Figure 1.

Model illustration. A species pool of top consumers (a) with some trait z (e.g. birds of prey with body size z) and a pool of competitive consumers (b) with trait v (e.g. granivorous birds with beak size v) are allowed to invade an island (c) with resources defined by trait u (e.g. seeds with size u), here u_min = v_min. The three trophic levels are distributed on the same trait dimension (e.g. size) here illustrated by color. The invasion fitness of a focal consumer or competitor is a function of its trait matching to its resources, the traits of its competitors on the same trophic level and their niche widths (black and grey niche kernels). If the resource's trait distribution on the island only ranges over a small proportion of the species pool trait distribution (if |u_{max_pool} − v_{max_island}| is large), the competitive community will be habitat filtered. If the niche width of the competitors is high (high variance of black niche kernels), competition strength will be high in the system. The competitive community structure was used as a reference point for the effect of invading trophic consumers (a) with different efficiency and niche width (variance of grey niche kernels).