Illusion of a Density-Dependent Effect in Biology

Kazumi Sakuramoto

doi:10.4236/as.2015.65047

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.

Highlights

The existence of a density-dependent effect is assumed as a matter and doubts about this mechanism are typically not entertained
The result derived by Smith [5] greatly overshadowed the findings of Davidson and Andrewartha [1] [2], and thereafter almost all biologists assumed the existence of a density-dependent effect
Up to the present, many biologists discuss the existence of density-dependent effects using regression analysis and still assume the existence of density-dependent effects [6] [7] [16] [23]-[26]

Summary

Introduction

The existence of a density-dependent effect is assumed as a matter and doubts about this mechanism are typically not entertained. This consensus grew from a debate between scientists whose ideas differed drastically [1]-[7]. The result derived by Smith [5] greatly overshadowed the findings of Davidson and Andrewartha [1] [2], and thereafter almost all biologists assumed the existence of a density-dependent effect. This effect has been widely considered an important factor in controlling population fluctuations

Methods

Results

Conclusion