Ecological studies of anuran larvae in temporary freshwaters of the Australian wet-dry tropics

Jennifer Francis

    Research output: ThesisDoctoral Thesis

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    Abstract

    [Truncated abstract] In the Kimberley region of Australia's wet-dry tropics, temporary ponds are communities at risk from agricultural and other developments but also from the introduced, toxic cane toad, Rhinella marina. Frog communities in the Kimberley region are poorly known with little more than basic taxonomic descriptions of species available. We know nothing about the importance of either tadpoles or frogs as consumers or as contributors to nutrient flows in these ecosystems. Before generating hypotheses on tadpole community dynamics in these little known ecosystems, I undertook natural history surveys. By documenting anuran breeding phenology, tadpole abundance and composition, the abundance and composition of other fauna and the hydroperiod of temporary waterbodies I was able to gain an understanding of elements responsible for tadpole community assembly. I found several patterns that were consistent across spatial and temporal scales, including: 1) anurans use one of two strategies for breeding - explosive breeding or continuous breeding, 2) tadpole abundance (100-300 per m3) and species richness (7 to 8 species) is high, 3) time taken for tadpoles to metamorphose is species specific and varies from one week to eight weeks, 3) highly variable and unpredictable hydroperiod results in desiccation being a major source of tadpole mortality, 4) macroinvertebrate predators are the main predators in temporary ponds, and 5) very few fish inhabit temporary ponds. Using stable isotope analyses, my research then focused on several aspects of tadpole feeding ecology in temporary wetlands of the Kimberley, including trophic status and resources used for tadpole production. Within these elements I investigated whether 1) tadpoles are indiscriminate consumers or if they differentiate into feeding niches, 2) tadpole diets change with spatial scales (i.e. opportunistic consumption of available resources), and 3) whether tadpole diets change through ontogeny. My research showed that tadpoles in the wet-dry tropics of Australia are not a single trophic guild, as particular species fed fairly consistently as both specialist herbivores and predators, or, omnivores that ranged across trophic levels. Omnivorous tadpoles relied mainly on zooplankton for their animal material, while predatory tadpoles appeared to source their energy predominantly from heterospecific, largely first order consumer tadpoles. Epilithon was an important energy source for most tadpoles, although I also showed that tadpoles fed across all major carbon sources (seston, detritus, epilithon) and adding this to their high densities, makes them prominent components in nutrient transfer...
    Original languageEnglish
    QualificationDoctor of Philosophy
    Publication statusUnpublished - 2013

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