Invasion and eradication of a competitively superior species in heterogeneous landscapes

The effect of heterogeneous environments upon the dynamics of invasion and the eradication or control of invasive species is poorly understood, although it is a major challenge for biodiversity conservation. Here, we first investigate how the probability and time for invasion are affected by spatial heterogeneity. Then, we study the effect of control program strategies (e.g. species specificity, spatial scale of action, detection and eradication efficiency) on the success and time of eradication. We find that heterogeneity increases both the invasion probability and the time to invasion. Heterogeneity also reduces the probability of eradication but does not change the time taken for successful eradication. We confirm that early detection of invasive species reduces the time until eradication, but we also demonstrate that this is true only if the local control action is sufficiently efficient. The criterion of removal efficiency is even more important for an eradication program than simply ensuring control effort when the invasive species is not abundant.     

Alien species: to remove or not to remove? That is the question

Invasive alien species (IAS) are universally known for being a controversial management issue. What makes IAS management a particularly thorny question is that although numerous studies document the negative effects of IAS, the potential benefits of IAS are generally underreported. This may result in wrong assessments on the real socio-economic and environmental impact of IAS. This study aimed to provide new insights to support the decision making of IAS management. In particular, the biased approach to IAS management seems to be a likely consequence of the lack of appropriate metrics able to assess the real IAS impact. A basic aspect of IAS management is to decide whether and when IAS removal is a suitable action. Specifically, this study supported the idea that IAS removal may be considered as a possible solution only after establishing a tipping point relying on economic, cultural and pragmatic evaluations. This analysis should include the identification of the ecosystem services damaged and provided by IAS, the attribution of an economic value to such ecosystem services, and when expressing the interaction between IAS and culture is not possible in monetary terms, then social values and cultural traditions should be incorporated in any management plan. Novel ecosystems are now a fact worldwide that should prompt to be realistic about the extent of efforts required for IAS removal. A significant step towards well-pondered decisions should consider that a change in host communities does not imply necessarily harm, and that the functional roles of a species matter more than its origins.     

四联疗法治疗消化性溃疡的疗效观察

观察奥美拉唑、枸橼酸铋钾、阿莫西林及呋喃唑酮四联疗法对消化性溃疡的疗效.方法选取96例消化性溃疡、幽门螺杆菌(HP)阳性患者,给予口服奥美拉唑20 mg+枸橼酸铋钾240 mg+阿莫西林1 g+呋喃唑酮200mg2,次/日,共14日,观察症状,并复查胃镜和HP感染情况.结果绝大部分患者症状消失,行胃镜检查和HP检测,显示溃疡面治愈或明显好转,并HP转为阴性.结论四联疗法治疗消化性溃疡的疗效可靠,副作用少,价格便宜,值得临床推广.参10.     

Intraguild predation and mesopredator release effect on long-lived prey

Complete extirpation of a species can generate cascading effects throughout an ecosystem, yet are precisely the goal of island eradications of pest species. “Mesopredator release effect”, an asymmetrical special case of intraguild predation, has been hypothesised as a possible indirect effect from eradications, where superpredator removal can generate a mesopredator increase which may increase the impact on their shared prey. Theoretically this suggests that for intraguild predators, the superpredator may protect the shared prey from mesopredation, and removal of superpredators alone is not recommended. We create a model of long-lived age-structured shared prey and explore the non-equilibrium dynamics of this system. The superpredator can impact all prey life-stages (adult survival and reproductive success) whereas the smaller mesopredator can only impact early life-stages (reproductive success). This model is independently tested with data from a closed oceanic island system where eradication of introduced intraguild predators is possible for conservation of threatened birds. Mesopredator release only occurs in strongly top-down moderated (resource-abundant) systems. Even when mesopredator release can occur, the negative impact of more mesopredators is outweighed by the benefit of superpredator removal, allowing recovery of the prey population. Results are robust to 10% variation in model parameters. The consideration of age-structured prey contradicts previous theoretical results for mesopredator release effect and intraguild predation. Superpredator eradication is vital for population recovery of long-lived insular species. Nonetheless island conservation must retain a whole-ecosystem perspective given the complex trophic relationships among multiple species on islands.