves based on environmental conditions.