Geometry of biodiversity patterning: assemblages of benthic macroinvertebrates at tributary confluences

We assessed whether tributaries in upland catchments (=watersheds) affected assemblages of benthic macroinvertebrates in mainstems, as has been reported in northern hemisphere systems. Eight confluences of small to medium streams (stream orders 1–4, 2.2–10.8 m wide) were studied in the Acheron River basin in Victoria, Australia. For each confluence, two transects were sampled at each of five zones relative to the confluence: two zones upstream in the mainstem, one zone upstream in the tributary, one zone at the confluence and one zone downstream in the mainstem. Surveys were conducted in both high-flow and low-flow conditions. In mainstems, there was no change in macroinvertebrate density, taxonomic richness or functional feeding group composition downstream relative to upstream of the confluences. While tributaries statistically had distinctive benthic macroinvertebrate assemblages compared to mainstems, these distinctions were small. In low flows, densities in tributaries were substantially lower than in mainstems, but densities during high flows were more similar (albeit only about one-third as high as in low flow) in tributaries and mainstems. An inverse pattern was evident for taxonomic richness, where richness in tributaries and mainstems was similar in low flows but was greater in mainstems than in tributaries in high flows. We found little evidence of tributary effects in macroinvertebrate assemblages in this basin, which is at odds with some previous results from other continents. To explain this divergence, we suggest a conceptual model outlining factors that control variation in effects of tributaries on assemblages of benthic macroinvertebrates in mainstems.

[1]  J. Read,et al.  Variation in widths of riparian-zone vegetation of higher-elevation streams and implications for conservation management , 2008, Plant Ecology.

[2]  Brenda M. Pracheil,et al.  Tributaries influence recruitment of fish in large rivers , 2009 .

[3]  J. Reid.  Experimental Design and Data Analysis for Biologists , 2003 .

[4]  K. Cummins,et al.  Trophic Relations of Aquatic Insects , 1973 .

[5]  M. McCarthy.  Bayesian Methods for Ecology: CASE STUDIES , 2007 .

[6]  Robert K. Colwell,et al.  A new statistical approach for assessing similarity of species composition with incidence and abundance data , 2004 .

[7]  M. Klug,et al.  Feeding Ecology of Stream Invertebrates , 1979 .

[8]  R. M. Nally,et al.  Comparing patterns of spatial autocorrelation of assemblages of benthic invertebrates in upland rivers in south-eastern Australia , 2006, Hydrobiologia.

[9]  D. Schaeffer,et al.  The longitudinal distribution of riverine benthos: A river dis-continuum? , 1987, Hydrobiologia.

[10]  B. Rhoads,et al.  Response of bed morphology and bed material texture to hydrological conditions at an asymmetrical stream confluence , 2009 .

[11]  R. M. Nally.  Ecological boundary detection using Carlin–Chib Bayesian model selection , 2005 .

[12]  P. S. Lake,et al.  Disturbance, patchiness, and diversity in streams , 2000, Journal of the North American Benthological Society.

[13]  C. Swan,et al.  Dendritic network structure constrains metacommunity properties in riverine ecosystems. , 2010, The Journal of animal ecology.

[14]  L. M. M.-T..  Theory of Probability , 1929, Nature.

[15]  Daniel J. Miller,et al.  On Debris Flows, River Networks, and the Spatial Structure of Channel Morphology , 2007, Forest Science.

[16]  Stephen P. Rice,et al.  Tributaries, sediment sources, and the longitudinal organisation of macroinvertebrate fauna along river systems , 2001 .

[17]  R. Mac Nally,et al.  Do tributaries affect loads and fluxes of particulate organic matter, inorganic sediment and wood? Patterns in an upland river basin in south-eastern Australia , 2009, Hydrobiologia.

[18]  P. S. Lake,et al.  Macroinvertebrate diversity in headwater streams: a review , 2008 .

[19]  Gonzalo Castillo,et al.  Analysis of pelagic species decline in the upper San Francisco Estuary using multivariate autoregressive modeling (MAR). , 2009, Ecological applications : a publication of the Ecological Society of America.

[20]  R. Mac Nally,et al.  Spatial autocorrelation of assemblages of benthic invertebrates and its relationship to environmental factors in two upland rivers in southeastern Australia , 2005 .

[21]  M. Winterbourn.  The river continuum concept — reply to Barmuta and Lake , 1982 .

[22]  Jenny Davis,et al.  Longitudinal Changes in Near-Bed Flows and Macroinvertebrate Communities in a Western Australian Stream , 1994, Journal of the North American Benthological Society.

[23]  E. Castella,et al.  Disruption of a longitudinal pattern in environmental factors and benthic fauna by a glacial tributary , 2003 .

[24]  J. Best.  Sediment transport and bed morphology at river channel confluences , 1988 .

[25]  M. Parsons,et al.  The effect of habitat‐specific sampling on biological assessment of water quality using a predictive model , 1996 .

[26]  A. Chao.  Nonparametric estimation of the number of classes in a population , 1984 .

[27]  R. M. Nally,et al.  Geometry of Large Woodland Remnants and its Influence on Avifaunal Distributions , 2005, Landscape Ecology.

[28]  B. Cellot.  Influence of side‐arms on aquatic macroinvertebrate drift in the main channel of a large river , 1996 .

[29]  G. Poole.  Fluvial landscape ecology: addressing uniqueness within the river discontinuum , 2002 .

[30]  Yuichi Kayaba,et al.  Longitudinal macroinvertebrate organization over contrasting discontinuities: effects of a dam and a tributary , 2009, Journal of the North American Benthological Society.

[31]  P. S. Lake,et al.  Spatial Scale of Autocorrelation of Assemblages of Benthic Invertebrates in Two Upland Rivers in South-Eastern Australia and Its Implications for Biomonitoring and Impact Assessment in Streams , 2006, Environmental monitoring and assessment.

[32]  J. Webster,et al.  The role of macroinvertebrates in stream ecosystem function. , 1996, Annual review of entomology.

[33]  M. Wiley,et al.  Influence of Tributary Spatial Position on the Structure of Warmwater Fish Communities , 1992 .

[34]  Daniel R. Miller,et al.  The Network Dynamics Hypothesis: How Channel Networks Structure Riverine Habitats , 2004 .

[35]  M. Keough,et al.  Scaling of colonization processes in streams: Parallels and lessons from marine hard substrata , 1998 .

[36]  C. C. Fernandes,et al.  Amazonian Ecology: Tributaries Enhance the Diversity of Electric Fishes , 2004, Science.

[37]  C. Townsend.  Concepts in river ecology : pattern and process in the catchment hierarchy , 1996 .

[38]  J. Webster,et al.  Export of fine organic particles from headwater streams: Effects of season, extreme discharges, and invertebrate manipulation , 1991 .

[39]  Richard K. Johnson,et al.  Tracing recovery under changing climate: response of phytoplankton and invertebrate assemblages to decreased acidification , 2010, Journal of the North American Benthological Society.

[40]  Robert K. Colwell,et al.  Quantifying biodiversity: procedures and pitfalls in the measurement and comparison of species richness , 2001 .

[41]  Robert J. Naiman,et al.  Longitudinal patterns of ecosystem processes and community structure in a subarctic river continuum , 1987 .

[42]  George E. Host,et al.  Recent developments in landscape approaches for the study of aquatic ecosystems , 2010, Journal of the North American Benthological Society.

[43]  M. Raupach,et al.  Positive Indian Ocean Dipole events precondition southeast Australia bushfires , 2009 .

[44]  Nick R. Bond,et al.  What’s in a site? Variation in lotic macroinvertebrate density and diversity in a spatially replicated experiment , 2000 .

[45]  G. Minshall,et al.  Tributaries as modifiers of the river continuum concept analysis by polar ordination and regression models , 1984 .

[46]  J. Wiens.  Riverine landscapes: taking landscape ecology into the water , 2002 .

[47]  P. S. Lake,et al.  A Bayesian analysis of physical habitat changes at tributary confluences in cobble‐bed upland streams of the Acheron River basin, Australia , 2008 .