Male pregnancy and the evolution of body segmentation in seahorses and pipefishes

    Authors

    E. A. Hoffman; K. B. Mobley;A. G. Jones

    Comments

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    Abbreviated Journal Title

    Evolution

    Keywords

    axial skeleton; G-matrix; heritability; natural selection; quantitative; genetics; Syngnathus scovelli; vertebral number; SEX-ROLE REVERSAL; THREESPINE STICKLEBACK; GARTER SNAKE; G-MATRIX; MICROSATELLITE ANALYSIS; PHENOTYPIC EVOLUTION; GENETIC ARCHITECTURE; QUANTITATIVE TRAITS; AXIAL VARIATION; SELECTION; Ecology; Evolutionary Biology; Genetics & Heredity

    Abstract

    The evolution of complex traits, which are specified by the interplay of multiple genetic loci and environmental effects, is a topic of central importance in evolutionary biology. Here, we show that body and tail vertebral numbers in fishes of the pipefish and seahorse family (Syngnathidae) can serve as a model for studies of quantitative trait evolution. A quantitative genetic analysis of body and tail vertebrae from field-collected families of the Gulf pipefish, Syngnathus scovelli, shows that both traits exhibit significantly positive additive genetic variance, with heritabilities of 0.75 +/- 0.13 (mean +/- standard error) and 0.46 +/- 0.18, respectively. We do not find any evidence for either phenotypic or genetic correlations between the two traits. Pipefish are characterized by male pregnancy, and phylogenetic consideration of body proportions suggests that the position of eggs on the pregnant male's body may have contributed to the evolution of vertebral counts. In terms of numbers of vertebrae, tail-brooding males have longer tails for a given trunk size than do trunk-brooding males. Overall, these results suggest that vertebral counts in pipefish are heritable traits, capable of a response to selection, and they may have experienced an interesting history of selection due to the phenomenon of male pregnancy. Given that these traits vary among populations within species as well as among species, they appear to provide an excellent model for further research on complex trait evolution. Body segmentation may thus afford excellent opportunities for comparative study of homologous complex traits among disparate vertebrate taxa.

    Journal Title

    Evolution

    Volume

    60

    Issue/Number

    2

    Publication Date

    1-1-2006

    Document Type

    Article

    Language

    English

    First Page

    404

    Last Page

    410

    WOS Identifier

    WOS:000236383200018

    ISSN

    0014-3820

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