Multiple ITS Copies Reveal Extensive Hybridization within Rheum (Polygonaceae), a Genus That Has Undergone Rapid Radiation

During adaptive radiation events, characters can arise multiple times due to parallel evolution, but transfer of traits through hybridization provides an alternative explanation for the same character appearing in apparently non-sister lineages. The signature of hybridization can be detected in incongruence between phylogenies derived from different markers, or from the presence of two divergent versions of a nuclear marker such as ITS within one individual.In this study, we cloned and sequenced ITS regions for 30 species of the genus Rheum, and compared them with a cpDNA phylogeny. Seven species contained two divergent copies of ITS that resolved in different clades from one another in each case, indicating hybridization events too recent for concerted evolution to have homogenised the ITS sequences. Hybridization was also indicated in at least two further species via incongruence in their position between ITS and cpDNA phylogenies. None of the ITS sequences present in these nine species matched those detected in any other species, which provides tentative evidence against recent introgression as an explanation. Rheum globulosum, previously indicated by cpDNA to represent an independent origin of decumbent habit, is indicated by ITS to be part of clade of decumbent species, which acquired cpDNA of another clade via hybridization. However decumbent and glasshouse morphology are confirmed to have arisen three and two times, respectively.These findings suggested that hybridization among QTP species of Rheum has been extensive, and that a role of hybridization in diversification of Rheum requires investigation

Evaluation of coronary blood flow velocity during cardiac arrest with circulation maintained through mechanical chest compressions in a porcine model

<p>Abstract</p> <p>Background</p> <p>Mechanical chest compressions (CCs) have been shown capable of maintaining circulation in humans suffering cardiac arrest for extensive periods of time. Reports have documented a visually normalized coronary blood flow during angiography in such cases (TIMI III flow), but it has never been actually measured. Only indirect measurements of the coronary circulation during cardiac arrest with on-going mechanical CCs have been performed previously through measurement of the coronary perfusion pressure (CPP). In this study our aim was to correlate average peak coronary flow velocity (APV) to CPP during mechanical CCs.</p> <p>Methods</p> <p>In a closed chest porcine model, cardiac arrest was established through electrically induced ventricular fibrillation (VF) in eleven pigs. After one minute, mechanical chest compressions were initiated and then maintained for 10 minutes upon which the pigs were defibrillated. Measurements of coronary blood flow in the left anterior descending artery were made at baseline and during VF with a catheter based Doppler flow fire measuring APV. Furthermore measurements of central (thoracic) venous and arterial pressures were also made in order to calculate the theoretical CPP.</p> <p>Results</p> <p>Average peak coronary flow velocity was significantly higher compared to baseline during mechanical chests compressions and this was observed during the entire period of mechanical chest compressions (12 - 39% above baseline). The APV slowly declined during the 10 min period of mechanical chest compressions, but was still higher than baseline at the end of mechanical chest compressions. CPP was simultaneously maintained at > 20 mmHg during the 10 minute episode of cardiac arrest.</p> <p>Conclusion</p> <p>Our study showed good correlation between CPP and APV which was highly significant, during cardiac arrest with on-going mechanical CCs in a closed chest porcine model. In addition APV was even higher during mechanical CCs compared to baseline. Mechanical CCs can, at minimum, re-establish coronary blood flow in non-diseased coronary arteries during cardiac arrest.</p

Repeated long-distance dispersal and convergent evolution in hazel

Closely related species with a worldwide distribution provide an opportunity to understand evolutionary and biogeographic processes at a global scale. Hazel (Corylus) is an economically important genus of tree and shrub species found in temperate regions of Asia, North America and Europe. Here we use multiple nuclear and chloroplast loci to estimate a time-calibrated phylogenetic tree of the genus Corylus. We model the biogeographic history of this group and the evolutionary history of tree and shrub form. We estimate that multiple Corylus lineages dispersed long distances between Europe and Asia and colonised North America from Asia in multiple independent events. The geographic distribution of tree versus shrub form of species appears to be the result of 4–5 instances of convergent evolution in the past 25 million years. We find extensive discordance between our nuclear and chloroplast trees and potential evidence for chloroplast capture in species with overlapping ranges, suggestive of past introgression. The important crop species C. avellana is estimated to be closely related to C. maxima, C. heterophylla var. thunbergii and the Colurnae subsection. Our study provides a new phylogenetic hypothesis or Corylus and reveals how long-distance dispersal can shape the distribution of biodiversity in temperate plants

Evolutionary changes in correlations among functional traits in <i>Ceanothus</i> in response to Mediterranean conditions

<i>Ceanothus</i> is a widely speciated genus with two sections that differ markedly in size, patterns of biomass allocation and reproductive strategies. On greenhouse-grown seedlings we tested whether divergence occurred in single traits or in suites of traits, and whether taxonomic affinity or the ability to fix nitrogen (N) influenced the relationships among functional traits. Species of the subgenus <i>Cerastes</i> differed from species in the subgenus <i>Ceanothus</i> in the following characteristics: reproduction by seed rather than primarily resprouting, high rates of photosynthesis and high stomatal conductance, thick leaves, low root allocation, and high leaf allocation. Correlations of traits across the entire genus showed positive correlations among traits that maximize photosynthesis and tradeoffs between root allocation and carbon gain patterns frequently observed in other broad taxonomic comparisons. Trait correlations differed between the two subgenera (divergence in allocation-photosynthesis tradeoffs in <i>Ceanothus</i> and divergence of growth-related traits in <i>Cerastes</i>). Similarly, N-fixers, which were distributed broadly between the two subgenera, differed in trait correlations (primarily among traits related to photosynthesis) from non-fixers (primarily among traits related to growth and allocation). These results indicate that 1) divergence in genus <i>Ceanothus</i> was associated with changes in entire suite of traits, rather than independent changes in individual traits and 2) evolution occurring under different environmental or nutritional circumstances alters the suites of traits exhibited by plants

Haemodynamic outcomes during piston-based mechanical CPR with or without active decompression in a porcine model of cardiac arrest

Background Experimental active compression-decompression (ACD) CPR is associated with increased haemodynamic outcomes compared to standard mechanical chest compressions. Since no clinically available mechanical chest compression device is capable of ACD-CPR, we modified the LUCAS 2 (Physio-Control, Lund, Sweden) to deliver ACD-CPR, hypothesising it would improve haemodynamic outcomes compared with standard LUCAS CPR on pigs with cardiac arrest. Methods The modified LUCAS delivering 5 cm compressions with or without 2 cm active decompression above anatomical chest level was studied in a randomized crossover design on 19 Norwegian domestic pigs. VF was electrically induced and untreated for 2 min. Each pig received ACD-CPR and standard mechanical CPR in three 180-s. phases. We measured aortic, right atrial, coronary perfusion, intracranial and oesophageal pressure, cerebral and carotid blood flow and cardiac output. Two-sided paired samples t-test was used for continuous parametric data and Wilcoxon test for non-parametric data. P < 0.05 was considered significant. Results Due to injuries/device failure, the experimental protocol was completed in nine of 19 pigs. Cardiac output (l/min, median, (25, 75-percentiles): 1.5 (1.1, 1.7) vs. 1.1 (0.8, 1.5), p < 0.01), cerebral blood flow (AU, 297 vs. 253, mean difference: 44, 95% CI; 14–74, p = 0.01), and carotid blood flow (l/min, median, (25, 75-percentiles): 97 (70, 106) vs. 83 (57, 94), p < 0.01) were higher during ACD-CPR compared to standard mechanical CPR. Coronary perfusion pressure (CPP) trended towards higher in end decompression phase. Conclusion Cardiac output and brain blood flow improved with mechanical ACD-CPR and CPP trended towards higher during end-diastole compared to standard LUCAS CPR