Abstract
Fatty acids (FAs) are key nutrients for fitness which take part in multiple physiological processes over the ontogeny of organisms. Yet, we lack evidence on how FA nutrition mediates life-history trade-offs and ontogenetic niche shifts in natural populations. In a field study, we analyzed ontogenetic changes in the FAs of Eurasian perch (Perca fluviatilis L.), a widespread fish that goes through ontogenetic niche shifts and can have high individual niche specialization. Diet explained most of the variation in the FA composition of perch dorsal muscle over early ontogeny (28%), while the total length explained 23%, suggesting that perch significantly regulated FA composition over early ontogeny. Condition explained 1% of the remaining variation. 18:3n-3 (ALA) and 18:4n-3 (SDA) indicated planktivory; 18:1n-7, benthivory; and 22:6n-3 (DHA), piscivory in perch diet. Conversely, perch regulated long-chained polyunsaturated fatty acids (PUFAs), such as 20:5n-3 (EPA), 20:4n-6 (ARA) and 22:6n-3 (DHA) over ontogeny, emphasizing the role of such FAs in early growth and sexual maturation. Adult perch increasingly retained 16:1n-7 and 18:1n-9 suggesting higher energy storage in older perch. Furthermore, differences in DHA availability in diet correlated with intra-cohort differences in perch growth, potentially hindering the overall use of benthic resources and promoting earlier shifts to piscivory in littoral habitats. Overall, this study indicates that in addition to diet, internal regulation may be more important for FA composition than previously thought. Differences between FA needs and FA availability may lead to life-history trade-offs that affect the ecology of consumers, including their niche.
Highlights
Organisms often undergo life-history trade-offs in which they compromise the expression of different traits in order to maximize fitness (Stearns 1992)
Stable isotope mixing models revealed that perch went through ontogenetic niche shifts and showed different resource use in the different habitats (Fig. 1)
Sequential distancebased linear modelling (DistLM) model for 1+ to 3+ years old perch (R2 = 0.52) revealed that the total length, diet and perch condition factors were significantly related to changes in Fatty acids (FAs) composition of perch (Table 1)
Summary
Organisms often undergo life-history trade-offs in which they compromise the expression of different traits in order to maximize fitness (Stearns 1992). Changes in selective pressures over ontogeny affect life-history trade-offs, and Communicated by Donovan P. Besides the well-established role of FAs as trophic biomarkers, fatty acid regulation can scale with ontogenetic changes in life history, mediating life-history trade-offs. To understand life-history trade-offs and ontogenetic niche shifts in nature, it is necessary to incorporate food chemical composition into the framework, taking a closer look at nutrient allocation and nutrient regulation over ontogeny and whether those have measurable implications for consumer fitness
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