The Influence of Light Intensity on Competitive Ability

Despite its inferiority in a number of botanical characteristics supposed to be of advantage in competition, the barley variety Atlas is known to dominate populations in which it is grown in mixture with the variety Vaughn. When Atlas and Vaughn were grown in pure stands and in mixture under full daylight and three levels of shading, it was found that the relative competitive abilities of the two varieties remained constant irrespective of the competitive situation. The main conclusion from the experiment was that competition between Atlas and Vaughn is not associated with struggle for limited supplies of light. The relationship of this finding to population genetic studies concerned with season to season fluctuations of selective values in mixed populations is discussed.