1,720,976 research outputs found
The increase of an amphibian population: 11 years of Rana temporaria Egg-mass monitoring in 30 mountain ponds
No full textConsiderations on the vulnerability of the Eurasian water shrew Neomys fodiens to the presence of introduced brown trout Salmo trutta
No full textIntroduced fish represent a major threat for aquatic ecosystems and species and their impact on semiaquatic vertebrates, such as amphibians, has been extensively studied. On the other hand, little is known about their impact on semiaquatic mammals, such as water shrews (Neomys spp., Soricidae), although small mammals have been reported in their diet. The present note reports on a case of predation on an adult Eurasian water shrew Neomys fodiens by a large sized brown trout Salmo trutta belonging to a population introduced in a small pastureland pond in an Italian mountain area. The authors considered that shrews, including relatively large species such as Neomys spp., can be susceptible to predation by introduced fish and they use this finding to discuss about direct and indirect impacts of introduced fish on the populations of shrews inhabiting originally fishless habitats such as headwaters
Ecological impact of introduced fish in high altitude lakes: a case of study from the European Alps
No full textFish introduction is a major threat to alpine lake biota leading to the loss of native species and to the degeneration of natural food-webs. This study provides an extensive investigation on the impact of the introduced fish Salvelinus fontinalis on the native communities of alpine lakes in the Gran Paradiso National Park. We compared the macroinvertebrate and zooplankton communities of six stocked and nine fishless lakes with a repeated sampling approach during the summers 2006–2009. The impact of fish presence on alpine lake fauna is often mediated by the strong seasonality governing these ecosystems, and it dramatically affects the faunal assemblage of littoral macroinvertebrates and the size, structure, and composition of the pelagic zooplankton community with a strong selective predation of the more visible taxa. Direct ecological impacts include a decrease or extinction of nonburrower macroinvertebrates and of large zooplankton species, while small zooplankton species and burrower macroinvertebrates were indirectly advantaged by fish presence. Due to the existence of a compensation between rotifers and crustaceans, fish presence does not affect total zooplankton biomass and diversity even if fish are a factor of ecological exclusion for large crustaceans. These compensatory mechanisms are a key process surrounding the impact of introduced fish in alpine lakes
A dark shell hiding large variability: a molecular insight into the evolution and conservation of melanic Daphnia populations in the Alps
Full text linkZooplanktonic microcrustaceans of the Daphnia pulex group appear highly differentiated at high altitudes as a result of alternative colonizations and quick local adaptation to harsh environments. In particular, the occurrence of deeply differentiated mountain lineages of European Daphnia pulicaria (EuPC) is highly related to glacial advances and retreats during the Pleistocene. Nowadays, one single ancient EuPC lineage survives in the Pyrenees, with another inhabiting the High Tatra Mountains. Much less is known about populations inhabiting the Alps, where EuPC populations are extremely rare. Recently, four new melanic populations have been discovered in lakes in the Western Italian Alps, offering the opportunity to study their origin and adaptations. We inferred phylogenetic relationships of melanic high-mountain populations in order to disentangle their history and clarify the colonization patterns of alpine populations. Molecular data suggest that dark populations originated from at least two ancestors, one genetically close to boreal haplotypes, the other apparently related to refugial populations that survived in southern Europe. Therefore, dark pigmentation and obligate parthenogenesis evolved independently within both lineages inhabiting the studied lakes as extreme local adaptations to the alpine environment. Finally, since impacts of human-related activities and climate changes on mountain species are known to be dramatic, we pose strong issues for the conservation of these extremely localized endemisms
Changes in the insect emergence at the water–air interface in response to fish density manipulation in high altitude lakes.
No full textEmerging insects are important nutrient vectors for lake-to-land linkages, but they are affected by fish predation. We manipulated the fish density in four high altitude lakes in connection with a brook trout eradication project. We used a paired benthic and surface funnel trap design to test whether fish density affects abundance, size, and proportion of aquatic insects reaching the surface in the pelagic zone. The study was complemented with benthic macroinvertebrates and fish diet data. Due to sample size, we focused on midge pupae, which rely on water surface tension (water–air interface) to emerge. Conspicuous insects emerging along the shoreline (water–land interface) were rarely collected in the traps, even if they rapidly recovered through the eradication. There was a positive relationship between fish density and midge abundance, and negative relationship for size and proportion reaching the surface. The increase in the emergence of midges in the presence of fish supports several other studies, but we have provided evidence that this pattern exists in conjunction with a size reduction even when fish consume a substantial amount of midges. The inclusion of small Diptera emergence at the water–air interface is a likely keystone in understanding fish impact on insect subsidy
Predation by introduced fish can magnify the terrestrial arthropod subsidies in mountain lakes
Full text linkA portion of the terrestrial subsidies to lentic habitats consists of arthropods. In high mountain, originally fishless lakes, terrestrial arthropods are an important seasonal food resource for introduced fish. Here we investigate how brook trout Salvelinus fontinalis can alter the input of terrestrial arthropods in ten high mountain lakes contrasting for their stocking history (with and without fish, or manipulated for fish eradication). We used a food consumption model to calculate the minimum and maximum number/biomass of arthropods consumed by fish and we found that they can exceed several folds the number/biomass of arthropods sinking into the lakes, at least under the metabolic rates expected for fish for most of the summer. We interpret this result as an indirect indication that arthropods usually cannot overcome the surface tension at the lake surface and that fish can work as a vector across the water-air interface. We infer that pathways for dead and alive arthropods to leave the lakes do exist and fish can transfer into the water column many arthropods whose fate was leaving the lakes, which may have overlooked ecological and conservation implications.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author
Ecological impact of transhumance on the trophic state of alpine lakes in Gran Paradiso National Park
Full text linkTranshumance - the summer transfer of livestock to highland pastures - is a traditional practice in the European Alps and is considered an integral part of the mountain ecosystem.Mountain lakes are generally oligotrophic systems and are particularly sensitive to the nutrient input caused by livestock. The aim of the present study was to quantify the impact of livestock grazing on the trophic state of high-altitude lakes in an area where transhumance is a traditional practice (Gran Paradiso National Park, Western Italian Alps), taking into account its dual value of ecosystem component and potential threat to lakes\u27 trophic status. The impact of flocks and herds grazing was estimated on sensitive parameters related to the trophic state of alpine lakes: water transparency, nutrient content, bacterial load and chlorophyll-a concentration. Transhumance produced a significant increase in the trophic state of lakes with high grazing pressure, but little or no effect was found at soft-impacted lakes. Even though heavy-impacted lakes represent a minority of the studied lakes (three out of twenty), we indicated conservation measures such as fencing, wastewater treatment and livestock exclosure to be tested in Gran Paradiso National Park.La transhumance, transfert estival du b?tail vers les p?turages d\u27altitude, est une pratique traditionnelle dans les Alpes europ?ennes consid?r?e comme une partie int?grante de l\u27?cosyst?me de la montagne. Les lacs de montagne sont g?n?ralement des syst?mes oligotrophes particuli?rement sensibles ? l\u27apport de nutriments caus? par le b?tail. Le but de la pr?sente ?tude a ?t? de quantifier l\u27impact du p?turage du b?tail sur l\u27?tat trophique des lacs d\u27altitude dans une zone o? la transhumance est une pratique traditionnelle (Parc National du Grand Paradis, ouest des Alpes italiennes), en tenant compte de sa double valeur de composante de l\u27?cosyst?me et de menace potentielle pour l\u27?tat trophique des lacs. L\u27impact du p?turage des troupeaux a ?t? estim? sur les param?tres sensibles li?s ? l\u27?tat trophique des lacs alpins : la transparence de l\u27eau, la teneur en ?l?ments nutritifs, la charge bact?rienne et la concentration en chlorophylle a. La transhumance produit une augmentation significative de l\u27?tat trophique des lacs o? la pression de p?turage est forte, mais peu ou pas d\u27effet a ?t? trouv? dans les lacs moins touch?s.M?me si les lacs tr?s impact?s repr?sentent une minorit? des lacs ?tudi?s (trois sur vingt), nous avons indiqu? les mesures de conservation telles que les cl?tures, l\u27?puration des eaux us?es et la mise en d?fens du b?tail ? tester dans le parc national du Grand Paradis
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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