Evolution of Hermaphroditism in Fishes: Phylogeny and Theory

Abstract

AbstractThis chapter introduces the main features of functional hermaphroditism in fishes. It has been reported in 481 fish species belonging to 41 families of 17 teleost orders. Simultaneous hermaphroditism (or synchronous hermaphroditism) is known in 57 species of 13 families, and among species exhibiting sequential hermaphroditism, protogyny is much more common (314 species of 20 families) than protandry (62 species of 14 families) or bidirectional sex change (69 species of seven families). Recent phylogenetic trees have indicated that simultaneous hermaphroditism and protandry have evolved several times in not closely related lineages of Teleostei, whereas protogyny and bidirectional sex change have evolved only in Percomorphaceae. The evolution of hermaphroditism has been successfully explained by individual fitness, with two major hypotheses: the low-density model for simultaneous hermaphroditism and the size-advantage model for sequential hermaphroditism. The mating system of a species is one of the important drivers of the evolution of hermaphroditism, and the relationship between mating systems and hermaphroditism will be focused on in the following chapters. Additionally, sex change is socially controlled in many fishes, and its physiological mechanisms are briefly summarized.KeywordsBidirectional sex changeLow densityProtandryProtogynySimultaneous hermaphroditismSize-advantage