Hotspots of biodiversity or homogeneous landscapes? Farm dams as biodiversity reserves in Australia

In many countries the ubiquitous farm dam or pond is an integral component of agricultural landscapes. In Australia there are in excess of half a million farm ponds, used largely for irrigation or for watering stock. In contrast to Europe, these wetlands are being decommissioned in response to the introduction of government policy that regulates water usage from these dams. They are also being in-filled with expanding urbanisation without consideration of their benefits as reservoirs of biodiversity. We compared the diversity of macroinvertebrates in farm dams with nearby stream habitats on a cool temperate tableland in central New South Wales. There was greater diversity in-stream than in the dams; however, dam sites showed a larger mean diversity and total diversity per site than in-stream. Species recorded in-stream were more frequently represented by single individuals while species were recorded more consistently in dams. We also observed that macroinvertebrate assemblages were more similar to those in the same dam in different seasons than to adjacent dams in the same season. Some species recorded had not previously been recorded from farm dams. In contrast to the general consensus that Australian farm dams are homogeneous environments with a range of common widespread species, we showed that they provide a variety of sustainable reservoirs of biodiversity within the landscape. They also have the potential to provide ‘stepping stones’ between undisturbed and modified habitats, in part countering the fragmentation that occurs as a result of agricultural practices.     

Influence of riparian condition on aquatic macroinvertebrate communities in an agricultural catchment in south-eastern Australia

Riparian vegetation is known to affect aquatic macroinvertebrate communities through contributions of organic matter and shading. Despite the widespread degradation of riparian vegetation in Australia, there are relatively few studies examining the effect of changes in riparian vegetation on in-stream macroinvertebrate assemblages on individual catchments. In particular, information is lacking on the responses of macroinvertebrate communities in catchments dominated by agriculture, where farms that are managed at the paddock scale result in riparian vegetation condition varying over relatively short distances. In this study, macroinvertebrate assemblages were assessed from 12 reaches along a 25-km section of a small agricultural stream in south-eastern Australia. Riparian condition was assessed using in-stream coarse woody debris (CWD) levels and the rapid appraisal of riparian condition (RARC) index, a numerical system for categorising the health of riparian areas that incorporates sub-indices reflecting habitat continuity, vegetation cover, plant debris levels, native vegetation dominance, and other indicative features. There was a significant positive correlation between RARC scores and macroinvertebrate taxon richness (p < 0.01), and also between CWD scores and macroinvertebrate taxon richness (p < 0.05). In contrast, there was no significant correlation observed between riparian condition and the other macroinvertebrate indices (abundance, Shannon diversity, SIGNAL and SIGNAL2). Macroinvertebrate communities were significantly different in stream reaches from different riparian condition categories (ANOSIM; p < 0.05). Our results indicate that efforts to rehabilitate riparian vegetation may have a positive effect on in-stream biota even when implemented at a relatively small scale by individual landholders.     

Characterization,Ecological Status and Type-specific Reference Conditions of Surface Water Bodies in Wallonia (Belgium) using Biocenotic Metrics based on Benthic Invertebrate Communities

The river types in Wallonia (Belgium) were defined according to the system B of the European Water Framework Directive (WFD) taking into account obligatory and optional factors synthesized in three criteria: ‘size’, ‘slope’ and ‘natural region’. Under the hypothesis that benthic invertebrate assemblages would be specialized according to river type, a set of 627 faunal samples originating from an 11-year sampling period was tested to characterize river types with faunal assemblages. A multivariate approach led to gather 23 river types into seven groups exhibiting similar faunal assemblages. Using biocenotic metrics based on benthic invertebrate assemblages (e.g., the French standard IBGN), type-specific reference conditions and ecological status class limits were defined for each ‘natural’ river type group. Ecological potential was defined for heavily modified and for artificial (i.e., man-made canals) types. An ‘ecological status’ evaluation strategy was therefore developed and applied in the southern – and more natural – part of Wallonia, where many reference sites were available. In the northern part of Wallonia (i.e., the ‘Loess region’) where no high quality site was available, the expert judgement took a larger part in the definition of the reference conditions and of the ecological status class limits, in addition to the calculations. Two independent distribution gradients of taxa assemblages resulted from multivariate ordination: a first ‘saprobity axis’, as the taxa-sensitivity to organic contamination was increasing from ‘very resistant’ taxa (mainly located in the ‘Loess region’) to ‘sensitive’ and ‘very sensitive’ taxa (from the river types belonging to the Condroz, the Famenne, the Arden and the Jurassic regions) and a second axis characterizing the Meuse-specific faunal assemblage, gathering exotic species and typical limnophilous taxa of large heavily modified rivers. The ecological status monitoring management system developed in this study – i.e., the definition of faunal river type groups, related reference conditions and ecological status class limits – represents a proposal to be integrated in the ecological status assessment of biological elements for the implementation of the WFD and was tested in Wallonia. For the period 2000–2002 involving 349 different sites, the element ‘benthic invertebrate fauna’ was in that way classified ‘high status’ for 31.5% of sites, ‘good status’ for 31.5% and below ‘good status’ for 37% of sites. The best ecological status (i.e., 100% ‘high’ and ‘good’ status) was found in river type ‘Arden’s xenotrophic brooks with strong slope’ and in river types 8large rivers with medium slope’. The worst status was found in river types ‘Loess brooks and rivers with medium slope’.     

Macroinvertebrate communities in Phragmites australis (Cav.) Trin. ex Steud. reed beds and open bank habitats in central victorian streams in Australia

Reed invasion is a common phenomenon of open streams with disturbed riparian vegetation in river catchments. Knowledge of the effects of such vegetation change on aquatic communities is fundamental to river management. Macroinvertebrate fauna in Phragmites australis (Cav.) Trin. ex Steud. and open bank habitats were examined in three rivers in central Victoria in order to understand the effect of such littoral habitat on macroinvertebrates. Data were analysed using Partially Nested Factorial ANOVA with season, river and habitats as main effects. Habitat structure had a significant effect (p<0.05) on macroinvertebrate species richness, however this was not seasonally consistent across the three rivers. There was a significant increase (p<0.05) in macroinvertebrate taxa richness in Phragmites habitats during winter and spring seasons. Total abundance of taxa showed no consistent significant differences in the two habitats. Results of Canonical Analysis of Principle Coordinates indicated significant differences (p<0.05) in macroinvertebrate assemblages between Phragmites and bare bank habitats in all seasons. Habitat selection by taxa could be related to the microphysical environment of the habitats. This study suggests that reed beds create important littoral habitat structures which support diverse macroinvertebrate assemblages.     

Grasping the heterogeneity of kettle hole water quality in Northeast Germany

Riparian vegetation typically provides substantial allochthonous material to aquatic ecosystems where micro-organisms can play an important role in organic matter degradation which can support consumer biomass. We examined the effects of leaf litter quality (e.g., leaf nutrients, lignin and cellulose content), leaf species mixing, and microbial community diversity on in-stream breakdown rates of litter from dominant riparian trees (Melaleuca argentea, M. leucadendra, and Nauclea orientalis) in both a perennial and intermittent river in Australia’s wet-dry tropics. Leaf mass remaining after 82 days of in-stream incubation was negatively correlated (P < 0.05) with initial leaf N and P content while initial lignin and cellulose content had no statistically significant effect. Breakdown rates of incubated leaves of both Melaleuca and Nauclea were significantly higher in mixed litter bags compared with single species litter bags. Although it was expected that leaf N content would decrease from initial levels during decomposition, we found either similar or slightly higher N content following in-stream incubation suggesting microbial colonisation increased overall N content. Stable isotopes of δ¹³C and δ¹⁵N for the major sources and consumers in both rivers provide evidence that leaf litter was an important macroinvertebrate food source in the perennial river where heavy shading may limit algal production. However, in the intermittent river where riparian cover was low, benthic algae were the major organic carbon source for consumers. Our findings suggest that riparian tree species influence rates of in-stream organic matter processing, microbial community composition, and aquatic food web dynamics in tropical wet-dry streams.     

Beta diversity of a Gulf of California rocky-shore fish community

Synopsis Reef fish community composition in three segments of a peninsular rocky shoreline in the Gulf of California was estimated over four periods by visual observation. ‘Point’ and ‘bay’ segments had regular and distinct species compositions over most periods while a ‘middle’ segment was least distinct but consistently had the greatest number of species. Compositional change along the peninsula was least regular during the coldest sea temperature period (April). Mean species turnover between segments was highest between point and bay. Within segments, the point had greater compositional predictable composition (lowest species turnover). When species with regular frequency of encounter were classified into ‘point’, ‘middle’, ‘bay’, and ‘no trend’ groups it was found that comparatively more ‘point’ species had pelagic eggs and comparatively more ‘bay’ species had demersal eggs. Beta diversity of rocky-shore fishes along the physical gradient of the Punta Doble peninsula reflects a transition between exposed and protected rocky shoreline communities. The correlated physical environmental characteristics associated with exposed and protected habitats are discussed in relation to diversity regulation and dispersal strategies in reef fishes.     

The influences of climatic variation and vegetation on stream biota: lessons from the Big Dry in southeastern Australia

Aquatic biodiversity faces increasing threats from climate change, escalating exploitation of water and land use intensification. Loss of vegetation in catchments (= watersheds) has been identified as a substantial problem for many river basins, and there is an urgent need to better understand how climate change may interact with changes in catchment vegetation to influence the ecological condition of freshwater ecosystems. We used 20 years of biological monitoring data from Victoria, southeastern Australia, to explore the influences of catchment vegetation and climate on stream macroinvertebrate assemblages. Southeastern Australia experienced a severe drought from 1997 to 2009, with reductions of stream flows >50% in some areas. The prolonged drying substantially altered macroinvertebrate assemblages, with reduced prevalence of many flow‐dependent taxa and increased prevalence of taxa that are tolerant of low‐flow conditions and poor water quality. Stream condition, as assessed by several commonly used macroinvertebrate indices, was consistently better in reaches with extensive native tree cover in upstream catchments. Prolonged drought apparently caused similar absolute declines in macroinvertebrate condition indices regardless of vegetation cover, but streams with intact catchment and riparian vegetation started in better condition and remained so throughout the drought. The largest positive effects of catchment tree cover on both water quality and macroinvertebrate assemblages occurred above a threshold of ca. 60% areal tree cover in upstream catchments and in higher rainfall areas. Riparian tree cover also had positive effects on macroinvertebrate assemblages, especially in warmer catchments. Our results suggest that the benefits of extensive tree cover via improved water quality and in‐channel habitat persist during drought and show the potential for vegetation management to reduce negative impacts of climatic extremes for aquatic ecosystems.     

Changes in the population structure,growth and mortality of striped weakfish <Emphasis Type="Italic">Cynoscion guatucupa</Emphasis> (Sciaenidae,Teleostei) of southern Brazil between 1976 and 2002

Siphonophores are exclusively marine cnidaria and their predatory role in plankton food-webs is well recognised. In this study, we analyse the structure and the spatial extent of siphonophore assemblages in relation to changes in freshwater outflows and food availability in the southern Gulf of Mexico during a high (October) and a low (April) outflow periods. A total of 149 samples were collected using a 505 μm multiple closing net at 1–6 levels (0–100 m) of the water column, depending on the bathymetry. Data on siphonophore species biovolumes (ml 100 m⁻³) were treated by means of the Bray-Curtis Dissimilarity Index, and two distinctive assemblages were identified: the ‘inner’ and the ‘outer’ assemblages, located over the inner and outer shelves. Temperature, salinity, zooplankton biomass, and siphonophore species were included in a Principal Component Analysis (PCA) to identify the factors associated with each assemblage. Geographical distribution of the assemblages practically remained the same during both seasons and its cross-shelf variability was stronger than the vertical one. Seasonally, diversity values were higher in October, when the highest river discharges occur. Spatially, the lowest diversity and mean siphonophore biovolumes values were registered in the ‘inner assemblage’, where the highest and lowest salinity values were recorded. We suggest that even when extreme salinity values (>36.5 or <34) might depress siphonophore populations in the coastal area, enough food availability in the concerned areas might mitigate the negative effect of salinity, since a positive and significant (p < 0.05) relationship was found between siphonophores biovolume and zooplankton biomass. Bassia bassensis, Diphyes dispar and Enneanogum hyalinum, present in both assemblages during both seasons, were able to survive in a wide range of salinity values, following perhaps, their prey. All the 23 species here registered were found in the ‘outer assemblage’; however, Abylopsis eschscholtzi, Chelophyes appendiculata and Diphyes bojani were more associated with the ‘outer’ group according to the PCA results. Enneagonum hyalinum was the only species frequently encountered and abundant in the ‘inner assemblage’ during both seasons and, supporting previous observations, this species might be considered as an indicator of nearshore waters. Handling editor: K. Martens     

The distribution of invertebrate communities in a small South African river

Monthly samples of macroinvertebrates were collected from the stony-bed and marginal-vegetation habitats of a small river in the south western Cape Province, South Africa. Cluster analyses of the samples revealed assemblages of invertebrates (here referred to as communities) with clear spatial and temporal distribution patterns in the muer. The species composition of the communities, and their distribution, are described. The relation of the macroinvertebrate distribution to changes in the physico-chemical environment was investigated using stepwise multiple discriminant analysis. The results indicated a strong correlation between the two.     

The influence of prey communities on fish species assemblages on artificial reefs in Puget Sound,Washington

Synopsis Research on eleven artificial reefs in Puget Sound, Washington examined the relative importance of reef-produced prey items to recreationally important reef fish species assemblages. The colonization of potential prey items, and fish species assemblages to ten artificial reefs were examined for the reefs first two to five years, and observations were conducted on an eleventh reef during its forty-ninth productive year. Fish species became more abundant, or were seen more frequently on reef habitats whose substrates had successionally developed from barnalces to algal mats. Fish species most affected by this successional change foraged heavily on organisms which were associated with reef algae. Starfish and nudibranchs. who preyed on the barnacles, were identified as the ‘keystone’ predators of these subtidal reef habitats.     

Macrozoobenthic assemblages in littoral sediments in the enclosed Rhine-Meuse Delta

Littoral macrozoobenthos in the enclosed Rhine-Meuse Delta was investigated by taking 95 sediment samples from 17 sites between 1984 and 1990. In addition, a set of environmental parameters was determined. The aim was to identify the main assemblages and the environmental conditions under which they occur. By the use of TWINSPAN, three main littoral zoobenthic assemblages were distinguished, which were related to geographical zones and differences in sediment grain size distribution. The ‘litoral river sand’ assemblage was found in the most upstream part; it mainly consisted of ‘interstitial’ invertebrates, including the indicator speciesVejdovskiella comata, Propappus sp. andKloosia pusilla. The ‘littoral sedimentation area silt’ assemblage was dominated byGammarus tigrinus, Einfeldia dissidens andPisidium sp. It was found in several river sections and contained the indicator speciesEinfeldia dissidens, Potamopyrgus antipodarum andValvata piscinalis. The ‘littoral sandy basin’ assemblage was concentrated in the littoral fine sands of the Haringvliet and contained the indicator speciesPisidium henslowanum, P. moitessierianum, Cladotanytarsus sp. andLipiniella arenicola. These three assemblages are the reflection of an interaction between habitat, food and disturbance. Palaeoecological analysis of insect remains revealed that 14 out of the 24 insect taxa, that were formerly common in the river sand habitat, are now extinct from the Rhine. The river silt habitat seems less impoverished: two out of the 19 insect taxa found in palaeoecological analysis are now extinct from the Rhine and seven are rate. Exotic species (Corbicula fluminea, C. fluminalis andCorophium curvispinum) have recently colonized the Rhine-Meuse Delta, but their impact on the macrozoobenthos seems limited.Corbicula spp. have become abundant in the ‘littoral river sand’ assemblage only.     

Temporal and Spatial Distribution Patterns of Larval Trichoptera in Madeiran Streams

Temporal and spatial distribution patterns of lotic larval trichopteran assemblages in relation to environmental variables were investigated in Madeiran streams using multivariate analyses. TWINSPAN classification detected distinct faunal assemblages related to spatial factors between non-polluted high altitude sites and lower lying enriched sites where tolerant taxa were predominant but showed strong seasonal shifts in species composition and abundance. The 15 TWINSPAN end groups were grouped into five arbitrary clusters based upon the seasonal and spatial changes in the trichopteran assemblages detected by the analysis. Significant differences between environmental variables (distance from source, altitude, temperature, conductivity, alkalinity and nitrate) and the trichopteran assemblages (using trichopteran based metrics) of these clusters were confirmed by the Kruskal-Wallis test (H) and Dunn’s test. Chemical classification of samples within the clusters revealed a strong association between trichopteran assemblages and water quality. Canonical Correspondence Analysis and Monte Carlo global permutation tests also identified significant associations between the larval assemblages and physicochemical variables such as temperature and conductivity along a strong physical gradient (altitude, slope) and nitrate along a weaker seasonal gradient. Analysis of functional feeding group distribution patterns clearly showed that mid to high altitude indigenous woodland sites were trophically diverse whilst the lower reaches of the islands streams are trophically impoverished with strong seasonal shifts between two feeding groups of enrichment tolerant taxa. Trichopteran shredders are exclusive to indigenous woodland sites, indicating a limited distribution associated with land use, allochthonous input and habitat destruction. The results indicate that several ‘environmental filters’ operate at different levels upon the islands trichopteran fauna, producing temporally and spatially distinct ‘subsets’ of species best able to exploit conditions and resources at a given site or time, confounding the direct comparison of these insular systems with the findings of the River Continuum Concept, traditionally associated with unaffected continental lotic systems.     

Variability in flood disturbance and the impact on riparian tree recruitment in two contrasting river systems

The vegetation within the riparian zone performs animportant ecological function for in-stream processes.In Australia, riparian zones are regarded as the mostdegraded natural resource zone due to disturbancessuch as river regulation and livestock grazing. Thisstudy looks at factors influencing vegetation dynamicsof riparian tree species on two contrasting riversystems in Western Australia. The Blackwood River insouth-western Australia is influenced by aMediterranean type climate with regular seasonalwinter flows. The Ord River in north-western Australiais characterized by low winter base flows andepisodic, extreme flows influenced by monsoon rains inthe summer. For both rivers, reproductive phenology ofstudied overstory species is timed to coincide withseasonal river hydrology and rainfall. An evendistribution of size classes of trees on the BlackwoodRiver indicated recruitment into the population iscontinual and related to the regular predictableseasonal river flows and rainfall. In contrast, on theOrd River tree size class distribution was clustered,indicating episodic recruitment. On both rivers treeestablishment is also influenced by elevation abovethe river, microtopography, moisture status and soiltype. In terms of vegetation dynamics riparianvegetation on the Ord River consists of long periodsof transition with short lived stable states incontrast to the Blackwood river where tree populationstructure is characterized by long periods of stablestates with short transitions.     

Fish Assemblages in Different Shallow Water Habitats of the Venice Lagoon

The small-sized fish assemblages of the Venice Lagoon were investigated and compared among five shallow subtidal habitats (seagrass beds, sparsely vegetated habitats, unvegetated sand bottoms, mudflats and saltmarsh creeks) in the Northern lagoon basin. Sampling was carried out seasonally (Spring, Summer and Autumn of 2002) in 4–7 stations for each habitat type, by means of a fine-mesh, small beach seine. Two-way analysis of variance was applied to assess the differences in species richness, fish diversity, density and standing stock amongst habitats, whereas fish assemblage composition was investigated by using multivariate analyses (MDS, ANOSIM, SIMPER). The analyses indicated that seagrass beds and saltmarsh creeks are relevant shallow habitats in structuring the small-sized fish assemblages of the Venice Lagoon, supporting specialized and recognizable fish assemblages. Those in seagrass beds, in particular, were characterized by higher species richness and standing stock with respect to all the others. The structuring role of these habitats was discussed in terms of both habitat complexity and degree of confinement. In contrast, sandy bottoms, mudflats and sparsely vegetated habitats were identified as “transition” habitats, with highly variable fish assemblages, influenced by the contribution of the adjacent habitats, and acting probably as both ‘buffer zones’ between the other habitats and migration routes for many fish species in the lagoon.     

The use of ants and other soil and litter arthropods as bio-indicators of the impacts of rainforest clearing and subsequent land use

The present study investigated the impacts of rainforest clearance, and associated subsequent land␣use for pasture, on assemblages of soil and litter arthropods in eastern subtropical Australia. We assessed the utility of soil and litter arthropods as potential bio-indicators of cleared and forested habitats. Arthropods were sampled from 24 sites (12 sites each in rainforest and pasture) using two methods (extraction from litter, pitfall traps). Responses of taxa were analysed at various levels of taxonomic resolution, including ‘coarse’ arthropods (all arthropods sorted to Order/Class), ant genera and ant species. Multivariate analyses of arthropod composition indicated that an increase in the level of taxonomic resolution did not provide a commensurate increase in the sensitivity of assemblage response. Indicator values (IndVals), computed for each taxon, showed that a number of arthropod taxa may have potential as bio-indicators of habitat change. However the use of many of these, especially many ant species found in our study, may be unreliable because even after extensive numbers of sites were sampled, most species showed patchy distributions. To overcome this problem, we generated ‘composite indices’, by combining information from sets of indicator taxa. The utility of these composite indices is discussed.     

Sample coherence – a field study approach to assess similarity of macroinvertebrate samples

The EU-funded STAR-project provided an opportunity to analyse 1418 macroinvertebrate samples from 310 sampling sites throughout Europe. At most of the sites, samples were taken in two seasons using both national protocols and the project’s STAR-AQEM protocol. At a subset of sites (86), two replicate samples were taken by each method in each of the two seasons. The resulting taxalists were analysed in terms of community similarity using the Bray–Curtis Index, Jaccard, and Renkonen Indices. A new concept of sample ‘coherence’ is used to measure the relative strength of within-site, within-season and within-method similarity and to determine their importance on variability in community composition. Site-coherence (i.e., highest similarity to another sample from the same site) was much higher where replicate samples were available. Season-coherence of samples was nearly 100% even if different methods were compared. Season appeared to be one of the major determinants of in-stream fauna. The STAR-AQEM method is most comparable to the Nordic, Portuguese and Czech (PERLA) national methods and less comparable to the Italian (IBE) and Latvian methods. Samples collected by these latter methods had higher similarities to other sites sampled with the same methods than to samples of the same site using the STAR-AQEM method, thus there was low site-coherence. In three stream types from Italy, Latvia and Greece 28–38% of the samples were most similar to a sample from a different site than to a replicate sample from the same site. This fact could have serious consequences for follow up bioassessments or impact assessments by cluster analysis based on similarity measures. Replicate samples are less coherent within site, season or method if the taxonomic resolution is family rather than species. Electronic supplementary material Electronic supplementary material is available for this article at and accessible for authorised users.     

Macroinvertebrates in the Demmerik ditches (The Netherlands): The role of environmental structure

The relation between the different microhabitats and habitats and the quantitative distribution of macroinvertebrates was investigated as well as the applicability of different sampling devices. Data processing took place by means of multivariate analysis (Flexclus, Canoco). It was concluded that the spatial-physical structure is more important to macroinvertebrates than the plant species. In fact, this spatial physical structure can be indicated as the mesh size of a (micro-)habitat. In order from open vegetation, shore/dense vegetation, artificial substrate, bottom material, and filamentous algae the mesh size decresed. It is advisable to use different sampling devices to sample a macroinvertebrate community.     

Bank erosion hazard index as an indicator of near-bank aquatic habitat and community structure in a southeastern Piedmont stream

Streams in the southeastern Piedmont region display varying degrees of bank erosion, which in turn can influence multiple physical and biological processes. In efforts to assess and predict bank erosion, the multi-metric tool Bank Erosion Hazard Index (BEHI) is often calculated. As designed, the BEHI takes into consideration many physical phenomena and scores stream banks categorically from very low to extreme bank erosion hazard; however the power of this index to directly predict in-stream biological conditions is unknown. The predictive ability of BEHI was evaluated on near-bank aquatic biota and organic matter (OM) retention in an AL Piedmont stream with a range of bank conditions. Fifteen banks were characterized using the BEHI and subsequently, macroinvertebrates, crayfishes, fishes and organic matter associated with each bank were quantified. Results suggest increased macroinvertebrate richness and OM retention with low BEHI score. Multivariate analyses suggest functional similarity in macroinvertebrate assemblages associated with low BEHI banks and greater variation in assemblages as BEHI increased. Crayfish were more abundant at banks with high BEHI, a pattern attributed to increases in a generalist species in more-degraded habitats. Fish response showed no discernible pattern in relationship to BEHI score. These results suggest that BEHI may have applications as an informative ecological evaluation tool integrating physical and biological conditions in streams.     

Site effects outweigh riparian influences on ground-dwelling beetles adjacent to first order streams in wet eucalypt forest

In wet eucalypt forest with a rainforest understorey the vegetation adjacent to first order streams does not form a distinct riparian strip. This study investigated the riparian response of terrestrial ground-dwelling beetles adjacent to four such streams in Tasmania, Australia. Beetle assemblages varied more between the four sites than they did with distance from stream within sites, where they exhibited a measurable but subtle riparian response. The extent of the riparian zone varied between the four study sites, with a 1–5 m riparian zone at three sites and a gradually changing community up to 50–100 m upslope at one site. There was a trend for greater between plot variability immediately adjacent to the streams, possibly because this is a more highly disturbed environment. None of the habitat variables measured were consistently associated with riparian or upslope assemblages of beetles, probably explaining the subtlety of the beetles’ riparian response. Forest conservation efforts for terrestrial species should not necessarily be focused on the riparian zone in preference to upslope areas.     

The influence of substrate type on macroinvertebrate assemblages within agricultural drainage ditches

Artificial drainage ditches are common features in lowland agricultural catchments that support a wide range of ecosystem services at the landscape scale. Current paradigms in river management suggest activities that increase habitat heterogeneity and complexity resulting in more diverse floral and faunal assemblages; however, it is not known if the same principles apply to artificial drainage ditch systems. We examined the effects of four artificial substrates, representing increasing habitat complexity and heterogeneity (bricks, gravel, netting and vegetation), on macroinvertebrate community structure within artificial drainage ditches. Each substrate type supported a distinct macroinvertebrate community highlighting the importance of habitat heterogeneity in maintaining macroinvertebrate assemblages. Each substrate type also displayed differing degrees of community heterogeneity, with gravel communities being most variable and artificial vegetation being the least. In addition, several macroinvertebrate diversity metrics increased along the gradient of artificial substrate complexity, although these differences were not statistically significant. We conclude that habitat management practices that increase habitat complexity are likely to enhance macroinvertebrate community heterogeneity within artificial drainage channels regardless of previous management activities.