Connectivity with primary forest determines the value of secondary tropical forests for bird conservation

Species extinctions caused by the destruction and degradation of tropical primary forest may be at least partially mitigated by the expansion of regenerating secondary forest. However, the conservation value of secondary forest remains controversial, and potentially underestimated, since most previous studies have focused on young, single‐aged, or isolated stands. Here, we use point‐count surveys to compare tropical forest bird communities in 20–120‐year‐old secondary forest with primary forest stands in central Panama, with varying connectivity between secondary forest sites and extensive primary forest. We found that species richness and other metrics of ecological diversity, as well as the combined population density of all birds, reached a peak in younger (20‐year‐old) secondary forests and appeared to decline in older secondary forest stands. This counter‐intuitive result can be explained by the greater connectivity between younger secondary forests and extensive primary forests at our study site, compared with older secondary forests that are either (a) more isolated or (b) connected to primary forests that are themselves small and isolated. Our results suggest that connectivity with extensive primary forest is a more important determinant of avian species richness and community structure than forest age, and highlight the vital contribution secondary forests can make in conserving tropical bird diversity, so long as extensive primary habitats are adjacent and spatially connected.Abstract in Spanish is available with online material.     

In‐depth protein profiling of the postsynaptic density from mouse hippocampus using data‐independent acquisition proteomics

Located at neuronal terminals, the postsynaptic density (PSD) is a highly complex network of cytoskeletal scaffolding and signaling proteins responsible for the transduction and modulation of glutamatergic signaling between neurons. Using ion‐mobility enhanced data‐independent label‐free LC‐MS/MS, we established a reference proteome of crude synaptosomes, synaptic junctions, and PSD derived from mouse hippocampus including TOP3‐based absolute quantification values for identified proteins. The final dataset across all fractions comprised 49 491 peptides corresponding to 4558 protein groups. Of these, 2102 protein groups were identified in highly purified PSD in at least two biological replicates. Identified proteins play pivotal roles in neurological and synaptic processes providing a rich resource for studies on hippocampal PSD function as well as on the pathogenesis of neuropsychiatric disorders. All MS data have been deposited in the ProteomeXchange with identifier PXD000590 ( http://proteomecentral.proteomexchange.org/dataset/PXD000590 ).     

New Approaches for Absolute Quantification of Stable‐Isotope‐Labeled Peptide Standards for Targeted Proteomics Based on a UV Active Tag

Targeted proteomics depends on the availability of stable isotope labeled (SIL) peptide standards, which for absolute protein quantification need to be absolutely quantified. In the present study, three new approaches for absolute quantification of SIL peptides are developed. All approaches rely on a quantification tag (Qtag) with a specific UV absorption. The Qtag is attached to the peptide during synthesis and is removed by tryptic digestion under standard proteomics workflow conditions. While one quantification method (method A) is designed to allow the fast and economic production of absolutely quantified SIL peptides, two other methods (methods B and C) are developed to enable the straightforward re‐quantification of SIL peptides after reconstitution to control and monitor known problems related to peptide solubility, precipitation, and adhesion to vials. All methods yield consistent results when compared to each other and when compared to quantification by amino acid analysis. The precise quantitation methods are used to characterize the in vivo specificity of the H3 specific histone methyltransferase EZH2.     

Anti-Cancer Potential of MAPK Pathway Inhibition in Paragangliomas–Effect of Different Statins on Mouse Pheochromocytoma Cells

To date, malignant pheochromocytomas and paragangliomas (PHEOs/PGLs) cannot be effectively cured and thus novel treatment strategies are urgently needed. Lovastatin has been shown to effectively induce apoptosis in mouse PHEO cells (MPC) and the more aggressive mouse tumor tissue-derived cells (MTT), which was accompanied by decreased phosphorylation of mitogen-activated kinase (MAPK) pathway players. The MAPK pathway plays a role in numerous aggressive tumors and has been associated with a subgroup of PHEOs/PGLs, including K-RAS-, RET-, and NF1-mutated tumors. Our aim was to establish whether MAPK signaling may also play a role in aggressive, succinate dehydrogenase (SDH) B mutation-derived PHEOs/PGLs. Expression profiling and western blot analysis indicated that specific aspects of MAPK-signaling are active in SDHB PHEOs/PGLs, suggesting that inhibition by statin treatment could be beneficial. Moreover, we aimed to assess whether the anti-proliferative effect of lovastatin on MPC and MTT differed from that exerted by fluvastatin, simvastatin, atorvastatin, pravastatin, or rosuvastatin. Simvastatin and fluvastatin decreased cell proliferation most effectively and the more aggressive MTT cells appeared more sensitive in this respect. Inhibition of MAPK1 and 3 phosphorylation following treatment with fluvastatin, simvastatin, and lovastatin was confirmed by western blot. Increased levels of CASP-3 and PARP cleavage confirmed induction of apoptosis following the treatment. At a concentration low enough not to affect cell proliferation, spontaneous migration of MPC and MTT was significantly inhibited within 24 hours of treatment. In conclusion, lipophilic statins may present a promising therapeutic option for treatment of aggressive human paragangliomas by inducing apoptosis and inhibiting tumor spread.     

Immune Evasion,Stress Resistance,and Efficient Nutrient Acquisition Are Crucial for Intracellular Survival of Candida glabrata within Macrophages

Candida glabrata is both a human fungal commensal and an opportunistic pathogen which can withstand activities of the immune system. For example, C. glabrata can survive phagocytosis and replicates within macrophages. However, the mechanisms underlying intracellular survival remain unclear. In this work, we used a functional genomic approach to identify C. glabrata determinants necessary for survival within human monocyte-derived macrophages by screening a set of 433 deletion mutants. We identified 23 genes which are required to resist killing by macrophages. Based on homologies to Saccharomyces cerevisiae orthologs, these genes are putatively involved in cell wall biosynthesis, calcium homeostasis, nutritional and stress response, protein glycosylation, or iron homeostasis. Mutants were further characterized using a series of in vitro assays to elucidate the genes'' functions in survival. We investigated different parameters of C. glabrata-phagocyte interactions: uptake by macrophages, replication within macrophages, phagosomal pH, and recognition of mutant cells by macrophages as indicated by production of reactive oxygen species and tumor necrosis factor alpha (TNF-α). We further studied the cell surface integrity of mutant cells, their ability to grow under nutrient-limited conditions, and their susceptibility to stress conditions mirroring the harsh environment inside a phagosome. Additionally, resistance to killing by neutrophils was analyzed. Our data support the view that immune evasion is a key aspect of C. glabrata virulence and that increased immune recognition causes increased antifungal activities by macrophages. Furthermore, stress resistance and efficient nutrient acquisition, in particular, iron uptake, are crucial for intraphagosomal survival of C. glabrata.     

Active contractions in single suspended epithelial cells

Investigations of active contractions in tissue cells to date have been focused on cells that exert forces via adhesion sites to substrates or to other cells. In this study we show that also suspended epithelial cells exhibit contractility, revealing that contractions can occur independently of focal adhesions. We employ the Optical Stretcher to measure adhesion-independent mechanical properties of an epithelial cell line transfected with a heat-sensitive cation channel. During stretching the heat transferred to the ion channel causes a pronounced Ca²⁺ influx through the plasma membrane that can be blocked by adequate drugs. This way the contractile forces in suspended cells are shown to be partially triggered by Ca²⁺ signaling. A phenomenological mathematical model is presented, incorporating a term accounting for the active stress exerted by the cell, which is both necessary and sufficient to describe the observed increase in strain when the Ca²⁺ influx is blocked. The median and the shape of the strain distributions depend on the activity of the cells. Hence, it is unlikely that they can be described by a simple Gaussian or log normal distribution, but depend on specific cellular properties such as active contractions. Our results underline the importance of considering activity when measuring cellular mechanical properties even in the absence of measurable contractions. Thus, the presented method to quantify active contractions of suspended cells offers new perspectives for a better understanding of cellular force generation with possible implications for medical diagnosis and therapy.     

Effects of parental and own early developmental conditions on the phenotype in zebra finches (Taeniopygia guttata)

The performance of an individual can be critically influenced by its experience early in life as well as trans-generationally by the conditions experienced by its parents. However, it remains unclear whether or not the early experience of parents and offspring interact with each other and adapt offspring when the parental and own early environmental conditions match. Here, zebra finches (Taeniopygia guttata) that had experienced either early low or high nutritional conditions raised their offspring under either matched or mismatched nutritional conditions. Parental and offspring early conditions both separately affected the offspring’s adult phenotype, but early conditions experienced by parents and offspring did not interact as predicted. Offspring that grew up under conditions matching those their parents had experienced did not do better than those that grew up in a mismatched environment. Thus, transgenerational effects remain a lifelong burden to the offspring acting in addition to the offspring’s own early life experience. The lack of evidence for adaptive programming to matching environmental conditions may result from non-predictive environments under natural conditions in such opportunistic breeders.     

Facets of diazotrophy in the oxygen minimum zone waters off Peru

Nitrogen fixation, the biological reduction of dinitrogen gas (N₂) to ammonium (NH₄⁺), is quantitatively the most important external source of new nitrogen (N) to the open ocean. Classically, the ecological niche of oceanic N₂ fixers (diazotrophs) is ascribed to tropical oligotrophic surface waters, often depleted in fixed N, with a diazotrophic community dominated by cyanobacteria. Although this applies for large areas of the ocean, biogeochemical models and phylogenetic studies suggest that the oceanic diazotrophic niche may be much broader than previously considered, resulting in major implications for the global N-budget. Here, we report on the composition, distribution and abundance of nifH, the functional gene marker for N₂ fixation. Our results show the presence of eight clades of diazotrophs in the oxygen minimum zone (OMZ) off Peru. Although proteobacterial clades dominated overall, two clusters affiliated to spirochaeta and archaea were identified. N₂ fixation was detected within OMZ waters and was stimulated by the addition of organic carbon sources supporting the view that non-phototrophic diazotrophs were actively fixing dinitrogen. The observed co-occurrence of key functional genes for N₂ fixation, nitrification, anammox and denitrification suggests that a close spatial coupling of N-input and N-loss processes exists in the OMZ off Peru. The wide distribution of diazotrophs throughout the water column adds to the emerging view that the habitat of marine diazotrophs can be extended to low oxygen/high nitrate areas. Furthermore, our statistical analysis suggests that NO₂⁻ and PO₄³⁻ are the major factors affecting diazotrophic distribution throughout the OMZ. In view of the predicted increase in ocean deoxygenation resulting from global warming, our findings indicate that the importance of OMZs as niches for N₂ fixation may increase in the future.     

Thermobiological effects of temperature‐induced color variations in Aglais urticae (Lepidoptera,Nymphalidae)

Coloration of animals is important for camouflage, for social behavior, or for physiological fitness. This study investigates the color variation in adults of Aglais urticae obtained on subjecting some pre‐imaginal stages to different temperature conditions and their thermobiological consequences. To investigate the evolutionary–ecological interactions of temperature and pigmentation in butterflies, caterpillars, and pupae of the small tortoiseshell, Aglais urticae (Lepidoptera, Nymphalidae), larvae from Central Europe and Scandinavia were reared at temperatures between 7 and 34°C in the laboratory or in the field. After emergence, the intensity of pigmentation of the imagines and their increase in body temperature under defined full‐spectrum light irradiation were quantified by image analysis and thermal imaging. At constant conditions, ambient rearing temperature and pigmentation intensity of imagines were negatively and linearly correlated in Central European butterflies, regardless of whether the pupal stage alone or, additionally, the last period of the larval stage was exposed to these conditions: low temperatures induced darker coloration and high temperatures led to lighter individuals. A thermal pulse of a few days alone at the beginning of pupal dormancy led to a similar, albeit weakened, effect. Caterpillars of the Scandinavian subspecies A. urticae polaris, whose pupal dormancy took place under Central European field conditions, developed into strongly pigmented imagines. The thermobiological relevance of more intense pigmentation was shown by significantly higher absorption of light, and thus stronger increased body temperature after 5 min of defined illumination, but this difference ceased after 15 min. Our results show that phenotypic plasticity in wing coloration is adaptive since temperature‐induced developmental changes provide thermobiological benefit in adult butterflies. We propose that, in subpolar latitudes, darker coloration likely has a selection advantage favoring individuals with reaction norms gradually shifted to stronger pigmented phenotypes, possibly leading to the establishment of a pigmentation cline.     

Conservative N cycling despite high atmospheric deposition in early successional African tropical lowland forests

Plant and Soil - Many applied disciplines have recognized problems related to the practice of data analysis within their own communities. Some of them have even declared the existence of a...