An evaluation of the genetic structure and post-introduction dispersal of a non-native invasive fish to the North Island of New Zealand

The efficacy of invasive species management is dependent on a thorough understanding of the size, origin, and genetic structure of invasive populations. We evaluated the genetic diversity and structure of the western mosquitofish, Gambusia affinis, across the North Island of New Zealand in an effort to better understand the genetic structure and post-introduction dispersal mechanisms of this highly invasive estuarine species. We found clear evidence of founder effects and significant genetic structure for populations derived from populations initially established in New Zealand in the 1930s. Our findings indicate that G. affinis populations have succeeded through a combination of localized dispersal and human-assisted colonization. Additionally, we identify a series of populations in one region that are apparently genetically isolated from the other regions. This area could thus represent a significant eradication unit'' where re-colonization is unlikely. Our results highlight the utility and value of molecular tools as an efficient method to facilitate a richer understanding of the nature and condition of invasive species while identifying definitive management objectives.