TITLE:
Illusion of a Density-Dependent Effect in Biology
AUTHORS:
Kazumi Sakuramoto
KEYWORDS:
Arctic Oscillation Index, Density-Dependent Effect, Ricker Model, Sardine, Stock-Recruitment Relationship
JOURNAL NAME:
Agricultural Sciences,
Vol.6 No.5,
May
25,
2015
ABSTRACT: Population changes are believed to be controlled by multiple factors, including an important density-dependent effect. This paper reviews the literature on this topic and shows that this density-dependent effect does not exist. This paper also gives a typical example in which no density-dependent effect was detected in the stock-recruitment relationship in Japanese sardines. The recruitment was found to be determined in proportion to the spawning stock biomass and to be affected by environmental factors. This simple mechanism is applicable not only in fish species but also in insects such as Thrips imaginis in Australia. The reason that many biologists have not become aware that the density-dependent effect does not exist is discussed using a metaphor. This paper proposes a new concept in the study of population change. The new concept proposed here will replace the currently used basic concept that has been assumed to be correct for more than 50 years.