Intraspecific Variation in Elemental Composition of the Least Killifish Tracks Spatial Variation in Periphyton...

Area of Science:

• Ecology
• Aquatic Ecology
• Biogeochemistry

Background:

• Elemental composition varies significantly in freshwater fish populations.
• Understanding how this variation relates to interspecific patterns is crucial.
• The trophic niche of omnivores can shift among populations, influencing elemental composition.

Purpose of the Study:

• To investigate population-level variation in elemental composition of *Heterandria formosa*.
• To determine if fish elemental composition tracks basal resources (periphyton) or water chemistry.
• To assess the influence of trophic position on elemental composition in different habitats.

Main Methods:

• Studied eight populations of *Heterandria formosa* in freshwater springs and shallow lakes.
• Analyzed water chemistry, periphyton, and fish elemental composition (C, N, P) and stable isotopes (δ13C, δ15N).
• Used Mantel analyses to correlate elemental composition variations with environmental and resource data.

Main Results:

• Fish elemental composition strongly correlated with periphyton composition, not water chemistry.
• Carbon and nitrogen percentages in fish mirrored those in periphyton across populations.
• Trophic position varied, with spring populations at lower trophic levels than lake populations.

Conclusions:

• The elemental composition of *Heterandria formosa* populations is primarily determined by their basal resource (periphyton).
• Despite variations in trophic position and habitat, fish elemental composition shows remarkable consistency.
• This constancy contrasts with interspecific patterns and may reflect limited intraspecific trophic variation.