The role of propagule pressure and genetic diversity in successful invasion of the red imported fire ant (Solenopsis invicta) in Taiwan
Date Issued
2011
Date
2011
Author(s)
Lee, Chih-Chi
Abstract
Genetic diversity is one of the key determinants for species’ survival and evolution. From the conservation biology perspective, a small population is prone to extinction by inbreeding depression or accumulation of deleterious mutations. Invasive species, however, are generally successful in introduced ranges despite loss of genetic diversity due to small founder population sizes, which gives rise to a paradox between invasion and conservation biology in term of genetic diversity. Social insects, such as ants, wasps, and termites, represent a highly successful group of invasive species not only because their small founder population sizes often lack immediately recognizable signature but also their great dispersal power, high reproductive rate and the competitive ability of “super individuals”. One of the notorious ant invaders, the red imported fire ant (Solenopsis invicta), originating from South America, has been accidentally introduced into the USA, Australia, Taiwan and China. Invasions by fire ants in these areas provide an excellent framework to investigate the factors contributing to the successful establishment of social insects especially since this species utilizes a single locus complementary sex determination (sl-CSD) system. Theoretically, the genetic load is predicted to be much more profound for S. invicta due to the mass production of sterile diploid males imposed by loss of genetic diversity. This study therefore aimed to determine how fire ants overcome such a disadvantage using population genetic approaches. An assessment of genetic variation at 12 microsatellite loci in 120 fire ant colonies in northern Taiwan (Taoyuan) revealed that Taoyuan was colonized by ants on a minimum of two occasions. Furthermore, estimates of genetic diversity at the CSD locus by calculating the proportion of match matings (queens mated with males harboring identical CSD allele) do not differ significantly between fire ant populations in Taiwan and the putative source, the USA, suggesting that the successful invasion of fire ants is likely attributable to adequate genetic diversity maintained by larger propagule number (e.g, multiple invasions). In summary, this study not only highlights that cryptic invasions might be undetected until the deep genetic structure of focal populations has been revealed but also signifies the importance of genetic diversity in shaping the invasion success of fire ants.
Subjects
fire ant
invasion biology
microsatellite
population genetics
propagule pressure
Solenopsis invicta
Type
thesis
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