The invisible niche: weakly density-dependent mortality and the coexistence of species.
Weakly density-dependent effects, characterized by fractional scaling exponents close to one, are rarely studied in the ecological literature. Here, we consider the effect of an additional weakly density-dependent term on a simple competition model. Our investigation reveals that weak density-dependence opens up an "invisible niche". This niche does not constitute a new mechanism for coexistence, but is a previously unexplored consequence of known mechanisms. In the invisible niche a weaker competitor can survive at very low density. Coexistence thus requires large habitat size. Such niches, if found in nature, would have a direct impact on species-area laws and species-abundance curves and should therefore receive more attention.
Gross
Thilo
T
Max-Planck Institute for Physics of Complex Systems, Nöthnitzer Strasse 38, 01187 Dresden, Germany. thilo.gross@physics.org
Edwards
Andrew M
AM
Feudel
Ulrike
U
D000818:Animals; D003163:Competitive Behavior; D017753:Ecosystem; D053476:Extinction, Biological; D008954:Models, Biological; D015233:Models, Statistical; D009026:Mortality; D011156:Population Density