A Network of Dynamic Keystone Species

Takashi Ikegami¹⁾, Tomoharu Iwata¹⁾ and Koh Hashimoto²
Department of General Systems Sciences¹⁾,
The Graduate School of Arts and Sciences,
University of Tokyo, 3-8-1 Komaba, Meguro-ku, Tokyo 153-8902 Japan
Department of Applied Physics²⁾,
The Graduate School of Engineering,
University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 Japan

Abstract:

A concept of dynamic keystone species  is proposed based on simulation studies of replicator equations.  We report that the variables of this equation can be categorized into three groups based on their individual dynamic behaviour. They are dominant, neutral and recessive phenotypes. Because the growth rates are small in average, they are termed neutral phenotypes. 

Especially with a chaotic attractor, neutral phenotypes work as keystone species to control the stability of the system. The removal of neutral phenotypes may be a subtle perturbation, but it can have a large effect compared with its relative abundance, as it triggers an attractor switch. We also report that these neutral phenotypes form a network that can provide combinatorial effects on the attractor switch. A mere topological structure of the interacting matrix is not sufficient for determining which may be a keystone species; instead, it is determined by the kind of the attractors they organize.