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    Cycads in the insular South-west Pacific: dispersal or vicariance

    Access Status
    Fulltext not available
    Authors
    Keppel, Gunnar
    Hodgskiss, P.
    Plunkett, G.
    Date
    2008
    Type
    Journal Article
    
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    Citation
    Keppel, Gunnar and Hodgskiss, Paul D. and Plunkett, Gregory M. 2008. Cycads in the insular South-west Pacific: dispersal or vicariance. Journal of Biogeography. 35 (6): pp. 1004-1015.
    Source Title
    Journal of Biogeography
    DOI
    10.1111/j.1365-2699.2007.01869.x
    ISSN
    03050270
    School
    Department of Environment and Agriculture
    URI
    http://hdl.handle.net/20.500.11937/32550
    Collection
    • Curtin Research Publications
    Abstract

    Aim: Cycads constitute an ancient plant group that is generally believed to disperse poorly. However, one group of cycads (subsection Rumphiae) is thought to have dispersed relatively recently from a Malesian source area westwards to East Africa and eastwards into the Pacific, using a floatation-facilitating layer in their seeds. We use morphological and allozyme characters to investigate the relationships among the species within this group and to deduce whether the wide distribution was achieved by recent dispersal (as evidenced by high genetic similarity) or more distant vicariance events (high genetic differentiation). Location: We examined specimens collected throughout the range of subsection Rumphiae, from East Africa through Southeast Asia to Tonga in the South-west Pacific. Methods: We investigated relationships within subsection Rumphiae of the genus Cycas by analysing 18 variable (11 informative) morphological characters and 22 allozyme loci for seven of the 10 species currently assigned to this taxon. Results: Distinctive morphological characters are few and fail to resolve relationships within the group. Allozyme data show that species within this subsection are closely related and suggest that there are two groups within the subsection, one comprising Cycas thouarsii (East Africa) and C. edentata (the Philippines), and the other the remaining species (from Malesia and the Pacific). The Australian species C. silvestris is sister to subsection Rumphiae in the morphological analysis but is closely allied to C. rumphii (nested within the subsection) in the allozyme analysis, suggesting that Rumphiae may be paraphyletic and that characters thought to be taxonomically important may need to be re-evaluated. Main conclusions: Cycads within subsection Rumphiae are closely related, and the wide distribution of this group was probably achieved through relatively recent oceanic dispersal events. Separate events probably account for the dispersal of these cycads into the Pacific and to Africa. The origin and distribution of C. silvestris (Australia) could be explained by a dispersal event from New Guinea or may have resulted from a former land connection between Australia and New Guinea.

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