Habitat complexity and individual variation in diet and morphology of a fish species associated with macrophytes
2021
Paz Cardozo, Ana Lúcia | Quirino, Bárbara Angélio | Yofukuji, Kátia Yasuko | Ferreira Aleixo, Matheus Henrique | Fugi, Rosemara
Populations of generalist fish can be composed of individuals specialised to a small subset of food resources, a process known as individual specialisation. In this study, we hypothesised that variation in the diet and morphology of individuals is related to habitat complexity and that greater levels of individual specialisation are found at intermediate levels of macrophyte biomass. Fish and aquatic plants were sampled in 15 multispecific macrophyte stands with different biomasses in the Baía River (Upper Paraná River floodplain). We assessed habitat complexity using the biomass of aquatic macrophytes (three levels of classification: low, intermediate and high). The diet of Moenkhausia forestii was evaluated with the volumetric method. To assess individual diet specialisation, we used the IS (specialisation index) and NODF (nestedness based on overlap and decreasing fill) index and for individual morphological specialisation we used ecomorphological metrics. We tested for a correlation between diet and morphology with a Mantel test. Contrary to our hypothesis, IS and NODF values indicated greater individual specialisation in the diet of M. forestii from low macrophyte biomass. However, the greatest individual morphological specialisation was found in macrophyte stands with intermediate biomasses. The Mantel test showed that there was no significant correlation between diet and morphology. Thus, individual specialisation of M. forestii diet may be related to an increase in competition (likely intraspecific) in stands with low macrophyte biomass, while morphological specialisation is probably related to greater resources availability and accessibility within stands of intermediate macrophyte biomass.
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