In the case of recently established populations of Solenopsis invicta in Taiwan,analysis of genetic variation may provide various dimensions regarding the historical demographic events of this invasive species,which represents a novel opportunity to study the genetic consequences of invasiveness over an ex- tremely short time period.Here we describe genetic structure of two introduced S.invicta populations, Taoyuan and Chiayi,in Taiwan using two classes of markers,nuclear(microsatellites)and mitochondrial (mtDNA)genomes.Pronounced regional differentiation inferred from either AMOVA or Bayesian clustering approach at both genomes suggests that the two populations most likely originate from separate introductions. Furthermore,significant mtDNA but not nuclear differentiation between sympatric social forms suggests two scenarios that interform gene flow is mainly mediated by males,and queens of each form commonly fail to become egg-layers of alternate form.Isolation by distance(IBD)obtained from microsatellites is absent in monogynes,indicating sexuals of this form retain the superior dispersal ability to homogenize the nuclear sig- nature among spatially isolated areas;however,lack of IBD in less vagile polygyne may result from frequent human mediated jump dispersal that erodes the geographical restrictions of genetic exchange.The patterns observed here not only provide insights into how social organization influences the interform gene flow but also reinforce different breeding strategies pursued by two forms in the character of shaping the genetic varia- tion at two levels of genomes. In the case of recently established populations of Solenopsis invicta in Taiwan, analysis of genetic variation may provide various dimensions regarding the historical demographic events of this invasive species, which represents a novel opportunity to study the genetic consequences of invasiveness over an ex- tremely short time Period.Here we describe genetic structure of two introduced S.invicta populations, Taoyuan and Chiayi, in Taiwan using two classes of markers, nuclear (microsatellites) and mitochondrial (mtDNA) genomes.Pronounced regional differentiation inferred from either AMOVA or Bayesian clustering approach at both genomes suggests that the two populations most likely originate from separate introductions. Furthermore, significant mtDNA but not nuclear differentiation between sympatric social forms suggests two scenarios that interform gene flow is mainly mediated by males, and queens of each form typically fail to become egg- layers of alternate form. Isolation by distance (IBD) obtain ed from microsatellites is absent in monogynes, indicating sexuals of this form retain the superior dispersal ability to homogenize the nuclear sig- nature among spatially isolated areas; however, lack of IBD in less vagile polygyne may result from frequent human mediated jump dispersal that erodes the geographical restrictions of genetic exchange. The patterns observed here not only provide insights into how social organization influences the interform gene flow but reinforce different breeding strategies pursued by two forms in the character of shaping the genetic varia- tion at two levels of genomes.