Search

The establishment success of a population is a function of abiotic and biotic factors and introduction dynamics. Understanding how these factors interact has direct consequences for understanding and managing biological invasions and for applied ecology more generally. Here we use a mesocosm approach to explore how the size of founding populations and the number of introduction events interact with environmental conditions (temperature) to determine the establishment success of laboratory-reared Drosophila melanogaster. We found that temperature played the biggest role in establishment success, eclipsing the role of the other experimental factors when viewed overall. Under optimal temperature conditions propagule pressure was of negligible importance to establishment success. At adverse temperatures, however, establishment success increased with the total founding population size. This effect was considerably stronger at the cold than at the hot extreme. Whether the population was introduced all at once or by increments (changing the number of introduction events) had a negligible global effect. However, once again, a stronger effect of increasing number of introduction events was seen at adverse temperatures, with hot and cold extremes revealing opposite effects: adding flies incrementally decreased their establishment success at the hot extreme, but increased it at the cold extreme. These differing effects at hot and cold thermal extremes implies that different establishment mechanisms are at play at either extreme. These results suggest that the effort required to prevent (or conversely, to facilitate) the establishment of populations varies with the environment in ways that can be complicated but predictable.

Since alien species may threaten native ecosystems when becoming invasive, one of the main challenges is try to predict their potential spread. Despite bees are essential pollinators and provide important ecosystem services in their native areas, outside these areas they could represent a risk for the local bee fauna, e.g. by competing for resources or by transmitting pathogens, as it was observed for species of Megachile, the bee genus with the highest number of recorded alien species. Here, using two complementary methods (Multidimensional Envelope procedure (MDE) and the Maximum Entropy algorithm (MaxEnt)), we aim to explore environmental niche as well as to identify potential worldwide distribution of the giant resin bee Megachile sculpturalis, native to Asia and recently introduced in North America and Europe. The two methodological approaches predict an important expansion for the species and reveal a preference for areas of Palearctic and Nearctic regions with reduced temperature fluctuations and moderate precipitation regimes. The Southern hemisphere seems not having good conditions for this species. Estimations for the future (2070) predict a further, though limited expansion to northern areas in the North hemisphere. However, during roughly 25 years of spreading outside its native range, M. sculpturalis clearly expanded the range of inhabitable environmental conditions, which may increase its potential invasiveness in a pattern difficult to predict using only correlative methods. Physiological and ecological data are necessary to better assess the potential niche of this bee species and in consequence to better predict its future spreading dynamics.

The plant pathogen Xylella fastidiosa (Xf) is a significant threat to various economically important tree cash crops. Although previously found only in the Americas, the bacterium responsible for olive quick decline syndrome was detected in Apulia, Italy, in 2013. Since then, it has spread to approximately 54,000 ha of olive trees in the region, causing dramatic concern throughout the Mediterranean basin. As a result, it is crucial to comprehend its distribution and forecast its potential diffusion. The effect of the anthropogenic component of the landscape on the distribution of Xf remains little explored. The present study used an ecological niche model to identify how different land uses, used as proxies of different levels of human pressure across the Apulia territory, impacted the distribution of the Xf-infected olive trees in 2015-2021. Results demonstrated that the anthropogenic component significantly contributed to the epidemic, with the road system representing the main driver of diffusion and natural/seminatural areas hampering Xf spread at the landscape scale. This evidence highlighted the importance of explicitly considering the effects of the anthropogenic landscape when modelling Xf distribution and support the design of landscape-informed monitoring strategies to prevent Xf spread in Apulia and other Mediterranean countries., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. The work was carried out within the Agritech National Research Center and received funding from the European Union Next-GenerationEU (National Recovery and Resilience Plan (NRRP) – MISSION 4 COMPONENT 2, INVESTMENT 1.4 – D.D. 1032 17/06/2022, CN00000022). The work was also carried out within the Project 'DIACOX' funded by the Italian Ministry of Agriculture and Forest - DM 664531 - 28/12/2022. This manuscript reflects only the author’s views and opinions, neither the European Commission nor the Italian Ministry can be considered responsible for them., (Copyright © 2023 The Authors. Published by Elsevier B.V. All rights reserved.)