TRaCK: Tropical Rivers and Coastal Knowledge

Science and knowledge that governments, communities, industries for sustainable use of Australia's tropical rivers and estuaries

Environmental Filters Determine Strong Spatial Concordance among Multiple Species in Tropical Australian Riverscapes

TitleEnvironmental Filters Determine Strong Spatial Concordance among Multiple Species in Tropical Australian Riverscapes
Publication TypeConference Participation
Year of Publication2010
AuthorsWarfe, DM, Pettit, NE, Davies, PM, Pusey, BJ, Douglas, MD, Bunn, SE
Keywords5: Foodwebs and biodiversity

Predicting the consequences of anthropogenically-induced changes to tropical ecosystems is contingent on understanding the nature and causes of spatial variation in their biotic communities. We investigated the spatial distribution of vegetation, fish and macroinvertebrate assemblages from 46 sites across riverine landscapes in Australia’s wet-dry tropics to determine the relative importance of environmental, spatial and dispersal filters in structuring communities. There was highly concordant spatial structuring between the three assemblages, with each group showing relatively consistent variation between catchments and also within catchments, between tributaries, main channels and floodplain waterholes. Variation in each assemblage was primarily determined by environmental (58 – 67%) rather than spatial (~3%) or dispersal (3 – 5%) filters. This suggests that these freshwater communities were structured deterministically according to species-sorting processes along environmental gradients. Six to eight (of a possible 19) environmental factors explained a significant proportion of the variation and two of these, flow regime and channel width, were significant descriptors of variation in all three biotic assemblages. Channel width is typically an analogue of ecosystem size (or catchment area) and its importance is a manifestation of the species-area relationship, whereas different flow regimes result in different disassembly and reassembly processes structuring communities. Riverine landscapes in Australia’s wet-dry tropics are currently relatively hydrologically intact, and our results demonstrate that these intact flow regimes are responsible for a significant proportion of their biodiversity and represent a benchmark against which river health and water resource development can be assessed into the future.