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Understanding the factors that determine rates of range expansion is not only crucial for developing risk assessment schemes and management strategies for invasive species, but also provides important insight into the ability of species to disperse in response to climate change. However, there is little knowledge on why some invasions spread faster than others at large spatiotemporal scales. Here, we examine the effects of human activities, species traits and characteristics of the invaded range on spread rates using a global sample of alien reptile and amphibian introductions. We show that spread rates vary remarkably among invaded locations within a species, and differ across biogeographical realms. Spread rates are positively related to the richness of native congeneric species and human-assisted dispersal in the invaded range but are negatively correlated with topographic heterogeneity. Our findings highlight the importance of environmental characteristics and human-assisted dispersal in developing robust frameworks for predicting species' range shifts., (© 2014 John Wiley & Sons Ltd/CNRS.)

Chytridiomycosis, caused by the chytrid fungus Batrachochytrium dendrobatidis (Bd), has been implicated in amphibian population declines worldwide. However, no amphibian declines or extinctions associated with Bd have been reported in Asia. To investigate the history of this pathogen in China, we examined 1,007 museum-preserved amphibian specimens of 80 species collected between 1933 and 2009. Bd was detected in 60 individuals (6.0%), with the earliest case of Bd infection occurring in one specimen of Bufo gargarizans and two Fejervarya limnocharis, all collected in 1933 from Chongqing, southwest China. Although mainly detected in non-threatened native amphibians, Bd was also found in four endangered species. We report the first evidence of Bd for Taiwan and the first detection of Bd in the critically endangered Chinese giant salamander (Andrias davidianus). Bd appears to have been present at a low rate of infection since at least the 1930s in China, and no significant differences in prevalence were detected between decades or provinces, suggesting that a historical steady endemic relationship between Bd and Chinese amphibians has occurred. Our results add new insights on the global emergence of Bd and suggest that this pathogen has been more widely distributed in the last century than previously believed.

Aim The conservatism of the realized climatic niche is a pivotal assumption for predicting invasion risk under present and future climates. To date, however, no studies have identified the particular dimensions of realized climatic niches that are spatially and temporally conserved for a whole taxonomic group on a global scale. Understanding realized niche dynamics along each individual climatic variable separately is a key consideration for improving forecasts of invasive species distributions and anticipating future range expansions. Location Global. Methods Using 181 successful invasion events for 128 alien herpetofaunal species across the globe, we applied a robust niche dynamics framework and analysed the conservatism of the realized climatic niche and its influencing factors along 19 temperature and precipitation variables. Results We found that the magnitude of the niche expansion along the maximum temperature of the warmest month (or warmest quarter) was, on average, the lowest compared with the niche expansion magnitude along the minimum, average, range and seasonal temperature characteristics and all precipitation variables. Furthermore, the niche shift along the maximum temperature was only negatively correlated with native range size and was unrelated to residence time, species traits, introduction propagule pressure, topographic heterogeneity or equatorwards and polewards range expansion. Main conclusions We provide the first evidence that the realized climatic niche of alien herpetofaunal species is generally most conserved along maximum temperatures. This finding highlights the importance of preferentially choosing conserved climatic niche parameters to develop robust predictions of biological invasions or shifts in species ranges in response to climate change. [ABSTRACT FROM AUTHOR]

Understanding the locations of potential invasion hotspots and the extent to which they overlap with biodiversity hotspots is crucial for prioritizing efforts to reduce the impacts of alien species on global biodiversity. Using ensembles of species distribution models based on climate, anthropogenic predictors, vegetation, and water resources, we predict global potential invasion hotspots for alien herpetofauna (reptiles and amphibians). On average, when subjected to current and future climate scenarios, potential richness of alien herpetofauna per grid cell (the minimum unit of our spatial variables for modeling and projecting) in biodiversity hotspots is nearly 1.4 times higher than in other regions. Furthermore, potential invasion hotspots are projected to occupy a large proportion of the total area within biodiversity hotspots. These results suggest that biodiversity hotspots are at greater risk from alien herpetofaunal invasions than are other regions. Our results provide key information for globally targeting early detection and rapid-response programs to help prevent or mitigate future impacts of alien herpetofauna on biodiversity. [ABSTRACT FROM AUTHOR]