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.     

Do intruding predators and trap position affect the reliability of catches in activity traps?

Forty lakes in Sweden and Finland were sampled in 1990 with activity traps to evaluate the effects of trapped predators on invertebrate catch. Vertebrate (fish, newts) and invertebrate (leeches, dragonflies, water beetles, backswimmers and water scorpions) predators were considered separately. Invertebrate predators affected neither the abundance nor the taxonomic diversity of the catches. Vertebrate predators had no effect on the abundance but reduced the taxonomic diversity of the catches significantly. Thus, vertebrate predators are a possible source of bias in activity trap catches, but only concerning taxonomic diversity. Within the depth gradient studied (0.25–0.75 m), trap position (suspended in mid-water versus on the bottom) did not affect the percentages of nektonic and benthic invertebrates in the catches. The relative abundance of all taxa was similar in the catches from different trap positions, but the relative abundance of the most numerous taxa as well as the diversity of the catches differed between trap positions. We conclude that both mid-water and bottom traps are suitable for monitoring aquatic invertebrates, and that bottom traps may be preferred for practical reasons.     

Reduced abundance of insects and spiders linked to radiation at Chernobyl 20 years after the accident

Effects of low-level radiation on abundance of animals are poorly known. We conducted standardized point counts and line transects of bumble-bees, butterflies, grasshoppers, dragonflies and spider webs at forest sites around Chernobyl differing in background radiation by over four orders of magnitude. Abundance of invertebrates decreased with increasing radiation, even after controlling for factors such as soil type, habitat and height of vegetation. These effects were stronger when comparing plots differing in radiation within rather than among sites, implying that the ecological effects of radiation from Chernobyl on animals are greater than previously assumed.     

Is there intraguild predation between winter-active spiders (Araneae) on apple tree bark?

We studied whether there si intraguild predation among overwintering invertebrates in bark traps installed on apple trees. We found that 86% of the overwintering invertebrates in traps were predators, which were dominated by spiders (72%) of different guilds and different body sizes. Spiders had spatially segregated in the traps so that smaller specimens hid in an interstitial space that was inaccessible to larger specimens. Spiders of the bark-dwelling guild, Anyphaena and Philodromus, are winter-active and can prey on other smaller spiders. Analysis of their abundance in traps indicated a negative relationship between Anyphaena and Philodromus or other spiders. Inspection of traps during winter revealed an influx of spider specimens confirming their winter-activity. In a semi-field experiment, where overwintering in cardboard bands was studied under controlled conditions, we observed mortality of both winter-active Philodromus and Anyphaena spiders due to their interspecific predation. The mortality was affected by their size ratio – larger specimens consumed smaller ones. Presence of alternative prey, theridiid spiders, did not affect their mortalities, but the presence of shelters (interstitial spaces) did. In boards with interstitial spaces smaller spiders suffered lower mortality than in boards without the interstitial spaces. Obtained results suggest that intraguild predation between overwintering spiders can decrease their population density during winter.     

Landscape-scale Variation in Taxonomic Diversity in Four Groups of Aquatic Organisms: The Influence of Physical, Chemical, and Biological Properties

We evaluated several factors influencing the taxonomic richness of macrophytes, benthic invertebrates, snails, and fish in a series of northern Wisconsin lakes. We chose the study lakes to decouple the potential effects of ionic strength of lake water and stream connection, two factors that are usually highly correlated and therefore have been confounded in previous studies. In addition, our study lakes covered a wide range in a variety of characteristics, including residential development, abundance of exotic species, nutrient concentrations, predator abundance, and lake size. Species richness within each of the four taxonomic groups was significantly positively related to ionic strength (as measured by specific conductance); we also found secondary associations with other variables, depending on the specific group of organisms. The relationship between richness and lake area was dependent on the specific conductance of the lake and the vagility of the organisms; less vagile groups of organisms showed stronger and steeper species–area relationships in low-conductivity lakes. Further, after variance owing to specific conductance was removed, the presence of stream connections was positively related to species richness for fish, snails, and macrophytes as well as familial richness in benthic invertebrates. Our results indicate that lakes with relatively more groundwater input have lower extinction rates for all four groups of taxa and that lakes with stream inlets and outlets have enhanced immigration rates for fish, snails, benthic invertebrate families, and macrophytes. These findings link processes of immigration and extinction of four groups of organisms of varying vagility to landscape-level hydrologic characteristics related to the glacial history of the region.     

Efficiency of bio-indicators for low-level radiation under field conditions

Relatively little is known about biological consequences of natural variation in background radiation, and variation in exposure due to nuclear accidents, or even the long term consequences to human health stemming from the over-use of nuclear medicine and imaging technologies (i.e. CAT scans). This realization emphasizes the need for assessment and quantification of biological effects of radiation on living organisms. Here we report the results of an environmental analysis based on extensive censuses of abundance of nine animal taxa (spiders, dragonflies, grasshoppers, bumblebees, butterflies, amphibians, reptiles, birds, mammals) around Chernobyl in Ukraine and Belarus during 2006–2009. Background levels of radiation explained 1.5–26.5% of the variance in abundance of these nine taxa, birds and mammals having the strongest effects, accounting for a difference of a factor 18 among taxa. These effects were retained in analyses that accounted for potentially confounding effects. Effect size estimated as the amount of variance in abundance explained by background level of radiation was highly consistent among years, with weaker effects in years with low density. Effect sizes were greater in taxa with longer natal dispersal distances and in taxa with higher population density. These results are consistent with the hypotheses that costs of dispersal (i.e. survival) were accentuated under conditions of radioactive contamination, or that high density allowed detection of radiation effects. This suggests that standard breeding bird censuses can be used as an informative bio-indicator for the effects of radiation on abundance of animals.     

Species richness and abundance of forest birds in relation to radiation at Chernobyl

The effects of low-level radiation on the abundance of animals are poorly known, as are the effects on ecosystems and their functioning. Recent conclusions from the UN Chernobyl forum and reports in the popular media concerning the effects of radiation from Chernobyl on animals have left the impression that the Chernobyl exclusion zone is a thriving ecosystem, filled with an increasing number of rare species. Surprisingly, there are no standardized censuses of common animals in relation to radiation, leaving the question about the ecological effects of radiation unresolved. We conducted standardized point counts of breeding birds at forest sites around Chernobyl differing in level of background radiation by over three orders of magnitude. Species richness, abundance and population density of breeding birds decreased with increasing level of radiation, even after controlling statistically for the effects of potentially confounding factors such as soil type, habitat and height of the vegetation. This effect was differential for birds eating soil invertebrates living in the most contaminated top soil layer. These results imply that the ecological effects of Chernobyl on animals are considerably greater than previously assumed.     

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.     

The influence of environmental management and animal shelters in vector control of Culicoides (Diptera,Ceratopogonidae) in northeastern Brazil

We investigated whether biting midges in peridomestic environments are affected by environmental management practices and the presence of domestic animals. We used CDC light traps to collect midges in 112 residences across 24 locations along tourism routes of Maranhão, Brazil. The collection areas were characterized as follows: i) peridomestic area with domestic animals and without management (dirty); ii) peridomestic with domestic animals and management (clean); iii) peridomestic without animals and with management (clean); iv) peridomestic without animals and without management (dirty). The first two treatments had higher biting midge species richness and abundance, respectively. Generalized linear models indicated a positive correlation between the presence of domestic animals and midge abundance, with an approximate four‐fold increase in Culicoides (Diptera: Ceratopogonidae) abundance in peridomestic areas with animals. The same model showed that domestic animals have no influence on richness. Environmental management does not appear to influence species richness or abundance of biting midges.     

Controls on marine animal biomass through geological time

Total animal biomass depends on four factors: (1) food supply, (2) the efficiency with which animals consume available food, (3) the efficiency with which animals convert consumed food into biomass, and (4) the rate at which animals lose biomass to the environment through respiration or death. Each of these factors may change through geological time because each is a function of animal ecology and physiology. Animal ecology and physiology, in turn, are products of interacting evolutionary and environmental factors. The direction of change in animal biomass through time may be predicted given knowledge of environmental and ecological change. At a finer level, physiological differences among phyla or other higher taxa suggest that they would have had differential responses to specific environmental changes. Physiological features shared by all of life, such as the dependence of metabolic rate on ambient temperature, suggest that even a coarse time‐series of relative changes in animal biomass may enrich understanding of biogeochemical cycling among all organisms, including phytoplankton and microbes. Changes in the abundance of skeletal material in shallow marine deposits through geological time indicate that the biomass of benthic skeletal invertebrates has fluctuated significantly on timescales from millions to hundreds of millions of years. During the Ordovician radiation, increase in the complexity of animal food webs and increase in the efficiency of animal communities in removing available food from the water column and sediment appear most likely to account for a secular increase in animal biomass. Decrease in animal biomass after the end‐Permian extinction appears to have been driven by a combination of factors but particularly decreased aggregate growth efficiency and consumption efficiency. Comparing biomass and diversity trends through other major transitions in the history of animal life has the potential to shed light on the relationship between physical environmental change and ecosystems evolution.     

Impacts on invertebrate fungivores: a predictable consequence of ground-cover weed invasion?

Empirical impact evidence exists for few of New Zealand’s environmental weeds. Financial constraints prevent managers examining all impacts of all weeds. Therefore it is useful to seek generalisable rules which allow managers to predict impacts of new invasions. Invasive weeds may indirectly affect fungivorous invertebrates through mechanisms such as altered litter-fall, decomposition rates, and microclimate, all of which may alter fungal activity. I tested the hypothesis that fungivorous invertebrates would be consistently affected by three invasive weeds, and that this effect would be more pronounced than for other invertebrate functional groups. Using pitfall traps, I compared invertebrates beneath climbing asparagus, tradescantia and ginger with invertebrates of uninvaded lowland forest. Five out of six Coleoptera taxa which differed in abundance between invaded and uninvaded sites were fungivores; the remaining taxon was a saprophage. At least two taxa of fungivorous Coleoptera responded to each of the three weed species. Acari (mainly Oribatids, some of which are fungivores), Isopoda and Amphipoda (decomposers) were the only taxa to respond to the presence of all three weed species. These results provide some support for the hypothesis that fungivores are particularly responsive to ground-cover weed invasion, but suggest this could be extended to include decomposers as well. However, the direction of effect differed among weed species. Therefore, while changes in fungivore and decomposer abundance may be predicted as one of the more likely consequences of ground-cover weed invasion in New Zealand low-land forest, site- and taxa-specific effects make it difficult to predict the direction of effect.     

Are nesting seabirds important determinants of invertebrate community composition on subantarctic Adams Island?

Nesting seabirds import marine-derived nutrients into terrestrial food webs, affecting invertebrate abundance and community composition directly, through provision of decaying animal matter as a food source, and indirectly through effects on vegetation and prey abundance. Invertebrates have shown strong responses to seabird presence in some, but not all, ecosystems previously studied. In contrast to mainland range contractions, New Zealand’s subantarctic islands retain abundant seabird populations. We sampled ground invertebrates on mammal-free Adams Island, using pitfall traps. We surveyed sites in two vegetation types (tussock and forest) with either no nesting seabirds or nesting colonies of Gibson’s wandering albatross, sooty shearwaters or white-headed petrels. We collected 11 invertebrate orders and identified 20 Coleoptera species or higher taxa. The carrion beetle, Paracatops antipoda comprised over 50 % of Coleoptera individuals collected. P. antipoda was more abundant in forest than tussock and was positively associated with sooty shearwaters and negatively associated with white-headed petrels when compared with bird-free sites using a Poisson generalized linear model. Sooty shearwaters were also associated with elevated abundance of several herbivorous and invertebrate decomposer taxa. Nesting seabirds do appear to influence invertebrate community composition on Adams Island, but the direction of this effect appears to be taxa-specific. Further sampling with spatial replication of colonies is required to determine the extent to which these apparent taxa-specific responses are consistent across colonies and habitats.     

Patch- and reach-scale dynamics of a macrophyte-invertebrate system in a New Zealand lowland stream

Abundant growths of macrophytes are a common feature of streams in open lowland areas of New Zealand during summer, but the values of these to aquatic biota are poorly understood. We studied the temporal dynamics of, and associations amongst, elements of a macrophyte-invertebrate system to provide an improved information base for lowland stream management. The biomass of macrophytes increased significantly over the four quarterly sampling occasions from 43.8 g m^-2 in June to 370.8 g m^-2 in March; biomass was dominated by Egeria densa on all dates, except in December when Potamogeton crispus was dominant. We did not detect strong associations between epiphyton biomass and invertebrate abundance in our study, but this may reflect the fact that we sampled loosely-adhering epiphyton on young, surface-reaching shoots whereas invertebrates were collected from macrophytes growing through the water column. Density of some invertebrate species per gram dry weight of plant material varied by macrophyte type, with the chironomids Tanytarsus vespertinus and Naonella forsythi displaying positive correlations with Egeria and Potamogeton biomass, respectively. The shrimp Paratya curvirostris accounted for 50% of phytophilous invertebrate biomass, with Chironomidae the only other group to comprise more than 9%. Abundance of total phytophilous invertebrates displayed a positive linear relationship with macrophyte biomass in a sample (0.1 m²), and a humped relationship with species richness, such that highest numbers of taxa occurred at macrophyte biomass levels around 400 g dw m^-2. Our study suggests that intermediate macrophyte biomass levels are likely to enhance macroinvertebrate biodiversity in sandy-bottomed lowland streams. This revised version was published online in July 2006 with corrections to the Cover Date.     

Invertebrate dispersal and habitat heterogeneity: Expression of biological traits in a seagrass landscape

Seagrass meadows harbour diverse faunal assemblages, but the relative importance of landscapes attributes, settlement processes and biological traits of individual species for recruitment patterns is poorly understood. To quantify the influence of habitat heterogeneity on larval, juvenile and adult post-larval dispersal, invertebrates (> 125 µm) were collected in benthic settlement traps at five occasions (June-August) in three habitats; continuous seagrass, seagrass patches and bare sand. The study was carried out by SCUBA diving in a subtidal (2.5 m depth) seagrass landscape dominated by Zostera marina L. in the Baltic Sea. Traps collected totally > 30 taxa, with non-significant effects of habitat on species richness and total abundance. Total number of invertebrates exhibited strong temporal variability, probably driven by wind-induced bedload and water column transport. Surprisingly, traps located in small (< 12 m²) patches contained on average almost twice as many individuals as traps located in the continuous vegetation. Dominating taxa such as nematodes, copepods, and oligochaetes were found in similar densities across the landscape. In contrast, location within the landscape had strong effects on bivalve settlement and redistribution patterns, resulting in significantly lower densities in continuous vegetation compared to patches and bare sand. A biological trait analysis indicated that semi-mobile taxa with annual protracted direct development, and short-distance dispersal are probably of higher importance for the community assembly process in this environment than long-distance larval dispersal. Results suggest that seagrass landscapes are highly dynamic environments, characterized by time and species-specific effects of landscape attributes on animal dispersal and recruitment. A conceptual model illustrating interactions between settling larvae and landscape heterogeneity is presented.     

Does time since introduction influence enemy release of an invasive weed?

Release from natural enemies is considered to potentially play an important role in the initial establishment and success of introduced plants. With time, the species richness of herbivores using non-native plants may increase [species-time relationship (STR)]. We investigated whether enemy release may be limited to the early stages of invasion. Substituting space for time, we sampled invertebrates and measured leaf damage on the invasive species Senecio madagascariensis Poir. at multiple sites, north and south of the introduction site. Invertebrate communities were collected from plants in the field, and reared from collected plant tissue. We also sampled invertebrates and damage on the native congener Senecio pinnatifolius var. pinnatifolius A. Rich. This species served as a control to account for environmental factors that may vary along the latitudinal gradient and as a comparison for evaluating the enemy release hypothesis (ERH). In contrast to predictions of the ERH, greater damage and herbivore abundances and richness were found on the introduced species S. madagascariensis than on the native S. pinnatifolius. Supporting the STR, total invertebrates (including herbivores) decreased in abundance, richness and Shannon diversity from the point of introduction to the invasion fronts of S. madagascariensis. Leaf damage showed the opposite trend, with highest damage levels at the invasion fronts. Reared herbivore loads (as opposed to external collections) were greater on the invader at the point of introduction than on sites further from this region. These results suggest there is a complex relationship between the invader and invertebrate community response over time. S. madagascariensis may be undergoing rapid changes at its invasion fronts in response to environmental and herbivore pressure.     

Ectomycorrhizal fungal communities of Quercus liaotungensis along local slopes in the temperate oak forests on the Loess Plateau, China

Topographic factors strongly affect the diversity of plants and local environmental conditions, yet little is known about their effects on the distribution of ectomycorrhizal fungi (EMF). By combining morphological and molecular identification methods, we investigated the relationship between EMF communities of Quercus liaotungensis and topographic factors along local slopes in the temperate oak forest on the Loess Plateau of northwest China. ITS-RFLP analysis revealed a high diversity of EMF taxa (135 taxa) associated with Q. liaotungensis along three local slopes. EMF communities among slope sites or slope positions, tended to share major common EMF species, which accounted for more than 80 % of the total EMF abundance, and showed a diverse distribution, which mainly related to rare species. Ordination analyses showed that EMF taxa distribution was significantly correlated with several environmental variables (slope site, slope position, slope gradient, and soil C:N). Topography-mediated changes of environmental conditions may be important determinants of the distribution of EMF taxa along local slopes (slope position and slope site) in the central Loess Plateau.     

Cross-depth analysis of marine bacterial networks suggests downward propagation of temporal changes

Interactions among microbes and stratification across depths are both believed to be important drivers of microbial communities, though little is known about how microbial associations differ between and across depths. We have monitored the free-living microbial community at the San Pedro Ocean Time-series station, monthly, for a decade, at five different depths: 5 m, the deep chlorophyll maximum layer, 150 m, 500 m and 890 m (just above the sea floor). Here, we introduce microbial association networks that combine data from multiple ocean depths to investigate both within- and between-depth relationships, sometimes time-lagged, among microbes and environmental parameters. The euphotic zone, deep chlorophyll maximum and 890 m depth each contain two negatively correlated ‘modules'' (groups of many inter-correlated bacteria and environmental conditions) suggesting regular transitions between two contrasting environmental states. Two-thirds of pairwise correlations of bacterial taxa between depths lagged such that changes in the abundance of deeper organisms followed changes in shallower organisms. Taken in conjunction with previous observations of seasonality at 890 m, these trends suggest that planktonic microbial communities throughout the water column are linked to environmental conditions and/or microbial communities in overlying waters. Poorly understood groups including Marine Group A, Nitrospina and AEGEAN-169 clades contained taxa that showed diverse association patterns, suggesting these groups contain multiple ecological species, each shaped by different factors, which we have started to delineate. These observations build upon previous work at this location, lending further credence to the hypothesis that sinking particles and vertically migrating animals transport materials that significantly shape the time-varying patterns of microbial community composition.     

Symbiotic interactions in the Silurian of Baltica

Thirteen symbiotic associations occur in the Silurian of Baltica. Symbiosis was especially prominent among colonial animals, most commonly with stromatoporoids. These sponges hosted the most diverse fauna of endobiotic symbionts (including rugosans, Syringopora, ‘polychaetes’, cornulitids and lingulids). This pattern can be explained by the abundance of stromatoporoids in the Silurian of Baltica and their large skeletal volume, making them attractive hosts for smaller invertebrates. There is an evolutionary trend of an increasing number of different pairs of symbiotic taxa from the Llandovery to the Ludlow, with a remarkable increase in the Ludlow. This is likely related to an increase in the number of mutualistic taxa that could have had evolutionary advantages over organisms less amenable to symbiosis. The number of different pairs of symbiotic taxa also increased in the Wenlock, which may be linked to delayed recovery from the end‐Ordovician mass extinction.     

Long‐term patterns of invertebrate abundance and relationships to environmental factors in arid Australia

Resource pulses are a key feature of semi‐arid and arid ecosystems and are generally triggered by rainfall. While rainfall is an acknowledged driver of the abundance and distribution of larger animals, little is known about how invertebrate communities respond to rain events or to vegetative productivity. Here we investigate Ordinal‐level patterns and drivers of ground‐dwelling invertebrate abundance across 6 years of sampling in the Simpson Desert, central Australia. Between February 1999 and February 2005, a total of 174 381 invertebrates were sampled from 32 Orders. Ants were the most abundant taxon, comprising 83% of all invertebrates captured, while Collembola at 10.3% of total captures were a distant second over this period. Temporal patterns of the six invertebrate taxa specifically analysed (Acarina, ants, Araneae, Coleoptera, Collembola and Thysanura) were dynamic over the sampling period, and patterns of abundance were taxon‐specific. Analyses indicate that all six taxa showed a positive relationship with the cover of non‐Triodia vegetation. Other indicators of vegetative productivity (seeding and flowering) also showed positive relationships with certain taxa. Although the influence of rainfall was taxon‐dependent, no taxon was affected by short‐term rainfall (up to 18 days prior to survey). The abundance of Acarina, ants, and Coleoptera increased with greater long‐term rainfall (up to 18 months prior to survey), whilst Araneae showed the opposite effect. Temperature and dune zone (dune crest vs. swale) also had taxon‐specific effects. These results show that invertebrates in arid ecosystems are influenced by a variety of abiotic factors, at multiple scales, and that responses to rainfall are not as strong or as predictable as those seen for other taxa. Our results highlight the diversity of invertebrates in our study region and emphasize the need for targeted long‐term sampling to enhance our understanding of the ecology of these taxa and the role they play in arid ecosystems.     

Species–area relationship within benthic habitat patches of a tropical floodplain river: An experimental test

The curvilinear relationship between species richness and habitat area (species–area relationship (SAR)) is a fundamental ecological pattern. The relationship is often viewed from a long‐term perspective across relatively large spatial scales, reflecting a balance between immigration and extinction dynamics. We explored whether predictions of SAR also manifest over short time periods (days) in benthic habitat patches of a dynamic floodplain river where littoral faunal assemblages are continuously assembled and disassembled with changing water levels. We examined the relationship of patch size with faunal abundance (i.e. fish and aquatic invertebrates), taxonomic richness, trophic group richness and overall assemblage composition. Strong taxa–area relationships emerged despite the relatively short experimental time period (21 days); larger patches had more taxa and trophic groups. For the smallest patches, taxonomic richness was especially sensitive to abundance of individuals; abundance of individuals was a less important predictor of taxonomic and trophic group richness for the largest patches. Despite the relatively short time frame for study within this temporally dynamic ecosystem, our findings indicate a strong SAR for fishes and macroinvertebrates inhabiting patchy habitats in the littoral zone of this tropical river.