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Both gradual and extreme weather changes trigger complex ecological responses in river ecosystems. It is still unclear to what extent trend or event effects alter biodiversity and functioning in river ecosystems, adding considerable uncertainty to predictions of their future dynamics. Using a comprehensive database of 71 published studies, we show that event – but not trend – effects associated with extreme changes in water flow and temperature substantially reduce species richness. Furthermore, event effects – particularly those affecting hydrological dynamics – on biodiversity and primary productivity were twice as high as impacts due to gradual changes. The synthesis of the available evidence reveals that event effects induce regime shifts in river ecosystems, particularly affecting organisms such as invertebrates. Among extreme weather events, dryness associated with flow interruption caused the largest effects on biota and ecosystem functions in rivers. Effects on ecosystem functions (primary production, organic matter decomposition and respiration) were asymmetric, with only primary production exhibiting a negative response to extreme weather events. Our meta-analysis highlights the disproportionate impact of event effects on river biodiversity and ecosystem functions, with implications for the long-term conservation and management of river ecosystems. However, few studies were available from tropical areas, and our conclusions therefore remain largely limited to temperate river systems. Further efforts need to be directed to assemble evidence of extreme events on river biodiversity and functioning., This research was funded by the CLIMALERT ERA4CS project (CGL2017-88640-C2-1-R of the Spanish Ministry of Economy and Competitiveness; ERA4CS/0004/2016 of the Portuguese Foundation for Science and Technology). Additional support was received through the projects RIVSTRESS (PID2020-115708RB-C22) and STREAMECO (PTDC/CTA-AMB/31245/2017). ICRA researchers acknowledge funding from the CERCA program and the support through the Consolidated Research Group ICRA-ENV 2017 SGR 1124. The CBMA researchers acknowledge the Contrato-Programa UIDB/04050/2020 funded by Fundaçao para a Ciência e a Tecnologia. A.F. acknowledges the Juan de la Cierva program (IJC2019-039181-I) funded by MCIN/AEI.

The North Atlantic Basin (NAB) is seeing a significant increase in the frequency and intensity of tropical cyclones since the 1980s, with record-breaking seasons such as 2017 and 2020. However, little is known about how coastal ecosystems, particularly mangroves in the Gulf of Mexico and the Caribbean, are responding to these new “climate normals” at regional and subregional scales. Wind speed, rainfall, pre-cyclone forest structure, and hydro-geomorphology are known to influence mangrove damage and recovery following cyclones in the NAB. However, these studies have focused on site-specific responses and individual cyclonic events. Here, we analyze 25 years (1996-2020) of mangrove vulnerability (damage after a cyclone) and short-term resilience (recovery after damage) for the entire NAB and its subregions, using multi-annual, remote sensing-derived databases. We applied machine learning to characterize the influence of 22 potential drivers that include previously researched variables and new ones such as human development and long-term climate trends. The characteristics of the cyclones mainly drive vulnerability at the regional level, while resilience is largely driven by site-specific conditions. These include long-term climate conditions, such as air temperature and drought trends, pre-cyclone habitat conditions, such as canopy cover and height and soil organic carbon stock, and human interventions on the land. Rates and drivers of mangrove vulnerability and resilience vary across subregions in the NAB, and hotspots for restoration and conservation actions are highlighted within subregions. The impacts of increasing cyclone activity need to be framed in the context of climate change compound effects and heavy human influences in the region. There is an urgent need to value the restoration and conservation of mangroves as fundamental Nature-based Solutions against cyclone impacts in the NAB.

The use of English as the common language of science represents a major impediment to maximising the contribution of non-native English speakers to science. Yet few studies have quantified the consequences of language barriers on the career development of researchers who are non-native English speakers. Our survey demonstrates that non-native English speakers, especially early in their careers, spend more effort than native English speakers in conducting scientific activities, from reading and writing papers and preparing presentations in English, to disseminating research in multiple languages. Language barriers can also cause them not to attend, or give oral presentations at, international conferences conducted in English. We urge scientific communities to recognise and tackle these disadvantages to release the untapped potential of under-represented non-native English speakers in science.

Fire is a global disturbance that has a strong influence on biodiversity. Seasonal fires are common in neotropical savannas of South America, yet few studies have analyzed how the fauna of these habitats and nearby forests respond to fire. We evaluated the effects of fire on the community of non-volant small mammals in the Colombian llanos by comparing their populations in both unburned (no record of fire for the last 20 years) and recently burned areas (three years after the last fire event). Vegetation structure was monitored at 240 plots. We used hierarchical single-season occupancy modeling to determine potential effects of fire on small mammal detection and occupancy. Our results indicate that fire has long-term effects on plant diversity and richness, as well as on the species composition. Three years after the last fire event, the average richness of plant species at burned sites was lower than at unburned sites. Fire also affected the distribution of vegetation strata leading to an increased abundance and diversity of plants in the ground and herbaceous strata in burned plots. The hierarchical models indicate that mammals’ occupancy tracks these changes in vegetation structure. However, the effect of fire was not consistent among species. We found that fire may restrict (Didelphis marsupialis), promote (Zygodontomys brevicauda) or have no impact (Oecomys sp.) on the mammals’ distribution depending on how each species uses the strata that disappeared because of fire. These findings provide evidence toward wildfire prevention for biodiversity conservation in fire-sensitive ecosystems of northern South America.

AIM: Contemporary dispersal constraints and environmental conditions are broadly recognized as significant drivers of beta diversity patterns. However, beta diversity patterns may also reflect the legacy of past climatic and geological events. In this study, we investigated the relative importance of historical and contemporary factors as drivers of taxonomic, functional and phylogenetic beta diversity in Neotropical stream communities. LOCATION: The Colombian Orinoco basin. TAXON: Diatoms and insects. METHODS: We estimated taxonomic, phylogenetic and functional beta diversity using Baselga's (BAS) and Podani's (POD) frameworks. Following both frameworks, we further partitioned every biodiversity facet into turnover and nestedness or richness difference components. Then, we used generalized linear models (GLM) to relate each biodiversity facet with environmental, spatial and historical factors. RESULTS: We found that both historical and contemporary factors affected current patterns of beta diversity. Historical factors and water pH and temperature had the strongest effect on beta diversity patterns, particularly for taxonomic and phylogenetic facets. GLM models performed better for insects than for diatoms in all three facets. Within communities, our analysis also revealed a partial congruence between BAS‐ and POD‐based results. MAIN CONCLUSIONS: Due to their past geological history and contemporary environmental gradients, tropical montane streams are natural laboratories for disentangling the joint effects of ecological and biogeographical factors on biodiversity patterns. Our study reveals that present‐day distribution patterns cannot be fully explained without accounting for the effects of past geological and climatic events on mountain landscapes. In the Neotropics, montane geology sets the stage for speciation and landscape formation, with which ecological (e.g., dispersal limitation) and environmental factors interact to generate spatial variation in species turnover.

We assessed the relative influence of ecoregional features in explaining diatom distribution in the Orinoco river basin. Ecoregions in the Colombian Orinoco can be seen as imprints of the evolutionary history of the basin, for their current biodiversity and physiographic features are the result of the geological and climatic shifts that have occurred since the Tertiary. Thus, they represent an ideal testing ground for studying the interplay between ecological and evolutionary processes shaping diversity patterns of microorganisms, such as diatoms, in the present day. To study this interplay, we compared diatom community composition variance within and among seven ecoregions and assessed the explanatory power of environmental, spatial and historical drivers. This was done by a combination of correlation analyses, multivariate methods and constrained ordinations. We also deconstructed the whole community data set into ecological guilds (low- and high-profile, and motile) to explore their individual response to the contemporary and historical drivers. Taken together, these analyses indicated that contemporary constraints to species occurrence and dispersal, as well as the legacies of historical events, can provide an explanation for the contemporary distribution of diatoms in the Colombian Orinoco. Specifically, we provided evidence showing that both historical legacies and contemporary environmental conditions (temperature, pH, and phosphorus concentration) are interacting to determine diatoms' distribution. Our results suggest the need to consider ecoregional gradients for unraveling the mechanisms shaping tropical diversity as well as for designing conservation plans.

Land use policies and planning in Latin America have been partially successful in halting deforestation yet have not stopped forest degradation. Here, we study the different stakeholders’ perspectives of the drivers of forest degradation. We use Colombia as a case study for understanding synergies and trade-offs of the sustainable development goals (SDGs) and analyzed what the most important causes are, to whom it matters, and their regional contribution. We identified a common perception, but miscommunication and misunderstandings occur between local- and national-level actors in terms of their views on responsibilities and rates of change. The results are a call for action. Cross-scale governance is necessary to improve the design and implementation of policies for forest management at the subnational and local levels and to ensure that we move toward sustainable development without worsening existing inequalities. It is essential that countries provide the enabling conditions to develop a coherent governing framework., First of all we would like to thank all the participants from community-based organizations (farmers and indigenous and Afro-descendants), foresters, public entities, natural resource management authorities, municipalities, regional governments, academics and professionals from non-profit organizations (NGOs) that kindly answered the surveys. This work is a continuation of the information collected through the contract No. 2302831 2016 between UNAL and the United Nations for Food and Agriculture – FAO, and as such we would like to thank the Colombia UN-REDD programme and the Institute of Hydrology, Meteorology and Environmental Studies of Colombia – IDEAM who initially supported part of this research.

Water flow velocity is a strong environmental filter structuring benthic communities in lotic ecosystems. While many studies have determined its effect on the distribution and diversity patterns of insects, the role of water flow velocity on other groups of aquatic invertebrates (i.e., Oligochaeta) has remained unexplored. We sampled five lotic ecosystems to investigate the influence of water flow velocity on the species composition of Oligochaeta assemblages in a Neotropical floodplain. Our first hypothesis was that higher water flow velocity decreases Oligochaeta assemblages variability. Consequently, we expected a lower beta diversity among the mid-channels of the ecosystems (i.e., sites with higher water velocity) relative to channel margins (i.e., sites with lower water velocity). Our second hypothesis was that water flow velocity determines species composition of Oligochaeta. Consequently, we expected a different species composition between the mid-channel and the channel margins of lotic ecosystems. We found 19 Oligochaeta species across the five lotic ecosystems. We corroborated both hypotheses because we found lower Oligochaeta beta diversity among the mid-channels of the lotic ecosystems as well as a different species composition. Haplotaxis aedeochaeta and Narapa bonettoi were the taxa strongly associated with the mid-channel, because they are adapted to live among the sand grains in the bottom of the rivers with high depth and water velocity. Overall, water flow velocity should be considered as a strong driver of Oligochaeta species composition.

Several studies have revealed that beta-diversity patterns are tightly coupled to differences in habitat heterogeneity and the spatial distance among headwaters. However, addressing the relative role of these factors over time is yet to be done, particularly in those factors acting at the local scale. Here, we investigated the temporal responses of stream invertebrate communities to habitat simplification and flow variability in two stretches of a high-Andean stream: an undisturbed and a channelized stretch. Both stretches were sampled every month in two hydrologically different years: a “regular year” and a year under the influence of the La Niña phenomenon. Using four types of beta diversity (Jaccard, Percentage difference, Raup-Crick, and Gower), we tested two hypotheses: (H1) the temporal flow dynamics affect beta diversity, increasing its temporal variability. (H2) The effect of flow temporal dynamics would change because of the habitat simplification, being the temporal variability of beta diversity higher in the simplified (channelized) stretch. Contrarily to our expectations, we observed a significant mismatch between beta diversity metrics: while some indicated an increase, others indicated a decrease in the temporal variability. Nevertheless, taken together and interpreted in an ecological context, our results indicate that habitat simplification changes the temporal patterns of beta diversity. Specifically, our findings suggest that habitat simplification induces the functional homogenization of the community and diminishes the extent of change in community composition between sampling occasions. At the channelized stretch, we found that the community comprised species with adaptations to flow-related constraints primarily whose occurrence varied little among sampling occasions. These findings are relevant to Andean streams’ bioassessment, as certain programs rely on taking a ‘snapshot” to assess the ecosystem’s health or the effect of an anthropogenic stressor. Our study suggests that this snapshot may be biased if both the habitat heterogeneity and the history of high-flow events are not explicitly considered.

Aim To identify and characterize the distribution of invertebrate taxa in the Orinoco basin and how their distribution affects the metacommunity structure along the river network. Location Meta and Guaviare sub‐basins, Orinoco basin, Colombia, South America. Methods We characterized the invertebrate communities and environmental characteristics of 25 streams from six ecoregions in the Orinoco basin. The ecoregions present different historical evolution, altitude, slope, climate and vegetation features. We used multiplicative diversity partitioning to compare the contributions of riffle (α and β1), stream (β2) and ecoregional (β3) scales to the overall gamma diversity of the basin. We also applied the Elements of Metacommunity Structure framework to delineate metacommunity types and a distance‐based redundancy analysis to assess the relative relevance of environmental, spatial and ecoregional drivers in species compositions of invertebrate communities. Results Streams showed significant differences in community composition among the ecoregions. Several discrete pools of invertebrate taxa occurred in the basin that largely matched the distribution of the ecoregions. Consequently, the metacommunity in the basin resembled a Clementsian idealized structure. The species composition of invertebrate communities was mostly explained by ecoregion type and its interaction with the local environment, particularly its physiographic features. Main conclusions Historical and evolutionary processes have resulted in species pools differing between the ecoregions of the Orinoco basin. At the basin scale, the metacommunity structure seems to be constrained by ecoregional features rather than by spatial structure or the local environment. Hence, using the basin as a unit for biodiversity conservation and river management would not adequately reflect the diversity and distribution patterns in highly heterogeneous basins such as the Orinoco basin Universidad Nacional de Colombia. Grant Number: 34856

Deforestation is a major driver of biodiversity loss in the Tropical region, but the role of upstream refugia and dispersal ability on the community response to this disturbance is unknown. We assessed the relevance of undisturbed upstream patches (“refugia”) on the responses of benthic communities to forest cover loss. We selected four Andean rivers with a well-protected forest in their upstream section and different degree of forest cover loss downstream and evaluated the dissimilarity patterns of three benthic communities (diatoms, Chironomidae, and the assemblage of Ephemeroptera, Plecoptera and Trichoptera—‘EPT’) along their water courses. We evaluated the dissimilarity by using Euclidean (environment), Sorensen (incidence data) and Morisita–Horn (abundance data) pairwise distances. We found that diatom beta-diversity, as organisms with passive but higher dispersal ability, significantly tracked the environmental changes caused by forest loss. However, insect communities, whose a priori are active dispersers and can track for suitable conditions, were weakly affected by deforestation. These results provide evidences that the existence of well-preserved upstream reaches along patched corridors may allow non-tolerant species to remain extant throughout dispersal-driven feedbacks. This being the case in the Andean streams, effects of deforestation on benthic communities were small, and not uniform. Our results reinforce the strategy of preserving upstream sections in order to achieve successful restoration or rehabilitation goals.

Animal movement characteristics are not species-specific traits, but rather individual features that respond to various selective pressures. To understand patterns of animal movements, it is especially important to explore how they are affected by differences in landscape and habitat configuration. This paper presents an analysis of the movement patterns of a species of conservation concern in Northwest Amazon, the lowland tapir (Tapirus terrestris), in relation to landscape elements identified as resource concentration areas (palm stands and natural salt licks). We identify the structure of the movement behavior of a sub-adult male lowland tapir using Behavioral Change Point Analysis (BCPA) and a set of metrics capturing velocity and variance. We also estimate this tapir’s Utilization Distribution (UD) using the dynamic Brownian Bridge Movement Model (dBBMM) in order to better understand its trajectories and space-use patterns. Our results provide insights about this animal’s movement, making it possible to differentiate between foraging behaviors, characterized by long trips and selective resource use, and explorative behaviors, characterized by short displacements and a notable decrease in the usage of resource areas and its trajectories. The high influence of landscape elements on movement characteristics suggest that tapirs may perceive the Amazonian forest as heterogeneous rather than homogeneous mosaics. Therefore, the study of movement characteristics proves to be useful for the development of future studies and conservation plans.

Spatio-temporal variation of the aquatic macroinvertebrates in La Lindosa, Colombian Guiana. Introduction: Describing biodiversity patterns and the underlying drivers is relevant for tackling the rampant pressures on tropical freshwaters. This is particularly relevant in scarcely studied regions, such as in the Colombian Guiana shield. Objective: To describe the taxonomic and functional structure of macroinvertebrate communities and assess their variability across spatial and temporal scales. Methods: We sampled the invertebrate communities in four streams during the dry seasons of 2017 and 2018. Additionally, we assessed diversity patterns within and among streams and between different sampling months in one stream. To assess diversity patterns, we compared alpha (differences in taxon richness and abundance within communities) and beta (differences in taxon composition among communities) diversity patterns among and within rivers. Alpha diversity was estimated using the numbers of Hill, while beta diversity was estimated using the Sørensen and Morisita-Horn indices and compared using a similarities analysis (ANOSIM). Results: The taxon composition of the communities was different within (mesohabitat scale) and among streams (regional scale). However, the composition of FFGs changed among but not within streams. The comparison of the numbers of Hill and the taxon composition suggested that the mesohabitat type is a determining factor of the taxonomic but not FFG diversity across scales. At the temporal scale, alpha diversity was low for months with high precipitation (February-April) and high for the dry season (January). The temporal beta diversity was high among sampling periods, being nestedness processes driving beta diversity among years and turnover processes driving beta diversity within years. Conclusion: Streams from Serranía de la Lindosa host a high diversity of freshwater macroinvertebrates. Seasonality and differences in the in-stream habitat heterogeneity seem to determine the diversity patterns observed at different temporal and spatial scales. A deeper study is needed to understand the functioning of these ecosystems and improve the ability to generate management and conservation strategies Describir los patrones de biodiversidad y los mecanismos que los subyacen es indispensable para afrontar las desenfrenadas presiones sobre los ecosistemas de agua dulce en el trópico. Esto es particularmente relevante en regiones escasamente estudiadas como el escudo guayanés colombiano Objetivo: Describir la estructura taxonómica y funcional de las comunidades de macroinvertebrados, y evaluar su variación a lo largo de escalas espaciales y temporales Métodos: Las comunidades de macroinvertebrados de cuatro ríos fueron muestreadas durante la época seca del 2017 y 2018. Adicionalmente, se evaluaron los patrones de diversidad dentro y entre los ríos y entre diferentes meses de muestreo en uno de los cursos hídricos. Los patrones de diversidad fueron evaluados mediante la comparación de los patrones entre y dentro de los ríos de la diversidad alfa (diferencias en la riqueza y abundancia de taxones entre comunidades) y de la diversidad beta (diferencias en la composición de taxones entre comunidades). La diversidad alfa fue estimada usando los números de Hill, mientras que la diversidad beta se estimó usando los índices de Sørensen y Morisita-Horn y comparada usando un análisis de similaridad (ANOSIM). Resultados: La composición de taxones fue distinta dentro (escala de mesohábitat) y entre los ríos (escala regional). Sin embargo, la composición de FFG cambió entre, pero no dentro de los ríos. La comparación de los números de Hill y de la composición de taxones sugiere que el tipo de mesohábitat es un factor determinante de la diversidad taxonómica pero no de la diversidad de FFG en distintas escalas. En la escala temporal, la diversidad alfa fue baja para los meses con altas precipitaciones (febrero-abril) y alta para la temporada seca (enero). La diversidad beta temporal fue alta para los periodos muestreados y los procesos de anidamiento fueron el componente más notable de la diversidad beta a lo largo del año. Conclusión: Los ríos de la Serranía de la Lindosa albergan una alta diversidad de macroinvertebrados acuáticos. La estacionalidad y las diferencias en la heterogeneidad del hábitat dentro de los ríos parecen determinar los patrones de diversidad observados a diferentes escalas temporales y espaciales. Profundizar en su estudio es necesario para entender el funcionamiento de estos ecosistemas y mejorar la habilidad para generar estrategias de manejo y conservación

Urban wastewater inputs are a relevant pollution source to rivers, contributing a complex mixture of nutrients, organic matter and organic microcontaminants to these systems. Depending on their composition, WWTP effluents might perform either as enhancers (subsidizers) or inhibitors (stressors) of biological activities. In this study, we evaluated in which manner biofilms were affected by treated urban WWTP effluent, and how much they recovered after exposure was terminated. We used indoor artificial streams in a replicated regression design, which were operated for a total period of 56 days. During the first 33 days, artificial streams were fed with increasing concentration of treated effluents starting with non-contaminated water and ending with undiluted effluent. During the recovery phase, the artificial streams were fed with unpolluted water. Sewage effluents contained high concentrations of personal care products, pharmaceuticals, nutrients, and dissolved organic matter. Changes in community structure, biomass, and biofilm function were most pronounced in those biofilms exposed to 58% to 100% of WWTP effluent, moving from linear to quadratic or cubic response patterns. The return to initial conditions did not allow for complete biofilm recovery, but biofilms from the former medium diluted treatments were the most benefited (enhanced response), while those from the undiluted treatments showed higher stress (inhibited response). Our results indicated that the effects caused by WWTP effluent discharge on biofilm structure and function respond to the chemical pressure only in part, and that the biofilm dynamics (changes in community composition, increase in thickness) imprint particular response pathways over time. © 2019 Elsevier B.V., This study has been financially supported by the EU FP7 project GLOBAQUA [Grant Agreement No. 603629] and by the Generalitat de Catalunya [Consolidated Research Groups: 2017 SGR 01404−Water and Soil Quality Unit]. NM thanks SCIEX for generously providing the loaned instrument. Authors are grateful to Vicenç Acuña, Maria Casellas, Ferran Romero and Olatz Pereda for their support and advice during the experiment, and to Peter Eichhorn for his critical reading of the manuscript.

Few studies have explored the ecology and interrelationship with other organisms of the many endangered freshwater turtle species inhabiting the Neotropical region. The focus of the current study was to shed light on the relationship between Neotropical turtle carapaces and primary producers, insofar as the surface of former constitutes a suitable substrate for the colonization and establishment of the latter. The under-explored relationship between turtle carapaces and the diatom assemblages inhabiting them was investigated and characterized in terms of taxonomic and biological traits (bio-volume, life-form, and attachment). The carapaces of seven native turtle species were surveyed. Among these carapaces, a total of 45 diatom taxa were found, and diatom taxa varied among turtle species. Podocnemis vogli and Podocnemis expansa supported more diverse diatom assemblages than Podocnemis lewyana, Rhinoclemmys diademata, and Rhinoclemmys melanosterna, which were dominated by Navicula spp. Analysis, further showed that carapace size did not explain differences in diatom diversity. However, a trait-based analysis suggests that both carapace roughness and an assemblage’s successional stage might explain the differences in assemblage composition. Because turtles can serve as dispersal vectors, characterizing their epibiont diatom assemblages may contribute to our understanding of diatom distribution on larger scales, as well as, give us some clues as to the auto-ecology of turtles that help us to effectively determine conservation areas for these endangered species. Resumen De las especies de tortugas en estado crítico o vulnerable de conservación que habitan en la región Neotropical, son pocos los estudios que han ahondado en su ecología o relaciones con otros tipos de organismos. El presente estudio buscó caracterizar la asociación existente entre las diatomeas y el caparazón de especies de tortugas neotropicales, ya que este representa un sustrato adecuado para la colonización y establecimiento de este grupo de algas. Esta asociación fue estudiada considerando tanto la composición de especies como la de rasgos biológicos (biovolumen, forma de vida, y forma de adherencia) de la comunidad de diatomeas. En los caparazones de las 7 especies de tortugas muestreadas se encontraron un total de 45 táxones. La composición de táxones varió entre los caparazones de las especies. Se encontró una mayor diversidad en los caparazones de Podocnemis vogli y Podocnemis expansa, mientras que en Podocnemis lewyana, Rhinoclemmys diademata, y Rhinoclemmys melanosterna se encontró una comunidad de baja diversidad dominada principalmente por Navicula sp. Los resultados sugirieron que la rugosidad del caparazón junto al estado de la sucesión pueden explicar las diferencias observadas en la composición de táxones de los diferentes caparazones. Debido a que las tortugas pueden funcionar como vectores de dispersión, caracterizar las comunidades que pueden crecer sobre sus caparazones podría contribuir a entender la distribución de las diatomeas a escalas mayores. Además, esta caracterización podría darnos pistas clave para la delimitación de áreas de conservación efectivas para las especies más amenazadas.

Flow regulation can alter the structure and dynamics of lotic communities, especially in rivers with unpredictable high-flow events, such as those flowing through the Paramo, an endemic ecosystem of the high-altitude Neotropical Andes. This study evaluated how flow regulation affects invertebrate assemblage structure in a Paramo river. In both the wet and dry seasons, the study assessed flow history, water chemistry and mesohabitat characteristics in their relation to assemblage structures upstream (undisturbed reach) and downstream (disturbed reach) of a water diversion structure. The elimination of spates through flow regulation did not lead to a complete change in the assemblage components at the disturbed reach. Instead, it led to an assemblage structure with a greater genera-richness, a lower genera-evenness and a greater occurrence of certain genera, e.g., Pristina , Alotanypus , Polypedilum and Austrolimnius . These genera lacked resistance-resilience adaptations, which would allow them to survive in mesohabitat conditions resulting from increased hydromorphological stability, namely higher fine sediment retention, higher benthic organic matter (BOM) and lower hydraulic stress. Overall, the results of this study reinforce the assertion that, in Paramo rivers, the temporal dynamics of the natural flow regime significantly control the structure of invertebrate assemblages. Thus, to preserve these rivers' biotic assemblages, it will be necessary to implement new regulation plans that mimic their natural flow histories.

The importance of channel complexity in maintaining biological integrity and ecosystem functioning has been addressed by several researchers. In spite of this, High-Andean streams are being channelized without regard to the effect that channelization might have on stream communities. To attempt to determine these effects, the present study evaluated how caddisfly assemblages respond to channelization in a High-Andean stream. A trait-based approach was used to compare trait-based responses, and the degree of functional homogenization caused by channelization. A total of seven traits are described: (i) ‘Food,’ (ii) ‘Feeding habits,’ (iii) ‘Maximum body size,’ (iv) ‘Adaptation to flow constrains,’ (v) ‘Body flexibility,’ (vi) ‘Case-material,’ and (vii) ‘Case-shape.’ Both the functional structure of the assemblages and the channel complexity of the channelized site were characterized and compared to those of two undisturbed sites. The results suggest that certain genera become dominant as a result of the environmental changes caused by partial channelization. Specifically, assemblages underwent significant specialization in ‘Food,’ ‘Feeding habits,’ and ‘Case-shape,’ and this was linked to the homogenization in mesohabitat type and in hydraulic variability. The trends evident in the trait-based responses may serve as a basis for proposing and assessing strategies to restore the hydromorphological integrity of High-Andean streams.

The Chironomidae is a cosmopolitan family of Nematoceran flies with more than 20,000 species described. However the diversity of genera and species of the family in the Andean region beyond the 2,000 m.a.s.l are scarcely known. We conducted faunal surveys and biomonitoring research in different streams of Colombia, Ecuador and Peru from May 2005 to October 2011. Based on specimens collections, a taxonomic key was developed to identify pupae and pupal exuviae of 46 genera of midges (Diptera, Chironomidae) collected from streams at high altitude areas on the Andean tropical mountains. We included illustrations and brief taxonomic descriptions for all genera, of which several ones have not yet been formally described; in this latter case we used the nomenclature of RobackCoffman (1983). For two genera, Cricotopus and Genus 1, keys to the most com- mon morphospecies were provided. Results showed that in this area the chironomid assemblages are dominated by the members of the subfamily Orthocladiinae (22 genera) followed by the Chironominae (13). Six genera of Tanypodinae were identified, while only three and two genera were present from subfamilies Podonominae and Diamesinae. This key may be very useful for both studies about drift in streams, and for biomonitoring purposes.

Chironomidae es una familia cosmopolita de dípteros nematóceros que comprende más de 20 000 especies descritas. Sin embargo, la diversidad de géneros y especies presentes en la región andina del Neotrópico es poco conocida. Por tal motivo se desarrolló una clave taxonómica para identificar las pupas y exuvias pupales de 46 géneros de la familia Chironomidae presentes en ríos de alta montaña ubicados en la cordillera de los Andes por encima de los 2 000msnm. Se utilizó material de colección obtenido de levantamientos faunísticos y estudios de biomonitoreo en diferentes ríos y quebradas de Colombia, Ecuador y Perú. La clave incluye ilustraciones y breves descripciones taxonómicas de todos los géneros incluyendo algunos que aún no han sido descritos formalmente. Para estos últimos se siguió la nomenclatura usada por Roback & Coffman (1983). Para los géneros Cricotopus y Género 1 se incluyen claves para la determinación de las morfoespecies más comunes. En el ensamblaje de quironómidos de la región altoandina domina la subfamilia Orthocladiinae (22 géneros) seguida por Chironominae (13 géneros), patrón que contrasta con la dominancia de Chironominae en las zonas de menor altura de la región Neotropical. Se encontraron seis géneros pertenecientes a la subfamilia Tanypodinae, mientras que para Podonominae y Diamesinae estuvieron presentes tres y dos géneros respectivamente. Esta clave podría llegar a ser muy útil en estudios de la deriva y programas de biomonitoreo de los ríos altoandinos neotropicales.