Author:
Dave Cliff
Affiliation:
School of Engineering Mathematics and Technology, University of Bristol, Bristol BS8 1UB, U.K.
Keyword(s):
Agent-Based Mode Biodiversity, Cyclic Competition, Asymmetric Interaction, Species Coexistence, Evolutionary Spatial Games, Rock-Paper-Scissors-Lizard-Spock, Replication.
Abstract:
I present exploration of key results from the series of ablated five-species “Rock-Paper-Scissors-Lizard-Spock” minimal agent-based evolutionary models of biodiversity introduced by Zhong, Zhang, Li, Dai, & Yang in their 2022 paper “Species coexistence in spatial cyclic game of five species” (Chaos, Solitons and Fractals, 156: 111806). At the heart of Zhong et al.’s model of ecosystems coexistence is the Elementary Step (ES) algorithm in which one or two neighboring agents are chosen at random to engage in one or more interactions selected at random from the set {COMPETE, REPRODUCE, MOVE}. Minor revisions to the ES algorithm have recently been introduced to make it more computationally efficient in space and in time, and one contribution of this paper is to demonstrate that switching to this “Revised ES” (RES) has the unexpected effect of totally changing the outcomes of Zhong et al.’s simulation experiments. I present analysis of the RES-based experiments which shows that the key di
fference is that in RES the likelihood of an agent moving is decoupled from the likelihood of an agent reproducing or competing, whereas in the original ES the likelihoods of the three possible actions are interdependently coupled. The fact that such relatively minor changes to the ES algorithm result in such major changes in the experiment outcomes casts significant doubt on the extent to which results such as those from Zhong et al.’s original experiments can be trusted as truly representative of the real-world biological systems that they are supposedly intended to model. Python source-code available on GitHub can be used to replicate the results presented here.
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