The role of rare morph advantage and conspicuousness in the stable gold‐dark colour polymorphism of a crater lake Midas cichlid fish

摘要: Summary 1.Genetically based stable colour polymorphisms provide a unique opportunity to study the evolutionary processes that preserve genetic variability in wild. Different mechanisms are proposed promote stability of polymorphisms, but only few empirical examples have been documented, resulting an incomplete understanding these mechanisms. 2.A remarkable genetically-determined polymorphism is found Nicaraguan Midas cichlid species complex (Amphilophus cf. citrinellus). All cichlids start their life with dark-grey colouration (dark morph), individuals carrying dominant “gold” allele (~10%) lose melanophores later life, revealing underlying orange (gold morph). How this maintained remains unclear. Two main hypotheses proposed, both suggesting differential predation upon morphs as proximate mechanism. One predicts conspicuous gold morph more likely be preyed upon, disadvantage balanced by competitive dominance over dark morph. The second hypothesis suggests rare advantage where rarer experiences less predation. Empirical evidence for either still circumstantial and inconclusive. 3.We conducted two field experiments crater lake using wax models simulating determine pressure morphs. First, we tested interaction depth on attack rate. Second, fish size colouration. We contrasted pattern attacks from predicted patterns explain polymorphism's stability. 4.Large imitating were attacked at similar rates irrespectively position water column. Yet, small resembling juveniles directed mainly toward models. This resulted significant size-by-colour interaction. 5.We suggest experience when extremely uncommon. But effect reduced or disappears among adults, relatively common. Thus, conspicuousness, rather than those factors alone, mechanism cichlids. This article protected copyright. rights reserved.