Paula Lorenzo

The genus Acacia as invader: the characteristic case of Acacia dealbata Link in Europe

Abstract• We review current knowledge about the biology of the genus Acacia, and Acacia dealbata Link (silver wattle) in particular, as an invader in Europe, focusing on (i) the biology of the genus Acacia; (ii) biological attributes that are important for the invasiveness of the genus and A. dealbata; (iii) possible hypotheses for the invasion success; and (iv) control methods.• Several Australian wattles have been recorded as naturalized in Europe. Acacia has attained pest proportions in certain habitats and protected sites (notably coastal dunes, river courses, natural parks and biosphere reserves).• The spread of Acacia dealbata seems to be assisted by human interference such as soil disturbance and severe fires. The biological attributes favoring invasion by A. dealbata include tolerance of changing soil conditions, the ability to take advantage of environmental disturbance, phenotypic plasticity, vegetative reproduction, fire tolerance and allelopathic potential.• Different hypotheses explaining invasiveness and transition between invasion steps related to biological attributes as the key factor for A. dealbata invasion are discussed. Effects on the biodiversity of native flora are little understood and studies of suppression of autochthonous species are needed. It is desirable that further studies comparing Acacia at field sites in their native and exotic range should be done.• Understanding the biology of invasive wattles in Europe is the first step to an effective control method. Studies comparing plant invaders at field sites in their native and invaded areas seem to be most appropriate in order to be able to attack the most vulnerable stages.Résumé• Nous passons en revue les connaissances actuelles sur la biologie du genre Acacia et de Acacia dealbata Link, en particulier comme un envahisseur en Europe, en mettant l’accent sur : (i) la biologie du genre Acacia ; (ii) les attributs biologiques qui sont importants pour le caractère envahissant du genre et d’A. dealbata; (iii) les hypothèses possibles pour la réussite de l’invasion et (iv) les méthodes de contrôle.• Plusieurs acacias australiens ont été enregistrés comme naturalisés en Europe. Acacia a atteint la proportion de nuisible dans certains habitats et sites protégés (notamment des dunes côtières, des cours d’eau, des parcs naturels et des réserves de la biosphère).• La propagation de l’Acacia dealbata semble avoir été aidée par l’intervention humaine, telle que la perturbation des sols et de graves incendies. Les attributs biologiques favorisant l’invasion par A. dealbata incluent la tolérance aux changements des conditions du sol, la capacité à tirer profit des perturbations de l’environnement, la plasticité phénotypique, la reproduction végétative, la tolérance au feu, et le potentiel allélopathique.• Différentes hypothèses expliquant le caractère invasif et la transition entre les phases de l’invasion en relation avec les attributs biologiques comme facteur clé pour l’invasion d’A. dealbata sont discutées. Les effets sur la biodiversité de la flore sont mal compris et des études sur la suppression des espèces autochtones sont nécessaires. Il est souhaitable que d’autres études comparant Acacia sur le terrain dans leurs sites et dans des régions exotiques soient faites.• Comprendre la biologie des espèces d’Acacia invasives en Europe est la première étape d’une méthode de contrôle efficace. Les études comparant les envahisseurs végétaux sur le terrain dans leurs sites et dans les zones envahies semblent être plus appropriées afin d’être en mesure d’attaquer les étapes les plus vulnérables.

Inhibition of IκB Kinase-β and Anticancer Activities of Novel Chalcone Adamantyl Arotinoids

On the basis of the observations that chalcone 7 (MX781) and some related adamantyl arotinoids (AdArs) inhibit IkappaB alpha kinase beta (IKKbeta) activity, inhibit cell growth, and induce apoptosis in cancer cells, a new series of AdArs structurally related to 7 have been designed and synthesized. Modifications were intended to reduce or eliminate RAR activity, and we evaluated the effect of the novel analogues of 7 on IKKbeta activity and proliferation of a variety of cancer cell lines (leukemia, Jurkat; prostate, PC-3; breast carcinomas, T47D, MDA-MB-468). Consistent with the design principles, the biological activities of these AdArs do not appear to be RAR-mediated, since most analogues are unable to activate RAR-mediated transactivation and exhibit significantly diminished antagonist activity. All compounds are capable of inducing apoptosis in Jurkat cells, as demonstrated by elevated DEVDase activity and externalization of phosphatidylserine. Several of the analogues elicit stronger growth inhibitory activity against prostate (PC-3) and breast (MDA-MB-468) carcinoma cells, which contain elevated basal IKK activity; this antiproliferative activity correlates with increased inhibition of recombinant IKKbeta in vitro, suggesting that the anticancer activities of these AdArs might be related to the inhibition of IKK/NFkappaB signaling.

The effect of soil legacy on competition and invasion by Acacia dealbata Link

Plant–soil feedbacks can exacerbate competition between invasive and native species, although the net effect of the interaction between soil biota and competition is likely to be species-specific. Very few studies have addressed the combined effect of soil and competition on plant performance and invasion by exotic woody species. This study explores plant growth and competition between Acacia dealbata and Pinus pinaster in three different soils—native, disturbed and invaded—in Portugal. The invasion of native P. pinaster forests by A. dealbata can be explained by the stronger competition ability of the exotic tree species. Competition is stronger in the native soil, allowing the establishment of A. dealbata in this soil and the displacement of P. pinaster. During invasion, A. dealbata changes soil conditions and establishes positive plant–soil feedbacks that promote its own germination and growth and increase P. pinaster mortality. Soil disturbance by the introduction of a different exotic species, Eucalyptus globulus, did not promote invasion by A. dealbata. We found a significant effect of soil legacy on both growth and competitive ability of the invasive A. dealbata. The ability of A. dealbata to outcompete the native P. pinaster in its own soil and the positive plant–soil feedbacks established after invasion are important mechanisms for A. dealbata invasion.

Differential responses to allelopathic compounds released by the invasive Acacia dealbata Link (Mimosaceae) indicate stimulation of its own seed

Invasion by exotic species constitutes a major threat to natural ecosystems. One of the most invasive species of current concern in Europe is Acacia dealbata Link (Mimosaceae), the expansion of which is reducing populations of native species, and hence biodiversity. To investigate the potential involvement of allelopathic mechanisms in this process, we evaluated the germination and seedling growth performance of Lactuca sativa L. (Compositae), Zea mays L. (Gramineae), Dactylis glomerata L. (Gramineae), Arabidopsis thaliana (L.) Heynh. (Cruciferae) and A. dealbata, in the presence of mixtures of throughfall and litter leachate and of aqueous soil extracts collected under A. dealbata at different times of the year. Each test species responded differently to the solutions being assayed suggesting that A. dealbata allelochemicals may affect a variety of physiological growth parameters. In most cases the observed effects were stimulatory rather than inhibitory, which may have long-term deleterious effects on native plant populations since premature growth during periods of poor resources can be detrimental. Interestingly, increased radical growth of A. dealbata was detected with either extract suggesting a positive autoalleloapthy effect.

Invasion by the leguminous tree Acacia dealbata (Mimosaceae) reduces the native understorey plant species in different communities

Acacia dealbata Link (Mimosaceae) is a woody leguminous tree introduced to Europe from Australia that has become a serious environmental problem in north-western Spain, where it forms dense monospecific patches threatening native-plantbiodiversity.WedescribetheeffectsofinvasionbyA.dealbataonunderstoreyplantcompositioninshrubland, oak- and pine-forest communities in north-western Spain. Plant species richness and composition, plant density and total plantcoverweremeasuredandcomparedamongpatcheswithdifferentinvasionstatus(invaded,transitionandnon-invaded patches) in each studied community. A clear effect of the community type and invasion on the understorey vegetation was observed.Ingeneral,compositionofshrublandwasdifferentfromthatofoakandpineforests.Wefoundsignificanteffectsof invasion status on species richness, plant density and total plant cover; values were significantly lower in invaded than non- invaded patches. Invasion by A. dealbata also was associated with changes in species composition. In total, eight native species, including the endemic Daboecia cantabrica (thuds) K. Koch, were confined to non-invaded patches and were replacedbyothernativesininvadedandtransitionpatches.OurresultssuggestthatalthoughA.dealbatarepresentedaserious threat to all of the study communities, the severity of the impact depended on the community type.

Influence of soil microorganisms, allelopathy and soil origin on the establishment of the invasive Acacia dealbata

Background: The invasive success of Acacia dealbata is partially attributed to the release of allelopathic compounds and changes in soil characteristics. However, both mechanisms have been studied separately, which does not reflect field conditions. Aims: To test whether interactions of allelopathy, soil origin and soil microbiota affect plant germination and growth of A. dealbata. Methods: Soil sampling and collection of natural canopy leachates were conducted in Coimbra, Portugal. Germination and seedling growth were tested in sterilised and control soils from native forests and invasive acacia stands, watered either with acacia or native canopy leachates. Sapling growth was further studied in soils from native forests and invasive acacia stands. Results: No interaction between Acacia leachates and soil microbiota was detected. Leachates of A. dealbata had a negative effect on the growth of its own seedlings in native soils. Soil microbiota reduced seedling growth in native forests. Saplings of A. dealbata grew bigger in the invaded soil than in soil from native forests. Conclusions: Soil microorganisms have a positive effect on the initial establishment and growth of A. dealbata. The effect of Acacia leachates depends on the origin of the soil. Soil previously modified by A. dealbata seems to favour its own growth.

Role of Allelopathy During Invasion Process by Alien Invasive Plants in Terrestrial Ecosystems

Biological invasion is causing serious current biodiversity loss in different parts of the world and involves different stages: introduction, establishment, naturalization, and fast dispersion outside the normal ranks. Invasion may cause a reduction in abundance of native species or the elimination of populations of a particular species. Exotic species have to surpass different biological filters to get to be invaded in a new habitat. Importance of allelopathy in the invasion process may include the release of secondary chemical metabolites into the surrounding environment to inhibit the seedling establishment and other ecophysiological attributes of native biota. Temperature, drought, cold, association, and feedback from soil microorganism can also adversely affect the biological nutrient cycle, and other aspects that can favor the invading capacity of exotic species. Environmental problems generated by invading species can become serious in naturally protected and sensitive areas, where climatic circumstances may evolve in the shape of global warming. The purpose of this chapter is to highlight the role of allelopathy during the invasion process with special emphasis to ecophysiological relationships between exotic and native plants, and soil microorganisms.

Changes in microhabitat, but not allelopathy, affect plant establishment after Acacia dealbata invasion

Aims The tree legume Acacia dealbata Link is an aggressive Australian invader that severely affects abiotic and biotic compartments of ecosystems worldwide. This invasive species outcompetes native plant communities through direct competition, changes in microhabitat and soil properties under the canopy and the release of allelopathic compounds. However, these effects are usually studied separately and under controlled conditions. The objective of this study was to evaluate the combined effect of these modifications exerted by A. dealbata on the establishment of native and invasive species in the field. Methods A full factorial experiment was performed in order to test the combined effect of microhabitat, soil type and allelopathy on the establishment of the invasive A. dealbata and three native species in the field (North–West Spain). We sowed seeds of native or invasive species in pots with different soil type (soil collected under A. dealbata or Pinus pinaster), allelopathy status (soil treated or untreated with activated carbon) and microhabitat (under the canopy of A. dealbata or P. pinaster). The number and total biomass of established plants were evaluated after 8 months. Soil abiotic properties were determined in all soils. Important Findings The establishment of native and invasive species was significantly affected by the microhabitat, with a higher number of seedlings under the native forest (P. pinaster). The establishment of A. dealbata seedlings was also significantly promoted by its own soil. A negligible effect of allelopathy was detected on the establishment and growth of both invasive and native species. We conclude that (i) the main factor affecting seedling establishment was microhabitat rather than changes in soil properties or allelopathy, (ii) soil modifications by A. dealbata promote the establishment of its own seedlings, contributing to the progress of invasion and (iii) allelochemicals released by A. dealbata do not seem to play a key role for the establishment of native and invasive plants under field conditions in the European non-native range.

Adamantyl Arotinoids That Inhibit IκB Kinase α and IκB Kinase β

A series of analogues of the adamantyl arotinoid (AdAr) chalcone MX781 with halogenated benzyloxy substituents at C2′ and heterocyclic derivatives replacing the chalcone group were found to inhibit IκBα kinase α (IKKα) and IκBα kinase β (IKKβ) activities. The growth inhibitory capacity of some analogues against Jurkat T cells as well as prostate carcinoma (PC‐3) and chronic myelogenous leukemia (K562) cells, which contain elevated basal IKK activity, correlates with the induction of apoptosis and increased inhibition of recombinant IKKα and IKKβ in vitro, pointing toward inhibition of IKK/NFκB signaling as the most likely target of the anticancer activities of these AdArs. While the chalcone functional group present in many dietary compounds has been shown to mediate interactions with IKKβ via Michael addition with cysteine residues, AdArs containing a five‐membered heterocyclic ring (isoxazoles and pyrazoles) in place of the chalcone of the parent system are potent inhibitors of IKKs as well, which suggests that other mechanisms for inhibition exist that do not depend on the presence of a reactive α,β‐unsaturated ketone.

Catalyst‐ and Solvent‐Dependent Stereodivergence in the Intramolecular Et2Zn/Pd0‐Promoted Carbonyl Propargylation: Mechanistic Implications

Carbonyl-tethered propargylic benzoates undergo intramolecular carbonylpropargylation upon treatment with Et2 Zn in the presence of a catalytic amount of Pd(0) with the formation of 2-alkynylcyclopentanol products. A ligand/solvent effect on the cis/trans selectivity (referring to the relative positions of alkynyl and OH groups) of ring-closure has been found. In a non-coordinating solvent (benzene), increasing the electron-donating ability of the phosphine ligand (while decreasing its dissociation ability) leads to an increased tendency towards the trans product. On the other hand, the combination of a coordinating solvent (THF) and PPh3 , an easily dissociated phosphine, results in the exclusive formation of cis products. Experimental and computational results are compatible with a divergent behavior of an allenylethylpalladium intermediate that partitions between competitive carbonyl-addition and transmetalation pathways, each leading to a different diastereoisomer. These results also suggest that the dissociating ability of the phosphine regulates that behavior.