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Shifts between native and alien climatic niches pose a major challenge for predicting biological invasions. This is particularly true for insular species because geophysical barriers could constrain the realization of their fundamental niches, which may lead to underestimates of their invasion potential. To investigate this idea, we estimated the frequency of shifts between native and alien climatic niches and the magnitude of climatic mismatches using 80,148 alien occurrences of 46 endemic insular amphibian, reptile, and bird species. Then, we assessed the influence of nine potential predictors on climatic mismatches across taxa, based on species' characteristics, native range physical characteristics, and alien range properties. We found that climatic mismatch is common during invasions of endemic insular birds and reptiles: 78.3% and 55.1% of their respective alien records occurred outside of the environmental space of species' native climatic niche. In comparison, climatic mismatch was evident for only 16.2% of the amphibian invasions analyzed. Several predictors significantly explained climatic mismatch, and these varied among taxonomic groups. For amphibians, only native range size was associated with climatic mismatch. For reptiles, the magnitude of climatic mismatch was higher for species with narrow native altitudinal ranges, occurring in topographically complex or less remote islands, as well as for species with larger distances between their native and alien ranges. For birds, climatic mismatch was significantly larger for invasions on continents with higher phylogenetic diversity of the recipient community, and when the invader was more evolutionarily distinct. Our findings highlight that apparently common niche shifts of insular species may jeopardize our ability to forecast their potential invasions using correlative methods based on climatic variables. Also, we show which factors provide additional insights on the actual invasion potential of insular endemic amphibians, reptiles, and birds. [ABSTRACT FROM AUTHOR]

Our ability to predict the spread of alien species is largely based on knowledge of previous invasion dynamics of individual species. However, in view of the large and growing number of alien species, understanding universal spread patterns common among taxa but specific to regions would considerably improve our ability to predict future dynamics of biological invasions. Here, using a comprehensive dataset of years of first record of alien species for four major biological groups (birds, nonmarine fishes, insects, and vascular plants), we applied a network approach to uncover frequent sequential patterns of first recordings of alien species across countries worldwide. Our analysis identified a few countries as consistent early recorders of alien species, with many subsequent records reported from countries in close geographic vicinity. These findings indicate that the spread network of alien species consists of two levels, a backbone of main dispersal hubs, driving intercontinental species movement, and subsequent intracontinental radiative spread in their vicinity. Geographical proximity and climatic similarity were significant predictors of same-species recording among countries. International trade was a significant predictor of the relative timing of species recordings, with countries having higher levels of trade flows consistently recording the species earlier. Targeting the countries that have emerged as hubs for the early spread of alien species may have substantial cascading effects on the global spread network of alien species, significantly reducing biological invasions. Furthermore, using these countries as early-warning system of upcoming invasions may also boost national prevention and invasion preparedness efforts. [ABSTRACT FROM AUTHOR]

Abstract: Aim: Darwin's naturalization hypothesis states that dissimilarity to native species may benefit alien species establishment due to empty niches and reduced competition. We here add a new dimension to large‐scale tests of community invasibility, investigating the role that previously established alien species play in facilitating or hindering new invasions in plant communities. Location: Permanent grasslands across France (including mainland and Corsica), as a receding ecosystem of great conservation importance. Methods: Focusing on 121 alien plant species occurring in 7,215 vegetation plots, we quantified biotic similarity between new invaders and resident alien species (i.e., alien species with longer residence times) based on phylogenetic and trait distances. Additionally, we calculated distances to native species for each alien species and plot. Using multispecies distribution models, we analysed the influence of these biotic similarity measures and additional covariates on establishment success (presence/absence) of new invaders. Results: We found that biotic similarity to resident alien species consistently increased establishment success of more recently introduced species. Phylogenetic relatedness to previous invaders had an equally strong positive effect as relatedness to native species. Conversely, trait similarity to natives hindered alien establishment as predicted by Darwin's naturalization hypothesis. These results highlight that various mechanisms may act simultaneously to determine alien establishment success. Main conclusions: Our results suggest that, with greater similarity among alien species, invasion success increases. Such a pattern may arise either due to actual facilitation among invaders or as a result of weaker competitive interactions among invaders than between native and alien species, leading to an indirect facilitative effect. Alternatively, recent environmental changes (e.g., eutrophication, climate change) may have added new environmental filters. Determining how initial invasions might pave the road for subsequent invasions is crucial for effective multispecies management decisions and contributes a new aspect to our understanding of community assembly. [ABSTRACT FROM AUTHOR]