Metabolite analysis reveals flavonoids accumulation during flower development in Rhododendron pulchrum sweet (Ericaceae).

The azalea (Rhododendron simsii Planch.) is an important ornamental woody plant with various medicinal properties due to its phytochemical compositions and components. However little information on the metabolite variation during flower development in Rhododendron has been provided. In our study, a comparative analysis of the flavonoid profile was performed in Rhododendron pulchrum sweet at three stages of flower development, bud (stage 1), partially open flower (stage 2), and full bloom (stage 3). A total of 199 flavonoids, including flavone, flavonol, flavone C-glycosides, flavanone, anthocyanin, and isoflavone were identified. In hierarchical clustering analysis (HCA) and principal component analysis (PCA), the accumulation of flavonoids displayed a clear development stage variation. During flower development, 78 differential accumulated metabolites (DAMs) were identified, and most were enriched to higher levels at the full bloom stage. A total of 11 DAMs including flavone (chrysin, chrysoeriol O-glucuronic acid, and chrysoeriol O-hexosyl-O-pentoside), isoflavone (biochanin A), and flavonol (3,7-di-O-methyl quercetin and isorhamnetin) were significantly altered at three stages. In particular, 3,7-di-O-methyl quercetin was the top increased metabolite during flower development. Furthermore, integrative analyses of metabolomic and transcriptomic were conducted, revealing that the contents of isoflavone, biochanin A, glycitin, and prunetin were correlated with the expression of 2-hydroxyisoflavanone dehydratase (HIDH), which provide insight into the regulatory mechanism that controls isoflavone biosynthesis in R. pulchrum. This study will provide a new reference for increasing desired metabolites effectively by more accurate or appropriate genetic engineering strategies.

Phosphoproteomics of cold stress-responsive mechanisms in Rhododendron chrysanthum.

BACKGROUND: As an alpine plant, Rhododendron chrysanthum (R. chrysanthum) has evolved cold resistance mechanisms and become a valuable plant resource with the responsive mechanism of cold stress. METHODS AND RESULTS: We adopt the phosphoproteomic and proteomic analysis combining with physiological measurement to illustrate the responsive mechanism of R. chrysanthum seedling under cold (4 °C) stress. After chilling for 12 h, 350 significantly changed proteins and 274 significantly changed phosphoproteins were detected. Clusters of Orthologous Groups (COG) analysis showed that significantly changed phosphoproteins and proteins indicated cold changed energy production and conversion and signal transduction. CONCLUSIONS: The results indicated photosynthesis was inhibited under cold stress, but cold induced calcium-mediated signaling, reactive oxygen species (ROS) homeostasis and other transcription regulation factors could protect plants from the destruction caused by cold stress. These data provide the insight to the cold stress response and defense mechanisms of R. chrysanthum leaves at the phosphoproteome level.

Can species distribution models and molecular tools help unravel disjunct distribution of Rhododendron arboreum?

The apparent absence of Himalayan low-elevation taxa in the central Indian region and resumption of their distribution in the high elevation of Western Ghats has puzzled biogeographers for several decades. Many theories have been proposed to explain this but attempts remain futile owing to insufficient empirical support. Here, we have employed a montane tree species, Rhododendron arboreum to investigate this pattern by integrating past ecological niche modelling with molecular signatures. Reconstruction of paleo-ecological niche from interglacial to Last Glacial Maxima (LGM) portrayed a gradual depletion of vegetation cover with extreme impoverishment in the Holocene. A similar pattern was also reflected from genetic signatures; population history revealed a very recent split between the Himalayas and Western Ghats in the late Quaternary. A few other tree species exhibiting the same disjunction demonstrated a similar modification of paleo-ecological niche from last interglacial. The study clearly indicated that the populations in the Western Ghats to be a relictual remnants of a once continuous distribution of R. arboreum.

Photosynthetic regulation under fluctuating light at chilling temperature in evergreen and deciduous tree species.

Plants usually experience fluctuating light conditions at chilling temperatures during the autumn season. We hypothesized that photosystem I (PSI) and PSII are more susceptible to photoinhibition under fluctuating light at chilling temperatures in deciduous species relative to evergreen species. We measured the photosynthetic performances under fluctuating light at 6 °C in two evergreen and two deciduous broadleaf tree species. Within the first 10 s after light increased at 6 °C, none of these species could generate an enough trans-thylakoid proton gradient. Meanwhile, PSI was highly oxidised in evergreen species but was highly reduced in deciduous species. This transient over-reduction of PSI in deciduous species was mainly caused by the higher electron flow from PSII. Furthermore, the deciduous species showed a significantly smaller violaxanthin pool and lower non-photochemical quenching under high light conditions at 6 °C, leading to more excess light energy could not be dissipated in PSII. Hence, we propose that fluctuating light combined with chilling temperature cause the over-reduction of photosynthetic electron chain in deciduous species.

Effects of Plant Substrate, Insecticide, and Blood Meal Status on the Efficacy of Barrier Treatments Against Aedes albopictus.

The effects of 3 plant species (Cornus florida [dogwood], rhododendron X 'Chionoides' [rhododendron], and Ilex opaca [American holly]), 4 insecticide treatments (Demand® CS [lambda-cyhalothrin] at 6.25 ml[AI]/liter; Talstar® Professional [bifenthrin] at 7.81 ml[AI]/liter, and Suspend® Polyzone® [deltamethrin] at 11.72 ml[AI]/liter, and water), and 2 physiological states (blood-fed and unfed) were evaluated for knockdown (1 h) and mortality (24 h) against female Aedes albopictus over an 8-wk sampling period. Analyses determined that there was a significant interaction between the tested plant species and the insecticides evaluated. Significant differences were likewise observed between the insecticide treatments for unfed Ae. albopictus females, with Demand CS demonstrating the highest knockdown and mortality rates (from >90% to >10% at wk 8 and >95% to ∼50% at wk 8, respectively), followed by Talstar Professional (from >75% to <10% at wk 2 and >90% to <10% at wk 2, respectively) and Suspend Polyzone (from >20% to <10% at wk 8 and >25% to >50% at wk 8, respectively). All treatments were no longer significant for knockdown or mortality at the end of the 8-wk timeframe. Significant differences were also observed between insecticide treatments for blood-fed Ae. albopictus females; Demand CS showed high knockdown and mortality rates (from 100% to ∼50% at wk 8 and 100% to >60% at wk 8, respectively), Suspend Polyzone rates were similar to Demand CS (from >80% to ∼50% at wk 8 and ∼90% to >65% at wk 8, respectively), and both were followed by Talstar Professional (from 100% to <10% at wk 4 and 100% to <20% at wk 4, respectively). All tested pyrethroid sprays showed a significant increase in effectiveness against recently blood-fed Ae. albopictus females, as compared to the unfed females. These results suggest that Demand CS can be used as an effective barrier spray against Ae. albopictus adults due to the limited impact of target foliage, its long-term efficacy under environmental conditions, and its continued effectiveness regardless of the blood meal status of the target mosquito.

Metabolite profiling of violet, white and pink flowers revealing flavonoids composition patterns in Rhododendron pulchrum Sweet.

Flower color is the major characteristics and critical breeding program for most Rhododendron species. However, little is known about their coloration mechanism and color inheritance. In this study, petal pigment constituents of three Rhododendron pulchrum Sweet cultivars with different colors were clarified based on LCESI- MS/MS method. Using a broad-targeted metabolomic approach, a total of 149 flavonoids and their glycosylated or methylated derivatives were identified, including 18 anthocyanins (Pg, Cy, Dp, Pn, Pt, and Mv) and 32 flavonols (mainly kaempferol 3-O-glycosides and quercetin 3-O-glycosides). Moreover, anthocyanins were mainly represented by anthocyanidin-3-O-glycosides (glucoside, rutinoside, galactoside, and di-glycosides). Flavone and C-glycosylated flavone were major second metabolites responsible for the difference among three different R. pulchrum cultivars. The accumulation of total flavonoids displayed a clear phenotypic variation: cultivars 'zihe' and 'fenhe' were clustered together, while 'baihe' was clustered alone in the HCA analysis. The composition and content of anthocyanins were more complex in colored flowers ('zehe' and 'fenhe') than in white flower ('baihe'). This study further enhanced our understanding on the flavonoids profile of flower coloration and will provide biochemical basis for further genetic breeding in Rhododendron species.

Chromosome-level genome assembly of a parent species of widely cultivated azaleas.

Azaleas (Ericaceae) comprise one of the most diverse ornamental plants, renowned for their cultural and economic importance. We present a chromosome-scale genome assembly for Rhododendron simsii, the primary ancestor of azalea cultivars. Genome analyses unveil the remnants of an ancient whole-genome duplication preceding the radiation of most Ericaceae, likely contributing to the genomic architecture of flowering time. Small-scale gene duplications contribute to the expansion of gene families involved in azalea pigment biosynthesis. We reconstruct entire metabolic pathways for anthocyanins and carotenoids and their potential regulatory networks by detailed analysis of time-ordered gene co-expression networks. MYB, bHLH, and WD40 transcription factors may collectively regulate anthocyanin accumulation in R. simsii, particularly at the initial stages of flower coloration, and with WRKY transcription factors controlling progressive flower coloring at later stages. This work provides a cornerstone for understanding the underlying genetics governing flower timing and coloration and could accelerate selective breeding in azalea.

Attracting Chrysopidae With Plant Volatiles for Lace Bug (Hemiptera: Tingidae) Control in Rhododendrons and Azaleas.

The azalea lace bug (Stephanitis pyrioides Scott) (Hemiptera: Tingidae) is an invasive pest of rhododendrons and azaleas (Ericaceae: Rhododendron), which feeds on the underside of leaves causing chlorosis, reduced photosynthesis, and even plant death. While insecticides can control this pest, growers, landscape managers, and homeowners have requested softer alternatives. Augmentative release of predatory green lacewing Chrysoperla sp. (Neuroptera: Chrysopidae) eggs and larvae has reduced S. pyrioides, but large-scale implementation may not be practical nor cost-effective. Attracting naturally occurring Chrysopidae with plant volatiles may be an economical and convenient option. In this study, we tested whether volatile blends 1) attracted Chrysoperla sp., and 2) controlled S. pyrioides populations on Rhododendron spp. in farm or urban landscapes. Experimental plots contained different multicomponent lures placed aboveground next to infested plants. Adult Chrysoperla sp., other natural enemies, and S. pyrioides from egg to adult stages were monitored in both farm and urban landscapes for two summers. Overall, two out of three volatile blends consistently attracted Chrysoperla sp. to sticky traps near baited plants. Methyl salicylate + acetic acid + 2-phenylethanol (methyl salicylate blend) and acetophenone + acetic acid + 2-phenylethanol (acetophenone blend) captured more adult Chrysoperla sp. than control traps in farm landscapes. However, only the acetophenone blend was associated with a slight reduction of S. pyrioides. Additional research is needed to determine whether the phenology of the first generation of both species are synchronized for effective season biological control in the Pacific Northwest.

Soil nitrogen determines greenhouse gas emissions from northern peatlands under concurrent warming and vegetation shifting.

Boreal peatlands store an enormous pool of soil carbon that is dependent upon - and vulnerable to changes in - climate, as well as plant community composition. However, how nutrient availability affects the effects of climate and vegetation change on ecosystem processes in these nutrient-poor ecosystems remains unclear. Here we show that although warming promoted higher CH4 emissions, the concurrent addition of N counteracted most (79%) of this effect. The regulation effects of the vegetation functional group, associated with the substrate quality, suggest that CH4 emissions from peatlands under future warming will be less than expected with predicted shrub expansion. In contrast, N2O flux will be enhanced under future warming with predicted shrub expansion. Our study suggests that changes in greenhouse gas emissions in response to future warming and shifts in plant community composition depend on N availability, which reveals the complex interactions that occur when N is not a limiting nutrient.

Exploring microRNA profiles for circadian clock and flowering development regulation in Himalayan Rhododendron.

miRNA is a non-coding, yet crucial entity in remodeling the genetic architecture. Rhododendron arboreum of Himalayas grows and even flower under fluctuating climate. sRNA from leaves of vegetative and reproductive periods was sequenced to elucidate its seasonal associations. Conserved (256) and novel (210) miRNAs and their precursors were located based on homology with plant databases and transcriptome of the species. 27,139 predicted targets were involved with metabolism, reproduction, and response to abiotic stimuli. A comparative analysis showed differential expression of 198 miRNAs with season-specific abundance of 103 miRNAs. Specific isoforms of 11 miRNA families exhibited a temporal expression and targeted different genes implying a complex regulation. The variable miRNA expression among the tissues of different conditions can be associated with the adaptability of the species, which will prove essential for further study on miRNAs mediating seasonal response. Moreover, exogenous cues also mediate phase transition via networking of flowering pathways and their components. In this context, 18 known families and 77 novel miRNAs modulating 117 genes crucial in circadian entrainment were filtered. A negative correlation was obtained between the expression of 18 of these miRNAs and their targets when tested through quantitative-PCR. It highlighted the role of miRNA-target pairs in perceiving environmental variabilities and monitoring flowering growth. Furthermore, a phylogenetic clustering was performed, which supported the lineage-specific evolution and function of putative miR156 sequence in the species. This documentation of genome-wide profiling of miRNA, their targets, and expression will enhance the understanding of developmental and climate-tolerance strategies in high-altitude trees.

Transcriptome analysis and identification of genes associated with flower development in Rhododendron pulchrum Sweet (Ericaceae).

Flowering process is essential for plant development. However, the molecular mechanisms driving flower development of ornamental woody Rhododendron pulchrum Sweet are difficult to elucidate due to the lack of genomic data. In this research, high-throughput sequencing and comparative transcriptome analyses of R. pulchrum flowers collected at three key stages were performed: floral bud stage, early flowering stage, and full-flowering stage. Furthermore, expression of genes involved in flower development was also validated with quantitative real-time PCR (qRT-PCR). RNA-seq yielded 96,350,697 bp of clean reads, which were assembled into 98,610 unigenes with an average length of 717 bp. 58,279 (59.10%) unigenes could be annotated, including 324 major unigenes associated with floral development. In addition, ten modules (20,443 mRNAs) were dissected in the co-expression network. Especially, Flowering Locus (FLC) and Flowering Locus T (FT) were co-expressed. 9493 differentially expressed genes (DEGs) were scanned among three stages, and most DEGs existed between flower bud stage and early flowering stage. In particular, 79 DGEs associated with flowering process were enriched in 28 GO terms. Moreover, the expression levels of MYC2, EIN3, and ARR-B were all lowest at early flowering stage, while transcripts of MYC2, TIR1, CYCD3, COL-1, and EIN3 were all peaked at flower bud stage. Transcriptome profile presented here will benefit deep insights into molecular mechanism underlying R. pulchrum flowering process.

Clonal plasticity and diversity facilitates the adaptation of Rhododendron aureum Georgi to alpine environment.

Four small oval populations and five large intensive populations of Rhododendron aureum growing at the alpine in Changbai Mountain (China) were studied in two types of habitat (in the tundra and in Betula ermanii forest). Identification and delimitation of genets were inferred from excavation in small populations and from amplified fragment length polymorphism (AFLP) markers by the standardized sampling design in large populations. Clonal architecture and clonal diversity were then estimated. For the four small populations, they were monoclonal, the spacer length (18.6 ± 5.6 in tundra, 29.7 ± 9.7 in Betula ermanii forest, P < 0.05) was shorter and branching intensity (136.7 ± 32.9 in tundra, 43.4 ± 12.3 in Betula ermanii forest, P < 0.05) was higher in the tundra than that in Betula ermanii forest. For the five large populations, they were composed of multiple genets with high level of clonal diversity (Simpson's index D = 0.84, clonal richness R = 0.25, Fager's evenness E = 0.85); the spatial distribution of genets showed that the clonal growth strategy of R. aureum exhibits both guerilla and phalanx. Our results indicate that the clonal plasticity of R. aureum could enhance exploitation of resource heterogeneity and in turn greatly contribute to maintenance or improvement of fitness and the high clonal diversity of R. aureum increase the evolutionary rates to adapt the harsh alpine environment in Changbai Mountain.

Shrub growth and plant diversity along an elevation gradient: Evidence of indirect effects of climate on alpine ecosystems.

Enhanced shrub growth and expansion are widespread responses to climate warming in many arctic and alpine ecosystems. Warmer temperatures and shrub expansion could cause major changes in plant community structure, affecting both species composition and diversity. To improve our understanding of the ongoing changes in plant communities in alpine tundra, we studied interrelations among climate, shrub growth, shrub cover and plant diversity, using an elevation gradient as a proxy for climate conditions. Specifically, we analyzed growth of bilberry (Vaccinium myrtillus L.) and its associated plant communities along an elevation gradient of ca. 600 vertical meters in the eastern European Alps. We assessed the ramet age, ring width and shoot length of V. myrtillus, and the shrub cover and plant diversity of the community. At higher elevation, ramets of V. myrtillus were younger, with shorter shoots and narrower growth rings. Shoot length was positively related to shrub cover, but shrub cover did not show a direct relationship with elevation. A greater shrub cover had a negative effect on species richness, also affecting species composition (beta-diversity), but these variables were not influenced by elevation. Our findings suggest that changes in plant diversity are driven directly by shrub cover and only indirectly by climate, here represented by changes in elevation.

Microbial Decomposer Dynamics: Diversity and Functionality Investigated through a Transplantation Experiment in Boreal Forests.

Litter decomposition is the main source of mineral nitrogen (N) in terrestrial ecosystem and a key step in carbon (C) cycle. Microbial community is the main decomposer, and its specialization on specific litter is considered at the basis of higher decomposition rate in its natural environment than in other forests. However, there are contrasting evidences on how the microbial community responds to a new litter input and if the mass loss is higher in natural environment. We selected leaf litter from three different plant species across three sites of different altitudinal ranges: oak (Quercus petraea (Matt.) Liebl., 530 m a.s.l), beech (Fagus sylvatica L., 1000 m a.s.l.), rhododendron (Rhododendron ferrugineum L., 1530 m a.s.l.). A complete transplantation experiment was set up within the native site and the other two altitudinal sites. Microbial community structure was analyzed via amplified ribosomal intergenic spacer analysis (ARISA) fingerprinting. Functionality was investigated by potential enzyme activities. Chemical composition of litter was recorded. Mass loss showed no faster decomposition rate on native site. Similarly, no influence of site was found on microbial structure, while there was a strong temporal variation. Potential enzymatic activities were not affected by the same temporal pattern with a general increase of activities during autumn. Our results suggested that no specialization in microbial community is present due to the lack of influence of the site in structure and in the mass loss dynamics. Finally, different temporal patterns in microbial community and potential enzymatic activities suggest the presence of functional redundancy within decomposers.

Influence of Light Intensity and Photoperiod on the Seed Germination of Four Rhododendron Species in Taiwan.

BACKGROUND AND OBJECTIVE: There are 15 native Rhododendron species in Taiwan, among which 11 species are endemic and compose 73% of these native species. Although researchers predominantly use cuttings to propagate Rhododendron shrubs, there are no studies on the seed germination of Rhododendron species. The objective of this study was to evaluate the seed germination of four Rhododendron species in Taiwan under different light intensities and photoperiods. MATERIALS AND METHODS: Two experiments on the seed germination percentage of R. breviperulatum, R. kanehirai, R. ovatum and R. simsii were conducted in this study. The first experiment was to identify the seed germination percentage of these four Rhododendron species using different light intensities (0, 700, 1400 and 3200 lux). The second experiment was to clarify the seed germination percentage of these four Rhododendron species using different photoperiods (0, 1, 4 and 16 h). All statistical analyses were performed using Statistical Package for the Social Science (SPSS12.0) for Windows software program. The data were analyzed using Tukey's multiple range test at the p<0.05 significance level. RESULTS: After 30 days, no seed germination occurred in darkness. The highest average seed germination percentages were all observed at 700 lux: R. breviperulatum (83.3%), R. kanehirai (68.9%), R. ovatum (85.6%) and R. simsii (92.2%). The highest average germination percentages of seeds were observed in R. breviperulatum at 16 h (83.3%), R. kanehirai at 1 h (60.0%), R. ovatum at 16 h (84.4%) and R. simsii at 16 h (85.6%). According to the results, these four Rhododendron species required light for germination. There were significant differences (p<0.05) in the seed germination of these four Rhododendron species for light intensity greater than 700 lux. Similar results were observed with photoperiods. CONCLUSION: The seed germination percentage of R. breviperulatum, R. ovatum and R. simsii increased with increasing photoperiod.

Warm summers and moderate winter precipitation boost Rhododendron ferrugineum L. growth in the Taillefer massif (French Alps).

Rhododendron ferrugineum L. is a widespread dwarf shrub species growing in high-elevation, alpine environments of the Western European Alps. For this reason, analysis of its growth rings offers unique opportunities to push current dendrochronological networks into extreme environments and way beyond the treeline. Given that different species of the same genus have been successfully used in tree-ring investigations, notably in the Himalayas where Rhododendron spp. has proven to be a reliable climate proxy, this study aims at (i) evaluating the dendroclimatological potential of R. ferrugineum and at (ii) determining the major limiting climate factor driving its growth. To this end, 154 cross-sections from 36 R. ferrugineum individuals have been sampled above local treelines and at elevations from 1800 to 2100masl on northwest-facing slopes of the Taillefer massif (French Alps). We illustrate a 195-year-long standard chronology based on growth-ring records from 24 R. ferrugineum individuals, and document that the series is well-replicated for almost one century (1920-2015) with an Expressed Population Signal (EPS) >0.85. Analyses using partial and moving 3-months correlation functions further highlight that growth of R. ferrugineum is governed by temperatures during the growing season (May-July), with increasingly higher air temperatures favoring wider rings, a phenomenon which is well known from dwarf shrubs growing in circum-arctic tundra ecosystems. Similarly, the negative effect of January-February precipitation on radial growth of R. ferrugineum, already observed in the Alps on juniper shrubs, is interpreted as a result of shortened growing seasons following snowy winters. We conclude that the strong and unequivocal signals recorded in the fairly long R. ferrugineum chronologies can indeed be used for climate-growth studies as well as for the reconstruction of climatic fluctuations in Alpine regions beyond the upper limits of present-day forests.

Assessment of genetic relationship among Rhododendron cultivars using amplified fragment length polymorphism and inter-simple sequence repeat markers.

Genetic relationships of 17 Rhododendron cultivars, China, were assessed using inter-simple sequence repeat (ISSR) and amplified fragment length polymorphism (AFLP) markers. A total of 133 bands were obtained using nine selected ISSR primers, 129 (96.99%) of which were polymorphic; 267 bands were amplified by four AFLP primer pairs, 251 (94.01%) of which exhibited polymorphism. Based on these polymorphic products, a cluster analysis revealed similarities between the results of the ISSR and AFLP. All of the cultivars were clustered into two major branches; one branch contained the same four cultivars, and the other cultivars were separated into different groups in the other branch. The cluster results showed that the genetic relationships of the 17 cultivars were partly related to their morphological characteristics, particularly the flowering phase. Therefore, the results of this study support the classification of Rhododendron cultivars according to flowering phase. In addition, the cluster results can be used to select suitable parents for breeding.

Above- and Belowground Biomass Allocation in Shrub Biomes across the Northeast Tibetan Plateau.

Biomass partitioning has been explored across various biomes. However, the strategies of allocation in plants still remain contentious. This study investigated allocation patterns of above- and belowground biomass at the community level, using biomass survey from the Tibetan Plateau. We explored above- and belowground biomass by conducting three consecutive sampling campaigns across shrub biomes on the northeast Tibetan Plateau during 2011-2013. We then documented the above-ground biomass (AGB), below-ground biomass (BGB) and root: shoot ratio (R/S) and the relationships between R/S and environment factors using data from 201 plots surveyed from 67 sites. We further examined relationships between above-ground and below-ground biomass across various shrub types. Our results indicated that the median values of AGB, BGB, and R/S in Tibetan shrub were 1102.55, 874.91 g m-2, and 0.85, respectively. R/S showed significant trend with mean annual precipitation (MAP), while decreased with mean annual temperature (MAT). Reduced major axis analysis indicated that the slope of the log-log relationship between above- and belowground biomass revealed a significant difference from 1.0 over space, supporting the optimal hypothesis. Interestingly, the slopes of the allometric relationship between log AGB and log BGB differed significantly between alpine and desert shrub. Our findings supported the optimal theory of above- and belowground biomass partitioning in Tibetan shrub, while the isometric hypothesis for alpine shrub at the community level.

Assessing atmospheric concentration of polychlorinated biphenyls by evergreen Rhododendron maximum next to a contaminated stream.

Conifers are often used as an air passive sampler, but few studies have focused on the implication of broadleaf evergreens to monitor atmospheric semivolatile organic compounds such as polychlorinated biphenyls (PCBs). In the present study, the authors used Rhododendron maximum (rhododendron) growing next to a contaminated stream to assess atmospheric PCB concentrations. The present study area was located in a rural setting and approximately 2 km downstream of a former capacitor plant. Leaves from the same mature shrubs were collected in late fall 2010 and winter and spring 2011. Polychlorinated biphenyls were detected in the collected leaves, suggesting that rhododendron can be used as air passive samplers in rural areas where active sampling is impractical. Estimated ΣPCB (47 congeners) concentrations in the atmosphere decreased from fall 2010 to spring 2011 with concentration means at 3990 pg m(-3) , 2850 pg m(-3) , and 931 pg m(-3) in fall 2010, winter 2011, and spring 2011, respectively. These results indicate that the atmospheric concentrations at this location continue to be high despite termination of active discharge from the former industrial source. Leaves had a consistent pattern of high concentrations of tetra-CBs and penta-CBs similar to the congener distribution in polyethylene passive samplers deployed in the water column, suggesting that volatilized PCBs from the stream were the primary source of contaminants in rhododendron leaves. Environ Toxicol Chem 2016;35:2192-2198. © 2016 SETAC.

Factors Affecting Diet Variation in the Pyrenean Rock Ptarmigan (Lagopus muta pyrenaica): Conservation Implications.

The Pyrenean rock ptarmigan (Lagopus muta pyrenaica) lives at one of the southernmost limits of the ptarmigan range. Their small population sizes and the impacts of global changes are limiting factors in the conservation of this threatened subspecies. An effective conservation policy requires precise basic knowledge of a species' food and habitat requirements, information that is practically non-existent for this Pyrenean population. Here, we describe the diet of a ptarmigan population in the Eastern Pyrenees, the environmental factors influencing its variability and the relationship between diet floristic composition and quality. Diet composition was determined by microhistological analysis of faeces and diet quality was estimated from free-urate faecal N content. Our results show that grouse diet is based mainly on arctic-alpine shrubs of the Ericaceae family, as well as dwarf willows (Salix spp.) and Dryas octopetala. The most frequently consumed plant species was Rhododendron ferrugineum, but its abundance in the diet was negatively related to the diet nitrogen content. Conversely, the abundance of Salix spp., grass leaves and arthropods increased the nitrogen content of the diet. Seasonality associated with snow-melting contributed the most to variability in the Pyrenean ptarmigan diet, differentiating winter from spring/summer diets. The latter was characterised by a high consumption of dwarf willows, flowers, arthropods and tender forb leaves. Geographic area and sex-age class influenced diet variability to a lesser extent. Current temperature increases in the Pyrenees due to global warming may reduce the persistence and surface area of snow-packs where preferred plants for rock ptarmigan usually grow, thus reducing food availability. The high consumption of Rh. ferrugineum characterised the diet of the Pyrenean population. Given the toxicity of this plant for most herbivores, its potential negative effect on Pyrenean ptarmigan populations should be evaluated.