Yew Tree Research Articles

Screening and Characterization of Fungal Taxol from Leaf Spot Fungi

Plants are the tremendous source for the discovery of new biotherapeutic products with medicinal importance in drug development. Paclitaxel (Taxol) is a plant-derived natural product that exhibits potential anticancer activity. Taxol binding specifically with β-tubulin and prevents depolymerisation during the process of cell division in cancer cells as anticancer property. This billion dollar drug was first isolated in trace amounts (1kg taxol recovered from 13,500kg of bark) from the bark of Yew tree (<i>Taxus brevifolia</i>), but huge drawback is production rate was low and shortage of yew trees. Currently, endophytic fungi and pathogenic fungi are the best alternative source for the taxol production. In this study, twenty-seven different plants were used for infected leaves collection from Madurai Kamaraj University (MKU) campus. Fungi were isolated from infected leaf spots on PDA plates using hyphal tip method. All the isolated fungi were subjected to pathogenicity tests, and positive pathogenic fungi were re-isolated. Totally eighteen fungal plant pathogens were isolated. The positive isolates identified using morphological and molecular characters. All the positive pathogens are screened preliminarily for taxol production. Among the eighteen isolates, three fungi were produced taxol. The test fungus <i>Phoma moricola</i>, isolated from <i>Bauhinia tomentosa</i> was the first report for Taxol production. The amount of taxol produced by <i>Phoma moricola</i> was quantified by HPLC. The maximum amount of taxol produced was found to be 302μg/L.

Determination of Cabazitaxel (An Anti-prostate cancer agent) by reverse phase liquid chromatography

Cabazitaxel is used in the treatment of hormone-refractory prostate cancer. It is a semisynthetic taxane that can be used as a precursor molecule obtained from yew tree needles. The authors have developed a stability indicating liquid chromatographic method for the determination of Cabazitaxel in pharmaceutical products. Shimadzu Model CBM-20A/20 Alite HPLC system (PDA detector) with Zorbax SB C18 column (150 mm × 4.6 mm i.d., 3.5 µm particle size) was selected for the quantification of Cabazitaxel. A mixture of tetra butyl ammonium hydrogen sulphate and methanol was used as the mobile phase with a flow rate of 1.0 mL/min (UV detection at 210 nm). The proposed analytical method was statistically validated and forced degradation studies were conducted. Cabazitaxel has shown linearity over the concentration range 0.1-200 µg/mL with regression equation y = 26145x + 22943 (r2=0.9997) and considerable degradation was observed in acidic, alkaline and oxidation conditions. The method is specific as the resolution of Cabazitaxelwas good in presence of its degradation products. This validated stability indicating liquid chromatographic method can be used for the determination of Cabazitaxel in biological studies as well as for the pharmaceutical products.

Overview of the Formulations and Analogs in the Taxanes' Story.

Taxanes are a family of diterpenes produced by the yews (Taxus genus) that are extensively used in chemotherapy. The family encompasses paclitaxel, docetaxel and the recently added cabazitaxel, all of which were proven to be promising anti-cancer drugs. Due to the over harvesting danger threatening the yew trees as well as the many challenges faced by taxane-based chemotherapy, new formulations, analogs and delivery systems are required. Here, we undertook a structured search of the bibliographical database PubMed for peerreviewed research papers relying on key words and date of publication and organized the information based on the method of taxane drug delivery. Papers retrieved were from journals with significant impact and comparable scope. A total of 126 papers were reviewed, 81 of which published work related to the taxane formulations and nanoparticles, and 22 focused on the analogs derived from the three taxanes. Although recent articles investigate the effectiveness of taxane formulations, most of these formulations are still at the pre-clinical level. However, many of the taxane analogs are currently in clinical trials as second line treatment of aggressive cancers or are used in combination with other chemotherapeutic drugs. The findings corroborate the importance of developing new drug delivery strategies and taxane analogs to improve the efficacy of currently used chemotherapeutic drugs. This finding is further supported by the FDA-approved formulation of paclitaxel that eliminates the need for toxic solvents for drug administration, and the docetaxel analog cabazitaxel which has decreased affinity for efflux pumps.

Alternol inhibits the proliferation and induces the differentiation of the mouse melanoma B16F0 cell line

High malignant potential and low susceptibility to treatment are characteristics of malignant melanoma. Alternol, a novel compound purified from microbial fermentation products obtained from the bark of the yew tree, exhibits a variety of antitumor activities. Based on these findings, the aim of the present study was to extend the knowledge on the antineoplastic effect of alternol in the mouse melanoma B16F0 cell line. Alternol significantly inhibited the proliferation and colony formation of B16F0 cells in a dose-dependent manner as detected by MTT and soft agar colony formation assays. NaOH alkaline lysis and oxidation of Dopa indicated that alternol enhanced the melanin content and tyrosinase activity of the B16F0 cells and results also showed a dose‑response relationship. Morphologic changes accompanied by extended dendrites were discovered in the B16F0 cells after treatment with alternol. Furthermore, the mRNA levels of tyrosinase, Trp1 and Trp2 were increased by alternol. Our results confirmed that alternol possesses marked antineoplastic properties against melanoma cells, indicating that this microbial fermentation product is a promising agent for the differentiation therapy of cancer. The inhibition of cell proliferation and colony formation by alternol was associated with both cytotoxicity and induction of differentiation.

ChemInform Abstract: Advances in Exploring Alternative Taxol Sources

AbstractReview: 75 refs.

Environmental stress and elicitors enhance taxol production by endophytic strains of Paraconiothyrium variabile and Epicoccum nigrum.

This study examined the effect of different elicitors (seven, different concentrations) and environmental factors (water activity (aw), pH) on taxol production by strains of two endophytic fungi, Paraconiothyrium variabile and Epicoccum nigrum, isolated from temperate yew trees. A defined liquid broth medium was modified with elicitors, solute aw depressors at different pH values. For P. variabile, the best elicitor was salicylic acid at 50mg/l which gave a taxol yield of 14.7±4.8μg/l. The study of synergistic effects between elicitor, aw and pH on taxol production showed that the highest yield of taxol (68.9±11.9μg/l) was produced under modified ionic stress of 0.98aw (KCl) at pH 5 when supplemented with 20mg/l of salicylic acid. For E. nigrum, serine was the best elicitor which increased yield significantly (29.6 fold) when KCL was used as the aw depressor (0.98aw) at pH 5.0 with 30mg/l of serine. The maximum taxol yield produced by E. nigrum was 57.1±11.8μg/l. Surface response models were used to build contour maps to determine the conditions for maximum and marginal conditions for taxol yield in relation to the best elicitor and aw, and the best pH for the first time. This will be beneficial for identifying key parameters for improvement of taxol yields by endophytic fungi.

Seasonal-based temporal changes fluctuate expression patterns of TXS, DBAT, BAPT and DBTNBT genes alongside production of associated taxanes in Taxus baccata.

Environmental cues have synergistic or antagonistic regulatory roles on transcription activity and taxanes accumulation in yew, though DBAT activity is less influenced, could be accordingly a rate-limiting enzyme. The current work was undertaken to elucidate the consequences of some environmental cues (i.e., day length, temperature, sunlight and relative humidity) on the expression patterns of TXS, DBAT, BAPT and DBTNBT genes contributed to the taxol biosynthetic pathway along with the accumulation of some taxanes in needles and stems of Taxus baccata over year 2013-2014. In both tissues, light intensity and temperature correlated with the production of 10-DAB III and total taxanes, and TXS activity, while a lack of significant association was deduced for day length and relative humidity. Furthermore, in both tissues, a weak correlation was observed between BAC III and light intensity, temperature, day length and relative humidity, and the corresponding gene, DBAT. Surprisingly, DBAT activity was not co-induced with TXS in both tissues, and remained expressed at basal levels over year, supporting that the conversion of 10-DAB III into BAC III could presumably be a rate limiting step in the taxol biosynthetic pathway. Similar to BAC III, no strong correlation was detected between production of taxol in both tissues and all the meteorological data, while the corresponding genes BAPT and DBTNBT, in some cases, exhibited significant correlated results. Notably, despite higher activities of BAPT and DBTNBT in both tissues over year, taxol production was still in small quantities, probably owing to the low amounts of its precursors rather than low volumes of BAPT and DBTNBT transcripts. The results, altogether, could provide us new insights towards the potential regulatory roles of environmental cues on the production of taxanes in yew trees.

Growth-climate relationships at yew and wild service trees on the eastern edge of their range in Europe

Aim of study: The aim of the study was the construction of regional chronologies for South-Western Poland for yew (Taxus baccata L.) and wild service tree (Sorbus torminalis L.), two of the rarest native tree species on the edge of their range in Europe. The relationships growth-climate and incremental dynamics at both these species were investigated as well.Area of study: The eastern borders of the ranges of yew and wild service trees run across Poland. The majority of the yew occurrence sites are situated in South Poland, within the area of uplands and mountains, whereas the wild service tree grows in the western part of the country. The study plots (5 for yew trees, 4 for wild service trees) were located in nature reserves in SW Poland.Material and Methods: The research materials were cores from 200 trees (115 yew trees and 85 wild service trees). The annual growth widths were measured, then, local chronologies were constructed using classic methods of dating. Regional chronologies were based on yew trees with the Student’test t &gt; 6.0, and wild service trees with t &gt; 5.9. The chronologies were subjected to the indexation and used for dendroclimatological analyses: pointer years, correlation and response function.Main results: The yew chronology, spanning 219 years (1790-2008), was established on the basis of 51 samples, the average width of annual growths amounted to 0.61 mm. The wild service tree chronology, representing the period 1841-2013 (173 years), was produced from 37 samples, the average width of annual growth amounted to 0.60 mm (from 0.27 up to 0.58 mm). Dendroclimatological analyses of the yew indicated thermal conditions of the winter months and beginning of spring (straight correlations) as the predominating factor affecting the annual growth widths. Summer drought was an additional factor limiting growth. For the wild service trees cool and humid summer months in the growing season favour the formation of wide growths.Research highlights: On account of strong dispersion and limited small populations of these two tree species, there are few dendrochronological studies available. Therefore, every piece of information on the ecology of the yew and wild service tree allows us to broaden our knowledge of these rare species enriching the biodiversity of the native tree flora.Keywords: tree-ring width; Taxus baccata L.; Sorbus torminalis L.; dendroclimatology; Poland.

Yew matriarchies of the Sierra de Francia. Dynamics and ecology of recently identified Yew populations in the Central Iberian Mountain Range (Sistema Central)

Aim of study: Our study design presents two main objectives: 1) to create a census that details the number of yew individuals and their geographic distribution, and 2) to attempt to unravel possible reproductive relationships and their connection between true population nuclei and meta-population models.Area of study: Recently identified yew populations (Taxus baccata L.) were studied in the western sector of the Sistema Central mountain range of theIberian Peninsula, known as the Sierra de Francia. The study was carried out in five watersheds within Las Batuecas-Sierra de Francia Natural Park.Material and Methods: All yew specimens were counted and assigned to age groups. The notable differences observed in regeneration aof these communities propitiates population analysis aimed at explaining the landscape connectivity relationships between the different population nuclei and the possibility of defining the meta-population set. Ecological niche models were also created to define the main ecological characteristics of the different subpopulations studied, and to compare them.Main results: Yew in the Sierra de Francia live in an array of different Mediterranean forests, indicative of species dynamics in theIberian Peninsula. 2,450 specimens were recorded and classified into the three types of yew forest population dynamics: regressional-, naturally regenerating-, and incipient- (i.e. colonizing new territories).Research highlights: The essential role of connectivity between populations was recognized and confirmed in this study, specifically among the large female trees located at the headwaters. Based on the role of these female trees, we have created a model called “yew matriarchies”, which serves to express the relevance of large female yew trees in population dynamics.Keywords: Taxus baccata; census; connectivity; seed dispersal.

Taxus globosa Schltdl. (Mexican yew) and Taxus baccata L. (European yew): intra and interspecies analysis of taxol content and biological activity according to different sources

Aim of study: Taxus globosa is the only species of Taxus genus that grows in Mexico, and is a tree which is protected by the Mexican Government. This plant shares, with the European species T. baccata, the ability to produce taxanes, such as taxol. The objective of this work was to compare representative samples from two Taxus species: T. globosa Schltdl. (“Mexican yew”), and T. baccata L. (“European yew”), by employing different methodological chemical and pharmacological tests.Area of study: Representative samples of Mexican yew were collected from states of Nuevo León, Querétaro, Hidalgo, and Oaxaca. The samples of European yew were taken from a clonal live collection located in the CIEF-Vaersa-Valencia (Spain).Materials and Methods: The aerial parts of all samples were extracted with methanol and subjected to TLC and HPLC analysis. Five extracts were selected for their anti-inflammatory evaluation. The extracts were tested on male ICR mice with ear inflammation induced with TPA, at a dose of 3.2 mg/ear. For T. globosa, an acute toxicity assay in female mice, according to OECD, was also conducted. Main results: Taxol was only detected in the yew trees samples collected in States of Hidalgo and Nuevo León (Mexico). In the inflammatory assay, in all treatments (except for that of MX35) induced slight, but significant, inhibition of inflammation, and only European sample M-9 showed inhibition of edema of &gt;50%. T. globosa in the acute toxicity test causes only mild symptoms associated with a general depression of CNS, without being lethal.Research highlights: The aim of the present study was to perform a chemical analysis through quantification of taxol in the Mexican yew compared to European yew. In this research work was evaluated too for the first time the anti-inflammatory effect from both the Mexican and European yew.Keywords: Acute toxicity; anti-inflammatory activity; European yew; HPLC; Mexican yew.

Plant Immunity: A Little Help from Fungal Friends

Yew trees are famous for production of the anti-cancer drug Taxol (paclitaxel). A new study sheds light on why endophytic fungi that live inside Yew trees also make the same drug.

An Endophyte Constructs Fungicide-Containing Extracellular Barriers for Its Host Plant

Surface cracks create sites for pathogen invasion. Yew trees (Taxus) hyperbranch from long-lived buds that lie underneath the bark [1], resulting in persistent bark cracking and deep air pockets, potentially allowing pathogens to enter the nutrient-rich vascular system (vertical phloem and inter-connected radial medullary rays [MR]). Yew is famous as the source of the anti-cancer diterpenoid drug Taxol. A mystery has been why both the tree and its resident non-pathogenic fungi (endophytes) synthesize Taxol, apparently redundantly [2-7]. These endophytes, as well as pure Taxol, suppress fungal pathogens including wood-decaying fungi (WDF) [8-11]. Here we show that a Taxol-producing fungal endophyte, Paraconiothyrium SSM001 [12], migrates to pathogen entry points including branch cracks. The fungus sequesters Taxol in intracellular hydrophobic bodies that are induced by WDF for release by exocytosis, after which the bodies can coalesce to form remarkable extracellular barriers, laced with the fungicide. We propose that microbial construction of fungicide-releasing hydrophobic barriers might be a novel plant defense mechanism. We further propose that the endophyte might be evolutionarily analogous to animal immune cells, in that it might expand plant immunity by acting as an autonomous, anti-pathogen sentinel that monitors the vascular system.

The Monarchy Shapes Up: Arboreal Metaphors in Royal Propaganda and Court Panegyrics during the Reign of Louis XV

AbstractOn 25 February 1745, during a ball celebrating the Dauphin's marriage to the Infanta of Spain, Louis XV dressed up as a pruned yew tree. A large watercolour and hundreds of prints produced by the royal office of the Menus Plaisirs offered contemporaries a stunning image of this event. This article analyses the self‐fashioning implicit in the king's sartorial choice, arguing that it informed a new political script characterised by an increasingly technical arboreal discourse. Royal epithalamia in particular drew on tree metaphors to describe the health of the body politic in the second half of the eighteenth century.

Isolation, identification, and ecology of growth and taxol production by an endophytic strain of Paraconiothyrium variabile from English yew trees (Taxus baccata)

Endophytic fungi were isolated/screened from temperate Taxus baccata (Yew) for production of the anti-cancer drug taxol. Of 242 endophytic fungi isolated from surface-sterilised Yew tree twig segments, only two produced taxol in a defined liquid medium; confirmed by HPLC and LC-MS/MS analyses. They were identified by molecular means by sequencing of ITS1/ITS2 regions and shown to be Paraconiothyrium variabile and Epicoccum nigrum. They produced 1.75 and 1.32 μgL−1 taxol respectively in a defined medium. Studies focussed on the P. variabile strain as it produced higher taxol amounts. Solute type (NaCl, KCl, Glucose, Glycerol, sorbitol), temperature (20, 25 and 30 oC) and water availability (water activity, aw; 0.90–0.99) on growth and taxol production by P. variabile was determined. Growth was similar on media with different solutes (1.0–1.25 mm d−1), optimum at 0.99 aw and 25 oC. In contrast, optimum taxol production was in a defined medium modified with KCl, at 0.98 aw and 20/25 oC, with approx. 2.3 and 7 μgL−1 respectively. No taxol was produced at <0.96 aw, at 25–30 oC, and <0.94 aw at 20 oC. This suggests that taxol producing endophytic fungi are in English yew trees and may have potential for utilisation as cell factories for production of this pharmaceutically useful compound.

A Review of Paclitaxel and Novel Formulations Including Those Suitable for Use in Dogs.

Paclitaxel is a commonly used chemotherapeutic agent with a broad spectrum of activity against cancers in humans. In 1992, paclitaxel was approved by the U.S. Food and Drug Administration (FDA) as Taxol® for use in advanced ovarian cancer. Two years later, it was approved for the treatment of metastatic breast cancer. Paclitaxel was originally isolated from the bark of the Pacific yew tree, Taxus brevifolia in 1971. Taxanes are a family of microtubule inhibitors. As a member of this family, paclitaxel suppresses spindle microtubule dynamics. This activity results in the blockage of the metaphase‐anaphase transitions, and ultimately in the inhibition of mitosis, and induction of apoptosis in a wide spectrum of cancer cells. Additional anticancer activities of paclitaxel have been defined that are independent of these effects on the microtubules and may include the suppression of cell proliferation as well as antiangiogenic effects. Based on its targeting of a fundamental feature of the cancer phenotype, the mitotic complex, it is not surprising that paclitaxel has been found to be active in a wide variety of cancers in humans. This review summarizes the evidence in support of paclitaxel's broad anticancer activity and introduces the rationale for, and the progress in development of novel formulations of paclitaxel that may preferentially target cancers and that are not associated with the risks for hypersensitivity in dogs. Of note, a novel nanoparticle formulation of paclitaxel that substantially limits hypersensitivity was recently given conditional approval by the FDA Center for Veterinary Medicine for use in dogs with resectable and nonresectable squamous cell carcinoma and nonresectable stage III, IV and V mammary carcinoma.

The impact of introduced and indigenous woody plants on change of selected soil chemical properties in the arboretum Mlyňany

DOI: 10.15414/afz.2015.18.02.44–48 Received 17. December 2014 ǀ Accepted 08. November 2014ǀ Available online 29. June 2015 In this work has been studied the impact of changed vegetation on selected soil chemical characteristics of Stagni-Haplic Luvisol in the Arboretum Mlyňany. Soil samples from A horizons were collected under growths of anthropogenically introduced (cherry laurel and Jeffrey pine) and indigenous (Norway spruce, common yew and oak-hornbeam) tree species. Since the original vegetation in Arboretum was oak-hornbeam forest, the soil under rest of that forest was used as control. Obtained results suggest that anthropogenic change of vegetation highly significantly affected the soil chemizm in A horizons under both, indigenous and introduced tree species. Cherry laurels and Jeffrey pines (their litter, root exudates) had the most significant effect on changes of studied soil chemical properties compared to the soil under original oak-hornbeam forest. The most affected were values of sum of base cations, base saturation, content of available phosphorus and exchangeable aluminum.

Pilot studies on scale-up biocatalysis of 7-β-xylosyl-10-deacetyltaxol and its analogues by an engineered yeast

Paclitaxel content in yew tree is extremely low, causing a worldwide shortage of this important anticancer drug. Yew tree can also produce abundant 7-β-xylosyl-10-deacetyltaxol that can be bio-converted into 10-deacetyltaxol for semi-synthesis of paclitaxel. However, the bio-conversion by the screened natural microorganisms was inefficient. We have constructed the recombinant yeast with a glycoside hydrolase gene from Lentinula edodes and explored the bioconversion. Based on previously established reaction conditions, the bioconversion of 7-β-xylosyl-10-deacetyltaxol or its extract was further optimized and scaled up with the engineered yeast harvested from 200-L scale high-cell-density fermentation. The optimization included the freeze-dried cell amount, dimethyl sulfoxide concentration, addition of 0.5% antifoam supplement, and substrate concentration. A 93-95% bioconversion and 83% bioconversion of 10 and 15 g/L 7-β-xylosyltaxanes in 10 L reaction volume were achieved, respectively. The yield of 10-deacetyltaxol reached 10.58 g/L in 1 L volume with 15 g/L 7-β-xylosyl-10-deacetyltaxol. The conversion efficiencies were not only much higher than those of other reports and our previous work, but also realized in 10 L reaction volume. A pilot-scale product purification was also established. Our study bridges the gap between the basic research and commercial utilization of 7-β-xylosyl-10-deacetyltaxol for the industrial production of semi-synthetic paclitaxel.

The preference for yew (Taxus baccata) by a red (Sciurus vulgaris) only squirrel population

Context As invasive grey squirrels continue to spread, red only areas are becoming rarer. It has been reported that red squirrels can outcompete greys only in pure coniferous woodland. In areas of sympatry with grey squirrels, there are concerns about red squirrels’ dependence on certain coniferous tree species in light of recent tree diseases. Aims This study aimed to investigate tree selection by red squirrels in an area vulnerable to the spread of the grey squirrel, but currently free of this species. Methods During 2013–14, squirrels were trapped and monitored on a 315-ha managed island, with a woodland characterised by a mixture of deciduous and coniferous species. Radio-tracking revealed that squirrels clustered their activity along a network of yew trees, a preference they showed throughout the year. Trap success was also higher in traps placed on yew trees. Yew and beech were selected most commonly, but squirrels were also observed foraging on other items, such as sycamore flowers and lichen. Squirrels spent 35% of their time foraging, utilising the greatest number of tree species in June (n = 13). In spring, squirrels foraged to a greater extent on the ground than in the trees, and exploited a lower number of tree species. Conclusions There has been little previous data on the use of yew trees by red squirrels, but they have previously been listed as a species that is preferred by red squirrels rather than greys. This study has further emphasised the importance of this tree species to red squirrels. Implications The continued spread of the grey squirrel may lead to red squirrels becoming restricted to areas of intense management such as parks and, accordingly, optimum tree planting is required from the onset for the long-term maintenance of red squirrels. With recent concern about the disease vulnerability of other coniferous species, this study emphasises the relative importance of yew and other tree species in the distribution of red squirrels.

Evaluation of magnetic- and carbon-based nano-adsorbents application in pre-purification of paclitaxel from needles of Taxus baccata

In this investigation, the proficiency of a number of magnetic carbon-based nano-adsorbents is evaluated in pre-purification process of the crude paclitaxel extract obtained from fresh needles of yew tree (Taxus baccata L.). The effectiveness and removal ability of color and impurities from crude extracts, for three novel candidate nano-adsorbents (i.e., Fe3O4 nanoparticles (Fe3O4Nps), graphite oxide (GO), and their hybrids Fe3O4Nps/GO) are compared with commercial graphite in three different solvents. In general, both HPLC and UV–Vis spectroscopy results demonstrate that in less polar solvent (i.e., dichloromethane), the adsorption is greatly affected by the electrostatic attractions, while in more polar solvents (i.e., acetone and ethanol) π–π electron interactions taking place between adsorbent and adsorbate are the most dominant factors in sorption. Considering decolorization efficiency, purity of taxol, recovery and reusability of adsorbents, Fe3O4Nps/GO (50 g/L) in dichloromethane is selected as the best medium for pre-purification of paclitaxel. Additionally, in kinetic studies the sorption equilibrium can be reached within 120 min, and the experimental data are well fitted by the pseudo-second-order model. The Langmuir sorption isotherm model correlates well with the sorption equilibrium data for the crude extract concentration (500–2,000 mg/L). Our findings display promising applications of Fe3O4Nps/GO, as a cost-effective nano-adsorbent, to provide a suitable vehicle toward improvement of paclitaxel pre-purification.

Pollen limitation and fruit abortion in a declining rare tree, the Eurasian yew (Taxus baccata L.): A reproductive cost of ecological marginality

Populations of rare tree species such as the dioecious and anemophilous yew (Taxus baccata) are especially prone to extinction if they occupy marginal habitats. This is the case of yew populations growing in Mediterranean mountains under dry climate and a severe anthropogenic disturbance regime, which show insufficient regeneration. We examined two of the likely mechanisms driving this population decline. The study was conducted in a central Spanish yew population in 2005 and 2006. On one hand, we tested for the effect of the amount of pollen received by female flowers by means of a pollen addition experiment. On the other hand, we tested for the effect of initial fruit set on abortion and mature fruit production. Finally, we evaluated the effect of the spatial arrangement of male and female yew trees on realized fecundity. The success of fertilization and fruiting in the experimental population was pollen-limited. Female trees aborted ca. 70% of the fruit set in both years and treatments. Fruit set was significantly influenced by the females' neighbourhood, with fecundity decreasing exponentially with distance to the nearest male in both years. Overall, our results indicate that factors associated with ecological marginality have a strong influence on yew performance.