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

Abstract

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 realized 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 a 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 emphasize that patterns of exploitation of resources in multiple dimensions are driven by both competitive interactions and extrinsic factors such as local resource breadth.

Beyond ecological opportunity: Prey diversity rather than abundance shapes predator niche variation

“…Recent studies support the view that resource competition promotes niche variation among individuals within a population, including an important role of intra-specific competition for individual specialisation (Araújo et al, 2011;Costa-Pereira, Araújo, Souza, & Ingram, 2019;Mendes, Fernandes, Penha, & Mateus, 2019;Svanbäck & Bolnick, 2007;Tinker et al, 2012). There is also empirical support that fish species can display a generalist foraging behaviour independent of density-dependent intra-specific competition (Sánchez-Hernández & Cobo, 2013).…”

“…We accept the view that prey patchiness and broad potential trophic niches are fundamental to understand niche extension or compression of animals (e.g. Costa-Pereira et al, 2019;Svanbäck et al, 2011;Tinker et al, 2008), but diversity of available resources can have a stronger effect on individual and population trophic realised niches than the constraining effects of resource abundance (see Figure 1).…”

“…There is also empirical support that fish species can display a generalist foraging behaviour independent of density-dependent intra-specific competition (Sánchez-Hernández & Cobo, 2013). However, intra-specific niche variation is expectedly also influenced by ecological opportunity, which may have an even stronger diversifying effect on dietary niche width than the constraining effects of competition (Costa-Pereira et al, 2019).…”

Behaviour, morphology and microhabitat use: what drives individual niche variation?

“…This intraspecific niche diversity (i.e. individual specialization (IS)) has implications well beyond the structure of populations, affecting community assembly [2,3], ecological interactions [4,5] and eco-evolutionary dynamics [6]. Despite such broad relevance, only recently have ecologists begun to explore the underlying causes of intraspecific niche variation in natural populations [7].…”

Individual niche trajectories drive fitness variation

“…However, ecologists have recently reconsidered this simplification because of the increasingly recognized relevance of intraspecific ecological variation. Mounting evidence across diverse taxa suggests that individuals within populations often differ in their resource use (Araújo, Bolnick, & Layman, ; Bolnick et al, ), which may have important consequences for community structure (Bolnick et al, ; Costa‐Pereira, Araújo, Souza, & Ingram, ; Costa‐Pereira, Rudolf, Souza, & Araújo, ; Hart, Schreiber, & Levine, ; Violle et al, ).…”