Phytotelmata colonization in bamboo (Guadua sp.) culms in northeast Argentina

This study aimed to determine the susceptibility of stumps and internodes of bamboos to colonization by different types of macroinvertebrates and the formation of communities of different complexity. Semi-controlled field studies were carried out in a subtropical area of Argentina to analyse community structure, species richness of the aquatic macroinvertebrate communities and co-occurrences of predators and prey to delineate the food webs. Water-filled bamboos were sampled every season during a year by removing, without replacing, all water and macroinvertebrates. This study shows that the variation in the morphology of the container provides different resources, leading to segregation of species per container type, and allowing each of them to establish aquatic communities with differences in diversity. The Diptera was best represented in the communities of bamboos, where Culicidae showed the highest species richness and Ceratopogonidae were the most abundant numerically. Eleven taxa were present in both phytotelmata, 12 were unique in internodes and 13 in stumps. The community in internodes was composed of 21 taxa where mosquitoes were represented by Sabethini and Toxorhynchitini. By contrast, stumps were colonized by 24 taxa and Ceratopogonidae were numerically dominant. Regarding food webs established in stumps and internodes, no differences in length were found, except for the species that played equivalent roles in each of the studied phytotelmata.     

Winter macroinvertebrate communities in two montane Wyoming streams

Macroinvertebrate communities were examined on 4 winter dates over a 4-yr period in 2 high-altitude Rocky Mountain streams to document overwintering assemblages potentially experiencing spring acid pulses. Taxa richness values were comparable to other published lists for alpine and montane stream systems despite the fact that most literature reflected summer collections. Mean benthic density ranged from 1406 to 19,734 organisms/m 2 , and drift rates ranged from 0 to 1740 organisms/100 m 3 . Benthic collections showed higher taxa richness than drift collections while the Ephemeroptera and Plecoptera occurred in greater proportions in drift than in benthos. The Nemouridae (Plecoptera), Ephemerellidae and Heptageniidae (Ephemeroptera), Chironomidae (Diptera), and Hydracarina were the numerically dominant taxa in benthic collections. Grazer/scrapers and shredder/detritivores were always the numerically dominant functional feeding groups at all sites, composing 60-90% of the benthos. Predators, constituting approximately 15% of the community, occurred in the same relative proportion at all sites on all dates. Winter macroinvertebrate communities in these low-order, montane streams exhibit high taxonomic richness and benthic densities as great as lower-elevation mountain streams in the West.     

Aquatic macroinvertebrate assemblages associated with root masses of water hyacinths,Eichhornia crassipes (Mart.) Solms-Laubach, 1883 (Commelinales: Pontederiaceae) in Taabo Lake,Ivory Coast

We examined aquatic macroinvertebrates associated with Eichhornia crassipes roots at five sampling sites in Taabo Lake. An average density of 1644 individuals (ind.)/m² was recorded. In total, 68 macroinvertebrate taxa belonging to 34 families and 14 orders were identified. Among these, Insecta was predominant (77.94%). The highest densities were recorded at Taabo cité during both rainy and dry seasons. Taxon diversity differences were not observed among all stations according to a Kruskal–Wallis test. High densities of predators were recorded. Next most prevalent in the trophic structure were detritivores. Indicator taxa analysis, using the Indval method, showed that stations upstream of the lake were characterized by eight taxa, while 11 appeared as indicators of the station near the dyke. Predators and herbivores dominated within those indicators. Sites near bays were distinguished by 18 indicator taxa with a predominance of predators and detritivores. Conductivity, NH₄ ⁺, temperature, PO₄ ^3?, turbidity and dissolved oxygen were parameters that strongly influenced the macroinvertebrate community.     

Longitudinal development of macroinvertebrate communities below oligotrophic lake outlets

Benthic macroinvertebrates were collected at several sites downstream of three oligotrophic lake outfalls in July 1986. Total numbers, biomass, and species richness increased rapidly immediately downstream from the outlets and then either stabilized or continued to increase downstream in parallel with benthic organic matter standing crops. Filter feeder densities showed an initial buildup and then decline downstream from the outlets. Variability in longitudinal patterns of other functional feeding groups among lake outlets was related to differences in food quantity and quality, and microhabitat. An additional set of samples was collected at Pettit Lake outlet in August 1986. Species richness and total density peaked sooner under baseflow conditions in August than under spring runoff conditions in June. Distributions of all functional feeding groups, except filter feeders, also differed between the two periods, reflecting differences in the physical environment. We conclude that reduced lentic inputs of particulate organic matter seston and improved habitat suitability downstream are responsible for the progressive development of macroinvertebrate communities in oligotrophic lake outlets. These data imply the importance of the habitat templet in the structuring of benthic communities.     

Effects of livestock grazing exlosure on aquatic macroinvertebrates in a montane stream, New Mexico

Aquatic macroinvertebrate populations inhabiting reaches of a stream within areas excluded from livestock grazing for a decade were markedly different from those in grazed areas when density, biomass, biotic condition indices, and mean chi square indices of the two populations were compared. Increased densities and biomasses of more tolerant forms of macroinvertebrates were observed in grazed reaches. Because pretreatment data were not available, differences in macroinvertebrate populations and relative tolerances of taxa in grazed and ungrazed areas could be as easily attributed to linear changes in stream habitat as to removal of domestic livestock. Results of this study have implications for the design of future research on the effects of livestock grazing on stream environments and biota: (1) baseline/pretreatment information is prerequisite, and (2) the study should take a watershed (ecosystem) approach.     

Influence of fine sediment on macroinvertebrate colonization of surface and hyporheic stream substrates

Colonization of macroinvertebrates was assessed in a stream impacted by inputs of fine sediments. Colonization was examined at the stream surface and within the hyporheos with Whitlock-Vibert (W-V) boxes. Hyporheic areas accumulated much greater amounts of all size categories of sediment. No significant difference was observed in the amounts of organic matter accumulated at either depth. Only 150-μm sediment had significant effects on macroinvertebrate total numbers and number of taxa. Total numbers of invertebrates at 30 cm were only 20% of those at the surface. Canonical Correspondence of Analysis indicated that the strongest influence on macroinvertebrates colonizing W-V boxes at the surface was stream size and secondarily fine sediments. Within the hyporheos, abundance of fine sediment was the dominant influence on macroinvertebrate assemblages. Impacts of sedimentation on hyporheic environments can have significant and persistent impacts on streams.     

Disentangling prey-handling efficiency of larval newts through multivariate prey trait analysis

Multivariate prey trait analysis is a functional approach to understand predator–prey relationships. In the present study, six prey macroinvertebrate ecological traits were used to identify several key factors in the handling efficiency of seven predatory larval newt species. The results revealed a remarkable similarity in the feeding behaviour among species, suggesting a foraging behaviour convergence among species in the prey-handling efficiency of larval newts. Nevertheless, larvae of some newt species showed clear preferences for particular categories of ecological trait; for example, Lissotriton vulgaris tended to feed on macroinvertebrate taxa with random trajectory, and Calotriton asper fed on macroinvertebrate taxa with high agility. In contrast, Mesotriton alpestris showed a clear ability to feed on prey with movable accessories (cases/tubes) and patterned concealment. This study shows how multivariate approaches can complement traditional diet analyses, and the method has wide applicability across life-stages and species.     

Seasonal trends and colonization patterns of macroinvertebrate assemblages in two streams with contrasting flow regimes

Patterns of colonization by macroinvertebrates were examined in two streams that differ in flow regime: a snowmelt system and a mesic groundwater system. Experiments were conducted during spring runoff, summer baseflow, and winter baseflow using artificial substrata. Colonization patterns reflected seasonal changes in benthic macroinvertebrate assemblages and life histories in each stream. The density and biomass of benthic organisms were approximately 3X greater in winter than in either spring or summer for both streams. Similarly, colonization was greater in winter than in spring or summer for both streams. In spring, colonization patterns were different between streams, with colonization being imperceptible in the snowmelt stream. Macroinvertebrate abundance fluctuated during the summer colonization experiment at both sites, resulting from a complex interplay among population emergence, recruitment, and/or movement. Assemblages in the snowmelt system primarily comprised mobile or ruderal taxa, such as Beatis tricaudatus and Chironomidae, whereas relatively sessile taxa, such as Glossoma nigrior , were predominant in the mesic groundwater system. Seasonal patterns of colonization differed among stream types primarily because of the profound interplay of flow regime and temperature on benthic community structure and organism life history.     

Species-environment relationships among filter-feeding caddisflies (Trichoptera: Hydropsychidae) in Rocky Mountain streams

Species-environment relationships were determined for filter-feeding macroinvertebrates from 55 Rocky Mountain stream sites to establish species distribution patterns. Species abundance and 20 environmental variables were measured at each site with species-environment relationship determined using canonical correspondence analysis and stepwise multiple regression. Results suggest that the distribution of several taxa was strongly related to upstream-downstream environmental gradients. Arctopsyche grandis abundance increased with stream size (width and depth) and decreased with increasing turbulence (Reynolds number). Brachycentrus abundance also increased with stream size (depth). Hydropsyche abundance increased with increasing baseflow. Parapsyche elsis abundance also increased with stream size (depth). Hydropsyche abundance increased with increasing baseflow. Parapsyche elsis abundance demonstrated negative correlation with depth, Froude number, and conductivity. Taxa followed previously reported patterns, partitioning habitat according to stream size. Arctopsyche grandis , Brachycentrus , and Hydropsyche were found in larger (3rd- to 6th order) streams, while Parapsyche elsis was observed in small headwater (1st- and 2nd- order) streams. Other filter-feeding taxa such as Simulium, Pisidium and ostracods exhibited little or no apparent habitat partitioning among stream sites.     

Late Quaternary arthropods from the Colorado Plateau, Arizona and Utah

Late Quaternary-age arthropods were recovered from dry cave deposits and packrat middens located in the Grand Canyon, Canyonlands, and Glen Canyon region of the Colorado Plateau. This Quaternary data resource has not been analyzed before from the Colorado Plateau national parks. Radiocarbon dates on the various deposits containing arthropods range from 1510 to 30,660 yr B.P. The fossil assemblages yielded 57 identified taxa of insects, arachnids, and millipedes, including 15 taxa taken to the species level. The information from the fossil insect record of the Colorado Plateau is not yet sufficiently detailed to permit precise paleoenvironmental reconstructions. However, preliminary conclusions suggest a cooler, moister climatic regime during the late Wisconsin glacial and a mosaic of vegetation types, such as grassland and shrubby communities, unlike the present vegetation at the localities.     

Trichoptera and other macroinvertebrates in springs of the Great Basin: species composition, richness, and distribution

Detailed surveys of aquatic invertebrates in 28 springs along the western border of the Great Basin were made using pan traps, emergence traps, black lights, and benthic sampling devices from 1994 to 1998. Although all macroinvertebrate groups were collected, caddisflies (Insecta: Trichoptera) were sampled most intensively. Fifty-eight species of caddisflies were collected from the 28 springs, with up to 18 species from a single spring. Although several springs had very similar physicochemical characteristics, none had identical trichopteran species composition. Using Wards minimum variance clustering technique, and with all macroinvertebrates identified to the lowest possible level, we found 3 taxa assemblages. These assemblages occurred in springs with the following physical conditions: (1) warm water (15.9° C), low elevation (1794 m); (2) cold water (8.5° C), mid-elevation (2334 m); and (3) cold water (6.6° C), high elevation (1794 m). Although the warm water group had a distinct assemblage of invertebrates (amphipods, gastropods, Trichoptera), distinct assemblages did not separate the 2 cold water groups. Discriminant analysis indicated that temperature, conductivity, alkalinity, and elevation were most responsible for discriminating group 1 from groups 2 and 3; temperature and elevation distinguished the latter 2 groups. Spring permanence, lack of disturbance, and cold water temperatures were the factors most responsible for explaining higher species richness of Trichoptera.     

Diatom species composition and ecology of the Animas River Watershed, Colorado, USA

The diatom flora of selected sites in the Animas River Watershed, San Juan County, Colorado, was studied. Eighty diatom taxa were identified from 10 sites: 8 sites on the Animas River and 1 site each on the Cement and Cascade tributaries. The sample diatom abundance was dominated by Achnanthidium minutissimum , Encyonema silesiacum , Aulacoseira distans , Hannaea arcus , and Diatoma mesodon . The presence of teratologic specimens of Fragilaria and Achnanthidium in the samples indicated the possibility of metals contamination. Diatom diversity was low and Lange-Bertalot pollution index scores indicated little organic pollution evidenced from diatom composition. There was evidence that diatom composition at the sites was differentially affected by pH and possibly by the concentrations of Zn alone or in combination with Cd, Cu, and Fe.     

A comparison of riparian condition and aquatic invertebrate community indices in central Nevada

The importance of maintaining healthy riparian communities to sustain natural stream processes and function is well documented. Land management agencies in the West are currently developing methods to assess and monitor riparian community condition to adapt land use practices that would better protect rangeland ecosystems. To determine whether these methods also provide an indication of abiotic and biotic stream condition, we compared the classification system of riparian communities developed by the U.S. Forest Service (USFS) to physical parameters of stream condition and to aquatic invertebrate community assemblages. Thirty-three sites in 19 different streams of the Toiyabe Range in central Nevada were measured for water quality, substrate characteristics, and fish abundance and diversity. We sampled aquatic invertebrates and calculated community indices based on environmental tolerance levels, taxonomic diversity, and abundance of sensitive taxa. USFS personnel classified these sites by dominant riparian plant community type (meadow, willow, or aspen) and ecological status (low, moderate, or high) using plant abundance data, rooting depth, and soil infiltration to determine similarities to potential natural communities. Riparian condition indices as well as community diversity were significantly correlated to proportions of fine and small-diameter substrate in streambeds. Accumulation of silt was significantly related to plant community type, with meadow sites expressing highest proportions. Further examinations indicated that 2 of 6 invertebrate community indices were significantly related to ecological status, with highest diversity levels occurring mainly in willow- and aspen-dominated sites in moderate ecological condition. Nevertheless, we show that several other environmental variables, including substrate characteristics, dissolved oxygen, water temperature, and species richness of fish communities, were more strongly and consistently related to invertebrate assemblage patterns. Our results demonstrate that information on aquatic invertebrates and stream condition could augment the existing riparian classification system and provide useful monitoring tools to more thoroughly examine ecosystem health in rangelands.     

Aquatic vertebrate assemblages of the Upper Clear Creek Watershed, California

We sampled streams in the Upper Clear Creek Watershed in northwestern California in fall 2004 and fall 2005 to document assemblages of aquatic vertebrates and to provide resource managers with information on the importance of these assemblages in terms of regional biodiversity. We used single-pass backpack electrofishing to sample 15 sites in fall 2004 and the same 15 sites plus 4 new sites in fall 2005. We captured 10 fish taxa and 2 species of larval amphibians. Seven of the fish taxa were native species. Of the exotic species, only brook trout ( Salvelinus fontinalis ) occurred at more than 1 site. Ordinations by nonmetric multidimensional scaling indicated a gradient from sites with rainbow trout ( Oncorhynchus mykiss ), Pacific giant salamander ( Dicamptodon tenebrosus ), and tailed frog ( Ascaphus truei ) to sites dominated by riffle sculpin ( Cottus gulosus ), California roach ( Hesperoleucas symmetricus ), and Sacramento sucker ( Catostomus occidentalis ). The gradient in species composition was associated with changes in elevation, gradient, discharge, and substrate. The Upper Clear Creek Watershed represents a unique area of overlap between the North Coast California amphibian fauna and the Central Valley fish fauna with a notable paucity of exotic fishes and amphibians. Preservation of the integrity of native aquatic assemblages is an important goal for aquatic resource management in the region; our results provide a critcial baseline to gauge future management actions.     

Benthos recovery after an episodic sediment release into a Colorado Rocky Mountain river

During late September 1996, approximately 7000 m 3 of clay- to gravel-sized sediment was flushed from Halligan Reservoir, Larimer County, Colorado, into the North Fork Cache la Poudre River during dam inspections. Approximately 9.6 km of this river was partially or completely affected by this episodic sediment release. Pools up to 3.2 km downstream from the dam lost 50% of their volume. Hess samples taken from October 1996 to September 1997, 100 m downstream from the dam (site 1) and 3.2 km downstream (site 2), revealed effects of sediment on recovery patterns of benthic communities. A 2-way ANOVA was used to determine significant interactions using site and date as main factors. Pairwise differences were then compared using least squares means to determine significant dates within and between sites. Ten days after the sediment release, both density and taxa richness at site 1 (55 organisms per m 2 , 5 taxa) were significantly lower ( P 2 , 25 taxa). These differences remained until June when species richness and densities increased. Plecoptera and Trichoptera colonized from June to September after being eliminated at site 1 and reduced at site 2. No permanently flowing tributaries exist within the study area; therefore, passive downstream drift from such inputs apparently did not influence recovery. Increased densities of taxa such as Baetidae, Hydroptilidae, Hydropsychidae, Chironomidae, Simuliidae, and Oligochaeta occurred plausibly by rapid reproduction. Based on pre-event data, community function completely changed at site 2 from a scraper community to one dominated by collector-gatherers.     

Macroinvertebrate richness is lower in high-elevation lakes vs nearby streams: evidence from Grand Teton National Park,Wyoming

Mountain ecosystems will be strongly impacted by climate change, yet little is known of extant biodiversity in high-elevation lakes, particularly in North America. In this study, we sampled the littoral zone of six alpine and subalpine lakes in Grand Teton National Park (GRTE), Wyoming, to characterise invertebrate diversity and environmental variation in these climate change-threatened ecosystems. Overall, we collected 19 aquatic invertebrate taxa, and found that each lake harboured a unique assemblage of invertebrates despite close geographic proximity in some instances (e.g. less than 5 km). The results of this study complement previous efforts focused on macroinvertebrate diversity of streams in the Teton Range, highlighting much lower diversity in montane lakes vs nearby streams. Taken together, the two studies establish an important baseline understanding of mountain freshwater biodiversity in GRTE. With rapidly changing hydrologic inputs to mountain lakes driven primarily by the recession of alpine glaciers, these results may help target aquatic invertebrates to monitor as climate change affects the region. Moreover, these data clarify habitat factors, both biotic and abiotic, that influence high-elevation lake assemblages of the Teton Range.     

Marine biodiversity on the Algerian Continental Shelf (Mediterranean Sea)

The Mediterranean Sea is known as a biodiversity hot spot, with 16,848 species reported. Biodiversity is higher in coastal areas and decreases with depth. However, knowledge about the southwestern sector remains scarce. For the last three decades, sampling of soft-bottom communities along the 1180 km of the shallow Algerian coast (0–136 m) has recorded 1642 macrobenthic species. There is a decreasing west–east species-richness gradient, especially for the total species richness and the amphipods. In addition, quantitative sampling in Bou Ismail Bay in summer 1988 (98 sampling sites for a total of 841 species) shows that diversity indices (i.e. species richness, >100 species for 0.2 m^?2; Shannon diversity, >6.0; and ES₅₀, >34) are among the highest for similar sand and muddy-fine sand communities in the Mediterranean Sea and the northeastern Atlantic Ocean. Bou Ismail Bay appears to have the highest species richness among Algerian bays, probably because of its variety of benthic habitats and the absence of significant pollution in this area. Monitoring must be undertaken to survey this high biodiversity, and a national strategy should be proposed to preserve high diversity zones.     

Variation in ant populations with elevation, tree cover, and fire in a pinyon-juniper–dominated watershed

Climate change and fire suppression have facilitated expansion of pinyon-juniper woodlands into sagebrush-steppe ecosystems of the Great Basin, USA, resulting in a loss of biological diversity. To assess the effects of using prescribed fire in restoration efforts, ant abundance, species richness, and composition were examined pre- and post-burn along the elevation and tree cover gradients encompassed by a pinyon-juniper woodland in a central Nevada watershed. Ants were sampled using pitfall traps in 6 sites for the elevation study and in 2 sites for the tree cover study, representing paired burn and control sites in a randomized block design. Vegetation and ground cover variables were also sampled to determine how variation in ant populations was correlated with differences in vegetation and ground cover. Ant species richness remained unchanged for all treatments. Tree cover had no significant effect on ant populations. Significantly more ants were trapped after the burn treatment on burn plots. Variation in ant populations was not directly correlated with any of the vegetation or ground cover variables. According to ANOVA and multivariate analyses, elevation had the greatest effect on changes in ant communities, likely due to increased moisture availability. Our results suggest that management for conservation of sagebrush-steppe ecosystems in this and similar watersheds should include a range of elevations to ensure maximum ant species diversity.     

The peracarid epifauna associated with the ascidian Pyura chilensis (Molina, 1782) (Ascidiacea: Pyuridae)

Epifaunal peracarids inhabit a variety of biogenic substrata, including ascidians. Herein we examined the peracarid fauna living on the tunica of the sublittoral ascidian Pyura chilensis growing in offshore and nearshore conditions in Bahía San Vicente, Chile. From a total of 38 samples we collected 17 species of Amphipoda, five Isopoda and two Tanaidacea. The similarity between the sites was high (73.8%, Sorensen's index). Species diversity (H') was 2.8 and 2.6, evenness (J) was 0.7 and 0.6 at the offshore and nearshore site, respectively. Both species and individual number increased significantly with the size (volume) of the ascidian samples, and these relationships did not differ between the sites. Many species, in particular the most abundant ones, occurred at both sites, but some species were restricted either to the offshore (three species) or to the nearshore site (seven species). Amphipods and tanaids were the most abundant taxa at both sites. The peracarid fauna at both sites was dominated by suspension-feeding peracarids (>80% of the individuals), which utilize the ascidians primarily as shelter, feeding on allochthonous material, i.e. not originating from the ascidians. It is suggested that the high percentage of suspension-feeding species among the epifaunal peracarids is due to the fact that ascidians settle and grow at sites that provide optimal feeding conditions for these organisms.     

Bird community characteristics as indicators of sustainable management in olive grove ecosystems of Central Greece

The role of breeding birds as indicators of sustainable management in olive groves was investigated. The data revealed significantly higher alpha diversity in organic and abandoned olive groves and maquis than in conventional ones. The highest beta diversity was found between the following pairs: organic olive groves–maquis, and abandoned olive groves–maquis. Breeding bird diversity, Heteroptera, Hymenoptera, Hemiptera and Coleoptera densities positively influenced bird species richness in organic olive groves and maquis, and additionally, manure application positively influenced bird species richness in organic ones. Bird species richness was negatively influenced by pesticide and inorganic fertilizer application in conventional ones. Moreover, isopod density was unimportant in explaining breeding bird richness in organic olive groves. Finally, our study suggests a difference in bird communities of various olive groves as a result of different management and practices, and concludes that birds might serve as indicators of overall olive grove health. Furthermore, these findings could be used as a tool for prediction of breeding bird species richness probability in different olive grove management systems and maquis. Finally, the results of the present study may contribute to highlighting some aspects of the effect of different farming practices on the dynamics of Mediterranean bird communities.