Abstract
Individual specialization and high plasticity in feeding activity are common in natural populations. However, the role of these two in intraspecific competition is unclear. In this study, the rhythm of feeding activity, dietary composition, niche width, niche overlap, and individual specialization was explored in four different size groups of black amur bream (Megalobrama terminalis), using microscopic identification of foregut contents and stable isotope analysis (δ13C and δ15N) of dorsal muscle. Both methods observed ontogenetic shifts in dietary preference and individual specializations, and revealed that the total niche width of large individuals was greater than small individuals. Mixed linear models indicated that feeding activity was significantly influenced by time (p < 0.0001), and no significant changes among size groups was evident (p = 0.244). Niche overlaps revealed that there was intensive diet competition between different size groups of black amur bream. Individual specialization in small juveniles was likely to be stronger than sub-adult and adult groups. Pearson’s correlation analysis revealed that the individual specialization was positively correlated with mean diet similarity within a group. The results indicated that intraspecific competition is reduced mainly by individual dietary specialization, rather than shift in feeding activity.
Highlights
Individual specialization and high plasticity in feeding activity are common in natural populations
The prey items that were identified to the order level represent over 98% (%W and %N) of all prey examined in each group (Table 2)
Ontogenetic changes in dietary preference and plasticity in feeding activity are common in fish; the role of these two in intraspecific competition is unclear
Summary
Individual specialization and high plasticity in feeding activity are common in natural populations. The rhythm of feeding activity, dietary composition, niche width, niche overlap, and individual specialization was explored in four different size groups of black amur bream (Megalobrama terminalis), using microscopic identification of foregut contents and stable isotope analysis (δ13C and δ15N) of dorsal muscle. Both methods observed ontogenetic shifts in dietary preference and individual specializations, and revealed that the total niche width of large individuals was greater than small individuals. The most competitive or dominant individuals in a population negatively affect the foraging efficiency of weaker conspecifics, that lose the best foraging areas, and have reduced access to preferred r esources[21,22,23] This demonstrates that intraspecific competition strengthens individual specialization
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