Upscaling the niche variation hypothesis from the intra- to the inter-specific level
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The “niche variation hypothesis” (NVH) predicts that populations with wider niches should display higher among-individual variability. This prediction originally stated at the intra-specific level may be extended to the inter-specific level: individuals of generalist species may differ to a greater extent than individuals of a specialist species. We tested the NVH at intra- and inter-specific levels based on a large diet database of three large herbivore feces collected in the field and analyzed using DNA metabarcoding. The three herbivores (roe deer Capreolus capreolus, chamois Rupicapra rupicapra and mouflon Ovis musimon) are highly contrasted in terms of sociality (solitary to highly gregarious) and diet. The NVH at the intraspecific level was tested by relating, for the same population, diet breadth and inter-individual variation across the four seasons. Compared to null models, our data supported the NVH both at the intra- and inter-specific levels. Inter-individual variation of the diet of solitary species was not larger than in social species, although social individuals feed together and could therefore have more similar diets. Hence, the NVH better explained diet breadth than other factors such as sociality. The expansion of the population niche of the three species was driven by resource availability, and achieved by an increase in inter-individual variation, and the level of inter-individual variability was larger in the generalist species (mouflon) than in the specialist one (roe deer). This mechanism at the base of the NVH appears at play at different levels of biological organization, from populations to communities.
KeywordsIndividual heterogeneity Sociality Large herbivores DNA metabarcoding Null models
We warmly thank J.-M. Jullien and T. Chevrier for collecting the feces during the animal captures and field workers for feces sampling in the field. We also thank ONCFS and CNRS for funding the barcoding analyses and the Natural Regional Park of Bauges massif for data provision.
Author contribution statement
AL, DM and SS originally developed the idea. MB, SI, NGY, AL analyzed the data and wrote the first draft of the manuscript. SI and NGY developed the mathematical model of a new null model. CM, PT, CR, DR developed the DNA metabarcoding methods and applied it on feces. CR performed the feces sampling, laboratory experiments (DNA metabarcoding on feces), database treatment and preliminary analyses. FB and EC performed the statistical analyses and the database treatment of DNA sequences. All authors commented and approved the ms.
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