Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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    Similar factors underlie tree abundance in forests in native and alien ranges
    Sande, Masha T. van der; Bruelheide, Helge ; Dawson, Wayne ; Dengler, Jürgen ; Essl, Franz ; Field, Richard ; Haider, Sylvia ; Kleunen, Mark van; Kreft, Holger ; Pagel, Joern ; Pergl, Jan ; Purschke, Oliver ; Pyšek, Petr ; Weigelt, Patrick ; Winter, Marten ; Attorre, Fabio ; Aubin, Isabelle ; Bergmeier, Erwin ; Chytrý, Milan ; Dainese, Matteo ; Sanctis, Michele De; Fagundez, Jaime ; Golub, Valentin ; Guerin, Greg R. ; Gutiérrez, Alvaro G. ; Jandt, Ute ; Jansen, Florian ; Jiménez-Alfaro, Borja ; Kattge, Jens ; Kearsley, Elizabeth ; Klotz, Stefan ; Kramer, Koen ; Moretti, Marco ; Niinemets, Ülo ; Peet, Robert K. ; Penuelas, Josep ; Petřík, Petr ; Reich, Peter B. ; Sandel, Brody ; Schmidt, Marco ; Sibikova, Maria ; Violle, Cyrille ; Whitfeld, Timothy J.S. ; Wohlgemuth, Thomas ; Knight, Tiffany M. - \ 2020
    Global Ecology and Biogeography 29 (2020)2. - ISSN 1466-822X - p. 281 - 294.
    abundance - dissimilarity - forest - functional traits - global - plant invasion - trees

    Aim: Alien plant species can cause severe ecological and economic problems, and therefore attract a lot of research interest in biogeography and related fields. To identify potential future invasive species, we need to better understand the mechanisms underlying the abundances of invasive tree species in their new ranges, and whether these mechanisms differ between their native and alien ranges. Here, we test two hypotheses: that greater relative abundance is promoted by (a) functional difference from locally co-occurring trees, and (b) higher values than locally co-occurring trees for traits linked to competitive ability. Location: Global. Time period: Recent. Major taxa studied: Trees. Methods: We combined three global plant databases: sPlot vegetation-plot database, TRY plant trait database and Global Naturalized Alien Flora (GloNAF) database. We used a hierarchical Bayesian linear regression model to assess the factors associated with variation in local abundance, and how these relationships vary between native and alien ranges and depend on species’ traits. Results: In both ranges, species reach highest abundance if they are functionally similar to co-occurring species, yet are taller and have higher seed mass and wood density than co-occurring species. Main conclusions: Our results suggest that light limitation leads to strong environmental and biotic filtering, and that it is advantageous to be taller and have denser wood. The striking similarities in abundance between native and alien ranges imply that information from tree species’ native ranges can be used to predict in which habitats introduced species may become dominant.

    Aerial surveys of cetaceans and seabirds in Irish waters : occurrence, distribution and abundance in 2015-2017
    Rogan, E. ; Breen, P. ; Mackey, Mick ; Cañadas, Ana ; Scheidat, M. ; Geelhoed, S.C.V. ; Jessopp, Mark - \ 2018
    - 298 p.
    observe programme - aerial survey - cetacean - seabird - abundance - density - megafauna - distance sampling - Ireland - Atlantic - Celtic Sea - Irish Sea
    The diversity–disease relationship : evidence for and criticisms of the dilution effect
    Huang, Z.Y.X. ; Langevelde, F. van; Estrada-Peña, A. ; Suzán, G. ; Boer, W.F. de - \ 2016
    Parasitology 143 (2016)9. - ISSN 0031-1820 - p. 1075 - 1086.
    abundance - amplification effect - competence–extinction relationship - habitat fragmentation - identity effect - infection prevalence

    The dilution effect, that high host species diversity can reduce disease risk, has attracted much attention in the context of global biodiversity decline and increasing disease emergence. Recent studies have criticized the generality of the dilution effect and argued that it only occurs under certain circumstances. Nevertheless, evidence for the existence of a dilution effect was reported in about 80% of the studies that addressed the diversity–disease relationship, and a recent meta-analysis found that the dilution effect is widespread. We here review supporting and critical studies, point out the causes underlying the current disputes. The dilution is expected to be strong when the competent host species tend to remain when species diversity declines, characterized as a negative relationship between species’ reservoir competence and local extinction risk. We here conclude that most studies support a negative competence–extinction relationship. We then synthesize the current knowledge on how the diversity–disease relationship can be modified by particular species in community, by the scales of analyses, and by the disease risk measures. We also highlight the complex role of habitat fragmentation in the diversity–disease relationship from epidemiological, evolutionary and ecological perspectives, and construct a synthetic framework integrating these three perspectives. We suggest that future studies should test the diversity–disease relationship across different scales and consider the multiple effects of landscape fragmentation.

    Milk Oligosaccharide Variation in Sow Milk and Milk Oligosaccharide Fermentation in Piglet Intestine
    Difilippo, Elisabetta ; Pan, Feipeng ; Logtenberg, Madelon ; Willems, Rianne ; Braber, Saskia ; Fink-Gremmels, Johanna ; Schols, Henk Arie ; Gruppen, Harry - \ 2016
    Journal of Agricultural and Food Chemistry 64 (2016)10. - ISSN 0021-8561 - p. 2087 - 2093.
    abundance - chromatography - cow - mass analysis - pigs - sugars - variation

    Porcine milk oligosaccharides (PMOs) were analyzed in six colostrum and two mature milk samples from Dutch Landrace sows. In total, 35 PMOs were recognized of which 13 were new for the PMO literature: Neutral HexNAc-Hex, β4′-galactosyllactose, putative GalNAc(α/β1-3)Gal(β1-4)Glc, lacto-N-fucopentaose-II, lacto-N-tetraose, galactose substituted lacto-N-neohexaose, lacto-N-hexaose and difucosyl-lacto-N-hexaose, and acidic Neu5Ac(α2-6)GlcNAc(β1-3)Gal(β1-4)Glc, sialyllacto-N-tetraose-a and -b, Neu5Ac2-Hex3, and sialyllacto-N-fucopentaose-II. PMOs were analyzed using capillary electrophoresis with laser-induced florescence detection or mass spectrometry and using liquid chromatography with mass spectrometry. Interindividual variation regarding PMO presence and concentration was observed between porcine milks. Within a limited sample set, a 43% decrease of the major PMOs was found during a 1 w lactation period. Interestingly, while some PMOs decreased, some other PMOs increased in concentration. PMOs were also monitored in fecal samples of suckling piglets. In feces of 1-2 d old piglets, few intact PMOs were found, indicating considerable PMO fermentation at early stage of life.

    Strong recovery of dragonflies in recent decades in The Netherlands
    Termaat, T. ; Grunsven, R.H.A. van; Plate, C.L. ; Strien, A. van - \ 2015
    Freshwater Science 34 (2015)3. - ISSN 2161-9549 - p. 1094 - 1104.
    change odonata corduliidae - boreal forest lakes - climate-change - trends - conservation - assemblages - indicators - integrity - abundance - plants
    Many dragonfly species in The Netherlands declined in the 20th century because of acidification, eutrophication, and desiccation of lotic and lentic habitats and canalization of streams and rivers. These pressures peaked in the 1970s, when 26 of 65 native species had an unfavorable conservation status on the 1997 Dutch Red List. Since the 1980s, environmental regulations have led to improved water quality, and any habitat restoration projects have been carried out. We used standardized monitoring data (1999–2013) and unstandardized observations (1991–2013) to investigate how dragonflies have changed in the last 20 y on a national scale. We compared trends of dragonfly species from different habitat types and with southern vs northern distribution in Europe. Dragonflies recovered strongly in The Netherlands in a period of ~20 y, probably because of recent habitat improvements. Lotic species have benefitted more than lentic species, and southern species have more positive trends than northern species, suggesting that climate change has contributed to the recovery. Dragonflies were resilient and able to quickly recover when their habitats were restored. Recovery has led to a better conservation status for many species. Unstandardized data delivered results consistent with those from monitoring data and had greater statistical power to detect trends because many more unstandardized data than standardized data were available. Thus, when the goal is to provide a general overview of changes in dragonflies, unstandardized data can outperform standardized abundance data. However, abundance data may deliver complementary information for individual species. Our results support the suitability of dragonflies as indicators of freshwater habitat condition, but they recover more strongly in The Netherlands than many other insects, possibly because of their higher dispersal abilities or different habitat requirements.
    Rapid diversity loss of competing animal sppecies in well-connected landscapes
    Schippers, P. ; Hemerik, L. ; Baveco, J.M. ; Verboom, J. - \ 2015
    PLoS ONE 10 (2015)8. - ISSN 1932-6203 - 17 p.
    woodpecker dendrocopos-medius - squirrel sciurus-carolinensis - great spotted woodpeckers - neutral-theory - habitat fragmentation - riverine forest - climate-change - coexistence - abundance - metapopulations
    Population viability of a single species, when evaluated with metapopulation based landscape evaluation tools, always increases when the connectivity of the landscape increases. However, when interactions between species are taken into account, results can differ. We explore this issue using a stochastic spatially explicit meta-community model with 21 competing species in five different competitive settings: (1) weak, coexisting competition, (2) neutral competition, (3) strong, excluding competition, (4) hierarchical competition and (5) random species competition. The species compete in randomly generated landscapes with various fragmentation levels. With this model we study species loss over time. Simulation results show that overall diversity, the species richness in the entire landscape, decreases slowly in fragmented landscapes whereas in well-connected landscapes rapid species losses occur. These results are robust with respect to changing competitive settings, species parameters and spatial configurations. They indicate that optimal landscape configuration for species conservation differs between metapopulation approaches, modelling species separately and meta-community approaches allowing species interactions. The mechanism behind this is that species in well-connected landscapes rapidly outcompete each other. Species that become abundant, by chance or by their completive strength, send out large amounts of dispersers that colonize and take over other patches that are occupied by species that are less abundant. This mechanism causes rapid species loss. In fragmented landscapes the colonization rate is lower, and it is difficult for a new species to establish in an already occupied patch. So, here dominant species cannot easily take over patches occupied by other species and higher diversity is maintained for a longer time. These results suggest that fragmented landscapes have benefits for species conservation previously unrecognized by the landscape ecology and policy community. When species interactions are important, landscapes with a low fragmentation level can be better for species conservation than well-connected landscapes. Moreover, our results indicate that metapopulation based landscape evaluation tools may overestimate the value of connectivity and should be replaced by more realistic meta-community based tools.
    Macroecological factors explain large-scale spatial population patterns of ancient agriculturalists
    Xu, C. ; Chen, B. ; Abades, S. ; Reino, L. ; Teng, S. ; Ljungqvist, F.C. ; Huang, Z.Y.X. ; Liu, X. - \ 2015
    Global Ecology and Biogeography 24 (2015)9. - ISSN 1466-822X - p. 1030 - 1039.
    climate-change - last millennium - growth dynamics - autocorrelation - collapse - distributions - abundance - richness - ecology - europe
    Aim: It has been well demonstrated that the large-scale distribution patterns of numerous species are driven by similar macroecological factors. However, understanding of this topic remains limited when applied to our own species. Here we take a large-scale look at ancient agriculturalist populations over the past two millennia. The main aim of this study was to test the hypothesis that the patterns of agriculturalist populations were shaped by relevant macroecological factors. Location: China. Methods: Using detailed historical census data, we reconstructed spatial patterns of human population density over 13 imperial dynasties in ancient China, which was dominated by agrarian societies. We used simultaneous autoregressive models to examine the population densities of agriculturalists in relation to climatic, topographic, edaphic and hydrological variables, together with the spatial structure of a concentration of population toward national capitals. The pure and shared effects of these variables and the population-concentration structure were decomposed using a variation partitioning procedure. Results: Spatial population patterns of ancient agriculturalists can be well modelled by climate, topography, soil properties and local hydrological systems. A plausible explanation is that by influencing crop yield these environmental factors essentially drive the distribution of agriculturalists. The population-concentration structure can also explain agriculturalist patterns to a considerable extent. This structure and those environmental factors have largely shared effects in simultaneously shaping these agriculturalist patterns. Main conclusions: While humans can effectively temper environmental constraints at small spatial scales, our results demonstrate that macroecological factors underpin the spatial patterns of humans at large scales. Macroecological constraints and their relative importance are found to be similar for humans and other species, suggesting that similar mechanisms are likely to underlie these macroecological patterns. Our findings have potential implications for the assessment of future responses of humans to global environmental changes.
    Delivery of crop pollination services is an insufficient argument for wild pollinator conservation
    Kleijn, D. ; Winfree, R. ; Bartomeus, D. ; Carvalheiro, L.G. ; Bommarco, R. ; Scheper, J. ; Tscharntke, T. ; Verhulst, J. ; Potts, S.G. - \ 2015
    Nature Communications 6 (2015). - ISSN 2041-1723 - 8 p.
    ecosystem services - native bees - biodiversity conservation - european countries - plant diversity - fruit-set - abundance - productivity - decline - pollen
    There is compelling evidence that more diverse ecosystems deliver greater benefits to people, and these ecosystem services have become a key argument for biodiversity conservation. However, it is unclear how much biodiversity is needed to deliver ecosystem services in a cost-effective way. Here we show that, while the contribution of wild bees to crop production is significant, service delivery is restricted to a limited subset of all known bee species. Across crops, years and biogeographical regions, crop-visiting wild bee communities are dominated by a small number of common species, and threatened species are rarely observed on crops. Dominant crop pollinators persist under agricultural expansion and many are easily enhanced by simple conservation measures, suggesting that cost-effective management strategies to promote crop pollination should target a different set of species than management strategies to promote threatened bees. Conserving the biological diversity of bees therefore requires more than just ecosystem-service-based arguments.
    Loss of animal seed dispersal increases extinction risk in a tropical tree species due to pervasive negative density dependence across life stages
    Caughlin, T.T. ; Ferguson, J.M. ; Lichstein, J.W. ; Zuidema, P.A. ; Bunyavejchewin, S. ; Levey, D.J. - \ 2015
    Proceedings of the Royal Society. B: Biological Sciences 282 (2015)1798. - ISSN 0962-8452 - 9 p.
    spatial-patterns - rain-forest - recruitment - consequences - neighborhood - defaunation - habitat - uncertainty - diversity - abundance
    Overhunting in tropical forests reduces populations of vertebrate seed dispersers. If reduced seed dispersal has a negative impact on tree population viability, overhunting could lead to altered forest structure and dynamics, including decreased biodiversity. However, empirical data showing decreased animal-dispersed tree abundance in overhunted forests contradict demographic models which predict minimal sensitivity of tree population growth rate to early life stages. One resolution to this discrepancy is that seed dispersal determines spatial aggregation, which could have demographic consequences for all life stages. We tested the impact of dispersal loss on population viability of a tropical tree species, Miliusa horsfieldii, currently dispersed by an intact community of large mammals in a Thai forest. We evaluated the effect of spatial aggregation for all tree life stages, from seeds to adult trees, and constructed simulation models to compare population viability with and without animal-mediated seed dispersal. In simulated populations, disperser loss increased spatial aggregation by fourfold, leading to increased negative density dependence across the life cycle and a 10-fold increase in the probability of extinction. Given that the majority of tree species in tropical forests are animal-dispersed, overhunting will potentially result in forests that are fundamentally different from those existing now.
    An assessment of the terrestrial mammal communities in forests of Central Panama, using camera-trap surveys
    Meyer, N.F.V. ; Esser, H.J. ; Moreno, R. ; Langevelde, F. van; Liefting, Y. ; Ros Oller, D. ; Vogels, C.B.F. ; Carver, A.D. ; Nielsen, C.K. ; Jansen, P.A. - \ 2015
    Journal for Nature Conservation 26 (2015). - ISSN 1617-1381 - p. 28 - 35.
    rain-forest - habitat fragmentation - conservation status - neotropical forest - atlantic forest - tayassu-pecari - abundance - biodiversity - landscape - density
    The Isthmus of Panama, part of the planet’s third largest megadiversity hotspot, and connecting the faunas of North and South America, has lost more than half of its forest due to agriculture and economicdevelopment. It is unknown to what degree the remaining forest, which is fragmented and subject topoaching, still supports the wildlife diversity found in intact forests. Here, we use camera-trap surveysto assess whether forests in Central Panama, the narrowest and most disturbed portion of the Isthmus,still have intact communities of medium- and large-bodied terrestrial mammals. During 2005–2014,we collected camera-trap survey data from 15 national parks and forest fragments on both sides ofthe Panama Canal, and compared these to similar data from two sites in the intact Darién NationalPark in Eastern Panama, the nearest available reference. We found that most sites in Central Panama– including some of the national parks – had lower mammal species richness and evenness than thereference sites, and less structurally-complex mammal communities. Forests in Central Panama had littleor no apex predators and large terrestrial frugivores, with the exception of two sites directly connectedto the reference site. Our results indicate that the terrestrial mammal community in forests of CentralPanama is currently degraded, even inside national parks. These data provide a baseline for evaluating the success of conservation efforts to prevent the Panamanian Isthmus to become a bottleneck for movement of aniamls
    How to assess species richness along single environmental gradients? Implications of potential versus realized species distributions
    Goethem, T.M.W.J. van; Huijbregts, M.A.J. ; Wamelink, G.W.W. ; Schipper, A.M. - \ 2015
    Environmental Pollution 200 (2015). - ISSN 0269-7491 - p. 120 - 125.
    sensitivity distributions - field data - plant - diversity - abundance - macroinvertebrates - acidification - consequences - biodiversity - assemblages
    Quantifying relationships between species richness and single environmental factors is challenging as species richness typically depends on multiple environmental factors. Recently, various methods have been proposed to tackle this challenge. Using a dataset comprising field observations of grassland vegetation and measured pH values, we compared three methods for deriving species richness response curves. One of the methods estimates species richness close to the maximum species richness observed at the sites, whereas the other two provide estimates of the potential species richness along the environmental gradient. Our response curves suggest that potential species richness of grasslands is slightly more sensitive to acidification than realized plant species richness. However, differences in corresponding environmental quality standards (EQS) for acidification were small compared to intrinsic spatial differences in natural soil pH, indicating that natural background values are more important to consider in the derivation of EQS for pH than methodological differences between the three approaches.
    New lipid envelop-containing dsDNA virus isolates infecting Micromonas pusilla reveal a separate phylogenetic group.
    Martinez Martinez, J. ; Boere, A. ; Gilg, I. ; Lent, J.W.M. van; Witte, H.J. ; Bleijswijk, J.D.L. van; Brussaard, C.P.D. - \ 2015
    Aquatic Microbial Ecology 74 (2015)1. - ISSN 0948-3055 - p. 17 - 28.
    emiliania-huxleyi - dna viruses - phaeocystis-globosa - coastal waters - algal viruses - north-sea - abundance - prasinophyceae - diversity - dynamics
    Viral infection of phytoplankton has major implications for biochemical and energy cycles, community dynamics, and microbial evolution in the marine environment. The non-bloom forming picoplankter Micromonas pusilla, a significant component of the plankton community worldwide, is known to be susceptible to infection by both dsDNA and dsRNA viruses. Logically, comprehensive knowledge of the ecology of M. pusilla requires a better understanding of the diversity and infection mechanisms of their viruses. Here, we investigated 19 new M. pusilla-specific viruses (MpVs) isolated from different locations and years. We performed partial characterization of those MpVs including structural characteristics, genome size, phylogenetic analysis based on partial DNA polymerase gene sequences, host range, and stability at different temperatures and upon exposure to chloroform. Combined, these characteristics allowed classification of the MpVs into 2 groups. Exposure to chloroform led to loss of infectivity by all MpVs in one group, which suggests the presence of an outer lipid envelope. In addition, all except one of the members in that group formed a monophylogenetic clade that was distinct from all other MpV isolates. The distinctive characteristics of the 2 MpV groups suggest different infection strategies, which may have important implications for the ecology of both host and virus populations in the environment. Knowledge gained from our study adds value to the MpV isolates as a scientific resource as it will aid in developing and testing in the laboratory new hypotheses about the ecological and biogeochemical implications of M. pusilla viral infection in the environment.
    Dutch hedgehogs Erinaceus europaeus are nowadays mainly found in urban areas, possibly due to the negative Effects of badgers Meles meles
    Poel, J. van de; Dekker, J.J.A. ; Langevelde, F. van - \ 2015
    Wildlife Biology 21 (2015)1. - ISSN 0909-6396 - p. 51 - 55.
    abundance - populations - roads - odor
    In several west European countries, the distribution of hedgehogs Erinaceus europaeus is declining. In the UK, predation by the European badger Meles meles is considered to be the main death cause of hedgehogs. In the Netherlands, badger density is rising, which suggests the same cause for the decline. As landscape and land use largely diff er between the UK and the Netherlands, we investigated the relationship between the distribution of badgers and hedgehogs in the Netherlands. Th erefore, we used the presence of badgers and hedgehogs recorded in the period 2007 – 2010 in grid cells of 1 km 2 , together with environmental variables, i.e. land-use types and soil types, to describe the habitat of both species. Although the distribution of badgers in the Netherlands is still limited, we found indeed a negative eff ect of badger presence on hedgehog presence. We also found a positive eff ect of urban area, recreational land use and roads on hedgehog presence, whereas these types had a negative eff ect on badger presence. Our study suggests that hedgehogs in the Netherlands are nowadays found close to human occupation, possibly due to the negative eff ect of badgers. Th ese results contribute to understanding of the declining distribution of hedgehogs in western Europe.
    Intertidal biofilm distribution underpins differential tide-following behavior of two sandpiper species (Calidris mauri and Calidris alpina) during northward migration
    Jimenez, A. ; Elner, R.W. ; Favaro, C. ; Rickards, K. ; Ydenberg, R.C. - \ 2015
    Estuarine Coastal and Shelf Science 155 (2015). - ISSN 0272-7714 - p. 8 - 16.
    fraser-river estuary - western sandpipers - shorebird distribution - sediment - waders - microphytobenthos - invertebrates - predation - abundance - cycle
    The discovery that some shorebird species graze heavily on biofilm adds importance to elucidating coastal processes controlling biofilm, as well as impetus to better understand patterns of shorebird use of intertidal flats. Western sandpipers (Calidris mauri) and dunlin (Calidris alpina) stopover in the hundreds of thousands on the Fraser River estuary, British Columbia, Canada, during northward migration to breeding areas. Western sandpipers show greater modification of tongue and bill morphology for biofilm feeding than dunlin, and their diet includes more biofilm. Therefore, we hypothesized that these congeners differentially use the intertidal area. A tide following index (TFI) was used to describe their distributions in the upper intertidal during ebbing tides. Also, we assessed sediment grain size, biofilm (= microphytobenthic or MPB) biomass and invertebrate abundance. Foraging dunlin closely followed the ebbing tide line, exploiting the upper intertidal only as the tide retreated through this area. In contrast, western sandpipers were less prone to follow the tide, and spent more time in the upper intertidal. Microphytobenthic biomass and sediment water content were highest in the upper intertidal, indicating greater biofilm availability for shorebirds in the first 350 m from shore. Invertebrate density did not differ between sections of the upper intertidal. Overall, western sandpiper behaviour and distribution more closely matched MPB biofilm availability than invertebrate availability. Conservation of sandpipers should consider physical processes, such as tides and currents, which maintain the availability of biofilm, a critical food source during global migration.
    Porpoises: From predators to prey
    Leopold, M.F. ; Begeman, L. ; Hesse, E. ; Hiele, J. van der; Hiemstra, S. ; Keijl, G.O. ; Meesters, H.W.G. ; Mielke, L. ; Verheyen, D. ; Groene, A. - \ 2015
    Journal of Sea Research 97 (2015). - ISSN 1385-1101 - p. 14 - 23.
    seal halichoerus-grypus - bottle-nosed dolphins - harbor porpoises - phocoena-phocoena - violent interactions - wadden sea - digestion - abundance - fisheries - otoliths
    Along the Dutch shores hundreds of harbour porpoises Phocoena phocoena are stranded each year. A recurrent phenomenon in the Netherlands is a surge of strandings in late winter and early spring of severely mutilated porpoises, that are mostly in good nutritional body condition (thick blubber layer). These mutilated porpoises have parts of the skin and blubber, and sometimes of the muscle tissue missing. By reviewing photographs of stranded animals taken at the stranding sites as well as autopsy results we found 273 mutilated animals from 2005 to 2012. Mutilations could be classified into several categories, but wounds had been mostly inflicted to the sides of these animals, in a zigzag fashion, or to the throat/cheek region. The stomach contents of 31 zigzags, 12 throats/cheeks and 31 control animals that were not mutilated, from the same age and blubber thickness categories were compared; all these animals had stranded between December and April, 2006–2012. The diet of individuals with zigzag lesions to their sides consisted for a large part of gobies, while animals that had wounds at the throat/cheek had been feeding predominately on clupeids. In comparison, animals without mutilations had a more varied diet, including gobies and clupeids, but also a large proportion of sandeels and gadoids. The finding that the type of mutilation corresponds to a certain diet suggests that porpoises that were feeding on different prey, or in different micro-habitats, were hit in different ways. Animals feeding at the sea floor (on gobies) apparently run a risk of being hit from the side, while animals supposedly feeding higher in the water column (on schooling clupeids), were predominantly hit from below, in the throat region. The wider variation in the diets of non-mutilated porpoises is suggestive of them using a larger variety of micro-habitats.
    Earthworm assemblages as affected by field margin strips and tillage intensity: An on-farm approach
    Crittenden, S. ; Huerta, E. ; Goede, R.G.M. de; Pulleman, M.M. - \ 2015
    European Journal of Soil Biology 66 (2015). - ISSN 1164-5563 - p. 49 - 56.
    conservation tillage - land-use - soil - population - communities - diversity - abundance - systems - growth - term
    Earthworm species contribute to soil ecosystem functions in varying ways. Important soil functions like structural maintenance and nutrient cycling are affected by earthworms, thus it is essential to understand how arable farm management influences earthworm species. One aim of arable field margin strips and non-inversion tillage is to enhance agrobiodiversity, however their influence on earthworm species assemblages remains unclear. In particular, on-farm studies conducted over multiple years that capture variability across the landscape are rare. The current study monitored earthworm species assemblages on 4 farms in Hoeksche Waard, The Netherlands, from 2010 to 2012. It was hypothesised that arable field margin strips (FM) and non-inversion tillage (NIT; a reduced tillage system that loosens subsoil at 30-35 cm depth) would have higher earthworm species abundances (epigeics and anecics in particular), soil organic matter, and soil moisture than adjacent mouldboard ploughing (MP) fields, and that earthworm numbers would decrease with distance away from FM into arable fields (MP only). FM contained a mean total earthworm abundance of 284 m-2 and biomass of 84 g m-2 whereas adjacent MP arable fields had only 164 earthworms m-2 and 31 g m-2. Aporrectodea rosea, Lumbricus rubellus, Lumbricus terrestris, and Lumbricus castaneus were significantly more abundant in FM than adjacent arable soil under MP. However, no decreasing trend with distance from FM was observed in earthworm species abundances. A tillage experiment initiated on the farms with FM showed that relative to MP, NIT significantly increased mean total earthworm abundance by 34% to 275 m-2 and mean total earthworm biomass by 15% to 51 g m-2 overall sampling dates and farms. L. rubellus, A. rosea, and L. terrestris were significantly more abundant overall in NIT than MP. FM and NIT positively affected earthworm species richness and abundances and it is noteworthy that these effects could be observed despite variation in environmental conditions and soil properties between samplings, farms, and crops. Higher top-soil organic matter and less physical disturbance in FM and NIT likely contributed to higher earthworm species richness and abundances. The anecic species L. terrestris (linked to water infiltration and organic matter incorporation) was more abundant in FM, but densities remained very low in arable soil, irrespective of tillage system.
    Quirky patterns in time-series of estimates of recruitment could be artefacts
    Dickey-Collas, M. ; Hintzen, N.T. ; Nash, R.D.M. ; Schoen, P.J. ; Payne, M.R. - \ 2015
    ICES Journal of Marine Science 72 (2015)1. - ISSN 1054-3139 - p. 111 - 116.
    stock-assessment - marine fishes - assessment models - reference points - atlantic - variability - abundance - sea - populations - management
    The accessibility of databases of global or regional stock assessment outputs is leading to an increase in meta-analysis of the dynamics of fish stocks. In most of these analyses, each of the time-series is generally assumed to be directly comparable. However, the approach to stock assessment employed, and the associated modelling assumptions, can have an important influence on the characteristics of each time-series. We explore this idea by investigating recruitment time-series with three different recruitment parameterizations: a stock–recruitment model, a random-walk time-series model, and non-parametric “free” estimation of recruitment. We show that the recruitment time-series is sensitive to model assumptions and this can impact reference points in management, the perception of variability in recruitment and thus undermine meta-analyses. The assumption of the direct comparability of recruitment time-series in databases is therefore not consistent across or within species and stocks. Caution is therefore required as perhaps the characteristics of the time-series of stock dynamics may be determined by the model used to generate them, rather than underlying ecological phenomena. This is especially true when information about cohort abundance is noisy or lacking.
    A Mixed Modeling Approach to Predict the Effect of Environmental Modification on Species Distributions
    Cozzoli, F. ; Eelkema, M. ; Bouma, T.J. ; Ysebaert, T. ; Escaravage, V. ; Herman, P.M.J. - \ 2014
    PLoS ONE 9 (2014)2. - ISSN 1932-6203
    cockles cerastoderma-edule - natural animal assemblages - quantile regression - lanice-conchilega - body-size - ecosystem engineers - sediment transport - hydrobia-ulvae - abundance - oosterschelde
    Human infrastructures can modify ecosystems, thereby affecting the occurrence and spatial distribution of organisms, as well as ecosystem functionality. Sustainable development requires the ability to predict responses of species to anthropogenic pressures. We investigated the large scale, long term effect of important human alterations of benthic habitats with an integrated approach combining engineering and ecological modelling. We focused our analysis on the Oosterschelde basin (The Netherlands), which was partially embanked by a storm surge barrier (Oosterscheldekering, 1986). We made use of 1) a prognostic (numerical) environmental (hydrodynamic) model and 2) a novel application of quantile regression to Species Distribution Modeling (SDM) to simulate both the realized and potential (habitat suitability) abundance of four macrozoobenthic species: Scoloplos armiger, Peringia ulvae, Cerastoderma edule and Lanice conchilega. The analysis shows that part of the fluctuations in macrozoobenthic biomass stocks during the last decades is related to the effect of the coastal defense infrastructures on the basin morphology and hydrodynamics. The methodological framework we propose is particularly suitable for the analysis of large abundance datasets combined with high-resolution environmental data. Our analysis provides useful information on future changes in ecosystem functionality induced by human activities.
    Spill-over effect in media framing: Representations of wildlife conservation in Zimbabwean and international media, 1989-2010
    Gandiwa, E. ; Sprangers, S. ; Bommel, S. van; Heitkonig, I.M.A. ; Leeuwis, C. ; Prins, H.H.T. - \ 2014
    Journal for Nature Conservation 22 (2014)5. - ISSN 1617-1381 - p. 413 - 423.
    gonarezhou national-park - bushmeat trade - disaster - campfire - coverage - africa - management - government - abundance - katrina
    Myths and metaphors that occur in media frames play an important role in influencing public perceptions of an issue in times of war, political conflict, crisis and disaster. This, in turn, influences policy makers and (inter)national assistance and aid programmes. We investigated whether a metaphoric spill-over of frames used in connection with political events could explain the misrepresentation in the framing of wildlife conservation. Zimbabwe experienced a severe political conflict and economic downturn in 2000 when land reforms took place. We analyzed newspaper articles on Zimbabwe's wildlife conservation published between 1989 and 2010 from newspapers in Zimbabwe, the United Kingdom and the United States of America. We selected three issues about wildlife conservation in Zimbabwe in the local and international media, namely, the ivory ban, rhino protection, and Communal Areas Management Programme for Indigenous Resources to investigate the spill-over effect. Our results show that in the 1990s, the majority of newspaper articles highlighted that wildlife conservation in Zimbabwe was largely successful. However, two major changes occurred after 2000 following the land reforms in Zimbabwe. First, the international media showed little interest in wildlife conservation in Zimbabwe as evidenced by a sharp decline in published articles and second, the frames changed in the international media with the “political unrest and land reform” blame frame becoming more dominant. This transition in reporting, frames, and low frame parity shows that there was a spill-over effect of political frames into wildlife conservation following Zimbabwe's land reforms in 2000. Metaphoric spill-over effects may thus create myths in the readership, in turn influencing policy-derived actions in a sector that is not or poorly related to the actual disaster. Keywords Framing; Land reform; Metaphors; Nature conservation
    Blood feeding on large grazers affects the transmission of Borrelia burgdorferi sensu lato by Ixodes ricinus
    Pacilly, F.C.A. ; Benning, M.E. ; Jacobs, F. ; Leidekker, J. ; Sprong, H. ; Wieren, S.E. van; Takken, W. - \ 2014
    Ticks and Tick-borne Diseases 5 (2014)6. - ISSN 1877-959X - p. 810 - 817.
    lyme borreliosis - tick infestation - north-america - endemic area - roe deer - netherlands - prevalence - density - disease - abundance
    The presence of Ixodes ricinus and their associated Borrelia infections on large grazers was investigated. Carcases of freshly shot red deer, mouflon and wild boar were examined for the presence of any stage of I. ricinus. Questing ticks were collected from locations where red deer and wild boar are known to occur. Presence of Borrelia burgdorferi s.l. DNA was examined in a fraction of the collected ticks. Larvae, nymphs and adult ticks were found on the three large grazers. Red deer had the highest tick burden, with many of the nymphs and adult females attached for engorgement. Most larvae had not attached. The mean number of ticks on the animals varied from 13 to 67. Ticks were highly aggregated amongst the animals: some animals had no ticks, while others had high numbers. Larvae and nymphs were mostly found on the ears, while adult ticks were attached to the axillae. The Borrelia infection rate of questing nymphs was 8.5%. Unengorged wandering nymphs on deer had a Borrelia infection rate of 12.5%, while only 0.9% of feeding nymphs carried a Borrelia infection. The infection rate of unengorged adult male ticks was 4.5%, and that of feeding female ticks was 0.7%. The data suggest that ticks feeding on red deer and wild boar lose their Borrelia infections. The implications of the results are discussed with respect to Borrelia epidemiology and maintenance of a Borrelia reservoir as well as the role of reproductive hosts for Ixodes ricinus.
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