Intraspecific Variation in Color and Carotenoids across Environmental Extremes in an African Cichlid

Area of Science:

• Animal Behavior
• Evolutionary Biology
• Environmental Science

Background:

• Sexual selection relies on traits like color, which can be influenced by environmental changes.
• Environmental stressors may affect these traits differently across populations and sexes.

Purpose of the Study:

• To investigate the genetic, environmental, and gene-by-environment factors influencing color expression in a sexually dimorphic fish, *Pseudocrenilabrus multicolor*.
• To determine how environmental conditions (hypoxia, turbidity) affect color and carotenoid concentrations in males and females.

Main Methods:

• Rearing fish from swamp (hypoxic, clear) and river (normoxic, turbid) populations in a split-brood design manipulating oxygen and turbidity.
• Quantifying fish color and carotenoid concentrations under different environmental conditions.

Main Results:

• Females were less colorful than males. In males, hypoxia and turbidity altered color traits.
• Hypoxic conditions reduced male brightness, aligning with wild observations. Turbidity also marginally reduced ventral brightness.
• Turbid conditions decreased carotenoid concentrations in male skin, but carotenoids did not correlate with spectral color characteristics.

Conclusions:

• Environmental factors, not population-specific genetics, likely explain wild color variations, indicating phenotypic plasticity.
• Hypoxia and turbidity influence sexually selected signaling traits in this species, with implications for understanding adaptation to changing environments.