The role of geography,ecology, and hybridization in the evolutionary history of Canary Island Descurainia

Premise

Oceanic islands offer the opportunity to understand evolutionary processes underlying rapid diversification. Along with geographic isolation and ecological shifts, a growing body of genomic evidence has suggested that hybridization can play an important role in island evolution. Here we use genotyping-by-sequencing (GBS) to understand the roles of hybridization, ecology, and geographic isolation in the radiation of Canary Island Descurainia (Brassicaceae).

Methods

We carried out GBS for multiple individuals of all Canary Island species and two outgroups. Phylogenetic analyses of the GBS data were performed using both supermatrix and gene tree approaches and hybridization events were examined using D-statistics and Approximate Bayesian Computation. Climatic data were analyzed to examine the relationship between ecology and diversification.

Results

Analysis of the supermatrix data set resulted in a fully resolved phylogeny. Species networks suggest a hybridization event has occurred for D. gilva, with these results being supported by Approximate Bayesian Computation analysis. Strong phylogenetic signals for temperature and precipitation indicate one major ecological shift within Canary Island Descurainia.

Conclusions

Inter-island dispersal played a significant role in the diversification of Descurainia, with evidence of only one major shift in climate preferences. Despite weak reproductive barriers and the occurrence of hybrids, hybridization appears to have played only a limited role in the diversification of the group with a single instance detected. The results highlight the need to use phylogenetic network approaches that can simultaneously accommodate incomplete lineage sorting and gene flow when studying groups prone to hybridization; patterns that might otherwise be obscured in species trees.     

The Perforin Pore Facilitates the Delivery of Cationic Cargos

Cytotoxic lymphocytes eliminate virally infected or neoplastic cells through the action of cytotoxic proteases (granzymes). The pore-forming protein perforin is essential for delivery of granzymes into the cytoplasm of target cells; however the mechanism of this delivery is incompletely understood. Perforin contains a membrane attack complex/perforin (MACPF) domain and oligomerizes to form an aqueous pore in the plasma membrane; therefore the simplest (and best supported) model suggests that granzymes passively diffuse through the perforin pore into the cytoplasm of the target cell. Here we demonstrate that perforin preferentially delivers cationic molecules while anionic and neutral cargoes are delivered inefficiently. Furthermore, another distantly related pore-forming MACPF protein, pleurotolysin (from the oyster mushroom), also favors the delivery of cationic molecules, and efficiently delivers human granzyme B. We propose that this facilitated diffusion is due to conserved features of oligomerized MACPF proteins, which may include an anionic lumen.     

Reconstructed natural versus potential natural vegetation in vegetation mapping - a discussion of concepts

Reconstruction mapping of the natural (primary) vegetation of intensively cultivated land is based on: (1) classification of actually existing remains of natural or near-natural plant communities as mapping units; (2) delimitation of their habitat types; (3) detection of correlations between vegetation units and habitat types. Natural plant communities thus serve as indicators of abiotic habitat conditions. Reconstruction mapping is based on the extrapolation of the potential distribution of individual vegetation units to sites of similar habitat types where the natural vegetation does not exist any more. The same procedure is used for mapping the potential natural vegetation. Both types of natural vegetation maps are identical on sites where the abiotic natural habitat conditions (relief, geological substratum, climate, water regime, soils) remain practically unchanged. On sites where the natural habitat conditions have been considerably changed by man, e.g. in areas with superficial coal mining (complete destruction of the landscape, removal of soil cover, creation of large slag heaps) or in towns, no natural (primary) vegetation exists. This causes difficulties in the hypothetical concept of the potential natural vegetation and its definition. In contrast, in such sites reconstruction vegetation mapping uses the extrapolation of mapping units of the primary vegetation to the original natural habitat conditions.     

A Novel Three-dimensional Flow Chamber Device to Study Chemokine-directed Extravasation of Cells Circulating under Physiological Flow Conditions

Extravasation of circulating cells from the bloodstream plays a central role in many physiological and pathophysiological processes, including stem cell homing and tumor metastasis. The three-dimensional flow chamber device (hereafter the 3D device) is a novel in vitro technology that recreates physiological shear stress and allows each step of the cell extravasation cascade to be quantified. The 3D device consists of an upper compartment in which the cells of interest circulate under shear stress, and a lower compartment of static wells that contain the chemoattractants of interest. The two compartments are separated by porous inserts coated with a monolayer of endothelial cells (EC). An optional second insert with microenvironmental cells of interest can be placed immediately beneath the EC layer. A gas exchange unit allows the optimal CO₂ tension to be maintained and provides an access point to add or withdraw cells or compounds during the experiment. The test cells circulate in the upper compartment at the desired shear stress (flow rate) controlled by a peristaltic pump. At the end of the experiment, the circulating and migrated cells are collected for further analyses. The 3D device can be used to examine cell rolling on and adhesion to EC under shear stress, transmigration in response to chemokine gradients, resistance to shear stress, cluster formation, and cell survival. In addition, the optional second insert allows the effects of crosstalk between EC and microenvironmental cells to be examined. The translational applications of the 3D device include testing of drug candidates that target cell migration and predicting the in vivo behavior of cells after intravenous injection. Thus, the novel 3D device is a versatile and inexpensive tool to study the molecular mechanisms that mediate cellular extravasation.     

Phytochemical and chemotaxonomic investigation from the roots of Anemone vitifolia Buch.-Ham. (Ranunculaceae)

Phytochemical investigation from the roots of Anemone vitifolia Buch.-Ham. led to the isolation of eight compounds, including one triterpenoid saponin, two sugars, one coumarin, one amide, one saturated alkane, one olefin and one fatty acid. The structures of these metabolites were elucidated by spectroscopic data and comparisons with the data available in the literature. Among them, compound 7 ((6Z,9Z,12Z)-6,9,12-Eicosatriene) was isolated for the first time as a natural product. Furthermore, compounds 2 (D-(+)-raffinose), 3 (mixture of β-D-fructopyranose and β-D-fructofuranose) and 5 (bonaroside) were obtained from the Ranunculaceae family for the first time. Compounds 4 (siderin) and 6 (n-hexadecane) were isolated from A. vitifolia for the first time. The chemotaxonomic significance of the isolated compounds was discussed.     

Tree growth in the aftermath of A flood: A tree-ring based reconstruction of the impacts of the 1996-Biescas catastrophe

Catastrophic floods and large debris flows are natural hazards common in mountain areas. They cause injuries and impact the radial growth of trees growing in the affected basins. Reconstructing how these catastrophic events impact trees by using dendrochronology improves our understanding of natural hazards. The 1996-Biescas (Central Spanish Pyrenees) flood was a catastrophic event causing the loss of many lives in a campsite located on an active alluvial fan. We investigated using tree rings how this catastrophic flood impacted planted trees (poplars, cedars) located in the campsite. Conspicuous scars in the stem were more abundant in cedar trees (75 %) than in poplar (36 %) trees. Scarred cedar trees formed traumatic resin ducts after the flood. In cedar tree perimeter influenced the size of the wound formed after the flood, but this was not observed in poplar. On average, 63 % of trees showing scars formed them in the side of the stem (N-NW) where the impact of the flood was assumed to be strongest. We also detected sharp reductions of tree-ring width after the flood (–56 % and –16 % in poplar and cedar, respectively). However, this was not found when using basal area increment, which suggests there was an age effect on the post-flood growth changes. The two species mean chronologies were also more coupled after the flood in agreement with an increased responsiveness to climate, particularly a higher dependence of growth on June precipitation. To adequately reconstruct responses to flood and to assess the actual vulnerability of forests to debris flow impacts tree features such as species, age, growth rate and responsiveness to climate must be considered.     

Biological characterization of the lytic cycle of actinophage φA7 in Streptomyces antibioticus

Some basic parameters of the lytic development of phage phi A7 in Streptomyces antibioticus are described. One-step growth experiments demonstrated that at 28 degrees C phi A7 has a latent period of about 60 min and an exponential growth period of about 35 min. The average burst size ranged from 70-100 plaque forming units per infected cell. At the same temperature 50% of the virions were adsorbed to germ tubes of S. antibioticus in about 10 min. This corresponds to an adsorption constant of 6.5 x 10(-10) ml/min. The phage was unable to adsorb the host at other stages of the life cycle (spores or mycelium). Divalent cations are not required for phi A7 stability but Ca2+ proved to be essential for adsorption and also for a later stage of the vegetative development of the phage.     

Pyridine alkaloids with activity in the central nervous system

This review discusses all pyridine alkaloids with CNS activity, their therapeutic potential, and the interesting array of sources whence they originate.     

Application of a reverse dot blot DNA–DNA hydridization method to quantify host‐feeding tendencies of two sibling species in the Anopheles gambiae complex

A DNA–DNA hybridization method, reverse dot blot analysis (RDBA), was used to identify Anopheles gambiae s.s. and Anopheles arabiensis (Diptera: Culicidae) hosts. Of 299 blood‐fed and semi‐gravid An. gambiae s.l. collected from Kisian, Kenya, 244 individuals were identifiable to species; of these, 69.5% were An. arabiensis and 29.5% were An. gambiae s.s. Host identifications with RDBA were comparable with those of conventional polymerase chain reaction (PCR) followed by direct sequencing of amplicons of the vertebrate mitochondrial cytochrome b gene. Of the 174 amplicon‐producing samples used to compare these two methods, 147 were identifiable by direct sequencing and 139 of these were identifiable by RDBA. Anopheles arabiensis bloodmeals were mostly (94.6%) bovine in origin, whereas An. gambiae s.s. fed upon humans more than 91.8% of the time. Tests by RDBA detected that two of 112 An. arabiensis contained blood from more than one host species, whereas PCR and direct sequencing did not. Recent use of insecticide‐treated bednets in Kisian is likely to have caused the shift in the dominant vector species from An. gambiae s.s. to An. arabiensis. Reverse dot blot analysis provides an opportunity to study changes in host‐feeding by members of the An. gambiae complex in response to the broadening distribution of vector control measures targeting host‐selection behaviours.