| 1. |
- Saona, Nora M, et al.
(author)
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Environmental stresses mediate endophyte-grass interactions in a boreal archipelago
- 2010
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In: Journal of Ecology. - : Wiley. - 0022-0477 .- 1365-2745. ; 98:2, s. 470-479
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Journal article (peer-reviewed)abstract
- 1. Both evolutionary theory and empirical evidence from agricultural research support the view that asexual, vertically transmitted fungal endophytes are typically plant mutualists that develop high infection frequencies within host grass populations. In contrast, endophyte–grass interactions in natural ecosystems are more variable, spanning the range from mutualism to antagonism and comparatively little is known about their range of response to environmental stress. 2. We examined patterns in endophyte prevalence and endophyte–grass interactions across nutrient and grazing (from Greylag and Canada geese) gradients in 15 sites with different soil moisture levels in 13 island populations of the widespread grass Festuca rubra in a boreal archipelago in Sweden. 3. In the field, endophyte prevalence levels were generally low (range = 10–53%) compared with those reported from agricultural systems. Under mesic-moist conditions endophyte prevalence was constantly low (mean prevalence = 15%) and was not affected by grazing pressure or nutrient availability. In contrast, under conditions of drought, endophyte prevalence increased from 10% to 53% with increasing nutrient availability and increasing grazing pressure. 4. In the field, we measured the production of flowering culms, as a proxy for host fitness, to determine how endophyte-infected plants differed from uninfected plants. At dry sites, endophyte infection did not affect flowering culm production. In contrast, at mesic-moist sites production of flowering culms in endophyte-infected plants increased with the covarying effects of increasing nutrient availability and grazing pressure, indicating that the interaction switched from antagonistic to mutualistic. 5. A concurrent glasshouse experiment showed that in most situations, the host appears to incur some costs for harbouring endophytes. Uninfected grasses generally outperformed infected grasses (antagonistic interaction), while infected grasses outperformed uninfected grasses (mutualistic interaction) only in dry, nutrient-rich conditions. Nutrient and water addition affected tiller production, leaf number and leaf length differently, suggesting that tillers responded with different strategies. This emphasizes that several response variables are needed to evaluate the interaction. 6. Synthesis. This study found complex patterns in endophyte prevalence that were not always correlated with culm production. These contrasting patterns suggest that the direction and strength of selection on infected plants is highly variable and depends upon a suite of interacting environmental variables that may fluctuate in the intensity of their impact, during the course of the host life cycle.
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| 2. |
- Soolanayakanahally, Raju Y, et al.
(author)
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Comparative physiology of allopatric Populus species : geographic clines in photosynthesis, height growth, and carbon isotope discrimination in common gardens
- 2015
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In: Frontiers in Plant Science. - : Frontiers Media. - 1664-462X. ; 6
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Journal article (peer-reviewed)abstract
- Populus species with wide geographic ranges display strong adaptation to local environments. We studied the clinal patterns in phenology and ecophysiology in allopatric Populus species adapted to similar environments on different continents under common garden settings. As a result of climatic adaptation, both Populus tremula L. and Populus balsamifera L. display latitudinal clines in photosynthetic rates (A), whereby high-latitude trees of P. tremula had higher A compared to low-latitude trees and nearly so in P. balsamifera (p = 0.06). Stomatal conductance (g(S)) and chlorophyll content index (CCI) follow similar latitudinal trends. However, foliar nitrogen was positively correlated with latitude in P. balsamifera and negatively correlated in P. tremula. No significant trends in carbon isotope composition of the leaf tissue (delta C-13) were observed for both species; but, intrinsic water-use efficiency (WUEi) was negatively correlated with the latitude of origin in P. balsamifera. In spite of intrinsically higher A, high-latitude trees in both common gardens accomplished less height gain as a result of early bud set. Thus, shoot biomass was determined by height elongation duration (HED), which was well approximated by the number of days available for free growth between bud flush and bud set. We highlight the shortcoming of unreplicated outdoor common gardens for tree improvement and the crucial role of photoperiod in limiting height growth, further complicating interpretation of other secondary effects.
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| 3. |
- Abreu, Ilka, et al.
(author)
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UHPLC-ESI/TOFMS Determination of Salicylate-like Phenolic Gycosides in Populus tremula Leaves
- 2011
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In: Journal of Chemical Ecology. - : Springer Science and Business Media LLC. - 0098-0331 .- 1573-1561. ; 37:8, s. 857-70
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Journal article (peer-reviewed)abstract
- Associations of salicylate-like phenolic glycosides (PGs) with biological activity have been reported in Salix and Populus trees, but only for a few compounds, and in relation to a limited number of herbivores. By considering the full diversity of PGs, we may improve our ability to recognize genotypes or chemotype groups and enhance our understanding of their ecological function. Here, we present a fast and efficient general method for salicylate determination in leaves of Eurasian aspen that uses ultra-high performance liquid chromatography-electrospray ionization/time-of-flight mass spectrometry (UHPLC-ESI/TOFMS). The time required for the liquid chromatography separations was 13.5 min per sample, compared to around 60 min per sample for most HPLC protocols. In leaf samples from identical P. tremula genotypes with diverse propagation and treatment histories, we identified nine PGs. We found the compound-specific mass chromatograms to be more informative than the UV-visible chromatograms for compound identification and when quantitating samples with large variability in PG content. Signature compounds previously reported for P. tremoloides (tremulacin, tremuloidin, salicin, and salicortin) always were present, and five PGs (2'-O-cinnamoyl-salicortin, 2'-O-acetyl-salicortin, 2'-O-acetyl-salicin, acetyl-tremulacin, and salicyloyl-salicin) were detected for the first time in P. tremula. By using information about the formic acid adduct that appeared for PGs in the LTQ-Orbitrap MS environment, novel compounds like acetyl-tremulacin could be tentatively identified without the use of standards. The novel PGs were consistently either present in genotypes regardless of propagation and damage treatment or were not detectable. In some genotypes, concentrations of 2'-O-acetyl-salicortin and 2'-O-cinnamoyl-salicortin were similar to levels of biologically active PGs in other Salicaceous trees. Our study suggests that we may expect a wide variation in PG content in aspen populations which is of interest both for studies of interactions with herbivores and for mapping population structure.
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| 4. |
- Albrectsen, Benedicte R., 1960-, et al.
(author)
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Endophytic fungi in European aspen (Populus tremula) leaves - diversity, detection, and a suggested correlation with herbivory resistance
- 2010
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In: Fungal diversity. - : Springer Science and Business Media LLC. - 1560-2745 .- 1878-9129. ; 41:1, s. 17-28
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Journal article (peer-reviewed)abstract
- According to the geographic mosaic theory of coevolution (GMTC), clines of traits reflecting local co-adaptation (including resistance genes) should be common between a host and its parasite and should persist across time. To test the GMTC-assumption of persistent clinal patterns we compared the natural prevalence of two parasites on aspen Populus tremula trees: mining moths of the genus Phyllocnistis and leaf rust Melampsora spp. Damage data were collated from the Swedish National Forest Damage Inventory (2004–2006). In addition, occurrence of the parasites was scored in field conditions in two common gardens in the north and south of Sweden over five growing seasons (2004–2008), then related to biomass (stem height and diameter) and to concentrations of eleven leaf phenolics. Phyllocnistis mainly occurred in the northern garden, a distribution range which was confirmed by the countrywide inventory, although Phyllocnistis was more abundant on southern clones, providing evidence for possible local maladaptation. Melampsora occurred all over the country and in both gardens, but built up more quickly on northern clones, which suggests a centre of local clone maladaptation in the north. Stem growth also followed a clinal pattern as did the concentration of three phenolic compounds: benzoic acid, catechin and cinnamic acid. However, only benzoic acid was related to parasite presence: negatively to Phyllocnistis and positively to Melampsora and it could thus be a potential trait under selection. In conclusion, clines of Phyllocnistis were stronger and more persistent compared to Melampsora, which showed contrasting clines of varying strength. Our data thus support the assumption of the GMTC model that clines exist in the border between hot and cold spots and that they may be less persistent for parasites with an elevated gene flow, and/or for parasites which cover relatively larger hot spots surrounded by fewer cold spots.
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| 5. |
- Albrectsen, Benedicte R, 1960-, et al.
(author)
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Large scale geographic clines of parasite damage to Populus tremula L
- 2010
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In: Ecography. - : Wiley. - 0906-7590 .- 1600-0587. ; 33:3, s. 483-493
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Journal article (peer-reviewed)abstract
- In conclusion, clines of Phyllocnistis were stronger and more persistent compared to Melampsora, which showed contrasting clines of varying strength. Our data thus support the assumption of the GMTC model that clines exist in the border between hot and cold spots and that they may be less persistent for parasites with an elevated gene flow, and/or for parasites which cover relatively larger hot spots surrounded by fewer cold spots.
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| 6. |
- Albrectsen, Benedicte R., 1960-, et al.
(author)
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Nutrient addition extends flowering display, which gets tracked by seed predators, but not by their parasitoids
- 2008
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In: Oikos. - : Wiley-Blackwell. - 0030-1299 .- 1600-0706. ; 117, s. 473-480
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Journal article (peer-reviewed)abstract
- Although phenological matching between two and three trophic interactions has received some attention, it has largely been disregarded in explaining the lack of strong cascade dynamics in terrestrial systems. We studied the response of the specialist seed predator, Paroxyna plantaginis (Tephritidae) and associated generalist parasitoids (Chalcidoidea) to controlled fertilisation of individuals of naturally growing Tripolium vulgare (Asteraceae) on four island populations (Skeppsvik Archipelago, Sweden). We consistently found evidence of nutrient limitation: fertilised plants increased their biomass, produced more capitula (the oviposition units for tephritid flies), were more at risk of attack by the tephritids, and puparia were heavier in fertilised plants. During some parts of the season tephritids became more heavily parasitized, supporting the presence of cascade dynamics, however net parasitism over season decreased in response to nutrient addition. We found no evidence that capitulum size complicated parasitoid access to the tephritids, however the extended bud production prolonged the flowering season. Thus, tephritids utilized the surplus production of capitula throughout the entire season, while parasitoids did not expand their oviposition time window accordingly. Implications for top down regulation and cascade dynamics in the system are discussed.
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| 7. |
- Albrectsen, Benedicte R., et al.
(author)
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The diversity and identification of eulophid parasitic wasps (Hymenoptera: Chalcidoidea: Eulophidae) on Phyllocnistis labyrinthella (Lepidoptera: Gracillariidae) from Västerbotten, Sweden.
- 2012
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In: Entomologisk tidskrift. - 0013-886X. ; 133:3, s. 111-118
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Journal article (peer-reviewed)abstract
- Caterpillars of the mining micro-moth Phyllocnistis labyrinthella feed on leaves of aspen (Populus tremula) and are often parasitized by eulophid wasps. The parasitoids are a potential important cause of death for the miners. During 2009-2011 we collected mined leaves from an experimental stand of aspen trees in Västerbotten. Adults emerged from 17-35 percent of the mines and of these every second to third specimen appeared as wasps. These wasps represented seven species of eulophid parasitoids of which three were new to Västerbotten: Chrysocharis nitetis (Walker), Cirrospilus diallus (Walker) and Cirrospilus pictus (Nees). We include an identification key that may be used to identify these eulophid species.
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| 8. |
- Bernhardsson, Carolina, et al.
(author)
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Geographic structure in metabolome and herbivore community co-occurs with genetic structure in plant defence genes
- 2013
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In: Ecology Letters. - Hoboken : Wiley-Blackwell. - 1461-023X .- 1461-0248. ; 16:6, s. 791-798
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Journal article (peer-reviewed)abstract
- Plantherbivore interactions vary across the landscape and have been hypothesised to promote local adaption in plants to the prevailing herbivore regime. Herbivores that feed on European aspen (Populus tremula) change across regional scales and selection on host defence genes may thus change at comparable scales. We have previously observed strong population differentiation in a set of inducible defence genes in Swedish P. tremula. Here, we study the geographic patterns of abundance and diversity of herbivorous insects, the untargeted metabolome of the foliage and genetic variation in a set of wound-induced genes and show that the geographic structure co-occurs in all three data sets. In response to this structure, we observe local maladaptation of herbivores, with fewer herbivores on local trees than on trees originated from more distant localities. Finally, we also identify 28 significant associations between single nucleotide polymorphisms SNPs from defence genes and a number of the herbivore traits and metabolic profiles.
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| 9. |
- Bernhardsson, Carolina, et al.
(author)
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Population differentiation in arthropod community structure and phenotypic association with inducible defense genes in European Aspen (Populus tremula L., salicaceae)
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Other publication (other academic/artistic)abstract
- Plant-herbivore interactions are known to vary across a landscape due to both variation in abiotic and biotic factors. Such spatial variation tends to promoting local adaption of plants to the prevailing herbivore regime. Here we use data from a common garden to look for patterns across populations in the abundance and diversity of herbivorous insects. We also screen for variation in the untargeted metabolome of the foliage of a subset of the same trees. We also search for phenotypic associations between genetic variation in a number of wound-induced genes and phenotypic variation in herbivore abundance, diversity and in metabolomes. We observe significant genetic variation in a number of herbivore-related traits but low correlations between traits. We do observe substantial genetic structure in both herbivore community structure and in metabolic profiles and this structure is aligned with genetic structure we have previously documented for a set of defense genes. We also identify a number of significant associations between SNPs from wound-induced defense genes and a number of the herbivore traits and metabolic profiles. However, these associations are likely not causal, but are rather caused by the underlying population structure we observe. These results highlight to the importance of historical processes and the need to better understand both the current-day geographic distribution of different herbivore species as well as the post-glacial colonization history of both plants and herbivores.
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| 10. |
- Blumenstein, Kathrin, et al.
(author)
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Nutritional niche overlap potentiates the use of endophytes in biocontrol of a tree disease
- 2015
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In: BioControl (Dordrecht). - : Springer Science and Business Media LLC. - 1386-6141 .- 1573-8248. ; 60:5, s. 655-667
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Journal article (peer-reviewed)abstract
- Asymptomatic endophytic fungi are often regarded as potent biocontrol agents in plants, but the competitive interactions between endophytes and other microbes within the same host plant are poorly understood. We tested a hypothesis that as compared to asymptomatic endophytes, an aggressive pathogen inhabiting the same host is able to utilize carbon substrates more efficiently. Using phenotype microarray, we determined the carbon utilization profiles of the highly virulent Dutch elm disease (DED) pathogen Ophiostoma novo-ulmi, and four asymptomatic elm (Ulmus spp.) endophyte isolates that were selected based on their differential association to the DED-susceptibility pattern of the host elms. The competitive interactions between isolates were evaluated using a niche overlap index. In contrast to our hypothesis, the studied endophytes exhibited extensive niche overlap with the pathogen, suggesting that some endophyte strains might protect elms against DED-pathogen through competition for substrates and provide new tools for biocontrol of DED.
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