The influence of different spatial-scale variables on caddisfly assemblages in Flemish lowland streams

Abstract

1. Patterns in species assemblages are the result of the combined influence of processes acting on different spatial scales. Various studies describe the distribution of macroinvertebrate communities and their relationship with environmental factors at different geographical scales, but only a few of these studies concentrate on Western European lowlands.2. Using Flanders as representative for the densely populated Western-European lowlands, the specific aims of this study are: (i) to identify the different trichopteran species assemblages and to characterise them biologically using indicator species; (ii) to determine which environmental gradients most influence the observed species assemblages; and (iii) to analyse the relative importance of different spatial scale variables in constraining the Trichoptera distributions.3. Assessment of the main environmental gradients suggested that the absence of Trichoptera from certain locations was mainly due to elevated nutrient concentrations and lower oxygen contents, confirming their sensitivity to anthropogenic disturbance.4. Five Trichoptera species assemblages were distinguished based on Bray-Curtis dissimilarity coefficients. These assemblages did not differ significantly in species richness, but a shift in stream zonation preference was observed. In the ordination analysis 11 variables that were selected using a stepwise model building function manifested themselves as upstream-downstream and size-related gradients. The Trichoptera assemblages in lowland streams thus appear to follow a longitudinal succession pattern that corresponds with the species-specific preferences.5. Partitioning the variance over the different spatial scales indicated that the reach-scale variables were far more important in explaining the variation in species composition. The study design, which limited the minimum-maximum range of catchment-scale characteristics, however, may have led to an overestimation of the impact of the local-scale variables.

Distribution and ecology of the caddisflies (Trichoptera) of Flanders (Belgium)

“…As in the present study, they also found that stagnant waters differed in species composition from running waters. In addition, four clusters of running waters were recognized, which were reported to mainly differ in stream size (Gombeer et al, 2011). However, this separation is probably artificial due to the low number of sites because in the present study, differences between ecoregions were found to be much more important than stream size.…”

“…The sandy region and especially the polder and the dune area only contained an impoverished caddisfly fauna, which mainly consisted of ubiquist species. Recently, Gombeer et al (2011) sampled Trichotpera in 41 Flemish streams with a stream order j 3 and observed 34 taxa, half of which was only captured at one site. As in the present study, they also found that stagnant waters differed in species composition from running waters.…”

Characterizing macroinvertebrate communities across China: Large-scale implementation of a self-organizing map

“…Most of the temperate rivers worldwide are heavily altered by human activities such as flow regulation, water abstraction, pollution and species introductions. As a general consequence, most of the macroinvertebrate species in lowland temperate systems are tolerant species (Urban et al, 2006), whereas clean water species, including Rhithrogena japonica and Himalopsyche phryganea, tend to colonize high altitude areas in streams where the natural regime has been protected (Park et al, 2007;Gombeer et al, 2011).…”

“…To date, factors responsible for structuring macroinvertebrate communities on small spatial scales (e.g., microhabitat, or substrate and reach flow patterns) have received more attention (Cummins, 1962;Hynes, 1970;Benke et al, 1984;Minshall, 1984;Allan, 1995) than factors operating on larger scales (e.g., local and whole watershed) (Poff, 1997;Hawkins et al, 2000;Gombeer et al, 2011). To fill this gap, the objectives of this study are (1) to evaluate the geographical divisions of the macroinvertebrate communities in Chinese streams on a large-scale using the self-organizing map (SOM) method and (2) to characterize the distribution patterns of macroinvertebrates in relation to different environmental habitats.…”

“…Spatial patterns are the result of various processes that act on different spatial scales, and the occurrence of a species is the outcome of the combined influence of local environmental characteristics and large-scale geographical factors (Stevenson, 1997;Gombeer et al, 2011). Direct effects stem from aquatic habitat conditions related to temperature, altitude, catchment geology, hydromorphology, water quality, discharge, and substrate (Richards and Host, 1994) and indirect effects from shifts in primary (e.g., benthic algae) and secondary producers (e.g., fish; Richards and Host, 1994;Wang and Stevenson, 2005).…”