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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Can traits predict individual growth performance? A test in a hyperdiverse tropical forest
Poorter, Lourens ; Castilho, Carolina V. ; Schietti, Juliana ; Oliveira, Rafael S. ; Costa, Flávia R.C. - \ 2018
New Phytologist 219 (2018)1. - ISSN 0028-646X - p. 109 - 121.
acclimation - Amazon - defense - functional traits - growth - plant strategies - plasticity - tropical rainforest
The functional trait approach has, as a central tenet, that plant traits are functional and shape individual performance, but this has rarely been tested in the field. Here, we tested the individual-based trait approach in a hyperdiverse Amazonian tropical rainforest and evaluated intraspecific variation in trait values, plant strategies at the individual level, and whether traits are functional and predict individual performance. We evaluated > 1300 tree saplings belonging to > 383 species, measured 25 traits related to growth and defense, and evaluated the effects of environmental conditions, plant size, and traits on stem growth. A total of 44% of the trait variation was observed within species, indicating a strong potential for acclimation. Individuals showed two strategy spectra, related to tissue toughness and organ size vs leaf display. In this nutrient- and light-limited forest, traits measured at the individual level were surprisingly poor predictors of individual growth performance because of convergence of traits and growth rates. Functional trait approaches based on individuals or species are conceptually fundamentally different: the species-based approach focuses on the potential and the individual-based approach on the realized traits and growth rates. Counterintuitively, the individual approach leads to a poor prediction of individual performance, although it provides a more realistic view on community dynamics.
Supplementary Material for: Nasonia Parasitic Wasps Escape from Haller's Rule by Diphasic, Partially Isometric Brain-Body Size Scaling and Selective Neuropil Adaptations
Groothuis, J. ; Smid, H.M. - \ 2017
Haller's rule - brain - insect - Nasonia vitripennis - parasitic wasp - confocal laser scanning microscopy - plasticity - neuropil - mushroom body
Root responses of grassland species to spatial heterogeneity of plant–soil feedback
Hendriks, M. ; Visser, E.J.W. ; Visschers, I.S.G. ; Aarts, B.H.J. ; Caluwe, H. de; Smit-Tiekstra, A.E. ; Putten, W.H. van der; Kroon, H. de; Mommer, L. - \ 2015
Functional Ecology 29 (2015)2. - ISSN 0269-8463 - p. 177 - 186.
nutrient heterogeneity - temporal variation - individual plants - community - growth - plasticity - diversity - availability - succession - microbes
Plant roots selectively forage for soil nutrients when these are heterogeneously distributed. In turn, effects of plant roots on biotic and abiotic conditions in the soil, which result in so-called plant–soil feedback can be heterogeneously distributed as well, but it is unknown how this heterogeneity affects root distribution, nutrient uptake and plant biomass production. Here, we investigate plant root distribution patterns as influenced by spatial heterogeneity of plant–soil feedback in soil and quantify consequences for plant nitrogen uptake and biomass production. We conditioned soils by four grassland plant species to obtain ‘own’ and ‘foreign’ soils that differed in biotic conditions similar as is done by the first phase of plant–soil feedback experiments. We used these conditioned soils to create heterogeneous (one patch of own and three patches of foreign soils) or homogeneous substrates where own and foreign soils were mixed. We also included sterilized soil to study the effect of excluding soil biota, such as pathogens, symbionts and decomposers. We supplied 15N as tracer to measure nutrient uptake. In nonsterile conditions, most plant species produced more biomass in heterogeneous than in homogeneous soil. Root biomass and 15N uptake rates were higher in foreign than own soil patches. These differences between heterogeneous and homogeneous soil disappeared when soil was sterilized, suggesting that the effects in nonsterilized soils were due to species-specific soil biota that had responded to soil conditioning. We conclude that plants produce more biomass when own and foreign soils are patchily distributed than when mixed. We show that this enhanced productivity is due to nutrient uptake being overall most efficient when own and foreign soils are spatially separated. We propose that spatial heterogeneity of negative plant–soil feedback in species diverse plant communities may provide a better explanation of overyielding than assuming that plant–soil feedback effects are diluted.
The presence of a below-ground neighbour alters within-plant seed size distribution in Phaseolus vulgaris
Chen, B. ; During, H.J. ; Vermeulen, P.J. ; Anten, N.P.R. - \ 2014
Annals of Botany 114 (2014). - ISSN 0305-7364 - p. 937 - 943.
root competition - variable environments - optimal balance - number - recognition - germination - growth - consequences - adaptation - plasticity
* Background and Aims Considerable variation in seed size commonly exists within plants, and is believed to be favoured under natural selection. This study aims to examine the extent to which seed size distribution depends on the presence of competing neighbour plants. * Methods Phaseolus vulgaris plants rooting with or without a conspecific neighbourwere grown in soil with high or low nutrient availability. Seeds were harvested at the end of the growth cycle, the total nitrogen and phosphorus invested in seed production were measured and within-plant seed size distribution was quantified using a set of statistical descriptors. * Key Results Exposure to neighbours’ roots induced significant changes in seed size distribution. Plants produced proportionally more large seeds and fewer small ones, as reflected by significant increases in minimal seed size, mean seed size, skewness and Lorenz asymmetry coefficient. These effects were different from, and in several cases opposite to, the responses when the soil nutrient level was reduced, and were significant after correction for the amount of resources invested in seed production. * Conclusions Below-ground neighbour presence affects within-plant seed size distribution in P. vulgaris. This effect appears to be non-resource-mediated, i.e. to be independent of neighbour-induced effects on resource availability. It implies that, based on current environmental cues, plants can make an anticipatory adjustment of their investment strategy in offspring as an adaptation to the local environment in the future. Key words: Anticipatory maternal effect, bet-hedging, game theory, neighbour detection, Phaseolus vulgaris, kidney bean, root competition, seed-setting, seed size variation, size inequality, skewness. INTRODUCTION A considerable degree of variation in seed size within plants is commonly observed (Michaels et al., 1988; Silvertown, 1989; Ruiz de Clavijo, 2002; Vo¨ller et al., 2012). Such variation is often interpreted as an adaptive bet-hedging strategy (Harper et al., 1970; McGinley et al., 1987; McGinley and Charnov, 1988; Venable and Brown, 1988; Geritz, 1995). Many studies also reveal that plants modify the pattern of variation (i.e. distribution) to cope with their abiotic environmental conditions (e.g. temperature, Wulff, 1986; light, Galloway, 2001; nutrients, Galloway, 2001;water, Parciak, 2002). Herewe demonstrate that seed size distribution may also be modified in response to the presence of a below-ground neighbour. Within a species, seed size (following common practice, seed size refers to seedweight in this paper) often correlates positively with the competitiveness of the offspring (e.g. Houssard and Escarre´, 1991; Eriksson, 1999; Lehtila¨ and Ehrle´n, 2005; Dubois and Cheptou, 2012). Based on the trade-off, induced by resource limitation in plants, between competition (favours large seeds) and colonization (favours a large number of small seeds), Geritz (1995) extended an optimal offspring size model (Smith and Fretwell, 1974) by considering seedling competition and using
Artificial light at night causes diapause inhibition and sex-specific life history changes in a moth
Geffen, K.G. van; Grunsven, R.H.A. van; Ruijven, J. van; Berendse, F. ; Veenendaal, E.M. - \ 2014
Ecology and Evolution 4 (2014)11. - ISSN 2045-7758 - p. 2082 - 2089.
epirrita-autumnata lepidoptera - body-size - plutella-xylostella - utetheisa-ornatrix - diamondback moth - lobesia-botrana - flight ability - geometridae - biodiversity - plasticity
Rapidly increasing levels of light pollution subject nocturnal organisms to major alterations of their habitat, the ecological consequences of which are largely unknown. Moths are well-known to be attracted to light at night, but effects of light on other aspects of moth ecology, such as larval development and life-history, remain unknown. Such effects may have important consequences for fitness and thus for moth population sizes. To study the effects of artificial night lighting on development and life-history of moths, we experimentally subjected Mamestra brassicae (Noctuidae) caterpillars to low intensity green, white, red or no artificial light at night and determined their growth rate, maximum caterpillar mass, age at pupation, pupal mass and pupation duration. We found sex-specific effects of artificial light on caterpillar life-history, with male caterpillars subjected to green and white light reaching a lower maximum mass, pupating earlier and obtaining a lower pupal mass than male caterpillars under red light or in darkness. These effects can have major implications for fitness, but were absent in female caterpillars. Moreover, by the time that the first adult moth from the dark control treatment emerged from its pupa (after 110 days), about 85% of the moths that were under green light and 83% of the moths that were under white light had already emerged. These differences in pupation duration occurred in both sexes and were highly significant, and likely result from diapause inhibition by artificial night lighting. We conclude that low levels of nocturnal illumination can disrupt life-histories in moths and inhibit the initiation of pupal diapause. This may result in reduced fitness and increased mortality. The application of red light, instead of white or green light, might be an appropriate measure to mitigate negative artificial light effects on moth life history.
Endemic species have highly integrated phenotypes, environmental distributions and phenotype-environment relationships
Hermant, M. ; Prinzing, A. ; Vernon, P. ; Convey, P. ; Hennion, F. - \ 2013
Journal of Biogeography 40 (2013)8. - ISSN 0305-0270 - p. 1583 - 1594.
sub-antarctic islands - contrasting ecological breadth - southern-ocean islands - pringlea-antiscorbutica - biological aspects - california flora - late quaternary - climate-change - higher-plants - plasticity
Keywords: Abiotic environmental gradients; endemism level; functional biogeography; island biogeography; Kerguelen Islands; life-history traits; multi-species comparison; phenotypic integration; range size; sub-Antarctic Abstract Aim: Why are some species geographically restricted? Ecological explanations suggest that endemic species may have restricted distributions because limited phenotypic variability results in narrow niches. However, studying variability of traits independently may not fully explain the interactions within and between complex phenotypes and environments. Here, we hypothesize that endemic species are restricted to a narrow range of habitats due to strong phenotypic integration (i.e. strong correlations among traits), strong environmental integration (i.e. strong correlations among the environments occupied) and strong correlations among trait–environment combinations. Location: The Kerguelen Islands, sub-Antarctic. Methods: We measured flowering phenology, multiple morphological characters, and species distribution along three abiotic environmental gradients (elevation, soil moisture and soil salinity) in 14 plant species whose distributions range from strictly endemic to cosmopolitan. Results: We found that for individual species, trait means and variances were independent of endemism, but that endemics occupied higher and less variable microhabitats. However, phenotypic integration, environmental integration along the three gradients, and the strength of trait–environment correlations all increased with the level of species endemism. Main conclusions: Higher levels of integration within and between phenotypes and environments are associated with more restricted geographical ranges in the species studied. In endemic species phenotypic integration may explain range contraction during the taxon cycle and reduce the ability to adapt to novel microhabitats formed as a result of environmental change.
WormQTL—public archive and analysis web portal for natural variation data in Caenorhabditis spp
Snoek, L.B. ; Velde, K.J. van der; Arends, D. ; Li, Y. ; Beyer, A. ; Elvin, M. ; Fisher, J. ; Hajnal, A. ; Hengartner, M. ; Poulin, G. ; Rodriguez Sanchez, M. ; Schmid, T. ; Schrimpf, S. ; Xue, F. ; Jansen, R.C. ; Kammenga, J.E. ; Swertz, M.A. - \ 2013
Nucleic Acids Research 41 (2013)D1. - ISSN 0305-1048 - p. D738 - D743.
life-history traits - c. elegans - systems biology - qtl - polymorphism - genotype - environment - plasticity - platform - genome
Here, we present WormQTL (, an easily accessible database enabling search, comparative analysis and meta-analysis of all data on variation in Caenorhabditis spp. Over the past decade, Caenorhabditis elegans has become instrumental for molecular quantitative genetics and the systems biology of natural variation. These efforts have resulted in a valuable amount of phenotypic, high-throughput molecular and genotypic data across different developmental worm stages and environments in hundreds of C. elegans strains. WormQTL provides a workbench of analysis tools for genotype–phenotype linkage and association mapping based on but not limited to R/qtl ( All data can be uploaded and downloaded using simple delimited text or Excel formats and are accessible via a public web user interface for biologists and R statistic and web service interfaces for bioinformaticians, based on open source MOLGENIS and xQTL workbench software. WormQTL welcomes data submissions from other worm researchers.
Transgenerational Effects of Stress Exposure on Offspring Phenotypes in Apomictic Dandelion
Verhoeven, K.J.F. ; Gurp, T.P. van - \ 2012
PLoS One 7 (2012)6. - ISSN 1932-6203
arabidopsis-thaliana - trichome density - mimulus-guttatus - plants - responses - methylation - plasticity - herbivory - consequences - inheritance
Heritable epigenetic modulation of gene expression is a candidate mechanism to explain parental environmental effects on offspring phenotypes, but current evidence for environment-induced epigenetic changes that persist in offspring generations is scarce. In apomictic dandelions, exposure to various stresses was previously shown to heritably alter DNA methylation patterns. In this study we explore whether these induced changes are accompanied by heritable effects on offspring phenotypes. We observed effects of parental jasmonic acid treatment on offspring specific leaf area and on offspring interaction with a generalist herbivore; and of parental nutrient stress on offspring root-shoot biomass ratio, tissue P-content and leaf morphology. Some of the effects appeared to enhance offspring ability to cope with the same stresses that their parents experienced. Effects differed between apomictic genotypes and were not always consistently observed between different experiments, especially in the case of parental nutrient stress. While this context-dependency of the effects remains to be further clarified, the total set of results provides evidence for the existence of transgenerational effects in apomictic dandelions. Zebularine treatment affected the within-generation response to nutrient stress, pointing at a role of DNA methylation in phenotypic plasticity to nutrient environments. This study shows that stress exposure in apomictic dandelions can cause transgenerational phenotypic effects, in addition to previously demonstrated transgenerational DNA methylation effects.
Trampling, defoliation and physiological integration affect growth, morphological and mechanical properties of a root-suckering clonal tree
Xu, L. ; Yu, F.H. ; Drunen, E. van; Schieving, F. ; Dong, M. ; Anten, N.P.R. - \ 2012
Annals of Botany 109 (2012)5. - ISSN 0305-7364 - p. 1001 - 1008.
fragaria-chiloensis - psammochloa-villosa - bean-plants - tolerance - resistance - vegetation - plasticity - herbivory - stress - thigmomorphogenesis
Background and Aims Grazing is a complex process involving the simultaneous occurrence of both trampling and defoliation. Clonal plants are a common feature of heavily grazed ecosystems where large herbivores inflict the simultaneous pressures of trampling and defoliation on the vegetation. We test the hypothesis that physiological integration (resource sharing between interconnected ramets) may help plants to deal with the interactive effects of trampling and defoliation. Methods In a field study, small and large ramets of the root-suckering clonal tree Populus simonii were subjected to two levels of trampling and defoliation, while connected or disconnected to other ramets. Plant responses were quantified via survival, growth, morphological and stem mechanical traits. Key Results Disconnection and trampling increased mortality, especially in small ramets. Trampling increased stem length, basal diameter, fibrous root mass, stem stiffness and resistance to deflection in connected ramets, but decreased them in disconnected ones. Trampling decreased vertical height more in disconnected than in connected ramets, and reduced stem mass in disconnected ramets but not in connected ramets. Defoliation reduced basal diameter, leaf mass, stem mass and leaf area ratio, but did not interact with trampling or disconnection. Conclusions Although clonal integration did not influence defoliation response, it did alleviate the effects of trampling. We suggest that by facilitating resource transport between ramets, clonal integration compensates for trampling-induced damage to fine roots
Aging Uncouples Heritability and Expression-QTL in Caenorhabditis elegans
Viñuela Rodriguez, A. ; Snoek, L.B. ; Riksen, J.A.G. ; Kammenga, J.E. - \ 2012
G3 : Genes Genomes Genetics 2 (2012)5. - ISSN 2160-1836 - p. 597 - 605.
quantitative trait loci - cdna microarray data - life-history traits - gene-expression - c-elegans - age - arabidopsis - genomics - normalization - plasticity
The number and distribution of gene expression QTL (eQTL) represent the genetic architecture of many complex traits, including common human diseases. We previously reported that the heritable eQTL patterns are highly dynamic with age in an N2 × CB4856 recombinant inbred population of the nematode Caenorhabditis elegans. In particular, we showed that the number of eQTL decreased with age. Here, we investigated the reason for this decrease by combining gene expression profiles at three ages in the wild types N2 and CB4856 with the reported expression profiles of the RIL population. We determined heritability and transgression (when gene expression levels in the RILs are more extreme than the parents) and investigated their relation with eQTL changes with age. Transgressive segregation was widespread but depended on physiological age. The percentage of genes with an eQTL increased with a higher heritability in young worms. However, for old worms this percentage hardly increased. Using a single marker approach, we found that almost 20% of genes with heritability >0.9 had an eQTL in developing worms. Surprisingly, only 10% was found in old worms. Using a multimarker approach, this percentage increased to almost 30% for both age groups. Comparison of the single marker to a multiple marker eQTL mapping indicated that heritable regulation of gene expression becomes more polygenic in aging worms due to multiple loci and possible epistatic interactions. We conclude that linkage studies should account for the relation between increased polygenic regulation and diminished effects at older ages.
Horizontal, but not vertical canopy structure is related to stand functional diversity in a subtropical slope forest
Lang, A.C. ; Härdtle, W. ; Bruelheide, H. ; Kröber, W. ; Schröter, M. ; Wehrden, H. von; Oheimb, G. von - \ 2012
Ecological Research 27 (2012)1. - ISSN 0912-3814 - p. 181 - 189.
tree diversity - old-growth - competition - asymmetry - communities - environment - succession - plasticity - seedlings - crowns
The aim of this study was to analyse the relation of horizontal and vertical canopy structure to tree functional diversity of a highly diverse subtropical broad-leaved slope forest, stratified for different successional stages. This is of particular interest because many key ecosystem processes and functions are related to the arrangement of forest canopies. We assessed the effect of stand-related functional diversity (FDQ, measured as Rao’s quadratic entropy of leaf traits), together with other environmental variables on horizontal [measured as relative crown projection areas (CPAr)] and vertical [relative crown overlap, coefficients of variation (CV) of crown positioning variables] structure of the upper canopy at the local neighbourhood level. The analyses with mixed effects models revealed a negative relation (p = 0.025; estimate -0.07) between FDQ and CPAr. No significant effect of FDQ on vertical canopy structure has been found (p > 0.05). The findings are discussed with regard to resource partitioning and niche differentiation of canopy and sub-canopy species. Successional stage positively impacted the CV of crown length (p = 0.019; estimate 0.03) but did not affect other response variables. The sloping terrain strongly influenced vertical canopy structure as revealed by the significant effect of slope inclination on CV of crown length (p = 0.004; estimate -0.05) and of slope aspect on CV of mean crown height (p = 0.036; estimate -0.03). The high complexity of vertical crown positioning depending on the heterogeneous sloping terrain of the study area may have obscured relations of FDQ to vertical canopy structure
Interactive effects of nutrient heterogeneity and competition: implications for root foraging theory?
Mommer, L. ; Ruijven, J. van; Jansen, C. - \ 2012
Functional Ecology 26 (2012)1. - ISSN 0269-8463 - p. 66 - 73.
below-ground competition - size asymmetry - plant - placement - plasticity - ability - proliferation - communities - responses - patterns
1. Plants are known to respond to heterogeneous distribution of nutrients in the soil, and they also respond to the presence of neighbouring roots. However, it is unclear whether plants are able to distinguish between these factors and adjust their root responses accordingly. 2. We investigated whether the simultaneous response to nutrient heterogeneity and competition could be predicted from the responses to these factors separately. As a null model, we hypothesized that the responses to nutrients and competition are additive and thus no interactions occur. We performed a short-term competition experiment in the greenhouse with two floodplain species in homogeneous and heterogeneous conditions. The consequences of different root distributions for nutrient uptake were tested using 15N pulse-labelling. 3. Both species responded to nutrient heterogeneity by investing significantly more roots in the nutrient-rich patch, and both species showed a significant reduction in root growth in response to competition, albeit that the reduction was much more pronounced for the grass species. For Rumex palustris, the effects of heterogeneity and competition were additive. However, the response to nutrient heterogeneity of Agrostis stolonifera was reversed by competition: instead of proliferating in the nutrient-rich patch, it significantly increased root investments in the ‘empty’ (nutrient-poor) patches. As the partitioning of total N was less asymmetric than 15N uptake from the nutrient-rich patch, it appears that these altered root investments of A. stolonifera in the ‘empty’ patches have also been functional with respect to compensating N uptake. 4. Our results suggest that root responses to nutrient distribution in a competitive environment depend on the competitive strength of the neighbouring species. The foraging response of the superior species (R. palustris) was hardly affected, but that of the inferior species (A. stolonifera) was greatly inhibited and even reversed by competition: instead of proliferating in the nutrientrich patch, it increased root growth and foraging activity in less favourable patches. Incorporating competitive hierarchy into root foraging studies may help to explain the ambiguous results found in previous studies. Key-words: Agrostis stolonifera, below-ground competition, competitive hierarchy, 15N labelling, root foraging, Rumex palustris, selective root placement, soil heterogeneity,
DOG1 expression is predicted by the seed-maturation envornment and contributes to geographical variation in germination in Arabidopsis thaliana
Chiang, G.C.K. ; Bartsch, M. ; Barua, D. ; Nakabayashi, K. ; Debieu, M. ; Kronholm, I. ; Koornneef, M. ; Soppe, W.J.J. ; Donohue, K. ; Meaux, J. De - \ 2011
Molecular Ecology 20 (2011)16. - ISSN 0962-1083 - p. 3336 - 3349.
flowering time gene - natural-selection - dormancy - brassicaceae - evolution - field - diversification - adaptation - characters - plasticity
Seasonal germination timing of Arabidopsis thaliana strongly influences overall life history expression and is the target of intense natural selection. This seasonal germination timing depends strongly on the interaction between genetics and seasonal environments both before and after seed dispersal. DELAY OF GERMINATION 1 (DOG1) is the first gene that has been identified to be associated with natural variation in primary dormancy in A. thaliana. Here, we report interaccession variation in DOG1 expression and document that DOG1 expression is associated with seed-maturation temperature effects on germination; DOG1 expression increased when seeds were matured at low temperature, and this increased expression was associated with increased dormancy of those seeds. Variation in DOG1 expression suggests a geographical structure such that southern accessions, which are more dormant, tend to initiate DOG1 expression earlier during seed maturation and achieved higher expression levels at the end of silique development than did northern accessions. Although elimination of the synthesis of phytohormone abscisic acid (ABA) results in the elimination of maternal temperature effects on dormancy, DOG1 expression predicted dormancy better than expression of genes involved in ABA metabolism
Mitochondrial DNA signature for range-wide populations of Bicyclus anynana suggests a rapid expansion from recent refugia
Jong, M.A. de; Wahlberg, N. ; Eijk, M. van; Brakefield, P.M. ; Zwaan, B.J. - \ 2011
PLoS One 6 (2011)6. - ISSN 1932-6203 - 5 p.
lepidoptera - butterflies - plasticity - biology - systematics - haplotypes - neutrality - evolution - selection - markers
This study investigates the genetic diversity, population structure and demographic history of the afrotropical butterfly Bicyclus anynana using mitochondrial DNA (mtDNA). Samples from six wild populations covering most of the species range from Uganda to South Africa were compared for the cytochrome c oxidase subunit gene (COI). Molecular diversity indices show overall high mtDNA diversity for the populations, but low nucleotide divergence between haplotypes. Our results indicate relatively little geographic population structure among the southern populations, especially given the extensive distributional range and an expectation of limited gene flow between populations. We implemented neutrality tests to assess signatures of recent historical demographic events. Tajima's D test and Fu's FS test both suggested recent population growth for the populations. The results were only significant for the southernmost populations when applying Tajima's D, but Fu's FS indicated significant deviations from neutrality for all populations except the one closest to the equator. Based on our own findings and those from pollen and vegetation studies, we hypothesize that the species range of B. anynana was reduced to equatorial refugia during the last glacial period, and that the species expanded southwards during the past 10.000 years. These results provide crucial background information for studies of phenotypic and molecular adaptation in wild populations of B. anynana
Fatty acid compostion and extreme temperature tolerance following exposure to fluctuating temperatures in a soil arthropod
Dooremalen, C. van; Suring, W. ; Ellers, J. - \ 2011
Journal of Insect Physiology 57 (2011)9. - ISSN 0022-1910 - p. 1267 - 1273.
membrane-lipid-composition - thermal-reaction norms - chill coma recovery - drosophila-melanogaster - homeoviscous adaptation - cycling temperatures - cold resistance - heat-resistance - plasticity - acclimation
Ectotherms commonly adjust their lipid composition to ambient temperature to counteract detrimental thermal effects on lipid fluidity. However, the extent of lipid remodeling and the associated fitness consequences under continuous temperature fluctuations are not well-described. The objective of this study was to investigate the effect of repeated temperature fluctuations on fatty acid composition and thermal tolerance. We exposed the springtail Orchesella cincta to two constant temperatures of 5 and 20 °C, and a continuously fluctuating treatment between 5 and 20 °C every 2 days. Fatty acid composition differed significantly between constant low and high temperatures. As expected, animals were most cold tolerant in the low temperature treatment, while heat tolerance was highest under high temperature. Under fluctuating temperatures, fatty acid composition changed with temperature initially, but later in the experiment fatty acid composition stabilized and closely resembled that found under constant warm temperatures. Consistent with this, heat tolerance in the fluctuating temperature treatment was comparable to the constant warm treatment. Cold tolerance in the fluctuating temperature treatment was intermediate compared to animals acclimated to constant cold or warmth, despite the fact that fatty acid composition was adjusted to warm conditions. This unexpected finding suggests that in animals acclimated to fluctuating temperatures an additional underlying mechanism is involved in the cold shock response. Other aspects of homeoviscous adaptation may protect animals during extreme cold. This paper forms a next step to fully understand the functioning of ectotherms in more thermally variable environments
Genome structure and pathogenicity of the fungal wheat pathogen Mycosphaerella graminicola
M'Barek, S. Ben - \ 2011
University. Promotor(en): Pierre de Wit, co-promotor(en): Gert Kema. - [S.l.] : S.n. - ISBN 9789085859970 - 229
triticum aestivum - triticum turgidum - tarwe - mycosphaerella graminicola - plantenziekteverwekkende schimmels - genoomstructuur - eiwitexpressieanalyse - pathogeniteit - pathogenesis-gerelateerde eiwitten - genomen - plasticiteit - plant-microbe interacties - wheat - plant pathogenic fungi - genomic structure - proteomics - pathogenicity - pathogenesis-related proteins - genomes - plasticity - plant-microbe interactions

The phytopathogenic fungus Mycosphaerella graminicola (Fuckel) J. Schröt. in Cohn (asexual stage: Zymoseptoria tritici (Desm.) Quaedvlieg & Crous) causes septoria tritici leaf blotch (STB) in wheat and is one of the most important diseases of this crop worldwide. However, STB control, mainly based on the use of resistant cultivars and fungicides, is significantly hampered by the limited understanding of the genetic and biochemical bases of pathogenicity, and mechanisms of infection and resistance in the host. M. graminicola has a very active sexual cycle under field conditions, which is an important driver of STB epidemics. Moreover, it results in high genetic diversity of field populations that causes a major challenge for the development and sustainable management of resistant cultivars and the discovery of new antifungal compounds. Understanding the role of the sexual and asexual life cycles on genome composition of this versatile pathogen and its infection strategy is crucial in order to develop novel control methods.

Chapter 1 is an introduction to the biology and pathogenicity of M. graminicola. In addition, it shortly describes the impact of improved and novel technologies on the speed, scope and scale of comparative genomics research.

Chapter 2 provides detailed genetic analyses of two M. graminicola mapping populations, using mainly DArT markers, and the analysis of the meiotic transmission of unequal chromosome numbers. Polymorphisms in chromosome length and number were frequently observed in progeny isolates, of which 15–20% lacked one or more chromosomes despite their presence in one or both parents, but these had no apparent effect on sexual and pathogenic fitness. M. graminicola has up to eight so called dispensable chromosomes that can be easily lost - collectively called the dispensome - which is, so far, the highest number of dispensable chromosomes reported in filamentous fungi. They represent small-sized chromosomes and make up 38% of the chromosome complement of this pathogen. Much of the observed genome plasticity is generated during meiosis and could explain the high adaptability of M. graminicola in the field. The generated linkage map was crucial for finishing the M. graminicola genome sequence.

Chapter 3 describes the M. graminicola genome sequence with highlights on genome structure and organization including the eight dispensable chromosomes. The genome comprises a core set of 13 chromosomes and a dispensome, consisting of eight chromosomes that are distinct from the core chromosomes in structure, gene and repeat content. The dispensome contains a higher frequency of transposons and the genes have a different codon use. Most of the genes present one the dispensome are also present on the core chromosomes but little synteny is observed neither between the M. graminicola dispensome and the core chromosomes nor with the chromosomes of other related Dothideomycetes. The dispensome likely originates from ancient horizontal transfer(s) from (an) unknown donor(s).

Chapter 4 shows a global analysis of proteins secreted by M. graminicola in apoplastic fluids during infection. It focuses mainly on fungal proteins secreted in a compatible interaction. The study showed that many of the annotated secreted proteins have putative functions in fungal pathogenicity, such as cell wall degrading enzymes and proteases, but the function of a substantial number of the identified proteins is unknown. During compatible interactions proteins are primarily secreted during the later stages. However, many pathogenesis-related host proteins, such as PR-2, PR-3 and PR-9, accumulated earlier and at higher concentrations during incompatible interactions, indicating that fungal effectors are recognized by resistant plants and trigger resistant gene-mediated defence responses, though without a visible hypersensitive response.

Chapter 5 further details the initial identification and characterization of necrosis-inducing proteins that are produced in culture filtrates (CFs) of M. graminicola. The necrosis-inducing activity of CFs is light dependent and inactivated by proteinase K and heat treatment (100C). This is reminiscent of the necrosis-inducing properties of host selective toxins of other Dothideomycete pathogens such as Stagonospora nodorum and Pyrenophora tritici-repentis. Subsequent purifications of CFs and mass spectrometry identified several candidate proteins with necrosis-inducing activity. Heterologous expression of the two most prominent proteins in Pichia pastoris produced sufficient quantities for infiltration assays in a panel of wheat cultivars that showed differential responses, suggesting specific recognition.

Chapter 6 provides a general discussion of the thesis and puts the results obtained in a broader perspective with a focus on the genome structure of M. graminicola and its function. In addition, aspects of the hemi-biotrophic lifestyle, the relevance of secreted proteins for the wheat-M. graminicola pathosystem in relation to gene-for-gene models and the potential implications for resistance breeding strategies are discussed.

Contrasting root behaviour in two grass species: a test of functionality in dynamic heterogeneous conditions
Mommer, L. ; Visser, E.J.W. ; Ruijven, J. van; Caluwe, H. de; Pierik, R. ; Kroon, H. de - \ 2011
Plant and Soil 344 (2011)1-2. - ISSN 0032-079X - p. 347 - 360.
soil nutrient heterogeneity - foraging traits - plants bother - rich patches - proliferation - plasticity - placement - precision - responses - growth
Root systems are highly plastic as they express a range of responses to acquire patchily distributed nutrients. However, the ecological significance of placing roots selectively in nutrient hotspots is still unclear. Here, we investigate under what conditions selective root placement may be a significant functional trait that determines belowground competitive ability. We studied two grasses differing in root foraging behaviour, Festuca rubra and Anthoxanthum odoratum. The plants were grown in stable and more dynamic heterogeneous environments, by switching nutrient patches halfway through the experiment. A. odoratum was a factor of two less selective in placing its roots into nutrient-rich patches than F. rubra. A. odoratum produced overall higher root length densities with higher specific root length than F. rubra and acquired more nutrients. A. odoratum appeared to be the superior competitor, irrespective of the nutrient dynamics. Our results suggest that root behaviour consisting of producing high root length densities at relatively low biomass investments can be a more effective foraging strategy than placing roots selectively in nutrient hotspots. When understanding the functionality of root traits among different species, specific root length may play a key role
Between-year variability in the mixing of North Sea herring spawning components leads to pronounced variation in the composition of the catch
Bierman, S.M. ; Dickey-Collas, M. ; Damme, C.J.G. van; Overzee, H.M.J. van; Pennock-Vos, M.G. ; Tribuhl, S.V. ; Clausen, L.A.W. - \ 2010
ICES Journal of Marine Science 67 (2010)5. - ISSN 1054-3139 - p. 885 - 896.
clupea-harengus l - otolith microstructure - atlantic - recruitment - management - stocks - metapopulations - identification - populations - plasticity
North Sea herring (Clupea harengus) are managed as a single stock, but maintaining a diversity of spawning components is considered important. However, the total catch from each of these components cannot be estimated easily because the components mix during the summer feeding season. The spawning origin of herring is determined from patterns in the microstructure of the otolith core, from samples taken in the central and northern North Sea during summer of 2004–2007. The annual catch composition of Dutch vessels is determined within a statistical framework that takes account of the spatial patterns in mixing of spawning components and the classification success of the method. Mixing of components varied between years, with steep latitudinal gradients in compositions in some years, resulting in pronounced between-year differences in estimated catch compositions. Differences in lengths-at-age between spawning components, in particular of the 2000 year class, may have caused the observed between-year changes in mixing of components. Our results indicate that estimates of compositions change when assumptions of perfect spatial mixing and perfect classification are relaxed, and can be uncertain in particular as a result of misclassifications, and that it may not be appropriate to assume that ratios between components are constant through time
Hitch-hiking parasitic wasp learns to exploit butterfly antiaphrodisiac
Huigens, M.E. ; Pashalidou, F.G. ; Qian, M.H. ; Bukovinszky, T. ; Smid, H.M. ; Loon, J.J.A. van; Dicke, M. ; Fatouros, N.E. - \ 2009
Proceedings of the National Academy of Sciences of the United States of America 106 (2009)3. - ISSN 0027-8424 - p. 820 - 825.
long-term-memory - sex-pheromone - trichogramma - drosophila - behavior - consolidation - hymenoptera - dissection - plasticity - selection
Many insects possess a sexual communication system that is vulnerable to chemical espionage by parasitic wasps. We recently discovered that a hitch-hiking (H) egg parasitoid exploits the antiaphrodisiac pheromone benzyl cyanide (BC) of the Large Cabbage White butterfly Pieris brassicae. This pheromone is passed from male butterflies to females during mating to render them less attractive to conspecific males. When the tiny parasitic wasp Trichogramma brassicae detects the antiaphrodisiac, it rides on a mated female butterfly to a host plant and then parasitizes her freshly laid eggs. The present study demonstrates that a closely related generalist wasp, Trichogramma evanescens, exploits BC in a similar way, but only after learning. Interestingly, the wasp learns to associate an H response to the odors of a mated female P. brassicae butterfly with reinforcement by parasitizing freshly laid butterfly eggs. Behavioral assays, before which we specifically inhibited long-term memory (LTM) formation with a translation inhibitor, reveal that the wasp has formed protein synthesis-dependent LTM at 24 h after learning. To our knowledge, the combination of associatively learning to exploit the sexual communication system of a host and the formation of protein synthesis-dependent LTM after a single learning event has not been documented before. We expect it to be widespread in nature, because it is highly adaptive in many species of egg parasitoids. Our finding of the exploitation of an antiaphrodisiac by multiple species of parasitic wasps suggests its use by Pieris butterflies to be under strong selective pressure
Submergence-induced leaf acclimation in terrestrial species varying in flooding tolerance
Mommer, L. ; Wolters-Arts, M. ; Andersen, C. ; Visser, E.J.W. ; Pedersen, O. - \ 2007
New Phytologist 176 (2007)2. - ISSN 0028-646X - p. 337 - 345.
deep-water rice - amphibious plants - photosynthesis - plasticity - responses - elongation - shade - environments - communities - performance
Earlier work on the submergence-tolerant species Rumex palustris revealed that leaf anatomical and morphological changes induced by submergence enhance underwater gas exchange considerably. Here, the hypothesis is tested that these plastic responses are typical properties of submergence-tolerant species. ¿ Submergence-induced plasticity in leaf mass area (LMA) and leaf, cell wall and cuticle thickness was investigated in nine plant species differing considerably in tolerance to complete submergence. The functionality of the responses for underwater gas exchange was evaluated by recording oxygen partial pressures inside the petioles when plants were submerged. ¿ Acclimation to submergence resulted in a decrease in all leaf parameters, including cuticle thickness, in all species irrespective of flooding tolerance. Consequently, internal oxygen partial pressures (pO2) increased significantly in all species until values were close to air saturation. Only in nonacclimated leaves in darkness did intolerant species have a significantly lower pO2 than tolerant species. ¿ These results suggest that submergence-induced leaf plasticity, albeit a prerequisite for underwater survival, does not discriminate tolerant from intolerant species. It is hypothesized that these plastic leaf responses may be induced in all species by several signals present during submergence; for example, low LMA may be a response to low photosynthate concentrations and a thin cuticle may be a response to high relative humidity.
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