Projecting The Distribution Of The Suitable Area Of Conyza Sumatrensis In China And Its Spatial Shift Under Changing Climate

Conyza sumatrensis(Asteraceae:Conyza)is an annual or biannual weed indigenous in South America,but has been spread to a much wider range of tropics and subtropics worldwide.In 2014,the Ministry of Environment Protection(MOEP)of China listed C.sumatrensis in the "Third List of Invasive Alien Species in China".However,the biological,physiological,and ecological research of this weed is still rather limited,and its distribution range and pattern in China remains unclear to date.The present study aimed at the potential distribution range of C.sumatrensis in China,utilised the BioClim climatic variables to project the suitable areas of C.sumatrensis as well as analyse the spatial shift of such areas under climate change scenarios proposed by the IPCC AR5.The present study first built a 10 km × 10 km grid in ArcGIS to run a systematic resampling on the presence data points of C.sumatrensis collected via literature referring,botanical museum visiting,and field surveys.The resampled distribution dataset was used to run the ecological niche factor analysis(ENFA)with the 19 BioClim variables to screen the key influential environmental factors,which were later used to project the suitable areas in China in Maxent.The areas of each suitability rank,shift of suitable areas and altitude ranges were analysed in ArcGIS.The main findings are as follow.1.ENFA analysis identified eight BioClim variables,namely mean diurnal range(bio2),isothermality(bio3),temperature seasonality(bio4),maximum temperature of the warmest month(bio5),minimum temperature of the coldest month(bio6),temperature annual range(bio7),annual precipitation(bio12),and precipitation seasonality(bio15),as key influential environmental factors.The results indicated that C.sumatrensis is prone to areas with higher mean annual temperature and higher annual precipitation with less temperature and humidity range.2.The distribution of high suitable area of C.sumatrensis mainly concentrated in South and Southwest China,e.g.,the Yunnan-Guizhou Plateau,the Southeast Hills,Hainan,and Taiwan,with very limited range in South Tibet.The total area of high suitable area is 1648.7 × 103 km2,comprising 17.55%of China's land territory,and its northernmost limit is 32.770 °N.The medium suitable area mainly extends from Central China to the Shandong Peninsula,the total area of which is 880.4 × 103 km2,comprising 9.17%of China's land territory,and its northernmost limit is 37.712 °N.3.Under the changing climate,the high suitable area of C.sumatrensis in China would contract while the medium suitable area is expanding,resulting in an increase of total suitable area.In South Yunnan,central Sichuan Basin,Southeast coastal areas,and Hainan,the high suitable area would reduce to 937.26 × 103 10km2 under the RCP8.5 scenario in 2070,but the northernmost limit would move to 37.011 °N.The medium suitable area would begin to appear in South Gansu,South Shaanxi,Henan,and Anhui,with its total area expand up to 1770.67 × 103 km2 under the RCP8.5 scenario in 2070,and its northernmost limit move to 39.094 °N.Ultra-high suitable area would begin to appear in certain regions.Under RCP2.6 scenario in 2050,ultra-high suitable areas would begin to appear in Taiwan,while the area reach the maximum(281 km2)under RCP4.5 scenario in 2070.The northernmost limit of these ultra-high suitable areas is 25.227 °N.Generally,the upper limit suitable latitude and altitude would also increase.The entire suitable altitude range would expand from 0-3900 m up to 5400 m under the RCP8.5 scenario in 2070.However,the suitability in lower-altitude areas would decrease.Since C.sumatrensis is more likely to be found in farmlands,sparse bushes/forests,and grasslands,regions concentrated with such matrix should pay extra attention to massive and quick invasion of this weed.By comparing the spatial distribution of the suitable areas of C.sumatrensis obtained in the present study and the land utility satellite remote sensing images of China,the present study proposed that Southwest China,Guangxi,Guangdong and the associated coastal areas are very vulnerable to the invasion of C.sumatrensis.Regular survey,monitoring,and management precautions should be formulated for these areas in order to achieve effective prevention and management.