High-altitude Streams Research Articles

The roles of elevation and local environmental factors as drivers of diatom diversity in subarctic streams

Summary High latitude and altitude freshwater systems are highly sensitive to the effects of global warming and associated environmental changes. Diatoms are widely used as sentinels of environmental change, yet knowledge of diatom community patterns in high latitude and altitude streams remains limited. The aim of this study was to examine alpha and beta diversity of diatoms in subarctic streams in Finland and Norway, and to determine the importance of local environmental factors and elevation in shaping their community patterns. We also aimed at testing, for the first time, whether microbes conform to Rapoport's elevational rule, which states that species occurring at higher elevations have generally larger elevational ranges than species at lower elevations. Three streams (44 sites in total) with an altitudinal gradient of 21–877 m a.s.l. were sampled. Generalized linear models, hierarchical partitioning, and a boosted regression tree method were used to identify drivers of diatom species richness. We ran Mantel tests, and calculated initial similarities and elevational halving distances to examine beta diversity. There were no apparent richness–elevation relationships within streams. Across all study streams, the water depth was the most important factor for richness, with additional influences by stone size, conductivity, pH and elevation. Diatoms in subarctic streams did not conform to Rapoport's elevational rule. Community similarity decreased significantly with elevational distance while distance decay was weaker with environmental distance. Our results suggest that diatom alpha and beta diversity along stream elevational gradients are shaped by interacting local environmental factors such as water depth and substrate size, indicating vulnerability of diatoms to physical disturbances, and regional factors such as dispersal and geographical variables. Diatom diversity patterns do not seem to concur with patterns often observed for larger organisms as no consistent elevational patterns in richness or range sizes were found.

Integrated Taxonomy and DNA Barcoding of Alpine Midges (Diptera: Chironomidae).

Rapid and efficient DNA-based tools are recommended for the evaluation of the insect biodiversity of high-altitude streams. In the present study, focused principally on larvae of the genus Diamesa Meigen 1835 (Diptera: Chironomidae), the congruence between morphological/molecular delimitation of species as well as performances in taxonomic assignments were evaluated. A fragment of the mitochondrial cox1 gene was obtained from 112 larvae, pupae and adults (Diamesinae, Orthocladiinae and Tanypodinae) that were collected in different mountain regions of the Alps and Apennines. On the basis of morphological characters 102 specimens were attributed to 16 species, and the remaining ten specimens were identified to the genus level. Molecular species delimitation was performed using: i) distance-based Automatic Barcode Gap Discovery (ABGD), with no a priori assumptions on species identification; and ii) coalescent tree-based approaches as the Generalized Mixed Yule Coalescent model, its Bayesian implementation and Bayesian Poisson Tree Processes. The ABGD analysis, estimating an optimal intra/interspecific nucleotide distance threshold of 0.7%-1.4%, identified 23 putative species; the tree-based approaches, identified between 25–26 entities, provided nearly identical results. All species belonging to zernyi, steinboecki, latitarsis, bertrami, dampfi and incallida groups, as well as outgroup species, are recovered as separate entities, perfectly matching the identified morphospecies. In contrast, within the cinerella group, cases of discrepancy arose: i) the two morphologically separate species D. cinerella and D. tonsa are neither monophyletic nor diagnosable exhibiting low values of between-taxa nucleotide mean divergence (0.94%); ii) few cases of larvae morphological misidentification were observed. Head capsule color is confirmed to be a valid character able to discriminate larvae of D. zernyi, D. tonsa and D. cinerella, but it is here better defined as a color gradient between the setae submenti and genal setae. DNA barcodes performances were high: average accuracy was ~89% and precision of ~99%. On the basis of the present data, we can thus conclude that molecular identification represents a promising tool that could be effectively adopted in evaluating biodiversity of high-altitude streams.

Does tourism impact aquatic insects in a high altitude stream?

Human activity often has a negative effect on stream quality and the biodiversity of aquatic fauna. The present study investigated the distribution patterns of aquatic insect populations in the Sentinela stream in Biribiri State Park, Diamantina, Minas Gerais, Brazil, and we correlated the patterns to possible impacts caused by tourists. We sampled the aquatic insect population few days before and few days after the holidays and monthly during the year. Fifteen groups of samples were taken from January through December 2011 at four different sites. For each site, three sub-samples were taken by drifting the entomological net and disturbing the substrate using the kick method. 3601 individuals were collected, and 8 orders and 41 families were identified. Environmental indices showed excellent water quality for sites 1 and 2, which are minimally affected by tourism and average water quality for sites 3 and 4, which are highly impacted by tourism. Three of the four holiday periods analyzed showed a significant decrease in insect abundance after the holiday. The richness and diversity of the aquatic insect fauna did not show seasonal fluctuations, despite differences in stream flow velocity during the dry and rainy periods. Our results indicated that the disturbances caused by tourism affect directly the diversity and abundance of aquatic insects in the Sentinela stream. In addition, these insects were suitable for the evaluation of human impacts caused by tourism in the conservation of freshwater ecosystem.O Turismo Impacta os Insetos Aquáticos em um Riacho de Alta Altitude?Resumo. A atividade humana tem afetado negativamente a qualidade dos ambientes lóticos e a biodiversidade da fauna aquática. O presente estudo investigou os padrões de distribuição das populações de insetos aquáticos no córrego Sentinela no Parque Estadual do Biribiri, Diamantina, Minas Gerais, Brasil, e correlacionou esses padrões com possíveis impactos causados pelas atividades do turismo. As populações de insetos aquáticos foram amostradas alguns dias antes e alguns dias após dos feriados e mensalmente durante o ano, totalizando quinze amostras entre os meses de janeiro e dezembro de 2011 em quatro locais diferentes. Para cada local, foram realizadas três sub-amostras com a ajuda de rede entomológica e o substrato foi revolvido com os pés. Foram coletados 3601 indivíduos, os quais foram identificados 8 ordens e 41 famílias. Por meio dos índices ambientais foi possível observar que os pontos 1 e 2 possuem excelente qualidade da água e são minimamente afetados pelo turismo, por outro lado os pontos 3 e 4 possuem uma qualidade de água intermediária e são altamente impactados pelo turismo. Três dos quatro feriados estudados mostraram uma diminuição significativa na abundância de insetos após o feriado. A riqueza e a diversidade da fauna de insetos aquáticos não mostraram flutuações sazonais, apesar da ocorrência de diferentes velocidades de vazão durante os períodos seco e chuvoso. Nossos resultados indicaram que os distúrbios causados pelo turismo afetam diretamente na diversidade e abundância dos insetos aquáticos no córrego Sentinela. Além disso, esses insetos se mostraram adequados para a avaliação de impactos antropogênicos causados pelo turismo na conservação de ecossistemas lóticos.

Experimental evidence that predator range expansion modifies alpine stream community structure

Climate change is projected to facilitate altitudinal range expansions of ‘lowland’ taxa, creating novel species interactions. However, how range shifts will alter biotic interactions and community structure in alpine streams is not well understood. In the Pyrénées, climate-induced physicochemical habitat change is hypothesized to facilitate the colonization of high-altitude streams by Perla grandis, a carnivorous stonefly. A field-based experiment was conducted in mesocosm channels beside a hillslope spring (2000 m asl) in the Taillon-Gabiétous catchment, French Pyrénées. The influence of P. grandis predation on community structure, feeding trait composition, body-size spectrum, and algal chlorophyll a concentration was examined. Gut contents were analyzed and used to identify consumed prey. Total invertebrate density was not significantly reduced by P. grandis, but Baetis spp. densities were depressed in the treatment channels through a combination of direct consumption and predator avoidance (emigration/drift). However, despite fewer grazers in the predator treatment channels, the magnitude of the trophic cascade effect on basal resources (measured as chlorophyll a density) was comparable between treatment and control channels. The results of this experiment suggest that size/species-specific predation, intraguild predation, and interference competition are the likely mechanisms that altered the body-size spectrum in treatment channels. In synergy with climate-driven physicochemical habitat change, the extinction risk of some range-restricted taxa (prey and other predators) could be increased where P. grandis colonization occurs. Hence, conservation efforts are required to ensure that additional anthropogenic stressors (e.g., nutrient enrichment, cattle trampling, hydropower development, ski runs, and tourism) are limited to minimize further pressures on these unique and sensitive habitats.

Diversity and composition of macroinvertebrate assemblages in high-altitude Tibetan streams

Knowledge on the ecology of streams at extreme altitudes is relatively sparse. We conducted a preliminary survey of the macroinvertebrate fauna of Tibetan streams in June 2009 and August 2011 and compared streams with different water sources. We collected quantitative samples of macroinvertebrates and measured physicochemical variables at 16 sites (8 each sampling year) at altitudes ranging from 4315 to 5065 m a.s.l. and grouped the sites into 3 types according to origin: glacier-fed, rain-fed, and lake-outlets. We identified 38 taxa, with a mean of 8.9 taxa per site. Overall the benthic fauna was dominated by insects (71%), mainly Diptera (especially Chironomidae). Ephemeroptera, Plecoptera, and Trichoptera were found at nearly all sites but mostly in low numbers; however, the fauna was significantly different in the 2 sampling years, especially due to the proportions of Chironomidae (68% in June 2009 and 10% in August 2011) and Baetidae (6% vs. 35%, respectively). The 3 stream types had significantly different faunas. Rain-fed streams had the highest total taxon richness (γ-diversity), but glacier-fed streams had a slightly higher taxon turnover rate (β-diversity). Percent glacial cover in the catchment and water turbidity explained most of the variability in taxon richness. Although not particularly taxon rich compared to other high-altitude streams, the Tibetan stream fauna showed considerable spatial variability. The fast retreat of the glaciers and permanent snow fields in Tibet makes further studies on distribution patterns and driving forces for aquatic biodiversity urgent.

Leaf breakdown in a natural open tropical stream

Leaf breakdown is a primary process of nutrient cycling and energy flow, contributing to the functioning of aquatic ecosystems. In the present study, leaves of Baccharis platypoda and Coccoloba cereifera were incubated in a high-altitude stream in a rupestrian field. Two hypotheses were tested: i) intrinsic factors (quality of detritus) are more important than extrinsic factors (decomposer communities) in decomposition; and ii) low detritus quality hinders microbial colonization, thereby altering the composition and structure of the associated invertebrate community and slowing leaf breakdown. The breakdown coefficients of B. platypoda and C. cereifera leaves were low (k = -0.0019 day -1 and k = -0.0008 day -1 , respectively) and the proportions of structural compounds were high, delaying the remobilization of energy and nutrients into the aquatic ecosystem. Fungal biomass was higher at the end of the experiment, suggesting favorable conditions for colonization. The densities of invertebrates associated with the detritus increased coincident with the peak concentration of ergosterol, with the trophic groups collector-gatherer and scraper having the highest densities. The distribution of these groups was likely related to the growth of biofilm on the surface of the litters. As described for tropical streams, shredders had the lowest densities of any invertebrate group, suggesting a reduced participation of these invertebrates in leaf processing. The results suggest that slow decomposing species are important to both invertebrates and microorganisms as substrates and sources of particulate organic matter. The low palatability and nutritional quality of the detritus in the present study, associated with low dissolved nutrient concentrations in water, delayed the leaf conditioning process by microorganisms. Decomposition rates and invertebrate participation were reduced as a result, leading to major physical decomposition. Headwater tropical streams have chemically diverse detrital resources, and the intrinsic factors of litter may play key roles in the decomposition process.

Evidence from recently deglaciated mountain ranges thatBaetis alpinus(Ephemeroptera) could lose significant genetic diversity as alpine glaciers disappear

Climate change will cause relict alpine glaciers to disappear within decades. Associated high-altitude streams will face significant hydrological changes that might affect population genetic diversity of lotic species. In a recent study of glacier-fed streams in the Pyrenees, Finn et al. (2013) predicted that a large proportion of regional genetic diversity of the mayfly Baetis alpinus would be lost as glacial meltwater sources disappear. We expanded the analysis of Finn et al. to include genetic data (mitochondrial barcoding region) collected from B. alpinus occupying recently deglaciated locations including multiple basins in 2 mountain ranges (Sierra Nevada and Picos de Europa) on the Iberian Peninsula and 1 additional, deglaciated Pyrenean basin. We hypothesized that regional genetic diversity at scales of entire mountain ranges (γ diversity) and population structure within ranges (β diversity) would be lower in recently deglaciated mountain ranges than in the still-glaciated Pyrenees. For 4 cryptic lineages of the B. alpinus species complex in 3 mountain ranges, we found significantly lower genetic diversity in recently deglaciated than glaciated regions. β and γ genetic diversity were correlated, suggesting that population structure (β) strongly influences total regional diversity. Results support the hypothesis of Finn et al. (2013) that disappearance of alpine glaciers will result in substantial loss of genetic diversity. The distinctive hydrological environment created by glacial meltwater might drive an interaction between reproductive barriers (between highly and minimally glacier-influenced reaches within basins) and physical barriers (isolating highly glacier-influenced reaches among basins) that amplifies regional genetic diversity in mountain ranges still containing alpine glaciers.

Metals and altitude drive genetic diversity of chironomids in Andean streams

Summary Andean streams cover steep altitude gradients and locally leach metal‐rich bedrock, creating highly selective habitat conditions. Chironomids are among the few dominant insect taxa present under the harshest conditions in Andean high altitude streams, but it remains unclear whether their dominance is due to the adaptive capacity of a few species (population differentiation) or to a diversity of species with different capacities to cope with environmental extremes (species composition). Therefore, the aim of this study was to assess whether metals and altitude drive the genetic diversity of chironomids in Andean streams. We measured metal concentrations and altitude‐related conditions, such as UV‐B radiation, water temperature and oxygen, in reference and metal‐rich streams located at both 3000 and 4000 m a.s.l. The genetic composition of the chironomid communities from these streams was determined by mitochondrial cytochrome oxidase I (COI) gene sequencing, and a phylogenetic tree was constructed. The concentrations of all metals were higher in the metal‐rich streams than in the references streams. The UV‐B radiation level at 4000 m was notably higher than at 3000 m, while the water temperature followed the opposite trend. At 3000 m, the reference site was inhabited by six putative species, completely different from the three present at 4000 m. Only one putative species, which did not occur at the reference sites, was present at both the metal‐rich sites at 3000 and 4000 m. The differences in putative species composition between 3000 and 4000 m indicated a strong sorting of species according to altitude. However, the unique putative species present at the metal‐rich sites at both 3000 and 4000 m indicated that altitude‐driven selection was overridden by the extreme selection pressure exerted by metal exposure. We conclude that altitude limits the distribution of chironomid taxa, but metal selection leads to predominance of a unique metal‐tolerant taxon.

Distribution, Abundance and Molecular Analysis of Genus Barbadocladius Cranston & Krosch (Diptera, Chironomidae) in Tropical, High Altitude Andean Streams and Rivers.

The distribution of the genus Barbadocladius Cranston & Krosch (Diptera: Chironomidae), previously reported from Chile to Bolivia, has extended northwards. Larvae, pupae and pupal exuviae of this genus have been found in the high mountain tropical streams of Peru to 9°22'56″, but are restricted to very high altitude streams (altitudes over 3,278m asl) compared to the lower altitude streams (below 1,100m asl) in which the genus is reported in Chile and Argentina. Based on morphological studies, both described species in the genus, Barbadocladius andinus Cranston & Krosch and Barbadocladius limay Cranston & Krosch, have been found in Peru as pupae or pupal exuviae. Morphological analysis of the larvae and pupae revealed no differences between the two described species from Patagonia and Peru, which are of similar size and with a similar armament of hooklets and spines in pupal tergites and sternites. However, molecular analysis of larvae and pupae revealed that in Peru, there are at least two different evolutionary lines, one distributed widely and another restricted to one site. Phylogenetic analysis (using cox1 mitochondrial sequences) of all available sequences of Barbadocladius shows that the Chilean and Argentinean material differs from that of Peru. Therefore, a total of four molecular segregates are identified, although morphologically, neither larvae nor the pupae may be differentiated.

Persistence of Chironomids in Metal Polluted Andean High Altitude Streams: Does Melanin Play a Role?

In high altitude Andean streams an intense solar radiation and coinciding metal pollution allow the persistence of only a few specialized taxa, including chironomids. The aim of the present study was therefore to determine the mechanisms underlying the persistence of chironomids under these multiple stress conditions, hypothesizing that melanin counteracts both the adverse effects of solar radiation and of metals. Melanin was determined in chironomids from reference and metal polluted streams at 3000 and 4000 m altitude, being 2-fold higher at 4000 m compared to 3000 m, and 2-fold higher in polluted streams than in reference streams at both altitudes. The field observations were experimentally verified by assessing the combined effects of Cu and UV-B on the survival and melanin concentration in larvae of the model species Chironomus riparius (Chironomidae, Diptera). In laboratory exposures, the highest melanin concentrations were found in larvae surviving toxic Cu concentrations, but not in those exposed to the highest UV-B radiation. Pre-exposure to UV-B decreased the sensitivity of the larvae to UV-B and to Cu+UV-B. It is concluded that in the field, melanin may protect chironomids partially against both elevated metal concentrations and solar radiation, allowing them to persist under the harshest conditions in high altitude streams.

Oviposition of Aquatic Insects in a Tropical High Altitude Stream

The persistence of aquatic insect populations in streams depends on the recruitment of larval populations from egg masses deposited by adults, especially after disturbance. However, recruitment of aquatic populations by oviposition is a process that remains unstudied in streams and rivers. The objectives of our study were to document flying and oviposition patterns of aquatic insects in a high altitude tropical stream during both dry and wet seasons. In particular we studied 1) richness and abundance of adult forms of aquatic insects flying and ovipositing; 2) number of eggs (oviposition pattern), egg mass identity, and morphology; and 3) substrate preferences by ovipositing females. We found 2,383 aquatic insects corresponding to 28 families, with dipterans representing 89% of total individuals collected. Adult insects had lower richness (28 taxa) than larval diversity (up to 52 taxa) and distinct community composition. Richness and relative abundance of most taxa (adults) were not significantly different between seasons, behaviors, diel period, or all three. During both sampling periods we found females with eggs in a total of 15 different families (13 in the dry season and 14 in the wet season). There were no significant differences in the proportion of females with eggs between seasons, diel periods, or different behaviors (flying versus ovipositing traps) of the different female taxa. Few types of egg masses were found in rocks at the stream during both seasons, and most egg masses found corresponded to families Baetidae and Chironomidae. Finally, we provide the first description of eggs masses (size, shape, color, and number of eggs per female) of gravid females (10 taxa) and those found in the stream substrate (six taxa) of Andean macroinvertebrates. This is the first study reporting oviposition, adult diversity, and oviposition patterns of aquatic insects in the Andean region.

Invertebrate drift and colonization processes in a tropical Andean stream

We studied invertebrate drift (intensity, propensity, and diel changes) and the recolo - nization process of stones in a tropical high-altitude stream in Ecuador for a period of 7 to 25 d dur- ing the wet and dry seasons. Our aim was to identify whether seasonal differences in flow produce differences in drift parameters and in the recolonization process, and to examine the role of micro- habitat (fast-flow vs. slow-flow areas) in this process. Invertebrate community metrics in drift did not differ between seasons at base flow (<100 l s �1 ), but they were highly correlated with high flow events. As a result, drift propensity values for several taxa were higher during the wet season, when higher flows occurred, indicating that some taxa suffer catastrophic drift (e.g. Podonominae, Simuliidae). In the short-term experiment, taxa richness, density, and diversity of the colonizers increased with time (up to Day 7). On a longer scale (Days 7 to 25; mid-term experiment), time did not affect community metrics. Microhabitat had strong effects on the composition of colonized stones, and was related to the abundance of taxa in the drift. While some taxa that are scarce in drift were only found in slow-flow areas (e.g. Nectopsyche), suggesting that these species actively search for refuges in the stream, copious species in the drift (e.g. Baetodes) were very abundant on the recolonizing stones, especially during the wet season. The present study suggests that flow, the variability of flow (within and between seasons), and its consequences on the drift of several species play a pivotal role in invertebrate colonization and in the structuring of invertebrate communities in different microhabitats of high-altitude tropical streams.

Altitudinal differentiation of reproductive tactic plasticity despite the close proximity of two Aquarius remigis populations

AbstractIn the water strider (Aquarius remigis), direct and delayed reproductive tactics are largely canalized in southern and northern areas of North America, respectively. A transition zone occurs in upstate New York, defined as the area where lowland striders plastically express either tactic based on photoperiod and food abundance cues. We tested whether these cues similarly influence tactics among higher altitude transition zone populations. We compared the proportion of direct reproducers from a high altitude stream (HAS) and a low altitude stream (LAS) reared under low and high food abundance, as well as a normal and late-solstice photoperiod. With sexes combined, higher proportions of direct reproducers were found among LAS striders, and among striders reared in the late solstice photoperiod and high food abundance treatments. Among males, a food abundance × stream interaction was significant, suggesting greater canalization of reproductive tactics among HAS males. Among females, photoperiod was a significant factor, but did not interact with stream of origin. Field measurements showed that water surface temperatures and food abundance were lower in HAS compared to LAS. These conditions, as well as shorter season lengths, likely select against direct reproduction among HAS striders, possibly resulting in the observed canalization of reproductive tactics.

Metal‐induced shifts in benthic macroinvertebrate community composition in Andean high altitude streams

High altitude creates unique challenging conditions to biota that limit the diversity of benthic communities. Because environmental pollution may add further stress to life at high altitude, the present study explored the effect of metal pollution on the macroinvertebrate community composition in Andean streams between 3,500 to 4,500 meters above sea level (masl) during wet and dry seasons. At polluted sites, showing a high conductivity and a low pH, metal concentrations (e.g., Al, 13.07 mg/L; As, 3.49 mg/L; Mn, 19.65 mg/L; Pb, 0.876 mg/L; Zn, 16.08 mg/L) ranged from 8-fold up to 3,500-fold higher than at reference sites. The cumulative criterion unit allowed quantifying the potential toxicity of metal mixtures at the contaminated sites. Principal component analysis of physical chemical variables showed that reference sites were more likely to be structured by transparency, water discharge, and current velocity, while polluted sites appeared to be determined by metals and conductivity. Canonical correspondence analysis indicated a strong influence of highly correlated metals in structuring invertebrate communities, which were dominated by dipterans, coleopterans, collembolans, and mites at polluted sites. At reference sites crustaceans, ephemeropterans, plecopterans, and trichopterans were the most representative taxa. We concluded that severe metal pollution induced changes in macroinvertebrate community composition in high-altitude Andean streams, with a replacement of sensitive taxa by more tolerant taxa. Yet relatively species-rich communities persisted under harsh conditions.

Chironomid assemblages in high altitude streams of the Andean region of Peru

The diversity of genera and species of the family Chironomidae in the Andean region, as well as their variation with season and altitude, are scarcely known. Here, a semi-quantitative sampling was conducted at 35 stations with little or no human disturbance in the basin of the Canete River (Peru), situated on the western slope of the Andes, between 2553 and 4396 m a.s.l. during the dry (2004) and rainy (2005) season. A total of 38 genera of Chironomidae were found, of which 21 belong to the subfamily Orthocladiinae. No significant differences in richness of genera were found among the four different altitudinal ranges surveyed. A greater richness of genera was found during the rainy season. Most of the genera were distributed across the entire altitudinal gradient studied, especially species of the genus Cricotopus. Only Podonomopsis and Limnophyes showed evident preference for altitude range 4 (4000-4500m a.s.l.), Podonomus for altitude range 3 (3500-4000m a.s.l.), and Rheotanytarsus for altitude range 1 (2500-3000 m a.s.l.). The presence of many undetermined genera, especially Orthocladiinae, as well as the estimates indicated by the species accumulation curves, suggest that the real diversity of genera of Chironomidae in the Andean region is still far from being known.

Wood-inhabiting filamentous fungi in 12 high-altitude streams of the Western Ghats by damp incubation and bubble chamber incubation

The diversity and distribution of fungi on naturally submerged wood from 12 high-altitude streams of the Western Ghats in India were studied by damp chamber incubation and bubble chamber incubation. The damp chamber incubation of wood samples yielded 29 fungal taxa (17 anamorphs, 11 ascomycetes, 1 basidiomycete). Acrogenospora sphaerocephala, Canalisporium sp., Dictyosporium heptasporum, Leptosphaeria ginimia, L. typharum, Massarina australiensis, Sporoschisma saccardoi, and Sporoschismopsis australiensis were the most common taxa and were widely distributed on wood in streams of the Western Ghats. The bubble chamber incubation of bark and cambium revealed 30 aquatic hyphomycetes (bark, 28; cambium, 18). Anguillospora longissima, Flagellospora curvula, F. penicillioides, and Lunulospora curvula were most common in bark as well as cambium. There was only 1 species (Helicomyces roseus) that was identified following both incubation methods, indicating that methodology influences the detection of fungal communities. It is recommended that studies on freshwater fungi should incorporate both damp incubation and bubble chamber techniques.

A new species of Trichogenes from the rio Itapemirim drainage, southeastern Brazil, with comments on the monophyly of the genus (Siluriformes: Trichomycteridae)

A new species of the formerly monotypic genus Trichogenes is described from a high-altitude stream of the rio Itapemirim system, an isolated Atlantic drainage in the State of Espírito Santo, southeastern Brazil. Trichogenes claviger, new species, differs from all other trichomycterids by the sexually dimorphic posterior process of the opercle, much elongated in males; the terminal mouth; the deeply bifurcated anterior neural spines and the presence of a large anterodorsal claw-like process on the neural arches of the anterior four free vertebrae. The new species also differs from its only congener, T. longipinnis, by a number of additional traits, including the the lack of branched anal-fin rays in specimens of any size; the broader than long posterior nostril; the deeper head (head depth 72.9-86.6% HL); the presence of a fine dark line along the base of the anal fin; the lack of dark spots on cheeks; the shape of the interopercle; the presence of odontodes on a bony expansion on the posterodorsal margin of the interopercle; the fewer vertebrae (35); the absence of an antorbital; and the fewer pleural ribs (eight). Small juveniles of the new species are also strikingly different from those of all other Trichomycteridae, including T. longipinnis, having a very large lateral eye, an upturned mouth, and compressed head. Trichogenes claviger occurs in shaded sectors of a blackwater sluggish stream with sandy substrate and patchy accumulations of vegetable debris, a habitat markedly different from the rocky torrential environment known for T. longipinnis. A comparison of the internal anatomy of the two species provides the basis for a hypothesis of a monophyletic Trichogenes. Data from the new species further support a sister-group relationship between Trichogeninae and Copionodontinae, as well as the position of that clade as sister group to all remaining Trichomycteridae.

Wood-inhabiting filamentous fungi in 12 high-altitude streams of the Western Ghats by damp incubation and bubble chamber incubation

The diversity and distribution of fungi on naturally submerged wood from 12 high-altitude streams of the Western Ghats in India were studied by damp chamber incubation and bubble chamber incubation. The damp chamber incubation of wood samples yielded 29 fungal taxa (17 anamorphs, 11 ascomycetes, 1 basidiomycete). Acrogenospora sphaerocephala, Canalisporium sp., Dictyosporium heptasporum, Leptosphaeria ginimia, L. typharum, Massarina australiensis, Sporoschisma saccardoi, and Sporoschismopsis australiensis were the most common taxa and were widely distributed on wood in streams of the Western Ghats. The bubble chamber incubation of bark and cambium revealed 30 aquatic hyphomycetes (bark, 28; cambium, 18). Anguillospora longissima, Flagellospora curvula, F. penicillioides, and Lunulospora curvula were most common in bark as well as cambium. There was only 1 species (Helicomyces roseus) that was identified following both incubation methods, indicating that methodology influences the detection of fungal communities. It is recommended that studies on freshwater fungi should incorporate both damp incubation and bubble chamber techniques.

Some aspects of the biology of the stargazer mountain catfish, Amphilius uranoscopus (pfeffer); (Siluriformes: Amphiliidae) indigenous to Kenya streams

AbstractA study on some biological parameters of the mountain catfish, Amphilius uranoscopus Pfeffer 1889 (Silurifomes: Amphiliidae), was carried out in the Thego stream on the slopes of Mount Kenya from February to December 2002. Physical and chemical profiles of the Thego show that the water quality parameters is typical of high altitude streams with temperatures rarely exceeding 18°C, DO ranging from 7.9 to 8.2 mg l−1 and relatively high conductivity (97–137 μS cm−1) typical of perturbed lotic environments. A total of 1010 fish were caught by an electro‐fisher, with sizes ranging between 8 and 24 cm fork length. The population structure had a unimodal distribution with maxima at 14–16 cm. The length–weight relationship showed relatively narrow range in the slope ranging from 2.61 in April to 2.98 in February 2002, thereby suggesting isometric growth pattern. The fitted growth pattern of A. uranoscopus showed an asymptotic length (L∞) of 28.5 cm and a growth curvature (K) of 0.56 year−1 resulting in an estimated natural mortality coefficient (M) of 0.90 year−1. The Fulton’s condition factor (K) was also relatively stable with a peak in April (0.92 ± 0.21) and lowest value in June (0.86 ± 0.10). As A. uranoscopus is not under commercial exploitation, the seemingly depressed population is possibly attributed to the introduced exotic rainbow trout that heavily predates on the species and environmental perturbations arising from changes in land use. The implications of such changes on A. uranoscopus are discussed.

Relationships between stream habitat and breeding territory length of the Brown Dipper (Cinclus pallasii) in Taiwan

Dippers from the genus Cinclus are highly specialised predators on aquatic invertebrates, and occupy linear territories along rivers where measurements of variations in quality are relatively straightforward. For these reasons, they are ideal model species in which to examine factors affecting territory size. In this paper, we investigated the influence of stream habitats on the territory length of the Brown Dipper (Cinclus pallasii) in Taiwan. The biomass of aquatic insects and other stream habitat variables were analyzed to determine their relationships with the territory length of Brown Dippers from November 1988 to May 1989. Compared with slow-moving waters, riffle areas contained significantly greater insect biomass (paired t test, t 11 = 3.49, P < 0.01), of which trichopteran larvae contributed about 70%. Dippers spent more time foraging in riffles than in slow-moving waters. In addition, dippers preferred foraging in shallow riffles, but avoided deep, slow-moving waters (G = 62.53, df = 3, P < 0.001). Territory length (1,045 ± 165 m [SE], n = 14) was negatively related to proportion of riffles (r 2 = 0.5715, P < 0.01), total aquatic insect biomass (r 2 = 0.5840, P < 0.01), and altitude (r 2 = 0.7176, P < 0.001). In factor analysis, four factors were extracted from the 14 stream variables. However, only factor 1 was significantly related to territory length (r 2 = 0.5207, P < 0.01). Factor 1 explained 42.8% of the total variance and collectively revealed the importance of high food abundance. In other words, Brown Dipper territories were the shortest along high-altitude streams with abundant riffles, fewer pools and abundant aquatic insects. These results indicate that abundant supply of accessible invertebrate prey is the most important factor affecting the territory length of Brown Dippers. This is consistent with Cinclus species elsewhere, and reveals the importance of clean, productive river ecosystems.