Invasion success despite reduction of genetic diversity in the European populations of eastern mosquitofish (Gambusia holbrooki)

The introduction of a few individuals to new, isolated habitats (founder effect) is expected to reduce the genetic variability of a population. At the beginning of the last century a few eastern mosquitofish (Gambusia holbrooki) individuals were introduced to Southern Europe from North America to control malaria-carrying mosquitoes. We studied the effect of this severe bottleneck on genetic variability in four populations of eastern mosquitofish introduced to Spain and Italy in the early 1900s and compared them to a native population in North America. Using amplified polymorphic DNA-polymerase chain reaction (RADP-PCR) we found a strong reduction of genetic diversity, in terms of both number of polymorphic loci and heterozygosity, in all four European populations. Despite this great reduction in genetic diversity, eastern mosquitofish successfully invaded European internal waters causing eutrophication problems and threatening the extinction of local populations of native fish.