Trees Wanted—Dead or Alive! Host Selection and Population Dynamics in Tree-Killing Bark Beetles

Bark beetles (Coleoptera: Curculionidae, Scolytinae) feed and breed in dead or severely weakened host trees. When their population densities are high, some species aggregate on healthy host trees so that their defences may be exhausted and the inner bark successfully colonized, killing the tree in the process. Here we investigate under what conditions participating with unrelated conspecifics in risky mass attacks on living trees is an adaptive strategy, and what this can tell us about bark beetle outbreak dynamics. We find that the outcome of individual host selection may deviate from the ideal free distribution in a way that facilitates the emergence of tree-killing (aggressive) behavior, and that any heritability on traits governing aggressiveness seems likely to exist in a state of flux or cycles consistent with variability observed in natural populations. This may have implications for how economically and ecologically important species respond to environmental changes in climate and landscape (forest) structure. The population dynamics emerging from individual behavior are complex, capable of switching between “endemic” and “epidemic” regimes spontaneously or following changes in host availability or resistance. Model predictions are compared to empirical observations, and we identify some factors determining the occurrence and self-limitation of epidemics

Potential range of impact of an ecological trap network: the case of timber stacks and the Rosalia longicorn

Although the negative impact of timber stacks on populations of saproxylic beetles is a well-known phenomenon, there is relatively little data concerning the scale of this impact and its spatial aspect. Beech timber stored in the vicinity of the forest can act as an ecological trap for the Rosalia longicorn (Rosalia alpina), so in this study we have attempted to determine the spatial range of the impact of a network of timber stacks. Timber stacks in the species’ range in the study area were listed and monitored during the adult emergence period in 2014–2016. Based on published data relating to the species’ dispersal capabilities, buffers of four radii (500, 1000, 1600, 3000 m) were delineated around the stacks and the calculated ranges of potential impact. The results show that the percentage of currently known localities of the Rosalia longicorn impacted by stacks varies from 19.7 to 81.6%, depending on the assumed impact radius. The percentage of forest influenced by timber stacks was 77% for the largest-radius buffer. The overall impact of the ecological trap network is accelerated by fragmentation of the impact-free area. It was also found that forests situated close to the timber stacks where the Rosalia longicorn was recorded were older and more homogeneous in age and species composition than those around stacks where the species was absent. Such results suggest that timber stacks act as an ecological trap in the source area of the local population

Sodium hyaluronate increases the fibrinolytic response of human peritoneal mesothelial cells exposed to tumor necrosis factor alpha.

HYPOTHESIS: Sodium hyaluronate interferes with the fibrin degrading capacity of human peritoneal mesothelial cells exposed to tumor necrosis factor (TNF) alpha. DESIGN: Controlled laboratory experiment. INTERVENTION: Human peritoneal mesothelial cells were harvested from 5 patients undergoing laparotomy and cultured in vitro. Cells were treated with TNF-alpha, a cytokine typically involved in peritoneal inflammation, and sodium hyaluronate was added in a final concentration of 0.1%, 0.2%, or 0.4%. Controls received medium only. After 24 hours' incubation, tissue-type plasminogen activator (tPA), urokinase-type plasminogen activator (uPA), and plasminogen activator inhibitor type 1 (PAI-1) were measured in the medium and cell lysates using enzyme-linked immunosorbent assay techniques. Specific gene transcripts in cells treated with 0.4% sodium hyaluronate and controls were determined using a quantitative reverse transcription polymerase chain reaction. MAIN OUTCOME MEASURES: Concentrations of tPA, uPA, and PAI-1, and their specific gene transcripts. RESULTS: Sodium hyaluronate significantly increased tPA concentration in cell lysates without affecting its gene expression as determined after 24 hours (P =.02). The uPA concentration was significantly decreased by sodium hyaluronate in the medium but not in cell lysates (P<.0001). The uPA messenger RNA expression was 1000-fold increased compared with control. Sodium hyaluronate significantly decreased PAI-1 concentration in the medium and reduced its gene expression 500-fold (P =.04), while PAI-1 concentration in cell lysates did not change. CONCLUSION: Sodium hyaluronate affected the fibrinolytic response of TNF-alpha-stimulated human peritoneal mesothelial cells, most notably by decreasing PAI-1 transcription and release. This observation indicates that sodium hyaluronate counteracts the fibrinolytic decline induced by TNF-alpha and suggests a biological mechanism of action for sodium hyaluronate intra-abdominally