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Biological invasions are excellent systems to study rapid evolution of plant chemical defenses. Current hypotheses predict a divergence of plant chemical defenses in response to a decrease in herbivory after invasion (e.g. EICA hypothesis) or in response to novel climatic conditions. Post-invasive changes in plant chemistry can modify the interactions with herbivores and facilitate invasion success. However, whether plant toxicity is changed after invasion remains to be evaluated. Senecio pterophorus is a shrub native from Eastern South Africa and a recent invader in Western South Africa (~100 years ago), Australia (>70-100 years ago) and Europe (>30 years ago). These distributional regions of S. pterophorus differ in their summer drought stress and in their interactions with herbivores. As other Asteraceae, S. pterophorus contains pyrrolizidine alkaloids (PAs) toxic to vertebrate and invertebrate herbivores. Plants from 54 populations sampled throughout the entire known worldwide distributional area, including the native and three non-native ranges, were grown under controlled conditions. First, we analyzed the levels of chemical defenses and leaf morphological traits to determine whether plant genetically-based traits diverged between native and non-native populations. Second, we performed non-choice bioassays with generalist herbivores (e.g. Spodoptera sp) to evaluate changes in plant toxicity after invasion. Plants from different origins diverged in their chemical and morphological traits. Levels of chemical defenses were higher in the introduced populations, including the highly toxic 1,2-unsaturated PAs and the less toxic 1,2-saturated PAs. These results, indicative of higher toxicity in the invasive range, were consistent with the lower larval growth when insects consumed non-native plants. We discuss what factors, either chemical or morphological, determine the increase in plant toxicity after invasion. By comparing the genetic similarity across the native and non-native areas obtained by neutral markers we evaluate whether changes in toxicity are result of a rapid evolution.

Director de l'Aula d'Ecologia: Jaume Terradas i Serra

Conium maculatum L. (Apiaceae), or poison hemlock, is an invasive plant native to Europe that has become extensively naturalized throughout North America. This species contains piperidine alkaloids, including coniine and -coniceine, that are highly toxic to vertebrates. C. maculatum was relatively free from herbivores in North America until the accidental introduction 30 yr ago of its monophagous European associate Agonopterix alstroemeriana (Clerck) (Lepidoptera: Oecophoridae). At present, A. alstroemeriana is widespread across the United States, and in some areas, such as the Northwest, can inßict substantial damage on its host plant, leading to desiccation and death. A. alstroemeriana has been used in recent years for the biological control of C. maculatum, although its use has been limited by the availability of larvae, which are Þeld-collected from early to mid-spring, and by the lack of available information about its life history and feeding habits. Here we describe a laboratory-rearing protocol incorporating a simulated winter to induce diapause and a semideÞned artiÞcial diet that allows the production of multiple generations per year and enabled us to determine the number and duration of A. alstroemeriana developmental stages. The development of the artiÞcial diet also permitted studies of preference and performance of A. alstroemeriana in relation to hostplant chemistry. Rearing A. alstroemeriana on artiÞcial diet supplemented with 1.5% DW coniine had no adverse impact on ultimate instar growth or performance. In a feeding behavior assay, the presence of coniine in the diet increased A. alstroemeriana consumption three-fold relative to control diet. This behavioral response contrasts dramatically with that of Agonopterix clemensella, a native Apiaceae specialist that does not use C. maculatum as a host; of 30 larvae tested, 29 fed exclusively on diets lacking supplemental coniine. The rearing protocol and artiÞcial diet presented here can facilitate further studies of ecological and evolutionary responses of C. maculatum after its reassociation with a coevolved herbivore in North America.

Conium maculatum is an apiaceous species native to Eurasia that is highly toxic to vertebrates due to the presence of piperidine alkaloids, including coniine and γ-coniceine. More than 200 years after invading the United States this species remains mostly free from generalist insect herbivores. The presence of novel chemical defenses in the introduced range could provide invasive species with a competitive advantage relative to native plants. The cabbage looper (Trichoplusia ni) is a generalist lepidopteran found throughout the US that occasionally feeds on C. maculatum. We evaluated the toxicity of piperidine alkaloids to T. ni and determined putative resistance mechanisms, both behavioral and physiological, that allows this insect to develop successfully on C. maculatum foliage. T. ni larvae raised on diets enriched with coniine and γ-coniceine showed a decrease in consumption and longer development time, but no effects on growth were found at any alkaloid concentration. In a diet choice experiment T. ni larvae showed no avoidance of alkaloid-enriched diets, suggesting that the deterrence produced by alkaloids was related to a post-ingestive metabolic response. The ability of T. ni to consume diets high in alkaloid content could be due to at least three different mechanisms: 1) a decreased consumption rate, 2) efficient excretion of at least 1/3 of ingested alkaloids unmetabolized in frass, and 3) partial detoxification of alkaloids by cytochrome P450s, as shown by the decreased larval growth in the presence of piperonyl butoxide, a P450 inhibitor. Even though T. ni tolerates C. maculatum alkaloids, the use of this species as a host plant could be ecologically disadvantageous due to prolonged larval growth and thus increased exposure to predators. Novel plant secondary compounds do not guarantee increased resistance to generalist herbivores.

Divergence in plant traits and trait plasticity after invasion has been proposed as an important mechanism favoring invasion success. Current hypotheses predict a rapid evolution in response to changes in the abiotic conditions after invasion, or to changes in the herbivore consumption pressure caused by a decrease in the enemies associated at the area of origin (e.g. evolution of increased competitive ability -EICA- hypothesis). Here we have evaluated, simultaneously, the role of climate and herbivore consumption on the rapid geographical divergence in plant traits and trait plasticity of the exotic plant Senecio pterophorus (Asteraceae). S. pterophorus is a perennial shrub native from Eastern South Africa and a recent invader in Western South Africa (~100 years ago), Australia (>70-100 years ago) and Europe (>30 years ago). In Australia it has been declared a noxious weed subject to eradication. The four distributional regions of S. pterophorus differ in their summer drought stress and in their interactions with herbivores. We performed a common garden experiment with plants sampled throughout the entire known distributional area of S. pterophorus in the native and non-native ranges to test geographical differences in individual-level traits, leaf-level traits and reproductive-level traits, and their plastic response to water availability. Native and non-native populations differed in plant traits, but not in trait plasticity, in response to their local climatic conditions. However, our results are contrary to the role of herbivory as a selective factor after invasion.

Host plant selection by ovipositing females is a key process determining the success of phytophagous insects. In oligophagous lepidopterans, host-specific plant secondary chemicals are expected to be dominant factors governing oviposition behavior; distinctive compounds can serve as high-contrast signals that clearly differentiate confamilial hosts from non-hosts increasing the accuracy of host quality evaluation. Agonopterix alstroemeriana (Clerk) (Lepidoptera: Oecophoridae) and Conium maculatum L. (Apiaceae) form an extremely specialized plant-herbivore system, with A. alstroemeriana monophagous on C. maculatum, a plant with few other insect herbivores at least in part due to its virtually unique capacity among plants to produce piperidine alkaloids. Here we have studied the response of A. alstroemeriana oviposition to unique host plant secondary metabolites, piperidine alkaloids, and widespread compounds, mono- and sesquiterpenes, in a concentration-dependent fashion. Rates of oviposition were negatively correlated with Z-ocimene concentrations. To confirm the deterrent properties of this monoterpene for A. alstroemeriana oviposition, we conducted a choice experiment using artificially damaged C. maculatum plants, with higher emission of volatiles, and undamaged control plants. Damaged plants were less preferred as oviposition sites compared to the controls. The lack of association between oviposition and piperidine alkaloids, defenses unique to Conium species, suggests that quantitative changes of these species-specific chemicals do not play a predominant role in host selection by the monophagous A. alstroemeriana.

Descripció del recurs: 13 juny 2007 Conté: Rafael Argullol, Natura i ciutat en el canvi de mil·lenni ; Antoni Lloret, Energies per al segle XXI ; Jorge Wagensberg, Investigació científica i sostenibilitat: l'experiència amazònica ; Manuel Ludevid, El paper de les empreses en la societat sostenible ; Rafael Grasa, El paper de les ONG en la societat sostenible ; Luis Ángel Fernández Hermana, La comunicació en la transició cap a una societat sostenible ; Frederic Ximeno, Estratègies i eines de planificació territorial cap a una ciutat sostenible ; José Luis Porcuna, Estratègies agroecològiques cap a una agricultura sostenible ; Josep Germain, Estratègia catalana per a la biodiversitat ; Carles Gràcia, Els boscos i el funcionament sostenible del planeta ; Manuel Herce, El territori de la ciutat: criteris de sostenibilitat, ordenació i urbanització ; Josep Enric Llebot, Ciència i política del canvi climàtic ; Àlex Aguilar, L'extinció de les espècies: entre la ignorància i la tolerància ; Josep Olives, La ciutat com a idea d'equilibri ; Anna Cabré, Demografia i migracions al segle XXI: què és raonable preveure? ; Manolis Kogevinas, Càncer i exposicions mediambientals ; Ramon Arandes, L'aprofitament de les aigües del subsòl de Barcelona ; Rafael Simó, L'oceà i l'atmosfera, inseparables davant el canvi climàtic global ; Joan Caylà, Sobre el possible impacte mundial de la sida en la dècada 2000-2010 ; Jordi Serra Raventós, Ocupació del litoral i implicacions sobre el territori ; Joan Manuel Vilaplana, Catàstrofes i societat ; Montserrat Vilà, Causes i conseqüències de les invasions biològiques ; Josep Egozcue, Clonatge humà: tècnica i ètica ; Millán M. Millán, Contaminación fotoquímica en la cuenca mediterránea: revisión de los resultados de proyectos de investigación europeos ; Jaume Terradas i José Ángel Burriel, Mapa ecològic de Barcelona.

Altres ajuts: CICYT/AMB94-0199 Els alcaloides són un grup de productes del metabolisme secundari altament divers i distribuït majoritàriament en les angiospermes. En les plantes se'ls atribueix com a principal funció la defensa química contra herbívors i patògens. Les plantes alcalòidiques es localitzen preferentment a les regions tropicals i acostumen a ser plantes de creixement ràpid i de vida curta. Les concentracions d'alcaloides, més elevades en determinats òrgans i en períodes concrets del desenvolupament de la planta, sembla que són determinades pels constrenyiments evolutius ocasionats pels recursos del medi on la planta ha evolucionat, per la història coevolutiva entre plantes i fitòfags i per l'ambient físic immediat de la planta, principalment pels nutrients disponibles durant el seu cicle vital. Diverses hipòtesis han intentat explicar la variabilitat interespecífica i intraespecífica de defenses tractant aspectes particulars d'aquests factors. Basant-nos amb dades de plantes alcalòidiques, en aquest article hem elaborat una síntesi de les hipòtesis precedents i discutim la necessitat d'anar cap a una nova teoria global de defensa química. Aquesta nova visió integradora determina un marc conceptual ampli que ens ajuda a interpretar el com i el perquè de la presència i de la diversitat actual de les defenses químiques en plantes. Alkaloids are a large and very diverse group of secondary metabolites found principally in angiosperms. They play a defensive role in plants against herbivores and pathogens. Alkaloid-bearing plants are usually short life plants and they are localized preferently in tropical regions. Alkaloid concentrations vary in different plant parts and different plant development stages. They are determined by resource evolution constraints, by coevolution history between plants and animals and by plant immediate resouce availability. We present a global synthesis of previous plant chemical defense hypothesis in order to stablish a conceptual framework to understand the qualitative and quantitative diversity of plant defenses, with special emphasis on plant alkaloids.

Biological invasions are excellent systems to study rapid evolution of plant chemical defenses. Current hypotheses predict a rapid divergence of plant chemical defenses in response to changes in herbivore consumption pressure caused by a decrease in the enemies from the area of origin (e.g. evolution of increased competitive ability -EICA- hypothesis) or in response to differences in the climatic conditions. Senecio pterophorus (Asteraceae) is a perennial shrub native from Eastern South Africa that has recently invaded Western South Africa, Australia and Europe. The four distributional regions of S. pterophorus differ in their levels of herbivory1 and summer drought stress. Here we evaluated 1) whether native and introduced populations diverged in their genetically-based levels of chemical defenses, and 2) whether these biogeographical differences were driven by post-invasive changes in herbivory or climate. We performed a common garden with 54 populations of S. pterophorus sampled throughout the entire known worldwide distributional area, including the native and three non-native ranges. Genetically-based chemical defense concentrations varied among regions. Contrary to the EICA hypothesis we found higher levels of chemical defenses in the introduced populations. The role of enemy release and summer drought stress are simultaneously evaluated as potential drivers for the evolution of chemical defenses. This is the first study to evaluate rapid evolution of an exotic plant covering the entire known distributional area of a species. 1Castells et al. (2013) Reduced seed predation after invasion supports enemy release in a broad biogeographical survey. Oecologia 173: 1397-1409

Background During the coronavirus disease 2019 (COVID-19) outbreaks, health care workers (HCWs) are at a high risk of infection. Strategies to reduce in-hospital transmission between HCWs and to safely manage infected HCWs are lacking. Our aim was to describe an active strategy for the management of COVID-19 in severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)–infected HCWs and investigate its outcomes. Methods A prospective cohort study of SARS-CoV-2-infected health care workers in a tertiary teaching hospital in Barcelona, Spain, was performed. An active strategy of weekly polymerase chain reaction screening of HCWs for SARS-CoV-2 was established by the Occupational Health department. Every positive HCW was admitted to the Hospital at Home Unit with daily assessment online and in-person discretionary visits. Clinical and epidemiological data were recorded. Results Of the 590 HCWs included in the cohort, 134 (22%) were asymptomatic at diagnosis, and 15% (89 patients) remained asymptomatic during follow-up. A third of positive cases were detected during routine screening. The most frequent symptoms were cough (68%), hyposmia/anosmia (49%), and fever (41%). Ten percent of the patients required specific treatment at home, while only 4% of the patients developed pneumonia. Seventeen patients required a visit to the outpatient clinic for further evaluation, and 6 of these (1%) required hospital admission. None of the HCWs included in this cohort required intensive care unit admission or died. Conclusions Active screening for SARS-CoV-2 among HCWs for early diagnosis and stopping in-hospital transmission chains proved efficacious in our institution, particularly due to the high percentage of asymptomatic HCWs. Follow-up of HCWs in Hospital at Home units is safe and effective, with low rates of severe infection and readmission.

Supplemental material, sj-pdf-1-hol-10.1177_0959683620981677 for Buxus sempervirens and Laurus nobilis leaves from an archaeological site at 7300 cal BP (La Draga, Spain) provide a better understanding of past vegetation and human activities by Eva Castells, Valentina Araya-Piqué, Ada Behncké and Raquel Piqué in The Holocene

Les plantes invasores poden modificar la composició, l'estructura i el funcionament dels ecosistemes que colonitzen i sembla que podrien canviar la seva pròpia composició química i toxicitat. Per tal d'esbrinar si es produeixen aquests darrers canvis, el grup d'Ecologia Química i Toxicologia de la UAB ha analitzat la concentració de certes molècules de l'arbust Senecio pterophorus que són tòxiques per a organismes invertebrats i vertebrats en plantes recol·lectades a la seva zona nativa i en tres regions on s'ha convertit en espècie invasora. Las plantas invasoras pueden modificar la composición, la estructura y el funcionamiento de los ecosistemas que colonizan y parece que podrían cambiar su propia composición química y toxicidad. Para averiguar si se producen estos últimos cambios, el grupo de Ecología Química y Toxicología de la UAB ha analizado la concentración de ciertas moléculas del arbusto Senecio pterophorus que son tóxicas para organismos invertebrados y vertebrados en plantas recolectadas en su zona nativa y en tres regiones donde se ha convertido en especie invasora. Exotic plants can strongly affect the composition, structure and functioning of the invaded ecosystems and it seems that they are able to change their own chemical composition and toxicity. To determine whether these changes actually take place, the Chemical Ecology and Toxicology group at the UAB analysed the concentration of certain molecules of the Senecio pterophorus shrub toxic to vertebrates and invertebrates in plants collected in their native environment and in three non-native environments.

Les espècies d'origen sud-africà Senecio inaequidens i Senecio pterophorus envaeixen diferents hàbitats del Parc Natural del Montseny. L'establiment de noves interaccions amb els herbívors locals pot afectar negativament l'èxit d'invasió de les espècies exòtiques. Per tal de conèixer el paper dels insectes locals en el potencial invasor de S. inaequidens i S. pterophorus, com també els factors que influeixen en l'establiment de noves interaccions, es va fer un mostreig de sis localitats on coexistien les dues espècies exòtiques. Els resultats obtinguts mostren que algunes espècies d'insectes incorpporen a la seva dieta les espècies exòtiques consumint-ne les llavors. No obstant això, la pressió d'herbivorisme resultant de les noves interaccions podria no ser quantitativament suficient per alentir el procés d'invasió. No es descarta que en un futur els insectes locals puguin provocar efectes més significatius sobre la reproducció de les espècies exòtiques.

Una espècie exòtica es converteix en espècie invasora quan forma poblacions estables que s'expandeixen pel nou territori. Una de les hipòtesis que intenta explicar aquest procés prediu que les plantes exòtiques s'alliberen dels consumidors que tenien associats a l'àrea d'origen. Un estudi a nivell biogeogràfic que abraça tota l'àrea de distribució coneguda de l'arbust Senecio pterophorus mostra per primera vegada evidències consistents sobre la disminució d'herbívors després de la invasió d'aquesta espècie. Una especie exótica se convierte en especie invasora cuando forma poblaciones estables que se expanden por el nuevo territorio. Una de las hipótesis que intenta explicar este proceso predice que las plantas exóticas se liberan de los consumidores que tenían asociados en el área de origen. Un estudio a nivel biogeográfico que abarca toda el área de distribución conocida del arbusto Senecio pterophorus muestra por primera vez evidencias consistentes sobre la disminución de herbívoros después de la invasión de esta especie. An exotic species becomes an invasive one when it forms stable populations that expand on the new territory. One hypothesis attempting to explain this process predicts that exotic plants lose the herbivores associated with their area of origin. A biogeographical study covering the entire known distributional area of the shrub Senecio pterophorus shows for the first time consistent evidence of the decline of herbivores after the invasion of this species.