Herbivory is an important ecological filter, affecting plant establishment in restoration sites. One group of herbivores whose abundance has been increasing with environmental changes are the ...leaf-cutting ants (LCA). Here we evaluated the influence of the surrounding landscape on Atta sexdens nest density in restoration sites, by testing the hypothesis that sites farthest from forest fragments or with less surrounding habitat cover have higher nest density. The study was conducted in eleven reforestations with native species, amidst an agricultural matrix in southern Brazil. For each site, we estimated LCA nest density (active, inactive and total) and landscape metrics (distance to nearest forest fragment, surrounding habitat area and an index combining both distance and surrounding habitat area, the Proximity Index). There were negative relationships between active and total nest density and surrounding habitat area. These results suggest that increased isolation from forest fragments is a factor contributing to the relaxation of top-down control. Therefore, the increase in A. sexdens population density in restoration sites is a result, at least in part, of low pressure from natural enemies, since LCA are not limited by resource availability.
Leaf‐cutting ants (LCA) are generalist herbivores capable of causing severe plant damage. Negative impacts of ant herbivory vary according to the density of nests and availability of palatable ...plants; however, it is not yet clear how these herbivores affect tropical forest restoration sites. To investigate how LCA preference affects plant species performance, we evaluated the herbivory of Atta sexdens rubropilosa on native tree species seedlings in Atlantic Forest restoration sites. We expected pioneer species to suffer higher herbivory by LCA when compared with non‐pioneer species and that species with higher damage will have poorer growth and higher mortality. The experiment was conducted in three restoration sites in northern Paraná state, southern Brazil, with 1,500 seedlings of 5 pioneer and 5 non‐pioneer species. Sites share similar age, stand size, tree species composition, and LCA nest density. The number of attacks, degree of leaf damage, number of leaves, plant height, and survival were recorded. Specific leaf area, leaf polyphenols, flavonoids, tannins, and nitrogen content were analyzed for each species. Plant damage was similar between pioneer and non‐pioneer plant species. This could be explained by trait variability among species in each group and by LCA generalist foraging. Preferred species suffered decreases in growth and survival. Less preferred species suffered fewer ant attacks and no change in performance. Results suggest that ant herbivory can influence plant species establishment and thus species composition in restoration sites by reducing performance and increasing mortality of some, but not all species, making LCA an important ecological filter.
in Portuguese is available with online material.
➨Resumo
Formigas cortadeiras são herbívoros generalistas, causadores de altas taxas de dano às plantas. Os impactos negativos da herbivoria variam de acordo com a densidade de ninhos e a disponibilidade de plantas palatáveis. Entretanto, ainda não está bem claro como estas formigas afetam as comunidades vegetais em áreas de restauração ecológica com espécies nativas. Para investigar como a preferência destas formigas afeta o recrutamento de espécies vegetais, avaliamos a herbivoria de Atta sexdens rubropilosa em mudas de espécies arbóreas nativas em sítios de restauração da Mata Atlântica. Esperamos que as espécies pioneiras terão maior taxa de herbivoria pelas formigas cortadeiras quando comparadas com as espécies não pioneiras, e que as espécies com maior dano terão menor crescimento e maior mortalidade. O experimento foi conduzido em três sítios de restauração localizados no norte do estado do Paraná, região Sul do Brasil, transplantamos 1,500 mudas de cinco espécies pioneiras e cinco não pioneiras. Os sítios têm idade, largura da faixa de restauração, composição de espécies arbóreas e densidade de formigueiros similares. Grau de dano foliar, número de ataques, número de folhas, crescimento em altura e sobrevivência foram medidos em campo. Para cada espécie também foram estimadas a área foliar específica e a concentração de polifenóis, flavonóides, taninos condensados e nitrogênio. O nível de dano foi semelhante entre as espécies pioneiras e não pioneiras. Isso pode ser explicado pela variabilidade das características entre as espécies de cada grupo e pelo forrageamento generalista de LCA. As espécies mais preferidas cresceram menos e tiveram maior mortalidade. As espécies menos preferidas sofreram menos ataques de formigas e nenhuma alteração no desempenho. Os resultados sugerem que a herbivoria pelas formigas cortadeiras pode influenciar o estabelecimento das espécies vegetais e, portanto, a composição das espécies nos locais de restauração, reduzindo o desempenho e aumentando a mortalidade de algumas, mas não de todas as espécies, tornando as formigas cortadeiras um importante filtro ecológico.
There are reports suggesting that leaf-cutting ants can act as a biotic filter, selecting plant traits according to foraging preferences, and consequently affecting the species composition of plant ...communities. In order to test this hypothesis, we evaluated the relationship between the floristic and functional diversity of woody plants in fragments of Semideciduous Seasonal Atlantic Forest (SAF) with the presence or absence of
Atta sexdens
(Linnaeus, 1758) nests. We expected that, in places where
A. sexdens
nests is present, 1) floristic diversity is lower and 2) the plant community is dominated by species characterized by greater investment in anti-herbivore defenses and lower nutritional content. For this, we sampled nine SAF fragments in the north of Paraná state, in Brazil. The diversity of woody regenerants (> 1 m in height, < 2 cm diameter) was estimated and 10 functional traits were evaluated: gap dependence, deciduousness, leaf nitrogen and carbon content, leaf C/N ratio, presence of leaf trichomes, leaf thickness, specific leaf area, presence of latex and condensed tannins, for the 28 most abundant woody species. Contrary to expectations, there were no differences in floristic diversity between sites with or without
A. sexdens
, and functional diversity was also similar, reflecting the floristic similarity. We suggest that the herbivory pressure by
A. sexdens
on the woody regenerants of SAF fragments is not strong enough to cause significant mortality in individual species and, consequently, affect plant diversity and composition. This may in part be related to the fact that most nests of
A. sexdens
were established in the edges of the fragments and that ants from these nests forage not only in the forest but also in the agricultural matrix where food resources are abundant. We also suggest that longer-term studies are still needed to fully elucidate the effects of
A. sexdens
on the plant community of Atlantic Forest fragments.
•Caatinga deforestation by bare soil affects the soil properties.•Successive years of agricultural practices affected soil bulk density and total porosity.•Farmland abandonment has affects pH, and ...the content of various chemical elements.•Caatinga deforestation increases the minimum temperature, and vapor pressure deficit.•It is very likely that Caatinga removal promotes a reduction in precipitation.
The Brazilian semiarid region has been subjected to strong man-made actions since the 1970s, which have resulted in landscape transformation. The scientific literature presents several studies on the soil properties or microclimate of different types of landscapes; however, less attention was having been paid to the surface contrast between native vegetation and bare soil. The objective of this research was to evaluate the soil properties and microclimate of two common landscapes in the Brazilian semiarid region, a seasonally dry tropical forest (Caatinga) and a deforested area. Soil and microclimate data were obtained from two sites, both located in the State of Pernambuco, Brazil. Soil samples were collected on six dates and from layers, and microclimate variables were measured for three years. Soil properties and microclimatic data were evaluated using the Mann-Whitney test, as well as regression and principal component analysis. Successive years of agricultural practices affected the bulk density, promoting an increase in the total porosity of the soil in the deforested area site. In addition, changes were verified in the magnitude of many chemical properties (pH, P, K+, Mg2+, Cu2+, Fe, Mn, Zn2+ and Ca2+), indicating soil degradation. Compared with the Caatinga forest site, the minimum air temperature was 2.3 °C, and the maximum vapor pressure deficit was 7% higher in the deforested area site, and it is very likely that Caatinga removal there will lead to a reduction in precipitation. The results suggest that Caatinga vegetation removal followed by agricultural practices and subsequent land abandonment promotes significant changes in soil properties and the microclimate, which can contribute to advances in desertification and affects agricultural activities in the Brazilian semiarid region.
The influence of linkage disequilibrium (LD), epistasis, and inbreeding on genotypic variance continues to be an important area of investigation in genetics and evolution. Although the current ...knowledge about biological pathways and gene networks indicates that epistasis is important in determining quantitative traits, the empirical evidence for a range of species and traits is that the genotypic variance is most additive. This has been confirmed by some recent theoretical studies. However, because these investigations assumed linkage equilibrium, considered only additive effects, or used simplified assumptions for two- and higher-order epistatic effects, the objective of this investigation was to provide additional information about the impact of LD and epistasis on genetic variances in noninbred and inbred populations, using a simulated dataset.
In general, the most important component of the genotypic variance was additive variance. Because of positive LD values, after 10 generations of random crosses there was generally a decrease in all genetic variances and covariances, especially the nonepistatic variances. Thus, the epistatic variance/genotypic variance ratio is inversely proportional to the LD level. Increasing inbreeding increased the magnitude of the additive, additive x additive, additive x dominance, and dominance x additive variances, and decreased the dominance and dominance x dominance variances. Except for duplicate epistasis with 100% interacting genes, the epistatic variance/genotypic variance ratio was proportional to the inbreeding level. In general, the additive x additive variance was the most important component of the epistatic variance. Concerning the genetic covariances, in general, they showed lower magnitudes relative to the genetic variances and positive and negative signs. The epistatic variance/genotypic variance ratio was maximized under duplicate and dominant epistasis and minimized assuming recessive and complementary epistasis. Increasing the percentage of epistatic genes from 30 to 100% increased the epistatic variance/genotypic variance ratio by a rate of 1.3 to 12.6, especially in inbred populations. The epistatic variance/genotypic variance ratio was maximized in the noninbred and inbred populations with intermediate LD and an average allelic frequency of the dominant genes of 0.3 and in the noninbred and inbred populations with low LD and an average allelic frequency of 0.5.
Additive variance is in general the most important component of genotypic variance. LD and inbreeding have a significant effect on the magnitude of the genetic variances and covariances. In general, the additive x additive variance is the most important component of epistatic variance. The maximization of the epistatic variance/genotypic variance ratio depends on the LD level, degree of inbreeding, epistasis type, percentage of interacting genes, and average allelic frequency.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The aim of this study was to evaluate the effect of different controlled water regimes on the morphophysiological indicators, phenophases, and ideal cutting time of forage cacti clones grown in a ...semiarid environment. From 2016 to 2018, in the semi-arid region of Brazil, the Miúda (MIU), Orelha de Elefante Mexicana (OEM) and IPA Sertânia (IPA) clones were submitted to three regimes (40%, 80% and 120% ETc, where ETc is crop evapotranspiration) and to rainfed conditions (0% ETc). Cladode area index and the dry matter yield (DM) were used for calculating the morphophysiological indices. The cladode emission aided in delimiting the phenophases and, based on the DM accumulation, defined the ideal time for cutting the crop. The OEM clone excelled in terms of dry matter accumulation with a maximum value of 0.0441 Mg ha−1 °Cday−1. The water regimes above 80% ETc rise the number of phenophases in MIU and IPA clones. Cultivating forage cactus under water regime up to 40% ETc for OEM (895 °Cday) and 80% ETc for MIU and IPA (737 °Cday and 708 °Cday, respectively) anticipates the harvest time. Thus, a controlled reduction in the amount of water no negatively impact the growth dynamics, phenology, or cutting time.
•Water regimes changes morphophysiology, phenophase and cutting time of cactus clones.•Cactus O. stricta proved to be more efficient in accumulating dry matter.•Phenophase 2 showed greater sensitivity to increases in the water amount.•Cutting time showed variations due to the clones and, water regimes.•Controlled water deficit brings forward the harvest time of the cactus clones.
Abstract
Ruthenium complexes have been extensively explored as potential molecules for cancer treatment. Considering our previous findings on the remarkable cytotoxic activity exhibited by the ...ruthenium (II) complex 3-hydroxy-4-methoxybenzoate (hmxbato)-
cis
-Ru
II
(ŋ
2
-O
2
CC
7
H
7
O
2
)(dppm)
2
PF
6
against
Leishmania
promastigotes and also the similar metabolic characteristics between trypanosomatids and tumor cells, the present study aimed to analyze the anticancer potential of hmxbato against lung tumor cells, as well as the partial death mechanisms involved. Hmxbato demonstrated selective cytotoxicity against A549 lung tumor cells. In addition, this complex at a concentration of 3.8 µM was able to expressively increase the generation of reactive oxygen species (ROS) in tumor cells, causing an oxidative stress that may culminate in: (1) reduction in cellular proliferation; (2) changes in cell morphology and organization patterns of the actin cytoskeleton; (3) cell arrest in the G2/M phase of the cell cycle; (4) apoptosis; (5) changes in the mitochondrial membrane potential and (6) initial DNA damage. Furthermore, we demonstrated that the induction of programmed cell death can occur by the intrinsic apoptotic pathway through the activation of caspases. It is also worth highlighting that hmxbato exhibited predominant actions on A549 tumor cells in comparison to BEAS-2B normal bronchial epithelium cells, which makes this complex an interesting candidate for the design of new drugs against lung cancer.
El presente artículo tiene como objetivo principal caracterizar las claves de la propuesta aceleracionista de Nick Srnicek y Alex Williams para alcanzar una sociedad postrabajo como parte de su ...proyecto poscapitalista. En un contexto sociopolítico y cultural que glorifica y enaltece al trabajo como única forma válida y significativa para subsistir y autorrealizarse, el aceleracionismo de izquierda —con sus aciertos y fallas— se presenta como una alternativa político-filosófica que destaca, no solo por ofrecer una fuerte crítica a la institución del trabajo y la ética dominante que lo cimenta en tiempos de realismo capitalista, sino también por la búsqueda de corporizar una sociedad postrabajo que sea capaz de independizar a los sujetos del salario. Desde la perspectiva aceleracionista, ante el fracaso neoliberal en atender a las múltiples problemáticas que se desprenden de las lógicas de desarrollo y acumulación capitalistas, lo laboral, en sus variadas expresiones y manifestaciones, no se halla ajeno a los mandatos capitalistas que rigen y estructuran las aspiraciones, deseos y expectativas de los sujetos, donde pobres, desempleados y marginados son estigmatizados en nombre del dinero y del trabajo.
Some metallodrugs that exhibit interesting biological activity contain transition metals such as ruthenium, and have been extensively exploited because of their antiparasitic potential. In previous ...study, we reported the remarkable anti-Leishmania activity of precursor cis-RuIICl2(dppm)2, where dppm = bis(diphenylphosphino)methane, and new ruthenium(II) complexes, cis-RuII(η2-O2CC10H13)(dppm)2PF6 (bbato), cis-RuII(η2-O2CC7H7S)(dppm)2PF6 (mtbato) and cis-RuII(η2-O2CC7H7O2)(dppm)2PF6 (hmxbato) against some Leishmania species. In view of the promising activity of the hmxbato complex against Leishmania (Leishmania) amazonensis promastigotes, the present work investigated the possible parasite death mechanism involved in the action of this hmxbato and its precursor. We report, for the first time, that hmxbato and precursor promoted an increase in reactive oxygen species production, depolarization of the mitochondrial membrane, DNA fragmentation, formation of a pre-apoptotic peak, alterations in parasite morphology and formation of autophagic vacuoles. Taken together, our results suggest that these ruthenium complexes cause parasite death by apoptosis. Thus, this work provides relevant knowledge on the activity of ruthenium(II) complexes against L. (L.) amazonensis. Such information will be essential for the exploitation of these complexes as future candidates for cutaneous leishmaniasis treatment.
Low concentrations (0.52 μM) of the cis-RuII(η2-O2CC7H7O2)(dppm)2PF6 (hmxbato) induced to increased ROS generation, depolarization in mitochondrial membrane potential, DNA cleavage, alterations in the parasite morphology and formation of autophagic vacuoles. Taken together, these findings indicate that this complex induces apoptosis-like death. Display omitted
•Cell death mechanism in Leishmania triggered by ruthenium(II) complexes.•cis-{RuIIη2-O2CC7H7O2bis(diphenylphosphino)methane2}PF6 is abbreviated as hmxbato.•Hmxbato induces apoptosis-like cell death in Leishmania promastigotes.•Hmxbato and its precursor have similar mechanisms of death against promastigotes.•Low concentrations of hmxbato are required to cause death in Leishmania amazonensis.
En este artículo se explica por qué Compromís, alianza entre partidos competidores formada por Iniciativa del Poble Valencià (IdPV) y el Bloc Nacionalista Valencià (Bloc), se ha mantenido de forma ...estable desde el 2008 hasta la actualidad. La teoría ha esgrimido que este tipo de alianzas son inestables y que solo se mantienen en el tiempo si existe desigualdad entre sus partidos. Sin embargo, a través de un nuevo marco de análisis se argumenta que existen otros factores que pueden contribuir a la estabilidad y el mantenimiento de este tipo de alianzas: primero, las alianzas presentan incentivos que pueden ayudar a satisfacer objetivos de los partidos; segundo, la ideología no solo funciona como un elemento que depende de la organización, sino también como un instrumento de los partidos para alcanzar sus fines, entre otros, el mantenimiento de las alianzas. El análisis de la trayectoria y de la evolución ideológica de Compromís y sus partidos permite contrastar las expectativas teóricas presentadas, establecer una causalidad que justifica su mantenimiento y su estabilidad, así como reflexionar sobre las dinámicas ideológicas en las alianzas entre partidos.
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