Food web attributes in Webworld models that mediate the relationship between species richness and invasibility
N. P. Kristensen (submitted)
Keywords: invasibility, diversity, community assembly, multiple mediation, Webworld, food web, model
Abstract
The Webworld community assembly algorithm and multiple mediation
analysis are used to investigate invasibility in food web models with
multiple trophic levels. Invasion resistance
accumulates in a web as a web is assembled because of exhaustion
of the invader species' pool, increased species richness, and changes
in species composition and web attributes. When species are deleted
from mature webs, species richness and invasibility can be decoupled,
and the covarying web attributes that mediate the relationship between
species richness and invasibility can be identified.
They include the predator-prey ratio,
predator specialisation, connectance, and how well adapted predators
are to their prey.
Some covariates, like connectance, suppress the negative
relationship between species richness and invasibility.
Including multiple trophic levels reveals that some covariates,
like specialisation and predator-prey ratio, are
facilitators on one trophic level but suppressors on another.
In certain circumstances, attributes typical of mature webs, such as
predators that are highly adapted to their prey, can be retained when
species are deleted, leading to small yet highly invasion-resistant
webs.