Climate change has increased the global threats posed by three ragweeds (Ambrosia L.) in the Anthropocene

Invasive alien plants (IAPs) substantially affect the native biodiversity, agriculture, industry, and human health worldwide. Ambrosia (ragweed) species, which are major IAPs globally, produce a significant impact on human health and the natural environment. In particular, invasion of A. artemisiifolia, A. psilostachya, and A. trifida in non-native continents is more extensive and severe than that of other species. Here, we used biomod2 ensemble model based on environmental and species occurrence data to predict the potential geographical distribution, overlapping geographical distribution areas, and the ecological niche dynamics of these three ragweeds and further explored the environmental variables shaping the observed patterns to assess the impact of these IAPs on the natural environment and public health. The ecological niche has shifted in the invasive area compared with that in the native area, which increased the invasion risk of three Ambrosia species during the invasion process in the world. The potential geographical distribution and overlapping geographical distribution areas of the three Ambrosia species are primarily distributed in Asia, North America, and Europe, and are expected to increase under four representative concentration pathways in the 2050s. The centers of potential geographical distributions of the three Ambrosia species showed a tendency to shift poleward from the current time to the 2050s. Bioclimatic variables and the human influence index were more significant in shaping these patterns than other factors. In brief, climate change has facilitated the expansion of the geographical distribution and overlapping geographical distribution areas of the three Ambrosia species. Ecomanagement and cross-country management strategies are warranted to mitigate the future effects of the expansion of these ragweed species worldwide in the Anthropocene on the natural environment and public health.

[Studies on colonization risk and potential geographical distribution of Biomphalaria glabrata as an intermediate host of Schistosoma mansoni in Mainland China]

OBJECTIVE

To predict the colonization risk and potential geographical distribution of Biomphalaria glabrata in the Mainland China based on the past period temperature data.

METHODS

The survival extreme high temperatures and low temperatures of B. glabrata eggs, young and adult B. glabrata snails and the average effective accumulated temperature of generation development were determined in laboratory conditions. The temperature data in January and July from 1955 to 2010 were collected from the national meteorological monitoring sites in the southern part of China, including Chongqing, Zhejiang, Yunnan, Sichuan, Jiangxi, Hunan, Hainan, Guizhou, Guangdong, Guangxi and Fujian provinces (11 provinces). A database of ambient temperature related to B. glabrata was established based on the Geographic Information System (GIS). The colonization risk and potential geographical distribution of B. glabrata in the southern part of China were analyzed and predicted by ArcGIS 10.1 software.

RESULTS

The half lethal low temperatures of B. glabrata eggs, young and adult B. glabrata snails were 6.80, 6.34 ℃ and 6.60 ℃ respectively; the half lethal high temperatures of B. glabrata eggs, young and adult B. glabrata snails were 35.99, 33.59 ℃ and 32.20 ℃, respectively. The developmental threshold temperature was 7.16 ℃; the average effective accumulated temperature of generation development was (1 970.07 ± 455.10) days-degree. The GIS overlay analysis of the half lethal low and high temperatures of B. glabrata showed that the local temperature conditions in all Hainan and part regions in Yunnan, Guangxi, Guangdong and Fujian were conformed to the survival temperature of B. glabrata snails. The regions, where the average effective accumulated temperature was more than the average effective accumulated temperature of generation development of B. glabrata, were Guangdong and Hainan, and part regions of other 9 provinces. The overlay analysis of GIS maps of the survival extreme high temperatures and low temperatures of B. glabrata with the GIS map of the average effective accumulated temperature of generation development in 2010 showed that the whole region of Hainan and part regions of Guangdong, Guangxi, Yunnan and Fujian were potential geographical distribution regions of colonization risk of B. glabrata. The overlay analysis of GIS maps of the survival extreme high temperatures and low temperatures of B. glabrata with the GIS map of the average effective accumulated temperature of generation development from 1955 to 2010 showed that the potential geographical distribution regions of B. glabrata was expanding from the whole region of Hainan and part regions of Guangdong in 1955 to the whole region of Hainan and part regions of Guangdong, Guangxi, Yunnan and Fujian in 2010.

CONCLUSIONS

If B. glabrata snails were introduced into the Mainland China, the potential geographical distribution regions would be the whole region of Hainan and part regions of Guangdong, Guangxi and Yunnan. The changes of risk range and risk intensity present the trends of expanding and increasing from the south to the north gradually.