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Pleuronectiform relationships : a cladistic reassessment

1993; Rosenstiel School of Marine and Atmospheric Science; Volume: 52; Issue: 1 Linguagem: Inglês

1553-6955

François Chapleau,

Marine and fisheries research

Flatfish monophyly, interrelationships and intrarelationships are examined. The order Pleuronectiformes is monophyletic on the basis ofthree synapomorphies: cranial asymmetry associated with ocular migration, advanced position of the dorsal fin over the cranium and presence of a recessus orbitalis. Characters used to postulate a relationship between percoids and flatfishes are found to be plesiomorphic and the sister of flatfishes remains unknown. The monophyletic status of all suprageneric taxa of Pleuronectiformes is reexamined and a cladistic analysis is performed using a character state matrix of 39 polarized morphological (mainly osteological) characters, Eighteen equally parsimonious trees were generated. A consensus tree was constructed and discussed in detail. It is concluded that phylogenetic knowledge within flatfishes remains very incomplete. The monophyletic status of speciose taxa such as the Pleuronectinae and Paralichthyidae will have to be reassessed before any fruitful statement of relationships can be formulated. Hensley and Ahlstrom (1984) and Ahlstrom et al. (1984) provided the most recent synthesis on flatfish classification (Table 1), phylogeny (Fig. 1) and larval morphology. Hensley and Ahlstrom (1984) reexamined the homology of characters traditionally used to define higher flatfish taxa (i.e., suborders, families and subfamilies). They also introduced new characters and suggested the formation of a bothoid group made up of an array of dextral and sinistral flatfishes. The monophyletic status of all higher taxa within flatfishes was examined, but no attempts were made to build a cladogram depicting flatfish intrarelationships. This article reviews studies on flatfish phylogeny since the synthesis of Hensley and Ahlstrom (1984) and addresses the following issues: (1) Are flatfishes a monophyletic group? (2) In light of recent advances in percoid phylogeny, what can be said of Regan's (1910) and Norman's (1934) assertions that Psettodes, the most primitive flatfish, is an asymmetrical percoid that could almost be placed in the family Serranidae? (3) What is the monophyletic status of higher taxa (suborders, families and subfamilies) within the Pleuronectiformes and what do we know of their interrelationships? To visualize current knowledge on flatfish relationships, a cladistic analysis of familial and subfamilial relationships is performed using available ordered and polarized morphological characters. Except for the cladogram of Lauder and Liem (1983) based on a more limited data set, this cladistic analysis represents the first attempt to incorporate all available information to build a cladogram of intrarelationships within the Pleuronectiformes. MATERIALS AND METHODS The following taxa were used in the cladistic analysis (see below for justification): Psettodidae, Lepidoblepharon, Brachypleura, Citharoides, Citharus, Scophthalmidae, Paralichthyidae, Bothidae, Pleuronectinae, Poecilopsettinae, Rhombosoleinae, Samarinae, Achiridae, Soleidae, and Cynoglos-