Nichemodel

Nichemodel is a simple probabilistic model used to generate ecological networks, especially food webs, in order to study how basic rules can produce complex network structure. It was introduced as a stylized representation of trophic interactions that captures common patterns observed in real ecosystems.

In the model, each species is assigned a niche value n drawn from a uniform distribution on the interval [0, 1]. A feeding range r is assigned to the species, typically drawn from a distribution that results in a broad but species-specific diet. A center c is chosen within a permitted subinterval, and the predator is linked to all potential prey whose niche values fall within the interval around c defined by the feeding range. A key feature is that prey are drawn from lower niche values, reflecting a directional flow from prey to predator along the niche axis. The result is a directed food-web structure with links from consumers to their prey.

The niche model aims to reproduce qualitative properties of empirical webs, such as the distribution of the number of prey and predators, levels of connectance, clustering, and certain motif frequencies. It has become a reference point for testing hypotheses about how simple governing rules influence network architecture and stability.

Variants and criticisms exist, including different choices for the feeding-range distribution and adjustments to allow omnivory or alternative feeding constraints. Despite simplifications, the model remains influential in theoretical ecology as a baseline for understanding how structure emerges in ecological networks.