Abstract
A competition theory was established on the combined effects of resource competition and direct competition on species coexistence in Saito and Miki (2010) under the assumption that the maximum yield constant reflecting the conversion of resource to organisms is common in species4). Although the biological significance of obtained mathematical results is discussed satisfactorily there, the constant parameter should be different specifically in reality. This paper develops these considerations into a model that provides the variation of the maximum yield constant among species and then Theorems 1-3, Corollaries 1,2 and Remark 1 in Saito and Miki (2010)4) are generalized in more biological significance.
