Competitive consequences determined by phenotypic but not genetic distance: a study with asexual Daphnia genotypes

1. How evolutionary relatedness influences the strength of competitive interactions among genetically isolated populations has been a long-standing interest in ecology. Darwin's “Competition Relatedness Hypothesis (CRH)” states that, since closely related species should compete more strongly, they are less likely to coexist, while Herbert’s “Bimodal Competition Hypothesis (BCH)” predicts that competitive exclusion is less likely to occur when the competing species are genetically close or distant.
2. To test these hypotheses, we experimentally examined the difference in the competitive ability and life tables of fecundity and survivorship among four different genotypes of asexual Daphnia cf. pulex that diverged from a single ancestral genotype.
3. The experiments showed that the competitive consequences differed depending on the pairing of the competing genotypes, and that the degree of the competitive exclusion was lower when the competing genotypes were genetically closer to each othe...