Amphibian abundance and detection trends during a large flood in a semi-arid floodplain wetland
Amphibian abundance and occupancy are often reduced in regulated river systems near dams, but comparatively little is known about how they are affected on floodplain wetlands downstream or the effects of actively managed flows. We assessed frog diversity in the Macquarie Marshes, a semi-arid floodplain wetland of conservation significance, identifying environmental variables that might explain abundances and detection of species. We collected relative abundance data of 15 amphibian species at 30 sites over four months, coinciding with a large natural flood. We observed an average of 39.9 ± (SE) 4.3 (range, 0-246) individuals per site survey, over 47 survey nights. Three non-burrowing, ground-dwelling species were most abundant at temporarily flooded sites with low-growing aquatic vegetation (e.g., Limnodynastes tasmaniensis, Limnodynastes fletcheri, Crinia parinsignifera). Most arboreal species (e.g., Litoria caerulea) were more abundant in wooded habitat, regardless of water permanency. Remaining species had burrowing frog characteristics and low or variable abundance during the flood (e.g., Litoria platycephala, Uperoleia rugosa) with no significant environmental covariate influence. Consequently, behaviorally and physiologically similar species shared similar responses, despite some species-specific relationships to site- and survey-level variables. The Macquarie Marshes provided suitable habitat for a range of species with varying adaptations to semi-arid conditions, including those highly susceptible to water loss. It was likely regular inundation and natural flooding patterns were required to maintain these conditions.
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