Invasion Of The Red Imported Fire Ant (Solenopsis Invicta Buren) And Its Effects On The Diversity Of Indigenous Ants

Red imported fire ant (RIFA) Solenopsis invicta Buren is a highly invasive species reaches high densities in many of countries and has severe effects on the ecological environment, agriculture, forestry, human health and public safety. Since first found in Longyan City in September 2005, RIFA has spread to many other parts of Fujian Province. Past research has examined the feeding behaviors and activities, the structure and spatial distribution of mounds, population dynamics and chemical control in Fujian Province. This paper focuses on the possible sources of RIFA in Fujian Province, patterns of invasion and the population dynamics of indigenous ants.The mitochondrial cytochrome oxidaseâ… (COâ… ) gene of populations of RIFA in Fujian Province were examined. There appear to be three haplotypes of the COâ… gene. Haplotypeâ… was from the populations of Shanghang County, Wuping County and Huangmei Village Dachi Town in Xinluo District of Longyan City and Zhangpu County in Zhangzhou City, which can be speculated to come from cities of Shenzhen, Zhuhai, Zhongshan, Dongguan, Huizhou and Guangzhou. Haplotypeâ…¡was from the populations of Xiamen City and Jinjiang city, which can be speculated to come from cities of Yangchun and Wuchuan. Haplotypeâ…¢was from the populations of Nanyan Village Dachi Town of Xinluo District in Longyan City, where the haplotype was first found in Mainland China; it probably came from Hong Kong and Guangdong Province.Using a model fitting method, the primary parameters the invasion by RIFA in Fujian Province were analyzed to build up construct models of the relationships between time since introduction and the number of mounds, the densities of mounds in the invaded range and in different habitats. These results suggest that different populations have exhibited different patterns of invasion because they are invading different habitats and in different ways. The populations that were imported with reusable resources have so far occupied only relatively small ranges and their rate of invasion has been relatively slowly (28.1-116.4 m/yr). However, the densities of mounds would reach a relatively high level within a certain period. The populations that were imported with greensward and saplings have relatively large ranges and spread relatively rapidly (126.1-555.5 m/yr). Models relating to the densities of mounds, the number of mounds and time since invasion were constructed as follows, N=1003.9Ln(t)+336.27, D=0.0966e0.583t, where t denotes the time since invasion, N denotes the number of mounds and D denotes the density of mounds. These models suggest that RIFA invaded between January and October 2007 in Huli District of Xiamen City, between February 2007 and January 2008 in Tong'an District of Xiamen City, and between September 2003 and February 2004 in Zhangpu County of Zhangzhou City.A systematic investigation of ant communities in invaded and non-invaded areas revealed that they are dominated by the Myrmicinae (82% of individuals). Generally, more ants were trapped in autumn than in spring in terms of both numbers of species and numbers of individual. In invaded areas, the less severe the damage from RIFA, the faster the recovery of indigenous ant populations. In heavily invaded areas, the community composition of indigenous ants is significantly different from that of non-invaded areas and overall abundance is lower. In addition, the recovery of indigenous ant populations depends on the diversity and abundance of the primary population in the habitat. The more stable the population structure, the faster the recovery. Thus, the extent of recovery of indigenous ant populations is greatest in shrubby habitats, least in crop and roadside habitats and intermediate in orchards and waste grassland habitats.