Intraspecific competition reduces niche width in experimental populations

Area of Science:

• Ecology
• Evolutionary Biology
• Behavioral Ecology

Background:

• Intraspecific competition is theorized to promote niche expansion as populations utilize suboptimal resources to avoid competition.
• This concept is frequently used to explain phenotypic diversification, speciation, and adaptive radiation.
• However, foraging models present conflicting predictions, creating uncertainty about competition's role in niche expansion.

Purpose of the Study:

• To experimentally test if intraspecific competition alters the fitness landscape to favor niche expansion.
• To determine if competition indeed drives niche expansion as predicted by theory.

Main Methods:

• Experiments were conducted using Tribolium castaneum (flour beetles).
• Beetles were fed wheat (ancestral resource), corn (novel resource), or a mixture of both.
• Population density and resource choice were manipulated to assess their effects on diet and fitness.

Main Results:

• Fitness was maximized on a mixed diet of wheat and corn.
• Increased population density shifted the optimal diet towards greater corn consumption, supporting niche expansion.
• Conversely, when beetles could choose resources, competition led to niche contraction onto the ancestral wheat resource.

Conclusions:

• A mismatch exists between how competition modifies the fitness landscape and its actual effect on resource use.
• Optimality models may be misleading in predicting the outcomes of competition on niche breadth.
• Further research is needed to understand the mechanisms behind this observed discrepancy in beetle resource utilization.