Local-scale environmental filtering shape plant taxonomic and phylogenetic diversity in an isolated Amazonian tepui (Tepequém table mountain)

Evolutionary Ecology - Understanding how environmental drivers induce changes in plant composition and diversity across evolutionary time can provide important insights into community assembly...     

Floristic distributional patterns in a diverse ecotonal area in South America

The Paraguayan territory and region, in the centre of South America, is a huge transition area with a succession of various vegetation types. However, this area has received little attention from researchers, with few works published on its flora and its delimitations. We aimed to identify the most important environmental driving forces and delimit floristic patterns in this region, since understanding the forces that drive floristic variations in this ecotonal region could help comprehend the distribution of vegetation not only in this region but throughout South America. We obtained 1234 tree species occurrence records, 205 geographic coordinates and 23 environmental variables and altitude from the ‘NeoTropTree’ database and verified the influence and contribution of environmental factors through variance partition. We tested the floristic consistency of the different vegetation types using dendrogram, indicator species and ordination analyses. We also constructed multiple linear models to check the correlation between species distribution and environmental variables. We found eight consistent vegetation types. The spatial variables coupled with environmental variables were more important than individual environmental or spatial variables. Among the environmental variables, the aridity index was the most important. Despite the importance of spatial factors, due to environmental heterogeneity, we found a gradient related to climate and edaphic variables related to tree flora. The results confirm that the Paraguayan territory and region can be considered to be a diversified and important ecotone area in South America with respect to tree flora.     

Invasive alien species records are exponentially rising across the Earth

Humans are facilitating the introduction and range expansion of invasive alien species (IAS), which have negatively impacted ecological and socio-economic systems worldwide. Understanding the global diffusion of IAS is important for developing environmental policies and management strategies. We estimate the rate of increase and the doubling times of the number of new records of 178 IAS using a global dataset with c. 3.4 million records obtained over c. 100 years. Here, we show that the number of records of IAS have exponentially increased with a mean double time of c. 14 years across the Earth. For the most analysed species, the number of records increased faster in the non-native than native continents, suggesting that such IAS might be exponentially expanding their range size. We also found that each continent has a taxonomic group with a particular increase in IAS records. Governments and scientists should pay attention to these taxonomic groups to implement appropriate control or management actions. Our study provides an indication that the current local, regional and continental efforts to control invasions may be not sufficient at the global scale. This is a concerning situation given the great number of areas available for invasion worldwide.

     

Effects of Quaternary climatic fluctuations on the distribution of Neotropical savanna tree species

In order to develop niche models for tree species characteristic of the cerrado vegetation (woody savannas) of central South America, and to hindcast their distributions during the Last Glacial Maximum and Last Inter‐Glacial, we compiled a dataset of tree species checklists for typical cerrado vegetation (n = 282) and other geographically co‐occurring vegetation types, e.g. seasonally dry tropical forest (n = 355). We then performed an indicator species analysis to select ten species that best characterize typical cerrado vegetation and developed niche models for them using the Maxent algorithm. We used these models to assess the probability of occurrence of each species across South America at the following time slices: Current (0 ka pre‐industrial), Holocene (6 ka BP), Last Glacial Maximum (LGM – 21 ka BP), and Last Interglacial (LIG – 130 ka BP). The niche models were robust for all species and showed the highest probability of occurrence in the core area of the Cerrado Domain. The palaeomodels suggested changes in the distributions of cerrado tree species throughout the Quaternary, with expansion during the LIG into the adjacent Amazonian and Atlantic moist forests, as well as connections with other South American savannas. The LGM models suggested a retraction of cerrado vegetation to inter‐tableland depressions and slopes of the Central Brazilian Highlands. Contrary to previous hypotheses, such as the Pleistocene refuge theory, we found that the widest expansion of cerrado tree species seems to have occurred during the LIG, most probably due to its warmer climate. On the other hand, the postulated retractions during the LGM were likely related to both decreased precipitation and temperature. These results are congruent with palynological and phylogeographic studies in the Cerrado Domain.     

Climate and evolutionary history define the phylogenetic diversity of vegetation types in the central region of South America

Oecologia - In South America the biogeographic history has produced different biomes with different vegetation types and distinct floras. As these vegetation types may diverge in evolutionary...     

Antimicrobial activity of Brazilian propolis extracts against rumen bacteria in vitro

The antimicrobial activity of three Brazilian propolis extracts was evaluated on bacterial strains representing major rumen functional groups. The extracts were prepared using different concentrations of propolis and alcohol, resulting in different phenolic compositions. The propolis extracts inhibited the growth of Fibrobacter succinogenes S85, Ruminococcus flavefaciens FD-1, Ruminococcus albus 7, Butyrivibrio fibrisolvens D1, Prevotella albensis M384, Peptostreptococcus sp. D1, Clostridium aminophilum F and Streptococcus bovis Pearl11, while R. albus 20, Prevotella bryantii B₁4 and Ruminobacter amylophilus H18 were resistant to all the extracts. The inhibited strains showed also different sensitivity to propolis; the hyper-ammonia-producing bacteria (C. aminophilum F and Peptostreptococcus sp. D1) being the most sensitive. Inhibition of hyper-ammonia-producing bacteria by propolis would be beneficial to the animal. The extract containing the lowest amount of phenolic compounds (LLOS C3) showed the lowest antimicrobial activity against all the bacteria. The major phenolic compounds identified in the propolis extracts (naringenin, chrysin, caffeic acid, p-coumaric acid and Artepillin C) were also evaluated on four sensitive strains. Only naringenin showed inhibitory effect against all strains, suggesting that naringenin is one of the components participating to the antibacterial activity of propolis.     

Coagulation Activation in Children with Sickle Cell Disease Is Associated with Cerebral Small Vessel Vasculopathy

Background

Thrombotic complications in Sickle Cell Disease (SCD) arise since infancy, but the role of the coagulation system in children has been poorly explored. To determine its role in the development of clinical complications in childhood we measured coagulation and endothelial parameters in children with SCD at steady state.

Methods

Markers of thrombin generation, fibrin dissolution and endothelial activation were evaluated in 38 children with SS-Sβ°, 6 with SC disease and 50 age and blood group matched controls. Coagulation variables were correlated with markers of hemolysis and inflammation, with the presence of cerebral and lung vasculopathy and with the frequency of clinical complications.

Results

SS-Sβ° patients presented higher levels of factor VIII, von Willebrand factor antigen (VWF:Ag) and collagen binding activity, tissue plasminogen activator antigen (t-PA:Ag), D-dimer, p-selectin, prothrombin fragment1+2 (F1+2) and lower ADAMTS-13:activity/VWF:Ag (p<0.05) compared to controls and SC patients. In SS-Sβ° patients coagulation variables correlated positively with markers of inflammation, hemolysis, and negatively with HbF (p<0.05). Patients with cerebral silent infarcts showed significant decrease in t-PA:Ag and ADAMTS-13 Antigen and a tendency toward higher D-dimer, F1+2, TAT compared to patients without them. D-dimer was associated with a six fold increased risk of cerebral silent infarcts. No correlation was found between coagulation activation and large vessel vasculopathy or other clinical events except for decreased t-PA:Ag in patients with tricuspid Rigurgitant Velocity >2.5m/sec.

Conclusions

SS-Sβ° disease is associated with extensive activation of the coagulation system at steady state since young age. ADAMTS-13 and t-PA:Ag are involved in the development of cerebral silent infarcts.