Evolutionary interpretations of allelochemical interactions in phytoplankton algae

• Published in: The American naturalist 1986-02, Vol.127 (2), p.184-194
• Main Author: Lewis, W.M. Jr
• Format: Article
• Language: English
• Subjects: ALELOPATIA; ALGAE; ALGUE; Allelochemicals; ALLELOPATHIE; ALLELOPATHY; AMBIENTE ACUATICO; Animal and plant ecology; Animal, plant and microbial ecology; Antibiotics; AQUATIC ENVIRONMENT; Biological and medical sciences; Cell growth; Fundamental and applied biological sciences. Psychology; General aspects; MILIEU AQUATIQUE; Natural selection; Phytoplankton; PLANCTON; PLANKTON; Receptors; Synecology; Taxa
• ISSN: 0003-0147; 1537-5323
• DOI: 10.1086/284477

Although allelochemistry among phytoplankton species has been studied relatively little under natural conditions, it is widely thought to influence the increase and decrease of individual species in the course of a growing season in plankton systems. Some direct evidence supports this view. Allelochemistry involving growth suppression has often been viewed as beneficial to the releaser of allelochemicals, and thus as being maintained by selection pressures deriving from competition. This interpretation is indefensible, however, insofar as individual phytoplankton cells are unable, because of the movement of both the cells and the allelochemicals, to capture selectively the benefit of suppressing other individuals by means of allelochemicals; any such benefits would be shared by many other organisms. Other explanations must therefore be sought. Allelopathy can be considered passive from the viewpoint of the releaser but still capable of having detrimental effects on receptor organisms. This explanation also seems untenable in that it requires receptor organisms to be unable, even over many thousands of generations of exposure, to develop defenses against specific, passively released organic substances. An alternative explanation that avoids these difficulties, while allowing for the possibility that allelochemicals are important in natural systems, is based on the idea that the significance of allelochemicals lies strictly in the receptor and not the releaser. According to this explanation, allelochemicals are significant to the receptor organisms as cues that trigger physiological responses to an improving or deteriorating environment. This interpretation, unlike the traditional one, is consistent with observational and experimental evidence of allelochemical interactions and with the basic principles of natural selection.