The study by Svanbäck and Bolnick (2006) investigates the role of intraspecific competition in driving ecological diversification within natural populations. They manipulated the population density of three-spine sticklebacks (Gasterosteus aculeatus) in enclosures in a natural lake to observe changes in resource use and diet variation. Increased population density led to reduced prey availability, causing individuals to switch to alternative prey types, thereby increasing diet variation among individuals. The diet-morphology correlations also increased with higher competition, indicating stronger frequency-dependent interactions. These findings confirm that resource competition promotes niche variation within populations and show that this increased diversity can arise through behavioral plasticity alone, without the need for evolutionary changes. The study highlights the importance of intraspecific competition in maintaining ecological variation and suggests that behavioral diversification may facilitate evolutionary diversification by increasing the frequency dependence of selection.The study by Svanbäck and Bolnick (2006) investigates the role of intraspecific competition in driving ecological diversification within natural populations. They manipulated the population density of three-spine sticklebacks (Gasterosteus aculeatus) in enclosures in a natural lake to observe changes in resource use and diet variation. Increased population density led to reduced prey availability, causing individuals to switch to alternative prey types, thereby increasing diet variation among individuals. The diet-morphology correlations also increased with higher competition, indicating stronger frequency-dependent interactions. These findings confirm that resource competition promotes niche variation within populations and show that this increased diversity can arise through behavioral plasticity alone, without the need for evolutionary changes. The study highlights the importance of intraspecific competition in maintaining ecological variation and suggests that behavioral diversification may facilitate evolutionary diversification by increasing the frequency dependence of selection.