Ground invertebrate fauna associated with native shrubs and exotic pasture in a modified rural landscape, Otago, New Zealand

This study examined whether the diversity and relative abundance of ground-dwelling invertebrates changed in relation to type of vegetation cover. Invertebrate taxon diversity and relative abundance were assessed with pitfall traps placed under the native shrubs Olearia bullata and Coprosma propinqua, and in surrounding patches of exotic pasture. A total of 1935 invertebrates and at least 152 invertebrate taxa were recorded from 49 pitfall traps. The number of native taxa was c.63% of all taxa recorded, whereas exotic invertebrates represented only c.9%. The other c.28% were of undetermined origin. Taxon richness and relative abundance under the two shrub species were statistically similar, although all mean values (except for Coleoptera) were higher for traps set beneath C. propinqua. In contrast, taxon richness and relative abundance were significantly higher in the exotic pasture than under either of the shrub species. The same pattern was evident for exotic invertebrates and the relative abundance of native invertebrates, and for some of the most speciose orders. The data indicate that nearly half of native taxa occurred only under native shrubs. In contrast, 7 out of 12 exotic species were found in all three vegetation types, and all but one of them were recorded at least in exotic pasture. We conclude that the value of locally-modified and patchy vegetation cannot be underestimated for its potential in providing native biodiversity reservoirs for New Zealand’s native invertebrate fauna.     

Drift patterns of particulate matter and organisms during artificial high flows in a large experimental channel

Using a large experimental channel, five artificial high flows with different flow regimes were launched to reveal the precise temporal sequences of drifting particulate matter and organisms during the high flows. Drifting fine particulate matter and organisms were collected by sampling bottles and a water pump, respectively. The peaks of drift abundance occurred before the peak discharges, and the abundance declined quickly within several minutes during the rising phase of high flows. The major determinant of drift abundance of particulate matter and organisms was periods of stable conditions before each high flow (tested by determination coefficients in a correlation analysis). The drift of macroscopic plant material also accelerated the drifts of epiphytic fauna and infauna, which drifted with plants and bed sediments. The magnitude (discharge and duration of peak flows) of high flows only slightly affected drift abundance. The fauna more resistant to high flows were invertebrates that fasten their cases or retreats by silk threads on the substrata. Invertebrate taxa having sucking apparatus or high swimming activity were also resistant to high flows.     

高原鼢鼠干扰下高寒草甸大型土壤动物多样性对环境因子的响应

为研究高寒草甸大型土壤动物群落组成和分布对环境因子的响应,选取祁连山东段的甘肃省天祝县高原鼢鼠典型分布区域,以鼠丘密度代表干扰强度设置4个干扰区。调查各干扰区植被群落特征、土壤理化性质、大型土壤动物类群组成及其数量,采用约束性排序方法分析环境因子对大型土壤动物类群组成和分布的影响。结果表明：高原鼢鼠干扰下高寒草甸大型土壤动物优势类群为瓦娄蜗牛科、象甲科和短角亚目幼虫;极重度干扰区大型土壤动物类群的丰度、丰富度、Shannon指数显著高于重度干扰区（P<0.05）;多元回归分析表明大型土壤动物类群丰度、丰富度和Shannon指数与土壤温度呈显著负相关（P<0.05）,丰富度与土壤含水量呈显著负相关（P<0.05）,丰度与土壤紧实度呈显著负相关（P<0.05）,丰富度和Shannon指数与植物Shannon指数呈显著负相关（P<0.05）;冗余分析和偏冗余分析表明,土壤温度、紧实度和含水量是影响高寒草甸大型土壤动物类群组成和分布的主要环境因子。     

Patterns in benthic food webs: a role for omnivorous crayfish?

1. The biomass and species richness of macrophytes and invertebrates in artificial ponds at two sites in southern Sweden (twenty-one ponds at each site) were investigated. Alkalinity was high at one site (H ponds) and low at the other site (L ponds). The ponds chosen had different densities of signal crayfish (Pacifastacus leniusculus), with mean crayfish abundance (estimated by trapping and expressed as catch per unit effort) significantly higher in the L ponds (10.7) than in the H ponds (4.9). Macrophytes, invertebrates, the amount of periphyton on stones and the organic content of the sediment were determined in each pond. 2. Macrophyte biomass, cover and species richness declined with increasing crayfish density. Macrophyte species composition differed between ponds and was related to crayfish abundance. 3. The total biomass of invertebrates and the biomass of herbivorous/detritivorous invertebrates declined with increasing crayfish abundance, but the biomass of predatory invertebrates declined only in the L ponds. The relative biomass of Gastropoda and Odonata declined in ponds where crayfish were abundant. In ponds where crayfish were abundant the invertebrate fauna was dominated by sediment-dwelling taxa (Sialis (H and L ponds) and Chironomidae (H ponds)). 4. The number of invertebrate taxa in macrophytes declined with increasing crayfish abundance. The percentage of macrophyte-associated invertebrate taxa differed between ponds, but also between sites. The relative biomass of Gastropoda declined in H ponds where crayfish were abundant. In H ponds Trichoptera or Gammarus sp. and Heteroptera dominated where crayfish were abundant, whereas Odonata dominated in L ponds with abundant crayfish. 5. The organic content of the sediment decreased in ponds with high crayfish densities, while the amount of periphyton on stones was not related to crayfish density. 6. We conclude that the signal crayfish may play an important role as a keystone consumer in pond ecosystems, but lower trophic levels did not respond to changes in the abundance of the crayfish according to the trophic cascade model. Omnivorous crayfish may decouple the cascading effect.     

Effects of substratum stability on diversity of stream invertebrates during baseflow at two spatial scales

1. The effects of substratum stability on the diversity of stream invertebrates were assessed at two spatial scales in a Japanese stream during baseflow, from May to June 1998. Deposition and erosion were examined separately as distinct elements of substratum stability by a newly developed method using small steel pins. Stream invertebrates were sampled after 28 days of measurement of substratum stability. We also measured physical environmental variables, current velocity and depth, and food resource parameters including periphyton and particulate organic matter (POM) standing crops.
2. At the scale of the habitat patch, the effects of substratum stability on invertebrates were overwhelmed by those of POM standing crop. Moreover, higher taxon richness at high abundance may simply result from a higher likelihood of more taxa being included in samples. Therefore, this small scale revealed no role for substratum stability in explaining spatial pattern of community diversity.
3. At the reach scale ( n =10), taxon richness and evenness peaked at an intermediate level of deposition, whereas invertebrate abundance did not show any significant relationship. This result, and the pattern of relative abundance of common taxa, implies that the diversity of stream invertebrates was determined by subtle substratum movements and by the habitat preference of each taxon.
4. The difference in the determinant of community parameters between the habitat patch and the reach affirm the importance of a cross-scale analysis to choose an appropriate spatial scale for investigating the community structure of stream invertebrates. Prominent effects of substratum stability, particularly the deposition of substratum particles, during baseflow suggest that subtle and constant movement of small substratum particles can contribute to determine the diversity of stream invertebrates.     

Skink and invertebrate abundance in relation to vegetation, rabbits and predators in a New Zealand dryland ecosystem

We explored the relationships between ground vegetation, ground fauna (native skinks and invertebrates), rabbits, and predators in a modified New Zealand dryland ecosystem. We hypothesised that vegetation cover would provide habitat for ground fauna. We also hypothesised that rabbits (Oryctolagus cuniculus) would reduce the abundance of these fauna by reducing vegetation, and by providing prey for mammalian predators (cats Felis catus and ferrets Mustela putorius) that consume ground fauna as secondary prey. We measured these variables at 30 sites across three pastoral properties in the South Island in 1996 and 2002. There were mostly positive relationships between vegetation ground cover and fauna captures in pitfall traps. Relatively few beetles and caterpillars were caught where cover was less than 80%, no millipedes were caught where cover was less than 70%, and few spiders and mostly no skinks, crickets, flies or slugs were caught where vegetation cover was less than 50%. Most grasshoppers were caught where cover ranged from 30 to 80%. Faunal species richness was also positively related to cover. This supports our hypothesis that ground vegetation provides habitat for skinks and invertebrates in this ecosystem. The introduction of rabbit haemorrhagic disease in 1997 provided a natural experiment to test the hypothesised indirect effects of rabbits on ground fauna. Declines in rabbits varied between properties, and vegetation cover and predator abundance changed according to the magnitude of these declines. However, skink and invertebrate abundance did not track these changes as expected, but instead varied more or less consistently between properties. Some fauna increased (skink captures quadrupled and cricket captures nearly doubled), others declined (flies, caterpillars and spiders), and some did not change (beetles, millipedes, slugs and grasshoppers, and faunal species richness and diversity). Therefore, rabbits, predators and vegetation did not affect changes in skinks and invertebrates in consistent ways. The dynamics of ground fauna are likely to be more influenced by factors other than those we measured.     

Diverse invertebrate fauna using dry sediment as a refuge in semi-arid and temperate Australian rivers

Dormant aquatic invertebrates can remain viable in riverbed sediment during dry phases, forming a source for recolonisation during wet periods. Regional differences in capacity for invertebrates to survive drying in this way are poorly understood, but may indicate regional differences in vulnerability to altered flow regimes. We compared diversity of invertebrates in dry sediment from intermittent rivers in temperate and semi-arid Australia after 4–8 weeks of drying. We predicted adaptations of semi-arid biota to severe and unpredictable drying would make dry sediment a more significant recolonisation source, with higher relative diversity when compared with temperate rivers. Emerging aquatic invertebrate assemblages were compared to those sampled in nearby pools, as a common drying refuge. Relative taxa richness in rehydrated sediments was higher in the semi-arid region (83 ± 16% of pool taxa) than the temperate (47 ± 6% of pool taxa), despite lower overall richness (24 taxa in semi-arid, 32 taxa in temperate). Semi-arid rivers had greater potential for dry riverbeds to act as a source for recolonisation, given high relative diversity and abundance in dry sediment, combined with the frequent absence of alternative refuges. However, dry riverbeds in both regions provided a significant short-term refuge for aquatic invertebrates.     

北京东灵山土壤动物多样性海拔格局的尺度推绎规律

识别群落内部各类群多样性格局的复杂性是生态学家面临的挑战,而尺度推绎规律是揭示复杂生态结构的有效途径之一。本研究利用多重分形的方法探索了不同海拔土壤动物多样性格局的尺度推绎规律,对比分析了凋落物层和土壤层之间多重分形谱的差异。结果表明: 与之前对植物群落的分析结果相似,土壤动物多样性尺度推绎规律同样具有幂律特征,如丰富度、Shannon多样性指数和Simpson多样性的倒数。凋落物层和土壤层中不同相对多度土壤动物的丰富度也具有幂律尺度推绎规律。凋落物层和土壤层中土壤动物多样性格局都具有多重分形特征,但凋落物层中多样性的分形结构比土壤层更均匀,且两层间优势类群与稀有类群的尺度推绎特征在多重分形谱上不同格局。幂律尺度推绎规律对于有着较高丰富度与多度的土壤动物同样存在,从而有助于揭示地下生物多样性的空间分布机制。     

Habitat formation prevails over predation in influencing fouling communities

Coastal human‐made structures, such as marinas and harbors, are expanding worldwide. Species assemblages described from these artificial habitats are novel relative to natural reefs, particularly in terms of the abundance of nonindigenous species (NIS). Although these fouling assemblages are clearly distinctive, the ecosystem functioning and species interactions taking place there are little understood. For instance, large predators may influence the fouling community development either directly (feeding on sessile fauna) or indirectly (feeding on small predators associated with these assemblages). In addition, by providing refuges, habitat complexity may modify the outcome of species interactions and the extent of biotic resistance (e.g., by increasing the abundance of niche‐specific competitors and predators of NIS). Using experimental settlement panels deployed in the field for 2.5 months, we tested the influence of predation (i.e., caging experiment), artificial structural complexity (i.e., mimics of turf‐forming species), and their interactions (i.e., refuge effects) on the development of sessile and mobile fauna in two marinas. In addition, we tested the role of biotic complexity—arising from the habitat‐forming species that grew on the panels during the trial—on the richness and abundance of mobile fauna. The effect of predation and artificial habitat complexity was negligible, regardless of assemblage status (i.e., native, cryptogenic, and nonindigenous). Conversely, habitat‐forming species and associated epibionts, responsible for biotic complexity, had a significant effect on mobile invertebrates (richness, abundance, and community structure). In particular, the richness and abundance of mobile NIS were positively affected by biotic complexity, with site‐dependent relationships. Altogether, our results indicate that biotic complexity prevails over artificial habitat complexity in determining the distribution of mobile species under low predation pressure. Facilitation of native and non‐native species thus seems to act upon diversity and community development: This process deserves further consideration in models of biotic resistance to invasion in urban marine habitats.     

Changes in the abundance and diversity of coastal wetland fauna from the open water/macrophyte edge towards shore

Great Lakes coastal wetlands are widely recognized as areas of concentrated biodiversity and productivity, but the factors that influence diversity and productivity within these systems are largely unknown. Several recent studies have suggested that the abundance and diversity of flora and fauna in coastal wetlands may be related to distance from the open water/macrophyte edge. We examined this possibility for three faunal groups inhabiting a coastal wetland in Saginaw Bay, Lake Huron. We sampled crustacean zooplankton and benthic macro-invertebrates at five distances from open water in the summer 1994, and fish at three distances from open water in 1994 and 1995. We found significant spatial trends in the total abundance and diversity of zooplankton and fish, as well as the diversity of benthic macro-invertebrates. Zooplankton abundance and taxa richness were highest at intermediate distances from open water in a transition zone between the well-mixed bayward portion of the wetland, and the non-circulating nearshore area. Benthic macro-invertebrate taxa richness increased linearly with distance from open water. In contrast, fish abundance and species richness declined linearly and substantially (abundance by 78%, species richness by 40%) with distance from open water. Of the 40 taxa examined in this study, 21 had significant horizontal trends in abundance. This led to notable differences in community composition throughout the wetland. Our results suggest that distance from open water may be a primary determinant of the spatial distributions of numerous organismal groups inhabiting this coastal wetland. Several possible reasons for these distributions are discussed.     

Temporal and Taxonomic Variability in Response of Fauna to Riparian Restoration

Evaluating the success of restoration projects requires well‐designed studies. Among the decisions that need to be made are what taxonomic groups to study and when to conduct the monitoring. To explore how these decisions can influence assessments of restoration success, we examined species richness and composition data collected over several years on different terrestrial fauna (landbirds, rodents, bees, and beetles) at Sacramento River restoration and remnant riparian sites. Our selection of study organisms enabled us to ask whether variability in species richness among restoration sites is less for vagile taxa than for sedentary taxa, and if invertebrates display greater variability among sites than vertebrates. Our results demonstrate that responses to restoration can vary depending upon the season when it is assessed, and the taxa that are studied. For all taxa except bees, there was considerable variability in the relative performance of taxa at restoration sites from one sampling date to the next, such that the relative ranking of the sites often changed dramatically. Comparisons of β ‐diversity (variability in species richness across sites) revealed that certain taxonomic groups were more spatially variable in their response to restoration than others. Among vertebrates, sedentary taxa (rodents) had significantly higher variability in species richness across sites than highly vagile taxa (birds); however, no such pattern was observed for invertebrates. Overall, vertebrates had lower variability than invertebrates, suggesting that evaluations of restoration success based on a few better‐known taxonomic groups (e.g., birds, rodents) may be inadequate to represent the biodiversity response of other groups (e.g., insects).     

Dynamics of the Leaf-Litter Arthropod Fauna Following Fire in a Neotropical Woodland Savanna

Fire is an important agent of disturbance in tropical savannas, but relatively few studies have analyzed how soil-and-litter dwelling arthropods respond to fire disturbance despite the critical role these organisms play in nutrient cycling and other biogeochemical processes. Following the incursion of a fire into a woodland savanna ecological reserve in Central Brazil, we monitored the dynamics of litter-arthropod populations for nearly two years in one burned and one unburned area of the reserve. We also performed a reciprocal transplant experiment to determine the effects of fire and litter type on the dynamics of litter colonization by arthropods. Overall arthropod abundance, the abundance of individual taxa, the richness of taxonomic groups, and the species richness of individual taxa (Formiciade) were lower in the burned site. However, both the ordinal-level composition of the litter arthropod fauna and the species-level composition of the litter ant fauna were not dramatically different in the burned and unburned sites. There is evidence that seasonality of rainfall interacts with fire, as differences in arthropod abundance and diversity were more pronounced in the dry than in the wet season. For many taxa the differences in abundance between burned and unburned sites were maintained even when controlling for litter availability and quality. In contrast, differences in abundance for Collembola, Formicidae, and Thysanoptera were only detected in the unmanipulated samples, which had a lower amount of litter in the burned than in the unburned site throughout most of our study period. Together these results suggest that arthropod density declines in fire-disturbed areas as a result of direct mortality, diminished resources (i.e., reduced litter cover) and less favorable microclimate (i.e., increased litter desiccation due to reduction in tree cover). Although these effects were transitory, there is evidence that the increasingly prevalent fire return interval of only 1–2 years may jeopardize the long-term conservation of litter arthropod communities.     

Hydraulic influences on periphyton and benthic macroinvertebrates: simulating the effects of upstream bed roughness

1. Hydraulic conditions, periphyton biomass and invertebrate communities were compared on artificial substrates exposed to a range of upstream roughness conditions across an area of uniform current velocity and depth in a gravel-bedded river. The effect of river bed roughness was simulated by installing roughness elements upstream of artificial substrates.
2. Increasing upstream roughness reduced the average near-bed velocity above the substrates and increased short-term variability in velocity (i.e. turbulence).
3. Periphyton chlorophyll a density showed a general decline with near-bed velocity and was significantly lower on the substrates exposed to the river bed reference and 0 mm roughness treatments than the 110 mm roughness elements. Chlorophyll a was also negatively correlated with the abundance of larger collector-browsing invertebrates. This indicates that effects of the changes in hydraulic conditions on invertebrates may have contributed to the observed treatment effects on periphyton.
4. Invertebrate abundance and diversity declined with increasing upstream roughness. Filter-feeders, collector-browsers and predatory invertebrates all declined in abundance with increasing upstream roughness, but the effect was strongest for filter-feeders. Eight of the nine most common taxa showed significant treatment effects. The orthoclad chironomid, Eukiefferiella sp., was not influenced strongly by upstream roughness, but its abundance was correlated significantly with periphyton biomass.     

Benthic invertebrate assemblage in Samborombón River (Argentina,S. America), a brackish plain river

The spatial and temporal differences in the structure and composition of benthic invertebrates were studied at three sites of the Samborombón River, which is an important tributary of the Río de la Plata Estuary (Argentina), having a low slope and brackish drainage. Biological samples were taken during each season. Physico-chemical variables were measured to determine their association in the benthic fauna distribution. Site 1, in the headstream, was characterized by freshwater Pampean organisms; site 2 showed the highest density, taxa diversity, and richness; brackish species, e.g., Laeonereis culveri, were found here. Site 3, close to the Samborombón Bay, was characterized by an unstable taxonomic composition that is strongly influenced by the estuary. The lowest density and taxonomic diversity of organisms were registered and distinguished by estuarine species. The multivariate method (redundancy analysis) showed the benthic groups having an important spatial variability, superimposed on the temporal variability, associated with the salinity gradient of the river.     

Hydraulic influences on periphyton and benthic macroinvertebrates: simulating the effects of upstream bed roughness

1. Hydraulic conditions, periphyton biomass and invertebrate communities were compared on artificial substrates exposed to a range of upstream roughness conditions across an area of uniform current velocity and depth in a gravel-bedded river. The effect of river bed roughness was simulated by installing roughness elements upstream of artificial substrates.
2. Increasing upstream roughness reduced the average near-bed velocity above the substrates and increased short-term variability in velocity (i.e. turbulence).
3. Periphyton chlorophyll a density showed a general decline with near-bed velocity and was significantly lower on the substrates exposed to the river bed reference and 0 mm roughness treatments than the 110 mm roughness elements. Chlorophyll a was also negatively correlated with the abundance of larger collector-browsing invertebrates. This indicates that effects of the changes in hydraulic conditions on invertebrates may have contributed to the observed treatment effects on periphyton.
4. Invertebrate abundance and diversity declined with increasing upstream roughness. Filter-feeders, collector-browsers and predatory invertebrates all declined in abundance with increasing upstream roughness, but the effect was strongest for filter-feeders. Eight of the nine most common taxa showed significant treatment effects. The orthoclad chironomid, Eukiefferiella sp., was not influenced strongly by upstream roughness, but its abundance was correlated significantly with periphyton biomass.     

Distribution,abundance and diversity of macrozoobenthos in Aiba Reservoir,Iwo, Nigeria

Spatial and seasonal variation in macrozoobenthic composition, abundance and diversity in Aiba Reservoir were investigated bimonthy between June 2004 and April 2005 using a van Veen grab. A depauperate fauna of nine taxa was recorded. Generally, larger numbers of taxa were recorded during the dry season than in the wet season. Melanoides tuberculata and chironomid larvae dominated the macrozoobenthos and showed wide spatial distribution. Diversity and evenness were lower during the wet season than in the dry season, when densities of the major species were low. Melanoides tuberculata and chironomid larvae were recorded from maximum depths of 3.9 m and 2.6 m, respectively. Both taxa were also recorded from all substrate texture types, regardless of the amount of macrophyte material present. The benthic fauna is characterised as being poor in terms of density, taxonomic richness and diversity     

Relationship between invertebrate fauna and bromeliad size.

Several bromeliads species store water and organic substrates, allowing the establishment of phytotelmata and associated fauna on their leaves. In this study, we sampled 70 individuals of Vriesea sp. (Carrière) (Bromeliaceae), in rupestrian fields in the Serra de Ouro Branco-MG, Brazil. The relationships between invertebrate species richness and abundance and size of bromeliads were tested using multiple regression. We found 19 species associated with bromeliads, mainly Diptera larvae. The abundance of the phytotelmate fauna increased principally in relation to the volume of water in the bromeliad reservoir. Phytotelmata richness was affected principally by diameter of the reservoir. There was a significant relationship between the abundance and richness of invertebrates associated with leaves with diameter and height of the plant. Invertebrate richness was better explained by abundance of individuals. These results suggest that the increase of richness was attended by higher numbers of microhabitats and more space for colonization of bigger bromeliads. Additionally, there was more chance of sampling different species in locales with greater abundance of individuals.     

Diversity,Abundance and Community Structure of Benthic Macro- and Megafauna on the Beaufort Shelf and Slope

Diversity and community patterns of macro- and megafauna were compared on the Canadian Beaufort shelf and slope. Faunal sampling collected 247 taxa from 48 stations with box core and trawl gear over the summers of 2009–2011 between 50 and 1,000 m in depth. Of the 80 macrofaunal and 167 megafaunal taxa, 23% were uniques, present at only one station. Rare taxa were found to increase proportional to total taxa richness and differ between the shelf ( 100 m) where they tended to be sparse and the slope where they were relatively abundant. The macrofauna principally comprised polychaetes with nephtyid polychaetes dominant on the shelf and maldanid polychaetes (up to 92% in relative abundance/station) dominant on the slope. The megafauna principally comprised echinoderms with Ophiocten sp. (up to 90% in relative abundance/station) dominant on the shelf and Ophiopleura sp. dominant on the slope. Macro- and megafauna had divergent patterns of abundance, taxa richness ( diversity) and diversity. A greater degree of macrofaunal than megafaunal variation in abundance, richness and diversity was explained by confounding factors: location (east-west), sampling year and the timing of sampling with respect to sea-ice conditions. Change in megafaunal abundance, richness and diversity was greatest across the depth gradient, with total abundance and richness elevated on the shelf compared to the slope. We conclude that megafaunal slope taxa were differentiated from shelf taxa, as faunal replacement not nestedness appears to be the main driver of megafaunal diversity across the depth gradient.     

Regional‐scale patterns and predictors of species richness and abundance across twelve major tropical inter‐reef taxa

Species richness and abundance are biodiversity metrics widely used to describe and estimate changes in biodiversity. Studies of marine species richness and abundance typically focus on one, or just a few, taxa. Consequently, it is currently not possible to understand the performance of predictors of species richness and abundance across marine taxa. Using a taxonomically comprehensive dataset of twelve major taxa of flora and fauna from eight phyla sampled from the inter‐reef seabed region of the Great Barrier Reef, Australia, we used boosted regression trees to test the performance of fourteen environmental and spatial predictors of species richness and abundance. Sediment composition predicted richness best for all taxa: gravel contributed up to 39% relative influence for one group and all taxa had low richness in muddy habitats. Sea surface temperature, seabed current shear stress, depth and latitude were also influential predictors for species richness for eight groups. Sediment was frequently an influential predictor for abundance also, while distance to domain (reef/coast) and longitude were relatively influential for six taxa. Within‐site richness was correlated between nearly all pairs of taxa, as was within‐site abundance, however ρ values were low. Overall, model performance was high, explaining up to 62% deviance of species richness, and 38% of abundance. Typically, deviance explained was greater for richness than abundance and may indicate that some drivers of species richness operate independently of any effects on species richness mediated by their effect on abundance. Deviance explained differed most between richness and abundance for bryozoans (23.3% difference) and soft corals (15.2% difference). While sediments were consistently the best predictors across all taxa, the inconsistent influence of all other predictors across taxonomic groups, as well as the low correlation of richness and abundance across taxonomic groups, cautions against predicting regional patterns of species richness and abundance from few taxa.     

Benthic macro- and meso-invertebrates of a sandy riverbed in a mountain stream, central Japan

Quantitative samples of benthic invertebrates were collected from a sandy riverbed of a mountainous stream (Kozu site of Takami-gawa stream, Nara Prefecture), central Japan by core samplers in five sampling occasions through the years 2008–2009. A total of 120 taxa were identified, representing 55 families and 97 genera. Insects formed about 92% of the total recorded taxa and 88% of individuals’ abundance. A total of 111 taxa of aquatic insects, belonging to 49 families and 92 genera, were identified and represented by ten orders. Oligochaeta and Acari were dominant non-insect invertebrates. Diptera was the most diverse insect group, followed by Trichoptera and Ephemeroptera. Dominant taxa were mesoinvertebrates, younger stages of macroinvertebrates, both of which predominantly inhabit the interstitial zone of a sandy riverbed. Both taxon richness and invertebrate abundance were higher in February 2009 and lower in April and August 2008. A few major invertebrate taxa demonstrated distinct seasonal trends; i.e. Nymphomyia alba, Rheosmittia, and Corynoneura were abundant in February 2009. Newly hatched larvae of Larcasia akagiae were abundant in May 2008. This study also demonstrated the effectiveness of core samplers to collect small-sized benthic fauna that inhabit the interstitial or hyporheic zone of the sandy riverbed.