Covarying variances: more morphologically variable populations also exhibit more diet variation

Area of Science:

• Ecology
• Evolutionary Biology
• Animal Behavior

Background:

• Many populations consist of individuals with specialized diets, a concept known as individual specialization.
• The Niche Variation Hypothesis suggests that ecological release drives niche expansion through individual diet divergence, increasing morphological variation.
• Previous research correlated niche width with morphological variance, assuming a link between ecological and morphological diversity within populations, an assumption not yet tested.

Purpose of the Study:

• To investigate the correlation between intrapopulation diet variation and intrapopulation morphological variation.
• To test the Niche Variation Hypothesis in lacustrine populations of three-spine stickleback.
• To determine if morphological variance is a reliable indicator of diet variation across diverse populations.

Main Methods:

• Behavioral observations, stable isotope analysis, and gut content analysis were used to assess individual diet and microhabitat use.
• Dietary variation within and among 12 lacustrine populations of three-spine stickleback was quantified.
• Morphological variation within these populations was measured and correlated with dietary variation.

Main Results:

• Individuals within populations showed distinct microhabitat use and dietary preferences.
• Significant differences in dietary variation were observed among the studied stickleback populations.
• Populations with higher dietary variation also exhibited greater total morphological variance.
• The correlation between dietary variation and morphological variance was not significant when considering individual morphological traits, only total variance.

Conclusions:

• The study supports the Niche Variation Hypothesis by linking individual specialization to morphological variation.
• The relationship between diet and morphology can vary between populations, complicating direct comparisons.
• Morphological variance may not always be a robust predictor of diet variation when comparing diverse populations.