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Triassic limestone areas of Thuringia are well-known for their richness of hybrids between S. aria and S. torminalis (subgenus Tormaria). Those have been originally described as endemic taxa (i.e. Sorbus heilingensis, S. isenacensis). However, the former endemics have been recently synonymized with S. × decipiens (Karpatiosorbus × hybrida (Bechst.) Sennikov & Kurtto) due to diploidy and putative sexuality. Generally, crosses between diploid and sexual parents should segregate and intermediates as well as morphotypes close to the parents should be the outcome. To test for clonality versus segregation, we investigated progeny of 10 Tormaria mother trees, derived from open pollination. Three to ten seedlings of each mother tree were cultivated, and six leaf characters were measured being indicative for subgenus Aria, Tormaria and Torminalis. For genetic characterization, we used three ISSR microsatellite markers and one chloroplast marker. The progeny of nine mother trees segregated; the S. aria genome prevailed in pollen clouds. One polyploid mother tree, however, produced partly clonal progeny and proved to be polyploid and facultative apomictic. This means that in Thuringian Tormaria polyploidization occurs at low rates starting from diploid hybrids. Exact comparisons between geno- and phenotypes of the progeny proved a frequent uncoupling between genetic markers and genes responsible for leaf morphology, pointing to excessive genomic rearrangement within Tormaria mother trees. Only 1/3 of Tormaria-genotypes possessed the Tormaria-phenotype. Most of them belong to S. aria and to S. aria forma incisa, a S. aria type with slightly incise leaves. This means that plasticity of parental species may be explained by excessive introgression between S. aria and S. torminalis. [ABSTRACT FROM AUTHOR]

Question: Malus sylvestris is considered an endangered tree species in Central Europe. Hybridization with Malus domestica poses a serious threat to the genetic integrity of the wild species. Here we investigate whether M. sylvestris and the hybrid M. domestica × sylvestris occur in the same habitat or have different ecological niches and whether M. sylvestris is threatened by displacement by the hybrid. Location: Northern Bavaria. Methods: Taxon delimitation was accomplished using six genetic microsatellite markers and 613 Germany‐wide references of M. sylvestris and 75 cultivars. To determine differences in the ecological niches between M. sylvestris and hybrids, light availability for the trees was estimated via gap fractions in hemispherical photographs. Soil particle size fractions and pH values were determined for each horizon. Vegetation relevé data were collected, and mean Ellenberg indicator values calculated. For habitat differences, means in combination with frequency patterns of the parameters were compared, and logistic models and detrended correspondence analysis (DCA) of community data were calculated. Results: Genetic markers identified 22 M. sylvestris and 11 hybrid specimens, meaning that in the study area the wild taxon is much more frequent than the hybrid. Ecological site differences between M. sylvestris and its hybrid with M. domestica were best explained by light availability, pH and mean Ellenberg moisture value. In contrast to the ecological demands of the hybrid, Malus sylvestris tolerated wet soil and flooding and even somewhat shadier conditions in the later successional stages. DCA revealed that differences in the composition of the plant communities in which the taxa were found were primarily driven by soil moisture. Conclusions: Our data suggested different ecological niches, which are appropriate to reduce the risk of replacement of M. sylvestris by the hybrid M. domestica × sylvestris. Hence, these findings provide important implications for a more targeted planning of in‐situ conservation strategies of M. sylvestris genomes with low levels of admixture and help to protect plant communities suitable for the threatened wild apple. [ABSTRACT FROM AUTHOR]

Flavonoids, proanthocyanidins (PAs) and salicylic alcohol derivatives are the main groups of ingredients in Salix needed as defensive tools and signal molecules, but have also pharmaceutical importance. The present study investigated total PA content, complete PA pattern, the oligomeric/total PAs quotient and the contents of catechin and epicatechin during one growing-season for the leaves and this year's sprouts in ten willows ( Salix pentandra L. ♂, S . alba L. ♂, S. fragilis L. ♀, S. caprea L. ♂ & ♀, S. cinerea L. ♂, S. caprea x cinerea ♂, S. daphnoides Vill. ♂ & ♀ and S. purpurea L. ♀; all Salicaceae). Comparison of the different species revealed distinct seasonal fluctuations of the oligomeric and polymeric PA fractions, but the contents of both groups always developed in the same direction. All willows prefer the synthesis of PAs with DP-2 - DP-4 within the oligomeric fraction (DP-2 – DP-10) and species with rather low PA contents like S. purpurea (0.1–2.6 mg/g) as well as species with rather high PA contents like S. alba (3.8–14.7 mg/g) were found. Only slight gender specific differences could be observed for both sexes of S. daphnoides and S. caprea. The PA pattern of the hybrid S. caprea x cinerea seems to be influenced by both parents. Thus, the accumulation of the oligomeric PAs accorded to S. caprea and the polymeric PAs matched S. cinerea resulting in an overall depression of PAs in the sprouts and a varying seasonal trend in the leaves. In contrast, the content of catechin remained high and seemed to be not influenced in the hybrid. Although only one individual of each Salix species could be considered in this screening study, the present results demonstrate the variability of the flavan-3-ol pattern within the genus Salix but also some preliminary correlations could be observed. Future studies with more Salix species will provide more insights into chemotaxonomic correlations. [ABSTRACT FROM AUTHOR]

Ongoing climate change increasingly affects growth conditions of native conifers such as Picea abies (Norway spruce) and Pinus sylvestris (Scots pine) in Central Europe. These conifers are primarily cultivated for wood production. To obtain ecologically and economically stable forests, forestry seeks alternative species that might be less prone to novel climatic conditions, such as Cedrus libani (Lebanon cedar). We aim at investigating growth responses to climatic factors of C. libani compared to native P. abies and P. sylvestris in Central Europe for 25 years (1994–2019). Growth responses were used as a proxy for tolerance towards climatic stress events, such as heat and drought. Height, diameter at breast height (DBH) and radial increment were measured for 40-year-old tree stands of C. libani and native conifers. Radial growth responses to selected climate parameters were analysed using bootstrapped correlations with detrended growth index chronologies and growth response indices for drought years (2003, 2012, 2015, 2018). For C. libani, radial growth was positively correlated with high water availability in late winter and spring, while for P. abies, February and summer and for P. sylvestris, July showed such a relationship. Cedrus libani exhibited the highest resistance, recovery, and resilience in response to climatic extremes. Against the background of climate change, C. libani could serve as an alternative conifer species to establish climate-resistant viable forests in Central Europe. [ABSTRACT FROM AUTHOR]

Abstract: Common ash (Fraxinus excelsior) is a keystone tree species throughout temperate Europe whose future existence is threatened by an emerging invasive fungal disease. Ash dieback, which first appeared in Poland in the 1990s, has rapidly spread to most eastern, central and northern European countries. The causal agent of the disease, the ascomycete Hymenoscyphus pseudoalbidus (anamorph Chalara fraxinea), was recently described as a new species. Given that the disease lethally affects ash trees of all age classes, and that ash tree mortality levels are high, F. excelsior and the many organisms dependent on ash trees are under threat. Based on a literature survey, we provide an overview of the present knowledge on ash dieback, identify practical recommendations and point out research needs. The observation of relatively resistant individual ash trees (although at very low frequency) calls for a rapid germplasm collection effort to establish a breeding program for resistance or tolerance to the disease. Ash trees that appear to be tolerant to the pathogen should not be felled, unless they pose an unacceptable risk to people’s security. Given that the pathogen does not form propagules on wood, and given the importance of deadwood for biodiversity conservation, dead and dying ash trees should be left in the forest. Landscape pathology and genetic tools can be used to reconstruct the dispersal pathways of H. pseudoalbidus and to identify environmental features associated with variation in disease severity, so as to better predict the further development of the epidemic. Observations on differences in susceptibility of various ash species are needed to locate the geographic origin of the pathogen and to identify Fraxinus species which might be used for resistance breeding or even replacement of F. excelsior. Conservation biologists, landscape managers, restoration ecologists, social scientists and tree geneticists need to engage with forest pathologists and the various stakeholders throughout the distributional range of F. excelsior so as to tackle this pressing conservation challenge. [Copyright &y& Elsevier]

Most studies on Salix hybrids concerning the diversity in a hybrid complex included typical morphological characteristics of leaves, buds, twigs and flowers for comparison with genotypic traits. Our analyses are based on a set of phenotypical traits of 19 clones of the S. alba/S. fragilis-aggregate which includes characteristics as phenology, growth, and composition of secondary leaf compounds, for the first time additional to morphological traits. Three clearly distinct groups ( S. alba L., S. fragilis L., and S. × rubens Schrank) could be identified based on phenotypical traits and ITS1 and 5.8S nrDNA sequences. S. × rubens revealed additivities at variable ITS1 and 5.8S positions as well as intermediate morphology and secondary compound pattern, but was characterised by significant earlier foliation start. This property leads to a better utilization of the vegetation period and may explain the detected better growth compared to the parent species and therefore also may have contributed to the widespread occurrence of S. × rubens in Central Europe. [ABSTRACT FROM AUTHOR]

Aim Cold events determine the distributional range limits of woody species. Despite global warming, the magnitude of late frost events in boreal and temperate regions is not expected to change. Hence, the risk for late spring frost damage of woody species may increase with an earlier onset of the growing season. Here, we investigated biogeographical, phenological and phylogenetic effects on late frost sensitivity. Location Ecological-Botanical Gardens Bayreuth, Germany (49°55′45″ N, 11°35′10″ E). Methods We inspected 170 woody species in the Ecological-Botanical Gardens from across the entire Northern Hemisphere for frost damage after an extreme late frost event in May 2011 (air temperature −4.3 °C after leaf unfolding of all species). Distribution range characteristics, climatic parameters of place of origin and phenological strategy were linked to sensitivity to the late frost event. Results The northern distribution limit and the range in continentality across the distributional ranges correlated negatively with a taxon's late frost sensitivity (pseudo- R2 = 0.42, pseudo- R2 = 0.33, respectively). Sensitivity to the late frost event was well explained by the climatic conditions within species' native ranges (boosted regression trees; receiver operating characteristic 0.737). Average (1950-2000) May minimum temperature in species' native ranges was the main explanatory variable of late frost sensitivity (51.7% of explained variance). Phylogenetic relatedness explained additional variance in sensitivity to the late frost event. Sensitivity to the late frost event further correlates well with species phenological strategy. Frost-tolerant species flushed on average 2 weeks earlier than frost-sensitive species. Main conclusions Range characteristics and the prevalent climatic parameters across species native ranges are strongly related to their susceptibility to late spring frost damage. Further, more late frost-sensitive species unfolded their leaves later than more tolerant species and late frost tolerance is phylogenetically conserved. Thus, late frost sensitivity may challenge natural and human-assisted migration of woody species under global warming. [ABSTRACT FROM AUTHOR]

Temperate grasslands exhibit strong spatial and temporal variation in water regimes. Thus, grassland plants experience potentially stressful water regimes, which may influence their tissue silicon (Si) and nitrogen (N) concentrations. Plant Si and N concentrations play important ecological roles in temperate grasslands, for example, by influencing plant performance and herbivory, yet comparisons of species' responses to a broad range of water regimes, including drought, waterlogging and flooding, are lacking.We conducted a mesocosm experiment with 10 temperate grassland species of two life‐forms (grasses and forbs) exposed to four different soil water regimes (drought, a benign control, waterlogged and flooded conditions), and analysed their Si and N concentrations.Grasses showed lower Si concentrations under drought and flooding compared to the benign control and the highest concentrations emerged under waterlogging. Overall, plant Si responses of grasses were more uniform, while in forbs, responses varied both in direction and magnitude across species. For N concentrations, all species and life‐forms showed the highest concentrations under drought compared to the benign control, while half of the species exhibited decreasing concentrations under waterlogging and/or flooding. The water regimes, especially waterlogging and flooding, induced changes in species rankings of plant Si and N concentrations, with stronger shifts in forbs than in grasses.Our results indicate that spatial and temporal variation of water regimes may influence plant Si and N concentrations in temperate grassland species. Plant Si responses to water regimes might be highly species‐specific in forbs but more similar in grasses, whereas plant N responses are likely to be relatively uniform across species and life‐forms.The strong plasticity in plant Si and N concentrations we observed might have pervasive consequences for ecological processes, such as herbivory. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

Aim Species ranges are confined by environmental parameters such as minimum temperatures. Beyond correlations of ranges and climatic parameters, however, physiological tolerances (here: cold tolerance) have rarely been linked to the climate of species' ranges. We hypothesize that natural range shifts due to climate warming and proactive-assisted colonization may each be constrained by limits to the tolerance of species to rare frost events. Location Bayreuth, Germany, and the Northern Hemisphere. Methods We quantified cold tolerance ( LT50 obtained by relative electrolyte leakage method) of 27 native and exotic (Northern Hemisphere) tree species in the autumn, mid-winter and spring of 2011-12 at the Ecological Botanical Garden of the University of Bayreuth, Germany, and linked observed cold tolerances as well as changes in cold tolerance between sampling dates to the climate of the native ranges of the species. Results Observed cold tolerance was strongly related to the climate of the native ranges of the species (cross-validated correlations between climate and expressed cold tolerance determined by boosted regression trees were 0.50 in autumn, 0.49 in mid-winter, and 0.65 in spring). Cold tolerance was generally greater for species that experienced colder temperatures and lower levels of precipitation in their native ranges. Changes in cold tolerance between the three sampling dates over the winter, however, were not linked to the climate of the native ranges. Main conclusions Our results demonstrate the evolutionary importance of cold tolerance, which should be acknowledged in assisted colonization trials and projections of range shifts by considering absolute minimum temperature as an important ecological factor. [ABSTRACT FROM AUTHOR]

Floral scent, often a complex mixture of several volatile organic compounds ( VOCs), has generally been interpreted as an adaptation to attract pollinators. However, not many studies have analysed which VOCs are functionally relevant for the reproductive success of a plant. Here, we show that, in Salix caprea ( Salicaceae), temporal changes in floral scent emission during the day and night attract two different types of flower visitor: bees during the day and moths during the evening and night. We analysed the contribution of the two flower visitor groups to the reproductive success of the plant. The differences in scent emitted during the peak activity times of flower visitors (day versus night) were quantified and the response of 13 diurnal/nocturnal pollinator taxa to the floral scents was tested using gas chromatographic and electroantennographic techniques. Many of the c. 40 identified scent compounds were physiologically active, and bees and moths responded to nearly identical sets of compounds, although the response strengths differed. In bioassays, bees preferred the most abundant 1,4-dimethoxybenzene over lilac aldehyde, a compound with increased emission at night, whereas moths preferred lilac aldehyde over 1,4-dimethoxybenzene. Pollination by wind plus nocturnal pollinators (mainly moths) or by wind alone contributed less to seed set than pollination by wind plus diurnal pollinators (mainly bees). This suggests that the emission of scent during the night and attracting moths have no significant effect on reproductive success. It is possible that the emission of lilac aldehydes and other compounds at night is s result of phylogenetic constraints. Future studies should investigate whether moths may produce a marginal fitness gain in some years and/or some populations. © 2014 The Linnean Society of London, Botanical Journal of the Linnean Society, 2014, 175, 624-640. [ABSTRACT FROM AUTHOR]

Climate projections indicate large increases in temperature, requiring tree species to adapt or migrate faster than observed historic rates. In Central Europe, discussion in forest management has increasingly focused on how humans can assist these adaptation/migration processes, especially when important forest ecosystem services are at risk. One option is to introduce non-native tree species to help forest ecosystems adapt to climate change. We established a long-term experiment in autumn 2012 on five study sites in climatically different regions of Central Europe. The performance of five non-native tree species from warmer climates (Abies bornmuelleriana Mattf., Cedrus libani A. Rich., Fagus orientalis Lipsky, Tilia tomentosa Moench and Tsuga heterophylla Sarg.) was compared to that of one local species native to each site. We monitored sapling survival during the first 4 years after planting. Small differences in timing of inventory campaigns were overcome by fitting a Weibull function to survival curves and analysing time-harmonized estimates for equal biannual periods. Sapling mortality decreased over time, but early after planting, it differed between species. The native and the two non-native broadleaved species showed higher survival than the non-native coniferous species. Moreover, the site conditions of the open areas seemed to initially hamper the growth of shade-tolerant species. All species performed reasonably well during the relatively short observation period. Any differences between hazard rates almost vanished 4 years after planting, which suggests that all species tested are likely to thrive under current climate conditions. Long-term observations are, however, needed to corroborate these results. [ABSTRACT FROM AUTHOR]

Sorbus subgenus Aria in Europe consists of sexual diploid and predominantly apomictic polyploid taxa. Tetraploid taxa of Sorbus subgenus Aria , including S. danubialis and S. collina , are endemic to central Europe, but it is unclear from which taxa or populations they originated. South-eastern European taxa of subgenus Aria were suggested to have contributed to the tetraploids S. danubialis and S. collina by polyploidization or hybridization. Genetic microsatellite data, flow cytometry and multivariate morphometrics were used (1) to investigate the genetic relationship of the tetraploid taxa throughout Europe, (2) to disentangle the population structure of diploid S. aria from central and south-eastern Europe and (3) to use the resulting subgroups for estimating the parentage of polyploids. Parentage analyses revealed that the allele patterns of the polyploid central European taxa such as S. danubialis and S. collina and other as yet undescribed polyploids from south-western Germany could be explained in most cases by recurrent crosses between diploid S. aria from south-eastern and central Europe. These origins are discussed in the context of historical biogeography. Furthermore, we report the exceptional case of a polyploid subgenus Aria population from south-western Germany showing no clonal genetic structure at all, making its taxonomic treatment challenging. [ABSTRACT FROM AUTHOR]

Considering climate change, the discussion intensifies whether and to what extent exotic tree species should be taken into account for forest cultivation, especially when indigenous species are no longer able to fulfill essential forest functions. In this study, for the first time growth potential of Cedrus libani was evaluated under climatic conditions in Central Europe (Bayreuth, Germany). The sampled trees exhibited extraordinary growth with tree ring widths averaging 4.9 mm year during the past 23 years. A continuously available soil water supply enhanced radial stem growth. Thus, growth declined during the dry year of 2003, but recovered to average values the following year. Our results confirm that C. libani is a light-demanding species which is sensitive to competition and which shows a typical age trend. In a second study, we compared cambial growth in Bayreuth with a natural stand in Elmali (Turkey) in 2009. Cambial growing season in Bayreuth was 45 days longer, and radial growth rates in Bayreuth were four times higher than in Elmali. Interestingly, C. libani maintained a slow but continuous radial growth at Elmali even during the dry summer period, confirming its exceptional drought tolerance. Our results indicate a high adaption of C. libani to current and future climate conditions in Central Europe. It tolerates extreme cold in winter and prolonged droughts during summer. Thus, its promising potential for establishing stable and productive forest stands in Central Europe under a changing climate should be confirmed in further studies. [ABSTRACT FROM AUTHOR]

Comparisons between floral scent-based and DNA-molecular-based taxonomies are rare, yet such comparisons indicate that scent can provide useful taxonomic information. Here, we correlate the phytochemical differentiation in floral scent to the DNA-molecular-based differentiation in the genus Sorbus. Inflorescence scent patterns of the apomictic and endemic Sorbus latifolia microspecies Sorbus franconica, Sorbus adeana, and Sorbus cordigastensis originated by hybridization as well as their parental taxa Sorbus aria agg. and Sorbus torminalis were investigated with the dynamic headspace method. The scent data (presence/absence of compounds) were used to construct an UPGMA tree, to calculate a similarity matrix, and to correlate them with the published amplified fragment length polymorphism (AFLP) data of the same individuals, populations, and taxa. Flow cytometry was used to estimate the DNA-ploidy level of the taxa. Scent analyses showed a total of 68 substances, among them aromatic compounds, terpenoids, aliphatics, and nitrogen-containing compounds. The scent patterns were taxon-specific, and the number of scent components differed among taxa. The correlations with the published AFLP data on population and individual level are highly significant, indicating that the scent and AFLP data are highly congruent in the plants studied. Scent therefore provides useful taxonomic characters in Sorbus. [ABSTRACT FROM AUTHOR]

In dioecious, zoophilous plants potential pollinators have to be attracted to both sexes and switch between individuals of both sexes for pollination to occur. It often has been suggested that males and females require different numbers of visits for maximum reproductive success because male fertility is more likely limited by access to mates, whereas female fertility is rather limited by resource availability. According to sexual selection theory, males therefore should invest more in pollinator attraction (advertisement, reward) than females. However, our knowledge on the sex specific investment in floral rewards and advertisement, and its effects on pollinator behaviour is limited. Here, we use an approach that includes chemical, spectrophotometric, and behavioural studies i) to elucidate differences in floral nectar reward and advertisement (visual, olfactory cues) in dioecious sallow, Salix caprea, ii) to determine the relative importance of visual and olfactory floral cues in attracting honey bee pollinators, and iii) to test for differential attractiveness of female and male inflorescence cues to honey bees. Nectar amount and sugar concentration are comparable, but sugar composition varies between the sexes. Olfactory sallow cues are more attractive to honey bees than visual cues; however, a combination of both cues elicits the strongest behavioural responses in bees. Male flowers are due to the yellow pollen more colourful and emit a higher amount of scent than females. Honey bees prefer the visual but not the olfactory display of males over those of females. In all, the data of our multifaceted study are consistent with the sexual selection theory and provide novel insights on how the model organism honey bee uses visual and olfactory floral cues for locating host plants. [ABSTRACT FROM AUTHOR]

The Franconian Alb (Bavaria, Germany) is rich in endemic Sorbus taxa, considered as apomictic microspecies and derived by hybridization between Sorbus aria aggregate and Sorbus torminalis ( Sorbus latifolia aggregate). Molecular studies using the AFLP technique, neighbour joining, Bayesian clustering, principal coordinate analysis (PCo) and voucher studies were used to investigate genetic structure and origin of adult plants and cultivated offspring of three endemic S. latifolia taxa, namely Sorbus cordigastensis, Sorbus franconica and Sorbus adeana and probable parental species from the S. aria agg. and S. torminalis. The S. latifolia taxa, adults and progeny, showed low genetic variability and a more or less clonal structure, confirming an apomictic mode of reproduction. The investigated S. latifolia taxa were remarkably different among each other, confirming their status as microspecies. The AFLP data confirmed the hybrid origin of the S. latifolia taxa, they were 1.3-1.5 times more closely related to S. aria agg. than to S. torminalis. The S. aria agg. showed a complicate genetic structure and fell into four main groups, two intermediate groups besides Sorbus pannonica and Sorbus aria sensu stricto ( S. aria s.str.). Some progeny of S. pannonica was more variable than expected and clustered partly with other groups indicating gene flow within S. aria agg. Different subgroups of the S. aria aggregate may be parental for the S. latifolia taxa, contributing to the remarkable genetic distances between them. [ABSTRACT FROM AUTHOR]

The dynamics of six different needle parameters of Pinus sylvestris L. and Pinus ponderosa Dougl. ex P. & C. Laws. were examined retrospectively for a 112-year-old mixed stand in Brandenburg, Germany, using the needle trace method. Similarities were found in needle production, needle loss and needle density. However, needle age, needle retention and total number of needles revealed significant differences between the tree species, with higher values for P. ponderosa. Pinus ponderosa yielded approximately twice as much mean whole-crown needle dry mass as P. sylvestris. Furthermore, different branching systems could be detected between the species, with both pines following "Corner's rule". The results suggest that under identical growing conditions, P. ponderosa exhibits more efficient water use and can therefore maintain a bigger crown (as the basis for increased growth) than P. sylvestris. [ABSTRACT FROM AUTHOR]