Body size drives allochthony in food webs of tropical rivers

Timothy D. Jardine, Tom Rayner, Neil E. Pettit, Dominic Valdez, Douglas P. Ward, Garry Lindner, Michael M. Douglas, Stuart E. Bunn

    Research output: Contribution to journalArticleResearchpeer-review

    Abstract

    Food web subsidies from external sources (“allochthony”) can support rich biological diversity and high secondary and tertiary production in aquatic systems, even those with low rates of primary production. However, animals vary in their degree of dependence on these subsidies. We examined dietary sources for aquatic animals restricted to refugial habitats (waterholes) during the dry season in Australia’s wet–dry tropics, and show that allochthony is strongly size dependent. While small-bodied fishes and invertebrates derived a large proportion of their diet from autochthonous sources within the waterhole (phytoplankton, periphyton, or macrophytes), larger animals, including predatory fishes and crocodiles, demonstrated allochthony from seasonally inundated floodplains, coastal zones or the surrounding savanna. Autochthony declined roughly 10% for each order of magnitude increase in body size. The largest animals in the food web, estuarine crocodiles (Crocodylus porosus), derived ~80% of their diet from allochthonous sources. Allochthony enables crocodiles and large predatory fish to achieve high biomass, countering empirically derived expectations for negative density vs. body size relationships. These results highlight the strong degree of connectivity that exists between rivers and their floodplains in systems largely unaffected by river regulation or dams and levees, and how large iconic predators could be disproportionately affected by these human activities.

    Original languageEnglish
    Pages (from-to)505-517
    Number of pages13
    JournalOecologia
    Volume183
    Issue number2
    DOIs
    Publication statusPublished - 1 Feb 2017

    Fingerprint

    allochthony
    food webs
    food web
    body size
    Crocodylus porosus
    rivers
    crocodiles
    subsidies
    river
    floodplains
    floodplain
    animal
    animals
    autochthony
    fish
    diet
    dams (hydrology)
    periphyton
    macrophytes
    savanna

    Cite this

    Jardine, T. D., Rayner, T., Pettit, N. E., Valdez, D., Ward, D. P., Lindner, G., ... Bunn, S. E. (2017). Body size drives allochthony in food webs of tropical rivers. Oecologia, 183(2), 505-517. https://doi.org/10.1007/s00442-016-3786-z
    Jardine, Timothy D. ; Rayner, Tom ; Pettit, Neil E. ; Valdez, Dominic ; Ward, Douglas P. ; Lindner, Garry ; Douglas, Michael M. ; Bunn, Stuart E. / Body size drives allochthony in food webs of tropical rivers. In: Oecologia. 2017 ; Vol. 183, No. 2. pp. 505-517.
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    Jardine, TD, Rayner, T, Pettit, NE, Valdez, D, Ward, DP, Lindner, G, Douglas, MM & Bunn, SE 2017, 'Body size drives allochthony in food webs of tropical rivers', Oecologia, vol. 183, no. 2, pp. 505-517. https://doi.org/10.1007/s00442-016-3786-z

    Body size drives allochthony in food webs of tropical rivers. / Jardine, Timothy D.; Rayner, Tom; Pettit, Neil E.; Valdez, Dominic; Ward, Douglas P.; Lindner, Garry; Douglas, Michael M.; Bunn, Stuart E.

    In: Oecologia, Vol. 183, No. 2, 01.02.2017, p. 505-517.

    Research output: Contribution to journalArticleResearchpeer-review

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    Jardine TD, Rayner T, Pettit NE, Valdez D, Ward DP, Lindner G et al. Body size drives allochthony in food webs of tropical rivers. Oecologia. 2017 Feb 1;183(2):505-517. https://doi.org/10.1007/s00442-016-3786-z