HR: 14:30h
AN: NB43A-05    [Abstracts]
TI: A Method for Adapting Ecological Distance Matrices to Asymmetrical Autocorrelation Within Dendritic Stream Networks.
AU: * Padgham, M
EM: mark.padgham@sci.monash.edu.au
AF: Cooperative Research Centre for Freshwater Ecology, Water Studies Centre, Monash University, VIC 3800 Australia
AU: Walsh, C
EM: chris.walsh@sci.monash.edu.au
AF: Cooperative Research Centre for Freshwater Ecology, Water Studies Centre, Monash University, VIC 3800 Australia
AB: Ecological relationships within dendritic stream networks are inherently asymmetrical: upstream sites (U) are effectively independent, while downstream sites (D) are not. In expressing a stream network as a distance matrix, D may be closer to U than U is to D. (Or: you can't describe a stream network with a symmetrical matrix!) These kinds of asymmetrical distance matrices are not amenable to common methods of accounting for autocorrelation, such as partial Mantel tests. A method is presented to account for asymmetrical dendritic flow relationships that produces a newly modified, yet still symmetrical, ecological distance matrix that may then be used in ordinations. The method is applied to data relating macroinvetebrate community composition within the streams of the semi-urbanised environs of Brisbane, Australia, to one environmental driver, catchment imperviousness. The resultant descriptive model is considerably improved after modifying the ecological distance matrix to account for the stream network relationships, thereby supporting the efficacy of this approach. A further benefit of the method is in allowing a direct comparison between asymmetrical, or flow-directed effects, and symmetrical, or non-directed, effects of stream networks, giving a measure of the relative importance of flow in determining ecological composition.
DE: 1848 Networks
DE: 9810 New fields (not classifiable under other headings)
SC: North American Benthological Society [NB]
MN: 2005 Joint Assembly