Phylogeny of Living Parasitic Lampreys (Petromyzontiformes) Based on Morphological Data
Relationships among the 18 extant species of parasitic lamprey (Petromyzontiformes) were determined using a cladistic analysis of 32 mainly morphological characters. Because previous analyses support all known fossils as phylogenetically older or the same age as living lampreys, a composite agnathan fossil was used as an outgroup. A consensus of three equally parsimonious trees revealed a trichotomy between a monophyletic northern hemisphere clade and the southern hemisphere genera Geotria and Mordacia. The monophyletic status of the northern hemisphere lampreys and their classification in a single family Petromyzontidae was corroborated. It is suggested that the two southern hemisphere lamprey genera be retained as distinct families. Among northern hemisphere species, Ichthyomyzon and Petromyzon form a monophyletic group sister to the remaining genera. Caspiomyzon is sister to Tetrapleurodon + Entosphenus + Lethenteron + Eudontomyzon + Lampetra, with Tetrapleurodon in turn being sister to a group comprising Entosphenus and a clade containing Lethenteron and its sister group Eudontomyzon + Lampetra. Differences in many characters are related to differences in modes of feeding and behavior. In a phylogenetic context, dentitional characters are resolved as related either to blood feeding (Petromyzon, Ichthyomyzon, and Mordacia) and hypothesized to be plesiomorphic, or to flesh feeding (Eudontomyzon, Lampetra, and Geotria).Abstract
Strict consensus tree of three trees from the phylogenetic analysis of 32 morphological characters of the 18 species of living parasitic lampreys and using a composite fossil as the outgroup taxon. Node and Bremer decay indices appear to the left and right of the branches, respectively. Character state support is as follows: Node 1: Character 2 (state change 1→2), 6(1→3), 24(1→2), 28(1→2). Node 2: 3(3→2), 20(3→2), 23(3→2), 25(1→2). Node 3: 14(2→1). Node 4: 20(2→1), 22(3→1). Node 5: 7(1→2), 10(1→2), 12(1→2), 22(3→2), 27(2→1). Node 6: 5(1→2), 8(1→2), 11(1→2), 13(1→2). Node 7: 2(2→3). Node 8: 4(2→3), 6(3→2). Node 9: 27(1→2). Node 10: 13(2→3). Node 11: 3(2→1), 7(2→3), 8(2→3), 23(2→1). Node 12: 9(1→3). Node 13: 2(3→2). Node 14: 4(2→3), 11(2→1). Node 15: 4(2→4), 5(1→3), 8(1→5), 9(1→2), 15(1→2), 17(1→2), 18(1→2), 19(1→3), 25(1→3), 29(1→2), 30(1→3). Caspiomyzon wagneri: 1(1→2), 4(2→1), 6(3→2). Eudontomyzon danfordi: 13(2→3). Eudontomyzon morii: 22(2→3). Entosphenus minimus: 10(2→1), 12(2→1). Entosphenus similis: 23(2→1). Geotria australis: 1(1→3), 4(2→1), 5(1→4), 7(1→3), 8(1→4), 10(1→2), 11(1→2), 13(1→4), 14(2→3), 16(1→2), 19(1→2), 21(1→2), 26(1→3), 29(1→3), 30(1→2). Ichthyomyzon castaneus: 7(1→2). Ichthyomyzon unicuspis: 4(2→1). Lampetra ayresii: 13(2→1). Lampetra fluviatilis: 27(1→2). Lethenteron camtschaticum: 22(2→3). Mordacia mordax: 23(3→1). Mordacia lapicida: 17(2→3). Petromyzon marinus: 9(1→2), 26(1→2). Tetrapleurodon spadiceus: 13(2→3)
Contributor Notes
(HSG, ICP) School of Biological Sciences and Biotechnology, Murdoch University, Perth, Western Australia 6150, Australia; (CBR) Research Division, Canadian Museum of Nature, P.O. Box 3443, Station D, Ottawa, Ontario, K1P 6P4, Canada; (FC) Department of Biology, University of Ottawa, Ottawa, Ontario, K1N 6N5, Canada; and (RLM) Department of Biology, 3507 Laclede Avenue, Saint Louis University, St. Louis, Missouri 63103. maydenrl@slu.edu Send reprint requests to RLM.