ABSTRACT
Background: The accuracy of predictions of invasive species ranges is dependent on niche similarity between invasive and native populations and on our ability to identify the niche characteristics. With this work we aimed to compare the niche dynamics of two genetically related invasive populations of Vespa velutina (an effective predator of honeybees and wild pollinators), in two distinct climatic regions, one in central Europe and another one in the north-western Iberian Peninsula, and hence to identify uninvaded regions susceptible to invasion. Methods: Niche dynamics and shifts of V. velutina were assessed by comparing the environmental niches of the native and of the two invasive populations, using climatic, topographic and land use variables. We also ran reciprocal distribution models using different algorithms and records from both native and invasive ranges to compare model predictions and estimate which regions are at a greater risk of being invaded. Results: An apparent niche shift was detected in the population of the NW of Iberian Peninsula, where the species is living under environmental conditions different from the native niche. In central Europe, large suitable areas remain unoccupied. The fact that both invasive populations are well established, despite occupying environmentally distinct regions indicates that V. velutina has a high ability to successfully invade different environmental envelopes from those existing in its native range. For example, in north-western Iberian Peninsula the species is now thriving out of its native niche limits. Moreover, the large extent of still unoccupied environmental space with similar conditions to those used by the species in its native range suggests that there is still a large area of central and eastern Europe that can be potentially invaded by the species.
Subject(s)
Ecosystem , Wasps , Bees , Animals , Introduced Species , Europe , Europe, EasternABSTRACT
PURPOSE: Newly designed antiepileptic drugs (AEDs) are being evaluated for their efficacy in preventing seizures and for their toxic profiles. We investigated and compared the toxic effects of two dibenz[b,f]azepine derivatives with anticonvulsant activity, 10,11-dihydro-10-hydroxyimino-5H-dibenz[b,f]azepine-5-carboxamide (BIA2-024) and (S)-(-)-10-acetoxy-10,11-dihydro-5H-dibenz[b,f] azepine-5-carboxamide (BIA2-093), with the structurally related compounds carbamazepine (CBZ) and oxcarbazepine (OXC), both in current use for the treatment of epilepsy. METHODS: Primary rat hippocampal neurons were used to evaluate neuronal morphology and biochemical changes induced by the AEDs used in this study. Immunocytochemical staining against MAP-2 was used to evaluate neuronal morphology. Reactive oxygen species (ROS) and changes in mitochondrial membrane potential (Psim) were measured by fluorescence techniques. Intracellular adenosine triphosphate (ATP) levels were quantified by high-performance liquid chromatography (HPLC). RESULTS: Hippocampal neurons treated for 24 h with CBZ or OXC (300 microM) showed degeneration and swelling of neurites, but this effect was not observed in neurons treated with BIA 2-024 or BIA 2-093 (300 microM). ROS production also was increased in neurons treated with OXC, but not in neurons treated with the other AEDs. ATP levels were significantly decreased only in neurons treated with OXC, although the energy charge was not altered. Furthermore, OXC led to a decrease of Psim. CONCLUSIONS: In all parameters assayed, OXC was more toxic than the other AEDs used. Because the new putative AEDs have previously been shown to have an efficacy in preventing seizures similar to that of CBZ and OXC, and are less toxic to neuronal cells, they may be considered as alternatives to the current available therapies for the treatment of epilepsy.
