Urbanization affects oak-pathogen interactions across spatial scales

The world is rapidly urbanizing, thereby transforming natural landscapes and changing the abundance and distribution of organisms. However, insights into the effects of urbanization on species interactions, and plant-pathogen interactions in particular, are lacking. We investigated the effects of urbanization on powdery mildew infection on Quercus robur at continental and within-city scales. At the continental scale, we compared infection levels between urban and rural areas of different-sized cities in Europe, and investigated whether plant traits, climatic variables and CO2 emissions mediated the effect of urbanization on infection levels. Within one large city (Stockholm, Sweden), we further explored whether local habitat features and spatial connectivity influenced infection levels during multiple years. At the continental scale, infection severity was consistently higher on trees in urban than rural areas, with some indication that temperature mediated this effect. Within Stockholm city, temperature had no effect, while local accumulation of leaf litter negatively affected powdery mildew incidence in one out of three years, and more connected trees had lower infection levels. This study is the first to describe the effects of urbanization on plant-pathogen interactions both within and among cities, and to uncover the potential mechanisms behind the observed patterns at each scale.Peer reviewe

Impacts of urbanization on insect herbivory and plant defences in oak trees

Systematic comparisons of species interactions in urban versus rural environments can improve our understanding of shifts in ecological processes due to urbanization. However, such studies are relatively uncommon and the mechanisms driving urbanization effects on species interactions (e.g. between plants and insect herbivores) remain elusive. Here we investigated the effects of urbanization on leaf herbivory by insect chewers and miners associated with the English oak Quercus robur by sampling trees in rural and urban areas throughout most of the latitudinal distribution of this species. In performing these comparisons, we also controlled for the size of the urban areas (18 cities) and gathered data on CO emissions. In addition, we assessed whether urbanization affected leaf chemical defences (phenolic compounds) and nutritional traits (phosphorus and nitrogen), and whether such changes correlated with herbivory levels. Urbanization significantly reduced leaf chewer damage but did not affect leaf miners. In addition, we found that leaves from urban locations had lower levels of chemical defences (condensed and hydrolysable tannins) and higher levels of nutrients (nitrogen and phosphorus) compared to leaves in rural locations. The magnitude of urbanization effects on herbivory and leaf defences was not contingent upon city size. Importantly, while the effects of urbanization on chemical defences were associated with CO emissions, changes in leaf chewer damage were not associated with either leaf traits or CO levels. These results suggest that effects of urbanization on herbivory occur through mechanisms other than changes in the plant traits measured here. Overall, our simultaneous assessment of insect herbivory, plant traits and abiotic correlates advances our understanding of the main drivers of urbanization effects on plant–herbivore interactions.This research was financially supported by a Spanish National Research Grant (AGL2015-70748-R), a Regional Government of Galicia Grant (IN607D 2016/001) and the Ramón y Cajal Research Programme (RYC-2013-13230).Peer reviewe

Impacts of urbanization on insect herbivory and plant defences in oak trees

Systematic comparisons of species interactions in urban versus rural environments can improve our understanding of shifts in ecological processes due to urbanization. However, such studies are relatively uncommon and the mechanisms driving urbanization effects on species interactions (e.g. between plants and insect herbivores) remain elusive. Here we investigated the effects of urbanization on leaf herbivory by insect chewers and miners associated with the English oak Quercus robur by sampling trees in rural and urban areas throughout most of the latitudinal distribution of this species. In performing these comparisons, we also controlled for the size of the urban areas (18 cities) and gathered data on CO 2 emissions. In addition, we assessed whether urbanization affected leaf chemical defences (phenolic compounds) and nutritional traits (phosphorus and nitrogen), and whether such changes correlated with herbivory levels. Urbanization significantly reduced leaf chewer damage but did not affect leaf miners. In addition, we found that leaves from urban locations had lower levels of chemical defences (condensed and hydrolysable tannins) and higher levels of nutrients (nitrogen and phosphorus) compared to leaves in rural locations. The magnitude of urbanization effects on herbivory and leaf defences was not contingent upon city size. Importantly, while the effects of urbanization on chemical defences were associated with CO 2 emissions, changes in leaf chewer damage were not associated with either leaf traits or CO 2 levels. These results suggest that effects of urbanization on herbivory occur through mechanisms other than changes in the plant traits measured here. Overall, our simultaneous assessment of insect herbivory, plant traits and abiotic correlates advances our understanding of the main drivers of urbanization effects on plant–herbivore interactions.info:eu-repo/semantics/acceptedVersio

Long-term follow-up and treatment in nine boys with X-linked creatine transporter defect

The creatine transporter (CRTR) defect is a recently discovered cause of X-linked intellectual disability for which treatment options have been explored. Creatine monotherapy has not proved effective, and the effect of treatment with L-arginine is still controversial. Nine boys between 8 months and 10 years old with molecularly confirmed CRTR defect were followed with repeated 1H-MRS and neuropsychological assessments during 4–6 years of combination treatment with creatine monohydrate, L-arginine, and glycine. Treatment did not lead to a significant increase in cerebral creatine content as observed with H1-MRS. After an initial improvement in locomotor and personal-social IQ subscales, no lasting clinical improvement was recorded. Additionally, we noticed an age-related decline in IQ subscales in boys affected with the CRTR defect

Urbanization affects oak–pathogen interactions across spatial scales

The world is rapidly urbanizing, thereby transforming natural landscapes and changing the abundance and distribution of organisms. However, insights into the effects of urbanization on species interactions, and plant–pathogen interactions in particular, are lacking. We investigated the effects of urbanization on powdery mildew infection on Quercus robur at continental and within-city scales. At the continental scale, we compared infection levels between urban and rural areas of different-sized cities in Europe, and investigated whether plant traits, climatic variables and CO2 emissions mediated the effect of urbanization on infection levels. Within one large city (Stockholm, Sweden), we further explored whether local habitat features and spatial connectivity influenced infection levels during multiple years. At the continental scale, infection severity was consistently higher on trees in urban than rural areas, with some indication that temperature mediated this effect. Within Stockholm city, temperature had no effect, while local accumulation of leaf litter negatively affected powdery mildew incidence in one out of three years, and more connected trees had lower infection levels. This study is the first to describe the effects of urbanization on plant–pathogen interactions both within and among cities, and to uncover the potential mechanisms behind the observed patterns at each scale.info:eu-repo/semantics/publishedVersio

The co‐existence of multiple oak leaf flushes contributes to the large within‐tree variation in chemistry, insect attack and pathogen infection

Many plant species produce multiple leaf flushes during the growing season, which might have major consequences for within-plant variation in chemistry and species interactions. Yet, we lack a theoretical or empirical framework for how differences among leaf flushes might shape variation in damage by insects and diseases. We assessed the impact of leaf flush identity on leaf chemistry, insect attack and pathogen infection on the pedunculate oak Quercus robur by sampling leaves from each leaf flush in 20 populations across seven European countries during an entire growing season. The first leaf flush had higher levels of primary compounds, and lower levels of secondary compounds, than the second flush, whereas plant chemistry was highly variable in the third flush. Insect attack decreased from the first to the third flush, whereas infection by oak powdery mildew was lowest on leaves from the first flush. The relationship between plant chemistry, insect attack and pathogen infection varied strongly among leaf flushes and seasons. Our findings demonstrate the importance of considering differences among leaf flushes for our understanding of within-tree variation in chemistry, insect attack and disease levels, something particularly relevant given the expected increase in the number of leaf flushes with climate change

Changes in the foliar fungal community between oak leaf flushes along a latitudinal gradient in Europe

Aim Leaves support a large diversity of fungi, which are known to cause plant diseases, induce plant defences or influence leaf senescence and decomposition. To advance our understanding of how foliar fungal communities are structured and assembled, we assessed to what extent leaf flush and latitude can explain the within- and among-tree variation in foliar fungal communities. Location A latitudinal gradient spanning c. 20 degrees in latitude in Europe. Taxa The foliar fungal community associated with a foundation tree species, the pedunculate oak Quercus robur. Methods We examined the main and interactive effects of leaf flush and latitude on the foliar fungal community by sampling 20 populations of the pedunculate oak Quercus robur across the tree's range. We used the ITS region as a target for characterization of fungal communities using DNA metabarcoding. Results Species composition, but not species richness, differed between leaf flushes. Across the latitudinal gradient, species richness was highest in the central part of the oak's distributional range, and foliar fungal community composition shifted along the latitudinal gradient. Among fungal guilds, the relative abundance of plant pathogens and mycoparasites was lower on the first leaf flush, and the relative abundance of plant pathogens and saprotrophs decreased with latitude. Conclusions Changes in community composition between leaf flushes and along the latitudinal gradient were mostly a result of species turnover. Overall, our findings demonstrate that leaf flush and latitude explain 5%-22% of the small- and large-scale spatial variation in the foliar fungal community on a foundation tree within the temperate region. Using space-for-time substitution, we expect that foliar fungal community structure will change with climate warming, with an increase in the abundance of plant pathogens and mycoparasites at higher latitudes, with major consequences for plant health, species interactions and ecosystem dynamics

Changes in the foliar fungal community between oak leaf flushes along a latitudinal gradient in Europe

Aim Leaves support a large diversity of fungi, which are known to cause plant diseases, induce plant defences or influence leaf senescence and decomposition. To advance our understanding of how foliar fungal communities are structured and assembled, we assessed to what extent leaf flush and latitude can explain the within- and among-tree variation in foliar fungal communities. Location A latitudinal gradient spanning c. 20 degrees in latitude in Europe. Taxa The foliar fungal community associated with a foundation tree species, the pedunculate oak Quercus robur. Methods We examined the main and interactive effects of leaf flush and latitude on the foliar fungal community by sampling 20 populations of the pedunculate oak Quercus robur across the tree's range. We used the ITS region as a target for characterization of fungal communities using DNA metabarcoding. Results Species composition, but not species richness, differed between leaf flushes. Across the latitudinal gradient, species richness was highest in the central part of the oak's distributional range, and foliar fungal community composition shifted along the latitudinal gradient. Among fungal guilds, the relative abundance of plant pathogens and mycoparasites was lower on the first leaf flush, and the relative abundance of plant pathogens and saprotrophs decreased with latitude. Conclusions Changes in community composition between leaf flushes and along the latitudinal gradient were mostly a result of species turnover. Overall, our findings demonstrate that leaf flush and latitude explain 5%–22% of the small- and large-scale spatial variation in the foliar fungal community on a foundation tree within the temperate region. Using space-for-time substitution, we expect that foliar fungal community structure will change with climate warming, with an increase in the abundance of plant pathogens and mycoparasites at higher latitudes, with major consequences for plant health, species interactions and ecosystem dynamics.This research was supported by grants from the Bolin Centre for Climate Research (RA8) and the Swedish Research Council (2021-03784) to AJMT. We are grateful for support from the National Genomics Infrastructure in Stockholm funded by Science for Life Laboratory, the Knut and Alice Wallenberg Foundation and the Swedish Research Council, and SNIC/Uppsala Multidisciplinary Center for Advanced Computational Science for as-sistance with massively parallel sequencing and access to the UPPMAX computational infrastructure. PDF and CM received funding from the European Research Council (ERC) under the European Union's Horizon 2020 Research and Innovation Programme (ERC Starting Grant FORMICA 757833).Peer reviewe