Data from: Competition and resource breadth shape niche variation and overlap in multiple trophic dimensions

Competition plays a central role in the maintenance of biodiversity. A
backbone of classic niche theory is that local coexistence of competitors
is favoured by the contraction or divergence of species’ niches. However,
this effect should depend on the diversity of resources available in the
local environment, particularly when resources vary in multiple ecological
dimensions. Here, we investigated how available resource breadth (i.e.,
prey diversity) and competition together shape multidimensional niche
variation (between and within individuals) and interspecific niche overlap
in 42 populations of congeneric tropical frog species. We modelled
realised niches in two key trophic dimensions (prey size and carbon stable
isotopes) and sampled available food resources to quantify two-dimensional
resource breadth. We found 14-fold variation in multidimensional
population niche width across populations, most of which was accounted for
by within-individual diet variation. This striking variation was predicted
by an interaction whereby individual niche breadth increased with resource
breadth and decreased with the number of congeneric competitors. These
ecological gradients also interact to influence the degree of niche
overlap between species, which surprisingly decreased with population
total niche width, providing novel insights on how similar species can
coexist in local communities. Together, our results emphasise that
patterns of exploitation of resources in multiple dimensions are driven by
both competitive interactions and extrinsic factors such as local resource
breadth.