Tidal Influence on Seismic Activity During the 2011–2013 El Hierro Volcanic Unrest

The El Hierro volcanic unrest started in July 2011, with an increase in observed seismicity rates and surface deformation. After the initial onset, hypocenters migrated southward through September 2011, culminating in a submarine eruption beginning on October 10, 2011 and finishing in February 2012. The seismic activity continued, with remarkable periods of unrest through 2012 and 2013. The most significant episodes of seismic activity during this unrest are related to magma migration at depth. In this work, we compute tidal stress for each earthquake, at its hypocenter depth, and assign them a tidal stress phase angle. We have found statistically significant correlations between the occurrence of earthquakes and tidal stress phase angles, corresponding mainly to increasing tidal stress change rates. We found primarily that the magnitude of vertical and E‐W horizontal tidal stress values and their changing rates with time were correlated with earthquake occurrence times. We also found that there is no correlation between tides and seismicity at times with no observed surface displacements, suggesting that tidal modulation might be related to overpressure during migration of magma. Tidal modulation changes with depth and the influence of ocean‐loading tides is stronger than the influence of solid Earth tides. Our results support the hypothesis that tidal stress may modulate the seismicity during volcanic unrest, particularly during shallow depth magma migration.

Miguelsanz, Luis; González, Pablo J.; Tiampo, Kristy F.; Fernández Torres, José

Tectonics 40(2), e2020TC006201: 1-53 (2021)
DOIDigital.CSIC

A Beginner’s Guide to Osmoprotection by Biostimulants

Water is indispensable for the life of any organism on Earth. Consequently, osmotic stress due to salinity and drought is the greatest threat to crop productivity. Ongoing climate change includes rising temperatures and less precipitation over large areas of the planet. This is leading to increased vulnerability to the drought conditions that habitually threaten food security in many countries. Such a scenario poses a daunting challenge for scientists: the search for innovative solutions to save water and cultivate under water deficit. A search for formulations including biostimulants capable of improving tolerance to this stress is a promising specific approach. This review updates the most recent state of the art in the field.

Jiménez-Arias, David; García-Machado, Francisco J.; Morales-Sierra, Sarai; García-García, Ana L.; Herrera, Antonio J.; Valdés, Francisco; Luis, Juan C.; Borges, Andrés A.

Plants 10(2), 363: 1-24 (2021)
DOIDigital.CSIC

Structural Diversity using Hyp “Customizable Units”: Proof‐of‐Concept Synthesis of Sansalvamide‐Related Antitumoral Peptides

The potential of “customizable units” to generate structural diversity for biological screenings is highlighted in this proof‐of‐concept synthesis of new peptides related to the potent antitumoral Sansalvamide A. Using L‐4‐hydroxyproline (Hyp) as a customizable unit in a linear parent peptide, an improved procedure for selective peptide modification was developed. A divergent Hyp scission‐reductive amination process was carried out, affording five linear peptides with cationic residues, and notably, an N‐alkyl moiety that affected the conformation of the peptide. After two steps (saponification and macrocyclization), sixteen differently N1‐substituted linear and cyclic peptides were obtained. For the first time, the activity of the linear and cyclic compounds was compared. Not only some linear analogs but also cyclic compounds with scarcely studied cationic residues were active against MCF7 breast cancer line. Thus, the structural diversity generated from customizable units can be valuable in drug discovery.

Cuevas, Fernando; Saavedra, Carlos J.; Romero-Estudillo, Iván; Boto, Alicia; Ordóñez, Mario; Vergara, Irene

European Journal of Organic Chemistry (6): 933-943 (2021)
DOIDigital.CSIC

Ovary Signals for Pollen Tube Guidance in Chalazogamous Mangifera indica L.

Most flowering plants show porogamy in which the pollen tubes reach the egg apparatus through the micropyle. However, several species show chalazogamy, an unusual pollen tube growth, in which the pollen tubes reach the embryo sac through the chalaza. While ovary signals for pollen tube growth and guidance have been extensively studied in porogamous species, few studies have addressed the process in chalazogamous species such as mango (Mangifera indica L.), one of the five most important fruit crops worldwide in terms of production. In this study, we characterize pollen–pistil interaction in mango, paying special attention to three key players known to be involved in the directional pollen tube growth of porogamous species such as starch, arabinogalactan proteins (AGPs), and γ-aminobutyric acid (GABA). Starch grains were observed in the style and in the ponticulus at anthesis, but their number decreased 1 day after anthesis. AGPs, revealed by JIM8 and JIM13 antibodies, were homogenously observed in the style and ovary, but were more conspicuous in the nucellus around the egg apparatus. GABA, revealed by anti-GABA antibodies, was specifically observed in the transmitting tissue, including the ponticulus. Moreover, GABA was shown to stimulate in vitro mango pollen tube elongation. The results support the heterotrophic growth of mango pollen tubes in the style at the expense of starch, similarly to the observations in porogamous species. However, unlike porogamous species, the micropyle of mango does not show high levels of GABA and starch, although they were observed in the ponticulus and could play a role in supporting the unusual pollen tube growth in chalazogamous species.

Lora Cabrera, Jorge; Pérez Méndez, Verónica; Herrero Romero, María; Hormaza Urroz, José Ignacio

Frontiers in Plant Science 11, 601706: 1-15 (2021)
DOIDigital.CSIC

Bioactive Metabolites from the Endophytic Fungus Aspergillus sp. SPH2

In the current study, an ethyl acetate extract from the endophytic fungus Aspergillus sp. SPH2 isolated from the stem parts of the endemic plant Bethencourtia palmensis was screened for its biocontrol properties against plant pathogens (Fusarium moniliforme, Alternaria alternata, and Botrytis cinerea), insect pests (Spodoptera littoralis, Myzus persicae, Rhopalosiphum padi), plant parasites (Meloidogyne javanica), and ticks (Hyalomma lusitanicum). SPH2 gave extracts with strong fungicidal and ixodicidal effects at different fermentation times. The bioguided isolation of these extracts gave compounds 1–3. Mellein (1) showed strong ixodicidal effects and was also fungicidal. This is the first report on the ixodicidal effects of 1. Neoaspergillic acid (2) showed potent antifungal effects. Compound 2 appeared during the exponential phase of the fungal growth while neohydroxyaspergillic acid (3) appeared during the stationary phase, suggesting that 2 is the biosynthetic precursor of 3. The mycotoxin ochratoxin A was not detected under the fermentation conditions used in this work. Therefore, SPH2 could be a potential biotechnological tool for the production of ixodicidal extracts rich in mellein.

Morales-Sánchez, Viridiana; Díaz, Carmen E.; Trujillo, Elena; Olmeda, Sonia A.; Valcarcel, Félix; Muñoz, Rubén; Andrés, María Fe; González-Coloma, Azucena 

Journal of Fungi 7(2), 109: 1-11 (2021)
DOIDigital.CSIC

Anthropogenic Perturbations to the Atmospheric Molybdenum Cycle

Molybdenum (Mo) is a key cofactor in enzymes used for nitrogen (N) fixation and nitrate reduction, and the low availability of Mo can constrain N inputs, affecting ecosystem productivity. Natural atmospheric Mo aerosolization and deposition from sources such as desert dust, sea‐salt spray, and volcanoes can affect ecosystem function across long timescales, but anthropogenic activities such as combustion, motor vehicles, and agricultural dust have accelerated the natural Mo cycle. Here we combined a synthesis of global atmospheric concentration observations and modeling to identify and estimate anthropogenic sources of atmospheric Mo. To project the impact of atmospheric Mo on terrestrial ecosystems, we synthesized soil Mo data and estimated the global distribution of soil Mo using two approaches to calculate turnover times. We estimated global emissions of atmospheric Mo in aerosols (<10 μm in diameter) to be 23 Gg Mo yr‐1, with 40 to 75% from anthropogenic sources. We approximated that for the top meter of soil, Mo turnover times range between 1,000 to 1,000,000 years. In some industrialized regions, anthropogenic inputs have enhanced Mo deposition 100‐fold, lowering the soil Mo turnover time considerably. Our synthesis of global observational data, modeling, and a mass balance comparison with riverine Mo exports suggest that anthropogenic activity has greatly accelerated the Mo cycle, with potential to influence N‐limited ecosystems.

Wong, Michelle Y.; Rathod, Sagar D.; Marino, Roxanne; Li, Longlei; Howarth, Robert W.; Alastuey, Andres; Alaimo, Maria Grazia; Barraza, Francisco; Carneiro, Manuel Castro; Chellam, Shankararaman; Chen Yu-Cheng; Cohen, David D.; Connelly, David; Dongarra, Gaetano; Gomez, Dario; Hand, Jenny; Harrison, R.M.; Hopke, Philip K.; Hueglin, Christoph; Kuang, Yuan-wen; Lambert, Fabrice; Liang, James; Losno, Remi; Maenhaut, Willy; Milando, Chad; Couto Monteiro, Maria Inês; Morera-Gómez, Yasser; Querol, Xavier; Rodríguez, Sergio; Smichowski, Patricia; Varrica, Daniela; Xiao, Yi-hua; Xu, Yangjunjie; Mahowald, Natalie M.

Global Biogeochemical Cycles (2021)
DOIDigital.CSIC

Exploring the role of life history traits and introduction effort in understanding invasion success in mammals: a case study of Barbary ground squirrels

Invasive species–species that have successfully overcome the barriers of transport, introduction, establishment, and spread—are a risk to biodiversity and ecosystem function. Introduction effort is one of the main factors underlying invasion success, but life history traits are also important as they influence population growth. In this contribution, we first investigated life history traits of the Barbary ground squirrel, Atlantoxerus getulus, a species with a very low introduction effort. We then studied if their invasion success was due to a very fast life history profile by comparing their life history traits to those of other successful invasive mammals. Next, we examined whether the number of founders and/or a fast life history influences the invasion success of squirrels. Barbary ground squirrels were on the fast end of the “fast-slow continuum”, but their life history was not the only contributing factor to their invasion success, as the life history profile is comparable to other invasive species that do not have such a low introduction effort. We also found that neither life history traits nor the number of founders explained the invasion success of introduced squirrels in general. These results contradict the concept that introduction effort is the main factor explaining invasion success, especially in squirrels. Instead, we argue that invasion success can be influenced by multiple aspects of the new habitat or the biology of the introduced species.

van der Marel, Annemarie; Waterman, Jane M.; López-Darias, Marta

Oecologia 195: 327–339(2021)
DOIDigital.CSIC

Time-Scales of Inter-eruptive Volcano Uplift Signals: Three Sisters Volcanic center, Oregon (USA)

A classical inflation-eruption-deflation cycle of a volcano is useful to conceptualize the time-evolving deformation of volcanic systems. Such a model predicts accelerated uplift during pre-eruptive periods, followed by subsidence during the co-eruptive stage. Some volcanoes show puzzling persistent uplift signals with minor or no other geophysical or geochemical variations, which are difficult to interpret. Such temporal behaviors are usually observed in large calderas (e.g., Yellowstone, Long Valley, Campi Flegrei, Rabaul), but less commonly for stratovolcanoes. Volcano deformation needs to be better understood during inter-eruptive stages, to assess its value as a tool for forecasting eruptions and to understand the processes governing the unrest behavior. Here, we analyze inter-eruptive uplift signals at Three Sisters, a complex stratovolcano in Oregon (United States), which in recent decades shows persistent inter-eruptive uplift signals without associated eruptive activity. Using a Bayesian inversion method, we re-assessed the source characteristics (magmatic system geometry and location) and its uncertainties. Furthermore, we evaluate the most recent evolution of the surface deformation signals combining both GPS and InSAR data through a new non-subjective linear regularization inversion procedure to estimate the 26 years-long time-series. Our results constrain the onset of the Three Sisters volcano inflation to be between October 1998 and August 1999. In the absence of new magmatic inputs, we estimate a continuous uplift signal, at diminishing but detectable rates, to last for few decades. The observed uplift decay observed at Three Sisters is consistent with a viscoelastic response of the crust, with viscosity of ∼1018 Pa s around a magmatic source with a pressure change which increases in finite time to a constant value. Finally, we compare Three Sisters volcano time series with historical uplift at different volcanic systems. Proper modeling of scaled inflation time series indicates a unique and well-defined exponential decay in temporal behavior. Such evidence supports that this common temporal evolution of uplift rates could be a potential indicator of a rather reduced set of physical processes behind inter-eruptive uplift signals.

Rodríguez-Molina, Sara; González, Pablo J.; Charco, María; Negredo, Ana M.; Schmidt, David A.

Frontiers in Earth Science 8, 645: 1-30 (2021)
DOIDigital.CSIC

ENMTools 1.0: an R package for comparative ecological biogeography

The ENMTools software package was introduced in 2008 as a platform for making measurements on environmental niche models (ENMs, frequently referred to as species distribution models or SDMs), and for using those measurements in the context of newly developed Monte Carlo tests to evaluate hypotheses regarding niche evolution. Additional functionality was later added for model selection and simulation from ENMs, and the software package has been quite widely used. ENMTools was initially implemented as a Perl script, which was also compiled into an executable file for various platforms. However, the package had a number of significant limitations; it was only designed to fit models using Maxent, it relied on a specific Perl distribution to function, and its internal structure made it difficult to maintain and expand. Subsequently, the R programming language became the platform of choice for most ENM studies, making ENMTools less usable for many practitioners. Here we introduce a new R version of ENMTools that implements much of the functionality of its predecessor as well as numerous additions that simplify the construction, comparison and evaluation of niche models. These additions include new metrics for model fit, methods of measuring ENM overlap, and methods for testing evolutionary hypotheses. The new version of ENMTools is also designed to work within the expanding universe of R tools for ecological biogeography, and as such includes greatly simplified interfaces for analyses from several other R packages.

Warren, Dan L.; Matzke, Nicholas J.; Cardillo, Marcel; Baumgartner, John B.; Beaumont, Linda J.; Turelli, Michael; Glor, Richard E.; Huron, Nicholas A.; Simões, Marianna; Iglesias, Teresa L.; Piquet, Julien C.; Dinnage, Russell

Ecography 44: 1-8 (2021)
DOIDigital.CSIC

Are Computational Methods Useful for Structure Elucidation of Large and Flexible Molecules? Belizentrin as a Case Study

Quantum mechanical NMR methods are progressively becoming decisive in structure elucidation. However, problems arise using low-level calculations for complex molecules, whereas methods using higher levels of theory are not practical for large molecules. This report outlines a synergistic effort employing computationally inexpensive quantum mechanical NMR calculations with conformer selection incorporating 3JHH values as a way to solve the structure of large, complex, and highly flexible molecules using readily available computational resources with belizentrin as a case study.

Hernández Daranas, Antonio; Sarotti, Ariel M.

Organic Letters 23(2): 503–507 (2021)
DOIDigital.CSIC