PS 48-17 - Is intraspecific variation driven by size? Examining changes in diet-morphology correlations in a Neotropical cichlid population

Thursday, August 10, 2017
Exhibit Hall, Oregon Convention Center
Hernán López-Fernández, Department of Ecology & Evolutionary Biology, University of Toronto, Toronto, ON, Canada; Department of Natural History, Royal Ontario Museum, Toronto, ON, Canada

Individual variation in resource use can have important ecological and evolutionary implications for populations, but remains relatively poorly studied in most taxa. Intraspecific differences can affect niche attributes and can have an important role in driving ecological speciation and adaptive radiation. Individual variation within a population can originate from ontogenetic size differences or random individual variation, among others. In here, I analyze individual variation in morphology and diet within a population of Satanoperca daemon, a lineage within the South American adaptive radiation of geophagine cichlid fishes. I analyzed diets of 195 individual S. daemon from the Aguaro river, Venezuela, and quantified relative importance of prey items as well as prey size. I also measured 23 morphological attributes related to feeding and analyzed correlations between morphometric variables and diet composition using Canonical Correspondence Analysis (CCA). Finally, I ask how much of intraspecific variation in S. daemon is related to size and ontogenetic trajectory, and how much to individual variation in morphology independent of size.


Both prey composition and size changed gradually with predator body size changes between 69.2 and 200.1 mm standard length (SL). Diet of smaller individuals (<75 mm SL) was dominated by water mites (Hydracarina, >70% relative importance). As size increased, water mite importance declined and shifted towards a prey dominated by dipteran larvae (>65% of diet in fishes >95 mm SL). To a lesser degree, other prey items were also common in the diet and appear to shift with ontogeny (e.g. cladocerans, mostly consumed by individuals 80-100 mm SL). CCA analysis revealed a very strong correlation between morphological traits and diet, with ~90% variance of the correlation between morphology and diet explained by the first four canonical axes. Most of this variation appears to be related to changes in size during ontogeny, but there was an important component of intraspecific variation which was independent of size but still correlated with specific morphological traits.