3849 research outputs found

    Fire and herbivory shape soil arthropod communities through habitat heterogeneity and nutrient cycling in savannas

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    Soil arthropods are important components of savannas, contributing to nutrient cycling and thus primary productivity. To investigate how fire and mammalian herbivores influ- ence arthropod food webs, we used two long term herbivore exclosures (ca. 20 y) and burning trials (ca. 5-y return) located along rivers in Kruger National Park, South Africa. Herbivory and fire will usually have negative effects on soil arthropods although this can be variable, and dependent on multiple aspects of habitat structure and nutrient cycling. We hypothesised that in our sites, the more chronic herbivory disturbance would have stronger and more effects than fire, and that both fire and herbivory would decrease arthropod abundance, biomass and diversity via changes to habitat structure and nutrient cycling. We used a structural equation model to investigate these mechanisms, and to compare these drivers. This model supported our hypothesis that herbivory had more and stronger effects than fire, largely through indirect flow-on effects. We also found evidence to support a ‘tolerance/avoidance’ hypothesis, in that herbivory increased soil arthropod diversity by decreasing soil nutrients. Herbivores also decreased arthropod biomass and abundance in total and in all trophic groups excluding omnivores. Fire and herbivory are closely linked, careful consideration should be made when making decisions in the management of either. In some areas either driver may be more dominant, as was the case in our research. Further studies should incorporate a range of fire fre- quencies and intensities, as well as herbivore types, densities and abundances. Disturbance Exclosures Fire Herbivory Path analysis Savannas Soil arthropods Soil food webspublishedVersio

    Species interactions, environmental gradients and body size shape population niche width

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    1. Competition for shared resources is commonly assumed to restrict population-level niche width of coexisting species. However, the identity and abundance of coexisting species, the prevailing environmental conditions, and the individual body size may shape the effects of interspecific interactions on species’ niche width. 2. Here we study the effects of interspecific and intraspecific interactions, lake area and altitude, and fish body size on the trophic niche width and resource use of a generalist predator, the littoral-dwelling large, sparsely rakered morph of European whitefish (Coregonus lavaretus; hereafter LSR whitefish). We use stable isotope, diet and survey fishing data from 14 subarctic lakes along an environmental gradient in northern Norway. 3. The isotopic niche width of LSR whitefish showed a humped-shaped relationship with increasing relative abundance of sympatric competitors, suggesting widest population niche at intermediate intensity of interspecific interactions. The isotopic niche width of LSR whitefish tended to decrease with increasing altitude, suggesting reduced niche in colder, less productive lakes. 4. LSR whitefish typically shifted to a higher trophic position and increased reliance on littoral food resources with increasing body size, although between-lake differences in ontogenetic niche shifts were evident. In most lakes, LSR whitefish relied less on littoral food resources than coexisting fishes and the niche overlap between sympatric competitors was most evident among relatively large individuals (>250 mm). Individual niche variation was highest among >200 mm long LSR whitefish, which likely have escaped the predation window of sympatric predators. 5. We demonstrate that intermediate intensity of interspecific interactions may broaden species’ niche width, whereas strong competition for limited resources and high predation risk may suppress niche width in less productive environments. Acknowledging potential humped-shaped relationships between population niche width and interspecific interactions can help us understand species’ responses to environmental disturbance (e.g. climate change and species invasions) as well as the driving forces of niche specialization

    Local prey shortages drive foraging costs and breeding success in a declining seabird, the Atlantic puffin

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    1. As more and more species face anthropogenic threats, understanding the causes of population declines in vulnerable taxa is essential. However, long-term datasets, ideal to identify lasting or indirect effects on fitness measures such as those caused by environmental factors, are not always available. 2. Here we use a single year but multi-population approach on populations with contrasting demographic trends to identify possible drivers and mechanisms of seabird population changes in the north-east Atlantic, using the Atlantic puffin, a declining species, as a model system. 3. We combine miniature GPS trackers with camera traps and DNA metabarcoding techniques on four populations across the puffins’ main breeding range to provide the most comprehensive study of the species' foraging ecology to date. 4. We find that puffins use a dual foraging tactic combining short and long foraging trips in all four populations, but declining populations in southern Iceland and north-west Norway have much greater foraging ranges, which require more (costly) flight, as well as lower chick-provisioning frequencies, and a more diverse but likely less energy-dense diet, than stable populations in northern Iceland and Wales. 5. Together, our findings suggest that the poor productivity of declining puffin populations in the north-east Atlantic is driven by breeding adults being forced to forage far from the colony, presumably because of low prey availability near colonies, possibly amplified by intraspecific competition. Our results provide valuable information for the conservation of this and other important North-Atlantic species and highlight the potential of multi-population approaches to answer important questions about the ecological drivers of population trends. biologging, diet, DNA metabarcoding, dual foraging, foraging ecology, intraspecific competition, population decline, seabirdspublishedVersio

    Natural forest regeneration on anthropized landscapes could overcome climate change effects on the endangered maned sloth (Bradypus torquatus, Illiger 1811)

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    Climate change and habitat loss have been identified as the main causes of species extinction. Forest regeneration and protected areas are essential to buffer climate change impacts and to ensure quality habitats for threatened species. We assessed the current and future environmental suitability for the maned sloth, Bradypus torquatus, under both future climate and forest restoration scenarios, using ecological niche modeling. We compared environmental suitability for two Evolutionarily Significant Units (ESUnorth and ESUsouth) using two climate change scenarios for 2070, and three potential forest regeneration scenarios. Likewise, we evaluated the protection degree of the suitable areas resulting from the models, according to Brazilian law: PA—Protected Areas; PPA—Permanent Protection Areas (environmentally sensitive areas in private properties); and LR—Legal Reserves (natural vegetation areas in private properties). Finally, we calculated the deficit of PPA and LR in each ESU, considering the current forest cover. Forest regeneration might mitigate the deleterious effects of climate change by maintaining and increasing environmental suitability in future scenarios. The ESUnorth contains more suitable areas (21,570 km²) than the ESUsouth (12,386 km²), with an increase in all future scenarios (up to 45,648 km² of new suitable areas), while ESUsouth might have a significant decrease (up to 7,546 km² less). Suitable areas are mostly unprotected (ESUnorth—65.5% and ESUsouth—58.3%). Therefore, PPA and PA can maintain only a small portion of current and future suitable areas. Both ESUs present a high deficit of PPA and LR, highlighting the necessity to act in the recovery of these areas to accomplish a large-scale restoration, mitigate climate change effects, and achieve, at least, a minimum forested area to safeguard the species. Notwithstanding, a long-term conservation of B. torquatus will benefit from forest regeneration besides those minimum requirements, allied to the protection of forest areas. Atlantic Forest, climate change, conservation, forest regeneration, landscape ecology, Pilosa, XenarthraNatural forest regeneration on anthropogenic landscapes could overcome climate change effects on the endangered maned sloth (Bradypus torquatus, Illiger 1811)acceptedVersio

    Peatland core domain sets: building consensus on what should be measured in research and monitoring

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    It is often difficult to compile and synthesise evidence across multiple studies to inform policy and practice because different outcomes have been measured in different ways or datasets and models have not been fully or consistently reported. In the case of peatlands, a critical terrestrial carbon store, this lack of consistency hampers the evidence-based decisions in policy and practice that are needed to support effective restoration and conservation. This study adapted methods pioneered in the medical community to reach consensus over peatland outcomes that could be consistently measured and reported to improve the synthesis of data and reduce research waste. Here we report on a methodological framework for identifying, evaluating and prioritising the outcomes that should be measured. We discuss the subsequent steps to standardise methods for measuring and reporting outcomes in peatland research and monitoring. The framework was used to identify and prioritise sets of key variables (known as core domain sets) for UK blanket and raised bogs, and for tropical peat swamps. Peatland experts took part in a structured elicitation and prioritisation process, comprising two workshops and questionnaires, that focused on climate (32 and 18 unique outcomes for UK and tropical peats, respectively), hydrology (26 UK and 16 tropical outcomes), biodiversity (8 UK and 22 tropical outcomes) and fire-related outcomes (13, for tropical peatlands only). Future research is needed to tackle the challenges of standardising methods for data collection, management, analysis, reporting and re-use, and to extend the approach to other types of peatland. The process reported here is a first step towards creating datasets that can be synthesised to inform evidence-based policy and practice, and contribute towards the conservation, restoration and sustainable management of this globally significant carbon store. evidence-based policy and practice, evidence synthesis, outcomes, standardisationpublishedVersio

    Group 2i Isochrysidales produce characteristic alkenones reflecting sea ice distribution

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    Alkenones are biomarkers produced solely by algae in the order Isochrysidales that have been used to reconstruct sea surface temperature (SST) since the 1980s. However, alkenone based SST reconstructions in the northern high latitude oceans show significant bias towards warmer temperatures in core-tops, diverge from other SST proxies in down core records, and are often accompanied by anomalously high relative abundance of the C37 tetra-unsaturated methyl alkenone (%C37:4). Elevated %C37:4 is widely interpreted as an indicator of low sea surface salinity from polar water masses, but its biological source has thus far remained elusive. Here we identify a lineage of Isochrysidales that is responsible for elevated C37:4 methyl alkenone in the northern high latitude oceans through next-generation sequencing and lab-culture experiments. This Isochrysidales lineage co-occurs widely with sea ice in marine environments and is distinct from other known marine alkenone-producers, namely Emiliania huxleyi and Gephyrocapsa oceanica. More importantly, the %C37:4 in seawater filtered particulate organic matter and surface sediments is significantly correlated with annual mean sea ice concentrations. In sediment cores from the Svalbard region, the %C37:4 concentration aligns with the Greenland temperature record and other qualitative regional sea ice records spanning the past 14 kyrs, reflecting sea ice concentrations quantitatively. Our findings imply that %C37:4 is a powerful proxy for reconstructing sea ice conditions in the high latitude oceans on thousand- and, potentially, on million-year timescales.publishedVersio

    Evaluation of genetic effects on wild salmon populations from stock enhancement

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    Many salmonid populations are of conservation concern, and the release of hatchery-produced juveniles is a frequently used measure to alleviate declines and increase harvest opportunities. While such releases may be of conservation value for some populations, stocking may also decrease the effective population size and subsequently impose additional strain on already threatened populations. In this study, we assessed how the cohort-wise effective number of breeders in five populations of Atlantic salmon (Salmo salar) were affected by supplementation. Altogether, 19 cohorts were studied (2–7 cohorts per population) by estimating the proportion hatchery-released individuals and the effective number of wild and captive breeders in each cohort of the respective populations. We show that the effect of releasing captive-bred individuals varies both between populations and between years within the same population. A Ryman–Laikre effect—where the effective number of breeders has decreased as a consequence of supplementation—was observed for 11 cohorts. We discuss how supplementation can be adapted to optimize the effective population size, demonstrate that evaluation of supplementation can be reliably achieved, and show that supplementation programmes that lead to high proportions of hatchery-origin fish on spawning grounds are more likely to induce a Ryman–Laikre effect. Atlantic salmon, effective population size, population genetics, Ryman–Laikre effect, Salmo salar, stockingpublishedVersio

    Annual and diel activity cycles of a northern population of the large migratory cyprinid fish asp (Leuciscus aspius)

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    Little is known about the exact movement parameters of migratory cyprinids listed as conservation priorities. A northern population of predatory asp, listed on the Bern Convention Appendix III, was studied in a near natural lake–river ecosystem by tracking adult fsh tagged with acoustic transmitters for 32 months. Activity levels in terms of swimming speed, swimming distance and movement range were four times higher during the warmer part of the year (water temperatures>12–15 °C, April/May–September), which coincides with their main feeding period, than other times of the year. All fsh had an annual riverine movement range larger than 40 km (max 110 km). Asp activity was afected by light, habitat type and water discharge. For most of the year, activity levels, in terms of number of movements per time unit, were higher during dawn and dusk than during day and night. Under poor light conditions and low temperatures, activity was also relatively high during the day. Fish were more likely to swim upstream around sunrise or during the day than during other diel periods. Knowledge about highactivity periods, which may render the fsh vulnerable to fshing and other impacts, can be used to develop and evaluate fshing regulations. Large annual movement ranges highlight the need for extensive continuous river systems open for migration between essential habitats. This study emphasises the need for region-specifc research on the ecology and behaviour of fsh populations in order to facilitate protection of the populations in the face of negative human impacts.publishedVersio

    Improving collaboration between ecosystem service communities and the IPBES science-policy platform

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    The end of the first working program of the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) provided an opportunity to draw lessons from its work. This perspective paper captures insights from ecosystem services (ES) researchers and practitioners, largely drawing from the Europeancontext (referred to herein as ‘ES community’), on this key science–policy interface. We synthesize reflections from a workshop on how (i) IPBES can engage the ES community; (ii) the ES community can engage with IPBES; and (iii) individual scientists can contribute. We note that IPBES constitutes a great advancement towards multidisciplinarity and inclusivity in ES research and practice. Key reflections for IPBES are that funding and visibility at ES research events could be improved, the contribution and selection processes could be more transparent, and communication with experts improved. Key reflections for the ES community include a need to improvepolicy-relevance by integrating more social scientists, researchers from developing countries, early-career scientists and policy-makers. Key reflections directed towards individual scientists include contributing (pro) actively to science–policy inter-face initiatives such as IPBES and increasing transdisciplinary research. These reflections intend to contribute to the awareness of challenges and opportunities for institutions, groups and individuals working on ES. IPBES; ESP; community of practice; ecosystem services; science-policy interfacepublishedVersio

    Changes in wetland habitat use by waterbirds wintering in Czechia are related to diet and distribution changes

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    1. Understanding species habitat use and factors affecting changes in their distribu-tions are necessary to promote the conservation of any biological community. We evaluated the changes in wetland use of the non- breeding waterbird community. Based on long-term citizen-science data (1988–2020), we tested the hypotheses that wetland use is associated with species diet and potential range-shift drivers (the tendency to occupy the same sites in consecutive years—site affinity—and the species' average temperature across its wintering range—species temperature index).2. We analysed species-specific wetland use of 25 species of waterbirds wintering in Czechia over a period of 33 years. The analyses explained variability in trends in numbers of the studied waterbird species across four inland wetland types: reser-voirs; fishponds; industrial waters created by flooding of former mining sites; and running waters.3. Trends in waterbird abundance positively correlated with species’ diet on fish-ponds, industrial and running waters. Among the diet groups, invertivores showed the largest increase in abundances on industrial waters, closely followed by her-bivores. Herbivores showed the largest increase in abundances in fishponds, and piscivores did so in running waters. Regarding range-shift drivers, species with higher site affinity showed higher abundances on running waters, while species with low species temperature index (i.e. wintering on average in sites with lower temperature) were more abundant on reservoirs. The abundance of both warm- dwelling and species with low site affinity increased on fishponds and industrial waters.4. Our findings suggest that the increased importance of the wetland types consid-ered here for wintering waterbirds is likely to be linked to diet related changes in habitat use and changes in species distributions; and highlight that wintering waterbirds are expected to select sites with higher availability of food, higher en-ergy content, and lower foraging cost.5. Recent and rapid changes in species distributions may lead to a decrease in the effectiveness of national and international conservation efforts. When planning conservation measures, it should be kept in mind that climate change does not only imply large-scale north/north- eastwards shifts of entire waterbird distribu-tions, but can also modify the use of the habitats by waterbird species inside their traditional wintering range. artificial wetlands, long-term monitoring, range-shift drivers, waterbirds, wetland typepublishedVersio


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