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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    Experimental evidence for inherent Lévy search behaviour in foraging animals
    Kölzsch, A. ; Alzate, A. ; Bartumeus, F. ; Jager, M. de; Weerman, E.J. ; Hengeveld, G.M. ; Naguib, M. ; Nolet, B.A. ; Koppel, J. van de - \ 2015
    Proceedings of the Royal Society. B: Biological Sciences 282 (2015)1807. - ISSN 0962-8452 - 9 p.
    correlated-random-walks - environmental complexity - wandering albatrosses - movement patterns - marine predator - flight - strategies - success - evolve - scale
    Recently, Lévy walks have been put forward as a new paradigm for animal search and many cases have been made for its presence in nature. However, it remains debated whether Lévy walks are an inherent behavioural strategy or emerge from the animal reacting to its habitat. Here, we demonstrate signatures of Lévy behaviour in the search movement of mud snails (Hydrobia ulvae) based on a novel, direct assessment of movement properties in an experimental set-up using different food distributions. Our experimental data uncovered clusters of small movement steps alternating with long moves independent of food encounter and landscape complexity. Moreover, size distributions of these clusters followed truncated power laws. These two findings are characteristic signatures of mechanisms underlying inherent Lévy-like movement. Thus, our study provides clear experimental evidence that such multi-scale movement is an inherent behaviour rather than resulting from the animal interacting with its environment.
    The influence of a water current on the larval deposition pattern of females of a diverging fire salamander population (Salamandra salamandra)
    Krause, E.T. ; Caspers, B.A. - \ 2015
    Salamandra : German Journal of Herpetology 51 (2015)2. - ISSN 0036-3375 - p. 156 - 160.
    microsatellite loci - genetic-distance - habitat - adaptation - amphibia - success - salmon - home
    Fire salamanders are amphibians that exhibit a highly specific reproductive mode termed ovo-viviparity. The eggs develop inside their mothers, and the females give birth to fully developed larvae. The larvae in our study area cluster in two distinct genetic groups that can be linked directly to the habitat (stream or pond) in which the larvae were deposited. Apart from the genetic differences, larvae belonging to the two different habitat types differ in morphological traits, indicating that female fire salamanders already show some type of ecological adaptation to the different habitats. In this study, we investigated whether pregnant fire salamander females of the two habitat-specific genotypes (stream and pond) specifically prefer to deposit larvae in flowing water bodies with a continuous current (i.e., simulating stream habitats) or in water bodies without a permanent water current (i.e., simulating pond habitats). We assumed that the presence of a current is used by the females as a cue to deposit their larvae in the matching aquatic habitat (flowing/standing) according to their own habitat-specific genotype. However, the female fire salamanders of the two habitat-specific genotypes did not show a preference for depositing their larvae in the water body with a water current matching their genotype cluster (stream/pond). Furthermore, the larval genotype did not match the water type in which the larvae were deposited. Overall, this study aimed to test whether fire salamander females of two different habitat-linked genotypes use a water current as a criterion for choosing an aquatic habitat for larval deposition. Our data do not support this hypothesis, leading to the assumption that fire salamander females use other environmental cues to select a water body for larval deposition.
    With the Help of Kin? Household Composition and Reproduction in The Netherlands, 1842-1920
    Rotering, P.P.P. ; Bras, H. - \ 2015
    Human Nature-An Interdisciplinary Biosocial Perspective 26 (2015)1. - ISSN 1045-6767 - p. 102 - 121.
    dutch fertility transition - demographic-transition - birth intervals - reproductive-behavior - historical krummhorn - genetical evolution - child-mortality - netherlands - survival - success
    Relatives play an important role in human reproduction according to evolutionary theories of reproductive behavior, but previous empirical studies show large differences in the effects of kin on fertility outcomes. In our paper we examine the effect of co-resident kin and non-kin on the length of birth intervals over the reproductive life course of Dutch women born between 1842 and 1920. We estimate Cox proportional hazard models for parity progression based on the presence of kin and non-kin in the household while controlling for a large number of individual and community-level characteristics. We find that couples living with their brothers experienced shorter birth intervals whereas couples residing with a widowed father had relatively longer birth intervals. The effects of these types of kin on reproduction were most pronounced up to the birth of the fifth child, but not thereafter. We found no effect for mothers or other types of kin.
    Effects of nocturnal illumination on life-history decisions and fitness in two wild songbird species
    Jong, M.J. de; Ouyang, J. ; Silva, A. Da; Grunsven, R.H.A. van; Kempenaers, B. ; Visser, M.E. ; Spoelstra, K. - \ 2015
    Philosophical Transactions of the Royal Society B. Biological sciences 370 (2015). - ISSN 0962-8436 - 8 p.
    chemical magnetoreception - photoperiodic control - birds - light - mechanism - success - vision - dawn - date
    The effects of artificial night lighting on animal behaviour and fitness are largely unknown. Most studies report short-term consequences in locations that are also exposed to other anthropogenic disturbance. We know little about how the effects of nocturnal illumination vary with different light colour compositions. This is increasingly relevant as the use of LED lights becomes more common, and LED light colour composition can be easily adjusted. We experimentally illuminated previously dark natural habitat with white, green and red light, and measured the effects on life-history decisions and fitness in two free-living songbird species, the great tit (Parus major) and pied flycatcher (Ficedula hypoleuca) in two consecutive years. In 2013, but not in 2014, we found an effect of light treatment on lay date, and of the interaction of treatment and distance to the nearest lamp post on chick mass in great tits but not in pied flycatchers. We did not find an effect in either species of light treatment on breeding densities, clutch size, probability of brood failure, number of fledglings and adult survival. The finding that light colour may have differential effects opens up the possibility to mitigate negative ecological effects of nocturnal illumination by using different light spectra.
    Health on impulse: when low self-control promotes healthy food choices
    Salmon, S.J. ; Fennis, B.M. ; Ridder, D.T.D. de; Adriaanse, M.A. ; Vet, E. de - \ 2014
    Health Psychology 33 (2014)2. - ISSN 0278-6133 - p. 103 - 109.
    physical-activity - limited-resource - ego depletion - behavior - interventions - metaanalysis - adolescents - success
    OBJECTIVE: Food choices are often made mindlessly, when individuals are not able or willing to exert self-control. Under low self-control, individuals have difficulties to resist palatable but unhealthy food products. In contrast to previous research aiming to foster healthy choices by promoting high self-control, this study exploits situations of low self-control, by strategically using the tendency under these conditions to rely on heuristics (simple decision rules) as quick guides to action. More specifically, the authors associated healthy food products with the social proof heuristic (i.e., normative cues that convey majority endorsement for those products). METHOD: One hundred seventy-seven students (119 men), with an average age of 20.47 years (SD = 2.25) participated in the experiment. This study used a 2 (low vs. high self-control) × 2 (social proof vs. no heuristic) × 2 (trade-off vs. control choice) design, with the latter as within-subjects factor. The dependent variable was the number of healthy food choices in a food-choice task. RESULTS: In line with previous studies, people made fewer healthy food choices under low self-control. However, this negative effect of low self-control on food choice was reversed when the healthy option was associated with the social proof heuristic. In that case, people made more healthy choices under conditions of low self-control. CONCLUSION: Low self-control may be even more beneficial for healthy food choices than high self-control in the presence of a heuristic. Exploiting situations of low self-control is a new and promising method to promote health on impulse.
    Correlated evolution in parental care in females but not males in response to selection on paternity assurance behaviour
    Head, M.L. ; Hinde, C.A. ; Moore, A.J. ; Royle, N.J. - \ 2014
    Ecology Letters 17 (2014)7. - ISSN 1461-023X - p. 803 - 810.
    nicrophorus-vespilloides - burying beetles - interacting phenotypes - sexual selection - sperm competition - biparental care - investment - conflict - tactics - success
    According to classical parental care theory males are expected to provide less parental care when offspring in a brood are less likely to be their own, but empirical evidence in support of this relationship is equivocal. Recent work predicts that social interactions between the sexes can modify co-evolution between traits involved in mating and parental care as a result of costs associated with these social interactions (i.e. sexual conflict). In burying beetles (Nicrophorus espilloides), we use artificial selection on a paternity assurance trait, and crosses within and between selection lines, to show that selection acting on females, not males, can drive the co-evolution of paternity assurance traits and parental care. Males do not care more in response to selection on mating rate. Instead, patterns of parental care change as an indirect response to costs of mating for females. Keywords: Parental care, sexual conflict, co-evolution, artificial selection, Nicrophorus vespilloides.
    How superdiffusion gets arrested: ecological encounters explain shift from Lévy to Brownian movement
    Jager, M. de; Bartumeus, F. ; Kölzsch, A. ; Weissing, F.J. ; Hengeveld, G.M. ; Nolet, B.A. ; Herman, P.M.J. ; Koppel, J. van de - \ 2014
    Proceedings of the Royal Society. B: Biological Sciences 281 (2014)1774. - ISSN 0962-8452 - 8 p.
    power-law distributions - flight search patterns - environmental complexity - walks evolve - predators - dynamics - animals - mussels - success
    Ecological theory uses Brownian motion as a default template for describing ecological movement, despite limited mechanistic underpinning. The generality of Brownian motion has recently been challenged by empirical studies that highlight alternative movement patterns of animals, especially when foraging in resource-poor environments. Yet, empirical studies reveal animals moving in a Brownian fashion when resources are abundant. We demonstrate that Einstein's original theory of collision-induced Brownian motion in physics provides a parsimonious, mechanistic explanation for these observations. Here, Brownian motion results from frequent encounters between organisms in dense environments. In density-controlled experiments, movement patterns of mussels shifted from Lévy towards Brownian motion with increasing density. When the analysis was restricted to moves not truncated by encounters, this shift did not occur. Using a theoretical argument, we explain that any movement pattern approximates Brownian motion at high-resource densities, provided that movement is interrupted upon encounters. Hence, the observed shift to Brownian motion does not indicate a density-dependent change in movement strategy but rather results from frequent collisions. Our results emphasize the need for a more mechanistic use of Brownian motion in ecology, highlighting that especially in rich environments, Brownian motion emerges from ecological interactions, rather than being a default movement pattern
    Breeding performance of the Grasshopper Buzzard (Butastur rufipennis) in a natural and a human-modified West African savanna
    Buij, R. ; Kortekaas, K. ; Krimpen, R.R.D. ; Wijk, H.J. van; Zanden, S. ; Iongh, H.H. de; Heitkonig, I.M.A. ; Snoo, G.R. de; Komdeur, J. - \ 2013
    Condor 115 (2013)1. - ISSN 0010-5422 - p. 47 - 57.
    nest-site selection - owls asio-otus - land-use - climate-change - survival estimation - raptor community - protected areas - arid savanna - habitat - success
    Few studies have examined raptor reproduction in response to land-use change in sub-Saharan Africa, hampering conservation efforts to address regional declines. To further our understanding of mechanisms underlying the dramatic declines of West African raptors, we examined the relationship between environmental conditions, nest density, and measures of reproduction in the Grasshopper Buzzard (Butastur rufipennis). Analyses were based on 244 nest sites divided between transformed and natural habitat in northern Cameroon. At the landscape scale, nest density increased with the density of preferred nest trees. Nests were more widely spaced in transformed than in natural habitat. Dispersion was adjusted to differences in availability of small mammals, which was negatively associated with distance to nearest neighbor, and in the area under cultivation, which was positively associated with distance to nearest neighbor. Productivity was positively associated with rainfall, canopy shielding the nest, availability of grasshoppers, and the nest's visibility from ground level; canopy shielding, grass cover, rainfall, and distance to nearest neighbor were positively associated with nest success. In natural habitat, losses of eggs and nestlings to natural predators were greater than in transformed habitats, while losses through human predation were small. Productivity and nest success were unaffected by land use because of the opposing effects of greater predation pressure, closer spacing of nests, and more food in natural habitat than in transformed habitat. Thus transformed habitat may provide adequate breeding habitat for the Grasshopper Buzzard, but declining rainfall and intensifying anthropogenic land use are likely to affect future reproductive output
    Identifying key performance indicators in food technology contract R&D
    Flipse, S.M. ; Sanden, M.C.A. van der; Velden, T. van der; Fortuin, F.T.J.M. ; Omta, S.W.F. ; Osseweijer, P. - \ 2013
    Journal of Engineering and Technology Management 30 (2013)1. - ISSN 0923-4748 - p. 72 - 94.
    biotechnology firms - innovation - industry - perspectives - experience - success - future - model - news
    Innovating companies increasingly rely on outsourcing to Contract Research Organisations (CROs) for their Research and Development (R&D), which are largely understudied. This paper presents the outcome of a case study in the field of food technology contract research, identifying context specific Key Performance Indicators (KPIs) for a CRO. KPIs were identified with a modified version of the Wageningen Innovation Assessment Tool, with which 72 finished successful and less successful projects were analysed. We developed a benchmarking tool to evaluate starting or running innovation project quality, which allows for direct, in situ project improvements by project leaders at CROs.
    Testing the Australian Weed Risk Assessment with different estimates for invasiveness
    Speek, T.A.A. ; Davies, J.A.R. ; Lotz, L.A.P. ; Putten, W.H. van der - \ 2013
    Biological Invasions 15 (2013)6. - ISSN 1387-3547 - p. 1319 - 1330.
    assessment system - plant invasiveness - success - invasion - europe - flora - history - tool
    The Weed Risk Assessment (WRA) has become an effective tool in predicting invasiveness of exotic plant species. In studies testing the WRA, exotic plant species are usually divided into major weeds, minor weeds and non-weeds. However, these divisions are qualitative, as the categories are assigned by experts. Many studies searching for plant traits that are indicative of plant invasiveness use quantitative estimates to measure invasiveness. We compared how quantitative and qualitative estimates of invasiveness may relate to WRA scores. As quantitative estimates we used regional frequency (spread), change in regional frequency and local dominance of naturalized exotic plant species in The Netherlands. To obtain a qualitative estimate we determined if the exotic plant species occurred on a black list in neighbouring regions. We related WRA scores of the exotic plant species to these qualitative and quantitative estimates of invasiveness. Our results reveal that the WRA predicted the qualitative (black list) estimate more accurately than the quantitative (dominance and spread) ones. The black list estimate matches with the overall impact of exotic species, which is assumed to incorporate regional spread, local dominance and noxiousness. Therefore, the WRA predicts the noxiousness component, but to a lesser extent the spatial components of impact of exotic species. On the other hand, studies that use regional spread and other quantitative estimates of invasiveness tend not to include the noxiousness component of impact. We propose that our analyses may also help to further solve the recent debate on whether or not performing research on exotic species.
    Transmission of a live Eimeria acervulina vaccine strain and response to infection in vaccinated and contact-vaccinated broilers
    Velkers, F.C. ; Bouma, A. ; Stegeman, J.A. ; Jong, M.C.M. de - \ 2012
    Vaccine 30 (2012)2. - ISSN 0264-410X - p. 322 - 328.
    avian coccidiosis - anticoccidial vaccines - chickens - diagnosis - efficacy - immunity - poultry - biology - success - design
    Live vaccines for coccidiosis control are infrequently used in broilers, mainly due to variability in efficacy and relatively high costs. More insight in transmission of vaccine and wild-type strains can facilitate optimization of vaccination strategies and might increase its use as an alternative for anticoccidial drugs. The aim of this study was to quantify transmission of a live Eimeria acervulina vaccine strain and to determine the degree of protection against a subsequent infection with a wild-type E. acervulina strain. An experiment was carried out with 4 groups of 22 SPF broilers. At 2 days of age, 11 birds of groups 2 to 4 were vaccinated directly by oral application of E. acervulina oocysts of the Paracox (TM) vaccine and 11 birds were placed in contact with these birds (contact-vaccinated). Birds in group 1 remained unvaccinated (controls) and were not exposed to vaccinated birds. At day 28 of age, 6 groups of 10 birds were formed, with 2 groups (duplo) for each treatment group, i.e. vaccinated, contact-vaccinated or unvaccinated control birds. Five birds of each group were orally inoculated with wild-type E. acervulina oocysts and five were contact-exposed. Single droppings were examined daily from days 5 to 49 of age for oocyst output and to determine the time of infection. The transmission rate of the vaccine strain was estimated to be 1.6 per day and of the wild-type strain 2.3, 8.7 and 20.8 per day for vaccinated, contact-vaccinated and unvaccinated birds, respectively. Although transmission of wild-type coccidia was not significantly reduced in vaccinated or contact-vaccinated groups, both groups were equally protected against high oocyst output after infection compared to unvaccinated groups. These results suggest that factors influencing transmission of live vaccine strains in flocks may be important targets for improvement of vaccine efficacy and warrant further research.
    Shorebird incubation behviour and its influence on the risk of nest predation
    Smith, P.A. ; Tulp, I.Y.M. ; Schekkerman, H. ; Gilchrist, H.G. ; Forbes, M.R. - \ 2012
    Animal Behaviour 84 (2012)4. - ISSN 0003-3472 - p. 835 - 842.
    daily energy-expenditure - site selection - parent birds - sandpipers - defense - pigmentation - patterns - habitat - success - waders
    Both nest survival and incubation behaviour are highly variable among shorebirds (Charadrii), and we tested whether more conspicuous incubation behaviour increased the risk of nest predation. During 2000-2006, we monitored nest fate at 901 shorebird nests at three study sites across the circumpolar Arctic. Using miniature video recorders and nest temperature sensors, we obtained 782 days of behavioural data for 161 nests of 11 species. We related nest fate to the rate and duration of adults' nest absences or restless movements on the nest, as well as the total proportion of each day that adult birds engaged in these activities. Nest predation was positively related to the proportion of time that each species left the nest unattended. After controlling for species effects, the likelihood of a successful nesting attempt was lower for individuals that spent more time off the nest, but among failed nests, the number of days that a nest survived prior to depredation was not significantly predicted by measures of incubation behaviour. To control for weather or seasonal effects, we paired observations from nests that were ultimately depredated with observations from successful nests of the same species on the same day. In this paired sample (dominated by two species: red phalaropes, Phalaropus fulicarius, and little stints, Calidris minuta), both incubation recesses and restless movements were more numerous among failed versus successful nests. Our results suggest that more conspicuous incubation behaviour is indeed related to a higher risk of nest predation, and that this relationship may underlie patterns of nest survival within and among shorebird species. (C) 2012 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.
    Seasonal distribution of meadow birds in relation to in-field heterogeneity and management
    Verhulst, J. ; Kleijn, D. ; Loonen, W. ; Berendse, F. ; Smit, C. - \ 2011
    Agriculture, Ecosystems and Environment 142 (2011)3-4. - ISSN 0167-8809 - p. 161 - 166.
    agri-environment schemes - lapwings vanellus-vanellus - godwit limosa-limosa - agricultural intensification - farmland birds - food resources - habitat - grasslands - success - england
    Effectiveness of European initiatives to restore populations of meadow breeding waders is heavily debated. We studied field preference of meadow birds throughout the breeding season in four areas of over 100 ha each and related observed patterns of individual birds to in-field heterogeneity, sward height and management. Over the four areas, most waders were observed in the more heterogeneous fields at both the period of nest site selection and incubation. Additionally, fields grazed at relatively low-intensity for longer consecutive periods (on average 6 cows/ha for 30 d instead of 20 cows/ha for 2 d) were hosting high densities of lapwings but also black-tailed godwits. Our results suggest that in-field heterogeneity may be important for meadow breeding waders at the nest site selection and incubation stages. Conservation initiatives aimed at meadow breeding waders might improve their effectiveness when they increase the heterogeneity of fields. Grazing for longer consecutive periods at relatively low stocking rates might be a way to achieve this, if carried out at stocking rates low enough to allow waders to reproduce successfully.
    Population admixture, biological invasions and the balance between local adaptation and inbreeding depression
    Verhoeven, K.J.F. ; Macel, M. ; Wolfe, L.M. ; Biere, A. - \ 2011
    Proceedings of the Royal Society. B: Biological Sciences 278 (2011)1702. - ISSN 0962-8452 - p. 2 - 8.
    silene-latifolia caryophyllaceae - genetic differentiation - intraspecific hybridization - multiple introductions - reproductive isolation - divergent selection - adaptive evolution - quantitative trait - plant - success
    When previously isolated populations meet and mix, the resulting admixed population can benefit from several genetic advantages, including increased genetic variation, the creation of novel genotypes and the masking of deleterious mutations. These admixture benefits are thought to play an important role in biological invasions. In contrast, populations in their native range often remain differentiated and frequently suffer from inbreeding depression owing to isolation. While the advantages of admixture are evident for introduced populations that experienced recent bottlenecks or that face novel selection pressures, it is less obvious why native range populations do not similarly benefit from admixture. Here we argue that a temporary loss of local adaptation in recent invaders fundamentally alters the fitness consequences of admixture. In native populations, selection against dilution of the locally adapted gene pool inhibits unconstrained admixture and reinforces population isolation, with some level of inbreeding depression as an expected consequence. We show that admixture is selected against despite significant inbreeding depression because the benefits of local adaptation are greater than the cost of inbreeding. In contrast, introduced populations that have not yet established a pattern of local adaptation can freely reap the benefits of admixture. There can be strong selection for admixture because it instantly lifts the inbreeding depression that had built up in isolated parental populations. Recent work in Silene suggests that reduced inbreeding depression associated with post-introduction admixture may contribute to enhanced fitness of invasive populations. We hypothesize that in locally adapted populations, the benefits of local adaptation are balanced against an inbreeding cost that could develop in part owing to the isolating effect of local adaptation itself. The inbreeding cost can be revealed in admixing populations during recent invasions
    A comparative analysis of restoration measures and their effects on hydromorphology and benthic invertebrates in 26 central and southern European rivers.
    Jähnig, S.C. ; Brabec, K. ; Buffagni, A. ; Erba, S. ; Lorenz, A. ; Ofenböck, T. ; Verdonschot, P.F.M. ; Hering, D. - \ 2010
    Journal of Applied Ecology 47 (2010)3. - ISSN 0021-8901 - p. 671 - 680.
    long-term recovery - stream restoration - ecological quality - habitat structure - diversity - macroinvertebrates - success - fish
    1. Hydromorphological river restoration usually leads to habitat diversification, but the effects on benthic invertebrates, which are frequently used to assess river ecological status, are minor. We compared the effects of river restoration on morphology and benthic invertebrates by investigating 26 pairs of non-restored and restored sections of rivers in Austria, Czech Republic, Germany, Italy and the Netherlands. 2. Sites were grouped according to (1) region: central Europe vs. southern Europe; (2) river type: mountain vs. lowland rivers; (3) restoration approach: active vs. passive restoration and (4) a combination of these parameters. All sites were sampled according to the same field protocol comprising hydromorphological surveys of river and floodplain mesohabitats, microhabitats at the river bottom and habitat-specific sampling of benthic invertebrates. Restoration effects were compared using Shannon–Wiener Indices (SWIs) of mesohabitats, microhabitats and invertebrate communities. Differences in metric values between non-restored and restored sites were compared for 16 metrics that evaluated hydromorphology and the benthic invertebrate community. 3. Mean SWIs differed for both mesohabitats (1·1 non-restored, 1·7 restored) and microhabitats (1·0 non-restored, 1·3 restored), while SWIs for invertebrate communities were not significantly different (2·
    Using Product Bundling to Facilitate the Adoption Process of Radical Innovations
    Reinders, M.J. ; Frambach, R.T. ; Schoormans, J.P.L. - \ 2010
    Journal of Product Innovation Management 27 (2010)7. - ISSN 0737-6782 - p. 1127 - 1140.
    consumer evaluations - prior knowledge - strategy - ad - attributes - preference - attitudes - purchase - success - analogy
    Generally, radical innovations are not easily adopted in the market. Potential adopters experience difficulties to comprehend and evaluate radical innovations due to their newness in terms of technology and benefits offered. Consequently, adoption intentions may remain low. This paper proposes bundling as an instrument to address these problems. More specifically, this paper examines how consumer comprehension, evaluation, and adoption intention of radical innovations may be enhanced by bundling such products with existing products. In addition, it is argued that the proposed effects are contingent upon the level of fit perceived to exist between the radical innovation and the product that accompanies it in the bundle. Furthermore, consumers' prior knowledge may affect the influence of bundling on the innovation adoption process as the interpretation of the meaning of new products may be strongly related to prior knowledge. This study therefore investigates whether consumer prior knowledge has such a moderating effect. Hypotheses are tested by means of an experimental study with three different radical innovations and distinguishing among offering the radical innovation separately, offering the radical innovation in a bundle with moderate perceived fit between the products, and offering the radical innovation in a bundle with high perceived fit between the products. Results show that product bundling enhances the new product's evaluation and adoption intention, although it does not increase comprehension of the radical innovation. Moreover, the results show that comprehension, evaluation and adoption intention of the innovation significantly decrease when consumers perceive a moderate fit between the products in a bundle. Taken together, these findings contribute to the bundling literature by showing not only that product bundling may indeed be an effective instrument to introduce a radical innovation but also that product bundling may be counterproductive when ignoring the critical role of perceived product fit as core characteristic of a product bundle. In addition, the notion that product bundling helps to enhance the evaluation and purchase intention of new and relatively complex products suggests a suitable strategy for new product managers to enhance benefits and reduce learning costs for radical innovations. Moreover, the effects of bundling on consumer appraisals of radical innovations are also shown to depend on the level of knowledge respondents possess regarding the product category of the radical innovation. More specifically, if bundled with a familiar product, novices tend to evaluate the innovative product more positively, but for experts no such effect can be detected. As such, these results provide additional specific implications for managers when introducing radical innovations in the market. Offering a radical innovation in a product bundle could be a fruitful strategy for companies that target customers with little or no prior knowledge in the product domain.
    Mixed mating system in the fern Asplenium scolopendrium: implication for colonization potential
    Bremer, P. ; Wubs, E.R.J. ; Groot, G.A. de; During, H.J. ; Vogel, J.C. ; Grundmann, M. ; Schneider, H. - \ 2010
    Annals of Botany 106 (2010)4. - ISSN 0305-7364 - p. 583 - 590.
    long-distance dispersal - reproductive-biology - genetic diversity - inbreeding depression - population-structure - blechnum-spicant - breeding-system - pteridophyta - establishment - success
    Background and Aims Human-mediated environmental change is increasing selection pressure for the capacity in plants to colonize new areas. Habitat fragmentation combined with climate change, in general, forces species to colonize areas over longer distances. Mating systems and genetic load are important determinants of the establishment and long-term survival of new populations. Here, the mating system of Asplenium scolopendrium, a diploid homosporous fern species, is examined in relation to colonization processes. Methods A common environment experiment was conducted with 13 pairs of sporophytes, each from a different site. Together they constitute at least nine distinct genotypes, representing an estimated approx. 95 % of the non-private intraspecific genetic variation in Europe. Sporophyte production was recorded for gametophytes derived from each parent sporophyte. Gametophytes were grown in vitro in three different ways: (I) in isolation, (II) with a gametophyte from a different sporophyte within the same site or (III) with a partner from a different site. Key Results Sporophyte production was highest in among-site crosses (III), intermediate in within-site crosses (II) and was lowest in isolated gametophytes (I), strongly indicating inbreeding depression. However, intragametophytic selfing was observed in most of the genotypes tested (eight out of nine). Conclusions The results imply a mixed mating system in A. scolopendrium, with outcrossing when possible and occasional selfing when needed. Occasional intragametophytic selfing facilitates the successful colonization of new sites from a single spore. The resulting sporophyte, which will be completely homozygous, will shed large amounts of spores over time. Each year this creates a bed of gametophytes in the vicinity of the parent. Any unrelated spore which arrives is then selectively favoured to reproduce and contribute its genes to the new population. Thus, while selfing facilitates initial colonization success, inbreeding depression promotes genetically diverse populations through outcrossing. The results provide further evidence against the overly simple dichotomous distinction of fern species as either selfing or outcrossing.
    Re-establishment of the North Sea houting in te River Rhine: Management and EcologicaL Note
    Borcherding, J. ; Heynen, M. ; Jaeger-Kleinicke, T. ; Winter, H.V. ; Eckmann, R. - \ 2010
    Fisheries Management and Ecology 17 (2010)3. - ISSN 0969-997X - p. 291 - 293.
    netherlands - whitefish - migration - success
    How social and human capital influence opportunity recognition and resource mobilization in India's handloom industry
    Bhagavatula, S. ; Elfring, T. ; Tilburg, A. van; Bunt, G.T. - \ 2010
    Journal of Business Venturing 25 (2010)3. - ISSN 0883-9026 - p. 245 - 260.
    weak ties - networks - entrepreneurship - embeddedness - performance - success - strategies - discovery - knowledge - market
    Small-scale firms in rural areas play an extremely important role in the development of any country, and especially in developing countries. To understand entrepreneurs who operate in a low-technology industry, we rely on the network perspective on entrepreneurship. In this paper, we investigate how the social and human capital of entrepreneurs (in this case master weavers in the handloom industry) influence their ability to recognize opportunities and mobilize resources. In addition to examining the direct effects, we also explore the possibilities of social capital mediating between human capital, on the one hand, and opportunity recognition and resource mobilization on the other. This paper adds to existing literature in two ways: firstly, we expand the social capital paradigm by including different cultural settings and links to existing studies regarding small enterprises. Secondly, we provide additional evidence to the ongoing debate as to what constitutes a `good network
    Evidence that tufted puffins Fratercula cirrhata use colony overflights to reduce kleptoparasitism risk
    Blackburn, G.S. ; Hipfner, J.M. ; Ydenberg, R.C. - \ 2009
    Journal of Avian Biology 40 (2009)4. - ISSN 0908-8857 - p. 412 - 418.
    atlantic puffins - great-island - arctica l - predation - seabirds - success - flight - gulls - wind - newfoundland
    Predation, foraging and mating costs are critical factors shaping life histories. Among colonial seabirds, colony overflights may enhance foraging or mating success, or diminish the risk of predation and kleptoparasitism. The latter possibility is difficult to test because low predation or kleptoparasitism rates could be due either to low danger or to effective counter-tactics by prey. Tufted puffins Fratercula cirrhata breeding at a large colony in British Columbia, Canada, deliver several loads of fish each day to their nestlings and are targets for kleptoparasitism by glaucous-winged gulls Larus glaucescens. In the present study, we documented the ecological conditions under which overflights occurred in order to assess when overflights were made and to statistically isolate the effect of overflights on kleptoparasitism risk at this site. Load-carrying puffins engaged in overflights under ecological conditions associated with relatively high rates of kleptoparasitism. Further, when ecological factors determining risk were statistically controlled, overflights were correlated with marginally lower chances of kleptoparasitism than when the risk factors were ignored. The results suggest that breeding puffins at this site use overflights for kleptoparasite avoidance. This tactic is used sparingly, suggesting it is costly. Costs of overflight behaviour might contribute to the impact of kleptoparasitism on the breeding success of tufted puffins.
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