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

Abstract

Generalist populations are often composed of individuals each specialized on only a subset of the resources exploited by the entire population. However, the traits underlying such niche variation remain underexplored. Classically, ecologists have focused on understanding why populations vary in their degree of intraspecific niche variation, with less attention paid to how individual-level traits lead to intraspecific differences in niches. We investigated how differences in behaviour, morphology and microhabitat affect niche variation between and within individuals in two species of spider Anelosimus studiosus and Theridion murarium . Our results convey that behaviour (i.e. individual aggressiveness) was a key driver of intraspecific trophic variation in both species. More aggressive individuals capture more prey, but particularly more Coleoptera, Hymenoptera and Diptera. These findings suggest that behavioural traits play a critical role in determining individuals' diet and that behaviour can be a powerful force in driving intraspecific niche variation.

Environmental heterogeneity and population density affect the functional diversity of personality traits in small mammal populations

“…B 287: 20201713 mechanism generating the observed patterns, the ecological implications are that a greater variety of behavioural phenotypes (and the associated ecological outcomes), should be expected in areas characterized by greater vegetation heterogeneity. As ecologists recognize the potential for intraspecific trait variation to impact community and ecosystem processes, a focus on the intraspecific niche has grown considerably in recent years [57], and interest in intraspecific behavioural variation is no exception [58]. Empirical studies that identify the drivers of trait variation (via functional diversity) in populations and that propose methods to promote variation are important avenues for further research.…”

A test of the Niche Variation Hypothesis in a ruminant herbivore

“…Functional trade‐offs that constrain individuals from broadening their diet have been hypothesized to promote the among‐individual dietary diversity that underlies individual diet specialization, and thus determine whether expansion of total niche width conforms to the predictions of the NVH or OFT (Araújo et al., 2011; Bolnick et al., 2003). Functional trade‐offs require that individual variation in cognition, physiology or morphology gives rise to variation in foraging efficiency, such that individuals are efficient at extracting energy from some foods but not others (Araújo et al., 2009; Araújo & Gonzaga, 2007; Bolnick et al., 2003; Costa‐Pereira & Pruitt, 2019; Svanback & Bolnick, 2005). Individual variation in cognition, physiology or morphology may be accentuated by disruptive selection to generate the dietary specializations illustrated in Figure 1a (Bolnick, 2004).…”

Within‐population variation in dietary traits: implications for vulnerability and impact of imperiled keystone predators

“…Although specific links between phenotypic traits and niche parameters will differ among systems—and even, change within a single population over time—intraspecific divergences in foraging locations, tactics, and prey types likely will occur in many species of apex predators. An extensive literature documents strong empirical links between phenotypes and niches (including food habits) within populations; for example, correlations between predator size and prey type are widespread in many predators (e.g., Shine et al 1998, Webb et al 2005); an individual’s behavioral profile (expression of boldness, aggression, and exploration) can also influence its diet (Costa‐Pereira and Pruitt 2019). Likewise, sex‐based differences in feeding habits are so consistent in some taxa that they have resulted in the evolution of sex differences in trophic morphology (e.g., Shine 1989).…”

“…Although the keystone role of apex predators has attracted increasing scientific interest (e.g., Ripple and Beschta 2003, Beschta and Ripple 2010), the role of individual variation in ecological traits within a population of apex predators has received less attention. Although many apex predators have broad diets at a population level, individuals often differ substantially in key ecological traits such as habitat use and diet (Zerba and Collins 1992, Pintor and Byers 2015, Costa‐Pereira and Pruitt 2019). Such intraspecific variation may create differences in vulnerability to anthropogenic threats (e.g., Webb et al 2005), and nonrandom mortality of this kind may affect the impact of a reduction in predator abundance on lower trophic levels (Svanbäck and Persson 2004, Pettorelli et al 2011).…”