Population genetic structure of the red imported fire ant, Solenopsis invicta, in Taiwan

Abstract

We generated and analyzed microsatellite genotypic data and mtDNA sequence data from the fire ant Solenopsis invicta collected from two separate infested areas (Taoyuan and Chiayi) in Taiwan to infer the population and colony structure of these recently established populations. These genetic analyses revealed the following patterns: 1) Relatedness among worker nestmates was significantly greater than zero for both social forms from both populations; 2) No significant isolation by distance was found among nests within each social form from either population; 3) Significant mtDNA but no nuclear differentiation occurs between sympatric social forms in Taoyuan; 4) Molecular signatures of genetic bottlenecks associated with recent introductions are evident in both populations; and 5) The two sampled populations, Taoyuan and Chiayi, are highly genetically differentiated at both the nuclear or mtDNA genomes and most likely derive from two separate introductions into Taiwan. While results from these analyses generally were consistent with predictions based on the known biology of these ants and similar studies of S. invicta in the U.S.A. and South America, some patterns likely reflect the recent introduction and human-mediated inadvertent transport of ants in Taiwan. This is the first study to investigate the population and colony structure of fire ants in Taiwan and results from our study represent an important contribution to the ongoing efforts aimed at eradicating this invasive pest in Taiwan.

Loss of microbial (pathogen) infections associated with recent invasions of the red imported fire ant Solenopsis invicta

“…The first mechanism is plausible in the case of S. invicta given the fact that previous population genetic studies suggest that relatively few numbers of founder queens likely were associated with introductions into these areas (Henshaw et al 2005;Yang et al 2008). This scenario is obviously the most parsimonious explanation for the absence of Wolbachia and V. invictae in these areas since the prevalence of these two microbes is quite low (perhaps even zero in the case of V. invictae, Oi and Valles, unpublished data) throughout the US, which appears to be most likely the source for these recent invasions (Shoemaker et al 2000(Shoemaker et al , 2003Bouwma et al 2006;Oi and Valles 2008).…”

“…1). Finally, while several lines of evidence suggest that other introduced populations likely come from the large US population (Henshaw et al 2005;Tschinkel 2006;Yang et al 2008), some doubts remain (Yang et al 2009;Ascunce et al, unpublished data), and it is still unknown which particular geographic area of the US might be the source population for these secondary introductions. Without such knowledge, we included all survey data from Florida, Louisiana and Texas since any are potential sources for these other areas and these are the only populations where all studied pathogen species have been surveyed and documented in the existing literature.…”

Four mutually incompatible Argentine ant supercolonies in Japan: inferring invasion history of introduced Argentine ants from their social structure

“…The red imported fire ant has invaded several regions of Asia (Zhang et al 2007). Furthermore, Yang et al (2008) suggested that the introduced populations of this species in Taiwan derived from two introductions. Establishment of the Argentine ant in Asia has not been reported other than from Japan, but Thailand and Singapore were recorded as the sources for Argentine ants transported to New Zealand (Corin et al 2007a).…”

“…Given the difficulties in eradicating or managing these ants (Silverman and Brightwell 2008), identifying the pathways of dispersal is an important subject to clarify the factors responsible for the recent successive invasions of these ants into Asia and to prevent the spread of them in this region. However, there have been few systematic studies to address the large scale dispersal events of these species Tsutsui et al 2001;Shoemaker et al 2006;Corin et al 2007a), and as for the introduced populations in Asia there have been very few attempts to elucidate their invasion history (Yang et al 2008).…”

The genome of the fire ant Solenopsis invicta

“…There is thus an urgent need to develop effective and safe alternative management techniques (7). Despite extensive quarantine and extermination efforts, S. invicta is now also found in many other countries including Australia, China, and Taiwan (8)(9)(10).…”