Graduate Thesis Or Dissertation
 

Phylogeny and zoogeography of glyptocephalines (Pisces: Pleuronectidae)

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/2r36v0817

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  • Hypotheses of phylogenetic and historical zoogeographic relationships of glyptocephalines (Glyptocephalus cynoglossus, G. zachirus, G. stelleri, Microstomus kitt, H. pacificus, H. achne, Embassichthys bathybius, and Tanakius kitaharae) were constructed based on comparative anatomy and external morphology. The phylogenetic approach was cladistic and character polarity was determined by using out-group comparison. One nominal in-group, Platichthys bicoloratus, is shown to be a derived out-group taxon. Two other out-group taxa used are Parophrys vetulus and Atheresthes stomias. Monophyly of glyptocephalines is suggested by the results of minimum distance clustering of shape, as well as asymmetrical jaw dentition and mi-serial arrangement of jaw teeth; loss of ural neural arch; median number of rays on fifth hypural greater than two; and median number of parhypural rays greater than three. Two monophyletic groups are identified within glyptocephalines: Clade M, Embassichthys and Microstomus; and Clade G, Tanakius and Glyptocephalus. Each clade includes a primitive monotypic genus and a derived genus with three species. The most recent speciation event in each clade separated an Atlantic species from a western Pacific species. One trans-Pacific dispersal event is hypothesized for the ancestor of Clade G and one recent trans-Arctic dispersal is hypothesized for both clades. The trans-Pacific dispersal probably occurred during the Miocene. The trans-Arctic dispersal probably occurred during the Pliocene. The western North Pacific or North Pacific is the most likely the center of origin of glyptocephalines, since this area possesses the most primitive taxa. Some ontogenetic data are discussed to corroborate glyptocephaline monophyly and phylogenetic relationships. Relative timing of ontogenetic events and ontogenetic shape changes corroborate generic groupings. A more thorough study of ontogenetic biometry may shed light on the robustness of glyptocephaline phylogeny. In addition, the specialized giant larvae of eastern North Pacific glyptocephalines deserves further study of ecologic and ontogenetic interactions.
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