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ABSTRACT: Synchrony, one of the main traits of population life histories, refers to the degree to which individuals complete a certain
stage of the life cycle at the same time. It can be governed by temperature, variations in temperature, photoperiodic cues,
detritus inputs, or discharge regimes. We investigated life cycles and secondary production of five caddisfly species in a
second order stream in the Patagonian Mountains. In addition, we analyzed what environmental variables were implied in the
caddisfly assemblage variation. Mastigoptila sp. (Glossosomatidae) and Eosericostoma aequispina (Helicophidae), Myotrichia murina (Sericostomatidae), Brachysetodes quadrifidus (Leptoceridae), and Neoatopsyche brevispina (Hydrobiosidae) showed univoltine life cycles, with an extended recruitment with no overlapping cohorts and a relatively
well-synchronized imaginal emergence taking place during spring summer seasons. However, Myotrichia murina (Sericostomatidae) displayed a complex life cycle with mixed populations taking 10–12months to develop, and pupae being
collected almost continuously. The annual secondary production per species varied from 11.06 (E. aequispina) to 310.5mgm−2year−1 (M. murina), being overall caddisfly production (0.5gm−2year−1) similar to that reported for cold springs in other regions. The highest growth rates (K) were observed during late winter and spring (mostly September) and ranged from 0.70 to 3.70% day−1 in M. longicornuta and N. brevispina, respectively. Redundancy analysis indicated that seasonally dynamic variables, water temperature, discharge, and detritus
biomass were the main predictors of caddisfly assemblage variation; consequently at this cold stream (mean annual 5.9°C),
with a regular availability of food supply, these parameters ruled Trichoptera life histories and secondary production. As
documented for other mountainous temperate areas, synchrony would be a dominant trait on life histories of Trichoptera species
inhabiting Patagonian streams.
KeywordsLife cycles–Trichoptera–Biomass–Mountain rivers–Voltinism–Secondary production
Hydrobiologia 05/2012; 673(1):137-151. · 1.78 Impact Factor
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ABSTRACT: Abstract Chironomid substrate-specific associations regarding the nature (organic-inorganic) and stability (stable-unstable) of different habitats were investigated at two low order Patagonian streams, during high and low water periods. Nant y Fall and Glyn rivers were visited twice (October 2007 and March 2008) and seven different habitat types were identified. A total of 60 samples were collected using a Surber sampler (0.09 m (-2) and 250 µm) and a set of 23 environmental descriptors including physicochemical parameters and different fractions of particulate organic matter were assessed. 35 Chironomidae taxa were recorded with Orthocladiinae (20), Chironominae (7), and Podonominae (4) being the most well-represented subfamilies. Paratrichocladius sp. 1, Parapsectrocladius sp. 2, Parametriocnemus sp. 1, Pseudochironomus sp., and Rheotanytarsus sp. were the most abundant taxa. According to the relative preference index, at least 14 taxa showed strong affinity for a particular substrate. The structurally complex macrophyte Myriophyllum quitense supported 11 taxa compared with only five taxa found on the less complex Isoetes savatieri. Generally, stable substrates (boulders, cobbles, and rooted plants) supported significantly higher chironomids richness, abundance, and diversity than unstable ones (gravel-sand). Canonical correspondence analysis revealed that detritus (leaves, seeds, and biomass), macrophyte biomass, and secondarily hydraulic variables had high explanatory power on chironomids species composition and structure. This work suggests that more complex substrates showing persistence in the temporal dimension supported a diverse array of chironomids, meaning that the maintenance of natural habitat heterogeneity is essential for the community. Land-use practices having significant effects on ecological stream attributes such as increased turbidity, sediment deposition, and runoff patterns will alter assemblages. Understanding environmental associations of the Chironomidae assemblage at the habitat scale is significant for conservation purposes and for the management of low order streams in Patagonia.
Journal of Insect Science 05/2012; 12(68):1-20. · 0.95 Impact Factor
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ABSTRACT: On May 2nd of 2008 the Chaitén Volcano (Chile, 42°50'S and 72°39'W) erupted explosively producing a strong emission of volcanic ash. As a result of this eruption wide areas on the Argentinean side became covered by ashes. In order to investigate the effects of ashfall on environmental features, water quality and macroinvertebrate communities we conducted a study on 10 rivers affected by ash deposition in their hydrographic basins. Sites were visited seasonally (June 2008-March 2010) and results were compared with data obtained from previous research projects. Measures of pH, conductivity, oxygen content, main nutrients, and total suspended solids (TSS) were taken. Macroinvertebrate samples were obtained from riffles and pools. Community attributes were measured and metrics were calculated. A strong and significant increase in TSS values at most sites was recorded and although the peak diminished rapidly during the following months, resuspension and remobilization of ash continue even 20 months after. No significant changes in pH, conductivity and nutrients, comparing with data previous to the ashfall, were detected. Most rivers showed a strong diminution on macroinvertebrate density and richness, being small rivers more severely affected than the big ones. Correspondence analysis based on abundance data allows distinguishing preeruption from posteruption dates at five rivers. Density data and species richness showed low values in March of 2010, indicating that the community was not completely recovered at some sites. At least 25 taxa resulted significantly and negatively affected. Increased mortality could be related to several factors such as habitat deterioration, food quality diminution, interference with breathing mechanisms and with other physiological and morphological characteristics. Specific-taxa responses on the recolonization process were related to dispersal mechanisms and specific strategies.
Science of The Total Environment 03/2012; 424:202-12. · 3.29 Impact Factor
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ABSTRACT: Changes in land-use practices have affected the integrity and quality of water resources worldwide. In Patagonia there is a strong concern about the ecological status of surface waters because these changes are rapidly occurring in the region. To test the hypothesis that greater intensity of land-use will have negative effects on water quality, stream habitat and biodiversity we assessed benthic macroinvertebrates, riparian/littoral invertebrates, fish and birds from the riparian corridor and environmental variables of 15 rivers (Patagonia) subjected to a gradient of land-use practices (non-managed native forest, managed native forest, pine plantations, pasture, urbanization). A total of 158 macroinvertebrate taxa, 105 riparian/littoral invertebrate taxa, 5 fish species, 34 bird species, and 15 aquatic plant species, were recorded considering all sites. Urban land-use produced the most significant changes in streams including physical features, conductivity, nutrients, habitat condition, riparian quality and invertebrate metrics. Pasture and managed native forest sites appeared in an intermediate situation. The highest values of fish and bird abundance and diversity were observed at disturbed sites; this might be explained by the opportunistic behavior displayed by these communities which let them take advantage of increased trophic resources in these environments. As expected, non-managed native forest sites showed the highest integrity of ecological conditions and also great biodiversity of benthic communities. Macroinvertebrate metrics that reflected good water quality were positively related to forest land cover and negatively related to urban and pasture land cover. However, by offering stream edge areas, pasture sites still supported rich communities of riparian/littoral invertebrates, increasing overall biodiversity. Macroinvertebrates were good indicators of land-use impact and water quality conditions and resulted useful tools to early alert of disturbances in streams. Fish and birds having a greater ability of dispersion and capacity to move quickly from disturbances would reflect changes at a higher scale.
Science of The Total Environment 01/2011; 409(3):612-24. · 3.29 Impact Factor
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ABSTRACT: The longitudinal distribution of Trichoptera species and environmental variables was analyzed in a large, regulated river from the arid area in Patagonia (Argentina). We examined caddisfl y abundance and richness patterns across a 1000 m altitudinal gradient. Samples were collected seasonally at 13 sites in the upper, middle and lower Chubut River basin. Fifteen species were recorded in the study. Smicridea annulicornis, Cailloma sp., Neoatopsyche chilensis, Neopsilochorema tricarinatum and Parasericostoma ovale were the most common species in tributaries and main channel upper basin sites, S. dithyra appeared mostly at the middle basin sites and Metrichia neotropicalis was the most ubiquitous species. Species richness and density were signifi cantly higher in the upper basin sites than in those on the middle and lower basin. Canonical Correspondence Analysis indicated altitude, stream order and total suspended solids as the stronger factors determining Trichoptera distribution patterns. However, variables that changed seasonally such as discharge and temperature explained the observed temporal changes in the most abundant species, with density being higher during a period of stable flow and high temperature. The analysis also revealed a clear gradient of eutrophication at the lower basin, with sites having higher chlorophyll-a and soluble reactive phosphorus values. This contrasted with upper basin sites showing lower nutrient concentration and caddisfl y species depending on the particulate organic matter supply.
Fundamental and Applied Limnology / Archiv für Hydrobiologie 07/2007; 169(4):307-318. · 1.14 Impact Factor
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ABSTRACT: The benthic coleopteran assemblages of the Chubut River basin were studied in order to assess the main factors affecting species composition and distribution along the upper, middle and lower catchments. A total of 13 sampling sites were selected and sampled seasonally. Eight taxa and 1,601 individuals were collected during the study. Richness was higher in the main channel of Chubut River at the upper basin than at the middle basin. Beetles were completely absent at the lower basin. Mean monthly density per sites varied from 0 to 85 ind m–2. Stethelmis kaszabi had a more restricted distribution whereas Hemiosus dejeanii, Austrelmis sp. and Austrolimnius spp. were more frequent and abundant. Austrelmis sp. appears as the most tolerant species, especially to higher TSS, ammonia, and conductivity values. Luchoelmis cekalovici was absent in stations associated with urban areas. A Canonical Correspondence Analysis shows that conductivity, total suspended solids, wet width, water temperature and pH were the most important variables structuring beetle assemblages. Land use related variables such as NH4, TP, and NO3 were less important but still significant. An increase in TSS affected negatively the coleopteran community; this could be related to both hydrogeological characteristics and agricultural activities (including overgrazing).This is the first approach to the knowledge of the ecological range of distribution of the coleopteran species in Patagonian rivers. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
Internationale Revue der gesamten Hydrobiologie und Hydrographie 09/2006; 91(5):423 - 437.
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ABSTRACT: We assessed the effects of land use on the structure of stream fish assemblages in Northwest Patagonia, Argentina. To this end, a total of 18 sites distributed in 15 streams were sampled during the low water period. At each site, 26 regional and local scale variables were used to describe the environmental conditions. The macroinvertebrate density, and the composition and abundance of fish were then recorded. Statistical associations between local assemblage structures and environmental variables were quantified by canonical correspondence analyses. The results revealed that, at a regional scale, the fish assemblages were primarily determined by watershed features like altitude and catchment area, and by land use effects (exotic forest and pasture). Assemblage compositions were also related to some local-scale features such as water velocity, food availability (density of benthic macroinvertebrates), instream characteristic and riparian features. Also, the observed fish species richness was low. Overall, exotic salmonids largely dominated in the samples both in numbers of individuals (98.9%) and in biomass (99.9%), whereas native fish (Hatcheria macraei and Odontesthes hatcheri) were scarcely represented. Rainbow trout (Oncorhynchus mykiss) was the most abundant fish, and was present in all streams. Native species were restricted to five streams located in the ecotone between the Andes and the steppe, where salmonids were also present. Salmonids were the only fish at Andean streams which suggest the existence of a strong geographic segregation between native and exotic species. Some aspects related to the incidence of the introduced species in the structure of fish assemblages are discussed.
http://dx.doi.org/10.1051/limn/2009030.
