Size diversity and species diversity relationships in fish assemblages of Western Palearctic lakes

Body size, coupled with abundance and taxonomy, may help to understand the mechanisms shaping community structure. Since the body size of fish is closely related to their trophic niche, size diversity (based on individual body size) of fish communities may capture intraspecific variations in fish trophic niches that are not detected by species diversity. Thus, the relationship between size diversity and species diversity may help to integrate variation at both intraspecific and interspecific levels. We studied the relationship between species diversity and size diversity as a measure of the degree of overlap in size among species and thereby the potential overlap in niches in a community. We hypothesized that the relationship between size diversity and species would be different across the European continent due to different levels of size overlap in fish communities. The data were derived from samplings of fish communities using standardised benthic gill nets in 363 lakes. At the continental scale, size diversity increased with species diversity; at the ecoregion scale, the slope of the relation changed across the continent, with the greatest mismatch occurring in northern Europe where communities comprised only one or a few species, but each of which exhibited a great range in size. There was an increase in slope towards the south with significant relations for four out of six ecoregions. The steeper size diversity‐species diversity slope at lower latitudes is attributable to a lower overlap in fish size and thus likely to finer niche separation. Our results also suggest that size diversity is not a strong surrogate for species diversity in European lake fish communities. Thus, particularly in fish communities composed of few species, measuring size diversity may help to detect potential functional variation which may be neglected by measuring species diversity alone.     

Liver injury after an aggressive encounter in male mice

Acute and intense psychological stressors induce cell damage in several organs, including the heart and the liver. Much less is known about social stress. In male mice, aggressive behavior is the most common social stressor. It is remarkable that upon fighting, submandibular salivary glands release a number of peptides into the bloodstream including epidermal growth factor (EGF). We showed previously that released EGF protects the heart from cell damage in this particular stressful situation. Here, we studied the effect of an aggressive encounter on the liver and whether EGF has a similar effect on this organ. An aggressive encounter in male mice caused inflammatory response and a transient increase in plasma alanine and aspartate transaminase activities. At 3 h, focal infiltration of neutrophils was observed in liver parenchyma. These cells accumulate on eosinophilic hepatocytes, which may correspond to dying cells. A few hours later, evidence of necrotic lesion was observed. Surgical excision of submandibular glands, sialoadenectomy, did not prevent the rise in plasma EGF concentration and did not affect the increase in plasma transaminase activities. Neither did the administration of tyrphostin AG-1478 (inhibitor of EGF receptor kinase) alter the increase in plasma alanine transaminase activity. However, it did enhance the rise in both aspartate transaminase and creatine kinase activity, suggesting heart damage. We conclude that an aggressive encounter causes mild liver damage and that released EGF does not protect this organ, in contrast to its effect on the heart.     

Deconstructing the native–exotic richness relationship in plants

Aim Classic theory suggests that species‐rich communities should be more resistant to the establishment of exotic species than species‐poor communities. Although this theory predicts that exotic species should be less diverse in regions that contain more native species, macroecological analyses often find that the correlation between exotic and native species richness is positive rather than negative. To reconcile results with theory, we explore to what extent climatic conditions, landscape heterogeneity and anthropogenic disturbance may explain the positive relationship between native and exotic plant richness. Location Catalonia (western Mediterranean region). Methods We integrated floristic records and GIS‐based environmental measures to make spatially explicit 10‐km grid cells. We asked whether the observed positive relationship between native and exotic plant richness (R²= 0.11) resulted from the addition of several negative correlations corresponding to different environmental conditions identified with cluster analysis. Moreover, we directly quantified the importance of common causal effects with a structural equation modelling framework. Results We found no evidence that the relationship between native and exotic plant richness was negative when the comparison was made within environmentally homogeneous groups. Although there were common factors explaining both native and exotic richness, mainly associated with landscape heterogeneity and human pressure, these factors only explained 17.2% of the total correlation. Nevertheless, when the comparison was restricted to native plants associated with human‐disturbed (i.e. ruderal) ecosystems, the relationship was stronger (R²= 0.52) and the fraction explained by common factors increased substantially (58.3%). Main conclusions While our results confirm that the positive correlation between exotic and native plant richness is in part explained by common extrinsic factors, they also highlight the great importance of anthropic factors that – by reducing biotic resistance – facilitate the establishment and spread of both exotic and native plants that tolerate disturbed environments.     

Whole-Genome Analysis of Diversity and SNP-Major Gene Association in Peach Germplasm

Peach was domesticated in China more than four millennia ago and from there it spread world-wide. Since the middle of the last century, peach breeding programs have been very dynamic generating hundreds of new commercial varieties, however, in most cases such varieties derive from a limited collection of parental lines (founders). This is one reason for the observed low levels of variability of the commercial gene pool, implying that knowledge of the extent and distribution of genetic variability in peach is critical to allow the choice of adequate parents to confer enhanced productivity, adaptation and quality to improved varieties. With this aim we genotyped 1,580 peach accessions (including a few closely related Prunus species) maintained and phenotyped in five germplasm collections (four European and one Chinese) with the International Peach SNP Consortium 9K SNP peach array. The study of population structure revealed the subdivision of the panel in three main populations, one mainly made up of Occidental varieties from breeding programs (POP1OC_B), one of Occidental landraces (POP2OC_T) and the third of Oriental accessions (POP3OR). Analysis of linkage disequilibrium (LD) identified differential patterns of genome-wide LD blocks in each of the populations. Phenotypic data for seven monogenic traits were integrated in a genome-wide association study (GWAS). The significantly associated SNPs were always in the regions predicted by linkage analysis, forming haplotypes of markers. These diagnostic haplotypes could be used for marker-assisted selection (MAS) in modern breeding programs.     

Recent trends in butterfly populations from north-east Spain and Andorra in the light of habitat and climate change

Although butterfly declines have been reported across Europe, no assessment based on detailed quantitative data has ever been made for any extensive area in the Mediterranean Basin. In 1994, a Butterfly Monitoring Scheme was launched in Catalonia (NE Spain), and in 2005 a similar, albeit much smaller, scheme started in the neighbouring Pyrenean country of Andorra. Here we provide a first thorough assessment of butterfly trends in both areas for the last 15 years. Several patterns emerged, above all a worrying decline of a substantial part of the fauna. It was also evident that habitat specialists are experiencing greater declines than habitat generalists, thereby butterfly communities becoming progressively dominated by common species. However, habitat indicators based on characteristic species also revealed that trends are actually associated with habitat types, grassland and scrub specialists declining strongly but woodland specialists showing a marginal increase. These differences are certainly related to profound landscape changes, mainly a dramatic reduction of semi-natural grasslands and open Mediterranean scrub, and a major increase in woodlands. The general effect of climatic warming on butterfly populations was investigated by using the temperature community index (CTI) approach. The thermal structure of butterfly communities remained very stable over time, except in one case where, contrary to the expectations, a significant negative trend in the CTI was noted. However, this surprising result can be explained by taking into account the above-reported pattern of butterfly communities becoming dominated by common species, characterized by low thermal indices in comparison with declining Mediterranean specialists.     

Targeting Dyrk1A with AAVshRNA attenuates motor alterations in TgDyrk1A, a mouse model of Down syndrome

Genetic-dissection studies carried out with Down syndrome (DS) murine models point to the critical contribution of Dyrk1A overexpression to the motor abnormalities and cognitive deficits displayed in DS individuals. In the present study we have used a murine model overexpressing Dyrk1A (TgDyrk1A mice) to evaluate whether functional CNS defects could be corrected with an inhibitory RNA against Dyrk1A, delivered by bilateral intrastriatal injections of adeno-associated virus type 2 (AAVshDyrk1A). We report that AAVshDyrk1A efficiently transduced HEK293 cells and primary neuronal cultures, triggering the specific inhibition of Dyrk1A expression. Injecting the vector into the striata of TgDyrk1A mice resulted in a restricted, long-term transduction of the striatum. This gene therapy was found to be devoid of toxicity and succeeded in normalizing Dyrk1A protein levels in TgDyrk1A mice. Importantly, the behavioral studies of the adult TgDyrk1A mice treated showed a reversal of corticostriatal-dependent phenotypes, as revealed by the attenuation of their hyperactive behavior, the restoration of motor-coordination defects, and an improvement in sensorimotor gating. Taken together, the data demonstrate that normalizing Dyrk1A gene expression in the striatum of adult TgDyrk1A mice, by means of AAVshRNA, clearly reverses motor impairment. Furthermore, these results identify Dyrk1A as a potential target for therapy in DS.     

Novel phospholipolytic activities associated with electronegative low-density lipoprotein are involved in increased self-aggregation

Electronegative low-density lipoprotein (LDL(-)) is a minor LDL subfraction present in plasma with increased platelet-activating factor acetylhydrolase (PAF-AH) activity. This activity could be involved in the proinflammatory effects of LDL(-). Our aim was to study the presence of additional phospholipolytic activities in LDL(-). Total LDL was fractionated into electropositive (LDL(+)) and LDL(-) by anion-exchange chromatography, and phospholipolytic activities were measured by fluorometric methods. Phospholipolytic activity was absent in LDL(+) whereas LDL(-) presented activity against lysophosphatidylcholine (LPC, 82.4 +/- 34.9 milliunits/mg of apoB), sphingomyelin (SM, 53.3 +/- 22.5 milliunits/mg of apoB), and phosphatidylcholine (PC, 25.7 +/- 4.3 milliunits/mg of apoB). LDL(-), but not LDL(+), presented spontaneous self-aggregation at 37 degrees C in parallel to phospholipid degradation. This was observed in the absence of lipid peroxidation and suggests the involvement of phospholipolytic activity in self-aggregation of LDL(-). Phospholipolytic activity was not due to PAF-AH, apoE, or apoC-III and was not increased in LDL(+) modified by Cu (2+) oxidation, acetylation, or secretory phospholipase A 2 (PLA 2). However, LDL(-) efficiently degraded phospholipids of lipoproteins enriched in LPC, such as oxidized LDL or PLA 2-LDL, but not native or acetylated LDL. This finding supports that LPC is the best substrate for LDL(-)-associated phospholipolytic activity. These results reveal novel properties of LDL(-) that could play a significant role in its atherogenic properties.     

Evolutionary combinatorial chemistry, a novel tool for SAR studies on peptide transport across the blood-brain barrier. Part 2. Design, synthesis and evaluation of a first generation of peptides.

The use of high-throughput methods in drug discovery allows the generation and testing of a large number of compounds, but at the price of providing redundant information. Evolutionary combinatorial chemistry combines the selection and synthesis of biologically active compounds with artificial intelligence optimization methods, such as genetic algorithms (GA). Drug candidates for the treatment of central nervous system (CNS) disorders must overcome the blood-brain barrier (BBB). This paper reports a new genetic algorithm that searches for the optimal physicochemical properties for peptide transport across the blood-brain barrier. A first generation of peptides has been generated and synthesized. Due to the high content of N-methyl amino acids present in most of these peptides, their syntheses were especially challenging due to over-incorporations, deletions and DKP formations. Distinct fragmentation patterns during peptide cleavage have been identified. The first generation of peptides has been studied by evaluation techniques such as immobilized artificial membrane chromatography (IAMC), a cell-based assay, log Poctanol/water calculations, etc. Finally, a second generation has been proposed.     

Probing meiotic recombination decisions

Meiotic recombination promotes genetic variation by mixing parental alleles. Two recent studies, one in this issue of Developmental Cell, have applied microarray-based methods that allow analysis of nearly all of the recombination events occurring in a single meiosis. These data provide insights into the molecular "decisions" that control the outcome of the recombination process.