DO LARVAL TRAITS RE-EVOLVE? EVIDENCE FROM THE EMBRYOGENESIS OF A DIRECT-DEVELOPING SALAMANDER, PLETHODON CINEREUS

Authors

  • Ryan R. Kerney,

    1. Biology Department, Dalhousie University, 1355 Oxford St., Halifax, Nova Scotia B3H 4J1, Canada
    2. E-mail: ryankerney@gmail.com
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    • These authors made equal contributions to this work

  • David C. Blackburn,

    1. Natural History Museum and Biodiversity Institute, University of Kansas, Lawrence, Kansas 66045
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    • These authors made equal contributions to this work

  • Hendrik Müller,

    1. Institut für Spezielle Zoologie und Evolutionsbiologie mit Phyletischem Museum, Friedrich-Schiller-Universität Jena, Erbertstr. 1, 07743 Jena, Germany
    2. Museum of Comparative Zoology and Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, Massachusetts 02138
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  • James Hanken

    1. Museum of Comparative Zoology and Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, Massachusetts 02138
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Abstract

Recent molecular phylogenies suggest the surprising reacquisition of posthatching metamorphosis within an otherwise direct-developing clade of lungless salamanders (family Plethodontidae). Metamorphosis was long regarded as plesiomorphic for plethodontids, yet the genus Desmognathus, which primarily includes metamorphosing species, is now nested within a much larger clade of direct-developing species. The extent to which the putative reacquisition of metamorphosis in Desmognathus represents a true evolutionary reversal is contingent upon the extent to which both larva-specific features and metamorphosis were actually lost during the evolution of direct development. In this study we analyze development of the hyobranchial skeleton, which is dramatically remodeled during salamander metamorphosis, in the direct-developing red-backed salamander, Plethodon cinereus. We find dramatic remodeling of the hyobranchial skeleton during embryogenesis in P. cinereus and the transient appearance of larva-specific cartilages. Hyobranchial development in this direct-developing plethodontid is highly similar to that in metamorphosing plethodontids (e.g., Desmognathus). The proposed reacquisition of hyobranchial metamorphosis within Desmognathus does not represent the “re-evolution” of a lost phenotype, but instead the elaboration of an existing developmental sequence.

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