Patterns of genetic variation in invasive populations of Gunnera tinctoria: an analysis at three spatial scales

Abstract

While there is evidence that the genetic structure of invasive populations may be distinct from native populations, it has proved difficult to establish the causes of any variation owing in part to the range of evolutionary processes involved. In order to assess differences in the genetic structure of invasive populations of Gunnera tinctoria, five native populations were compared to 23 geographically widely dispersed invasive populations using amplified fragment length polymorphic markers (AFLPs). In total, 221 individuals were sampled at three spatial scales: inter-regional, within-region, and at a high-resolution local scale. It was observed that there were high levels of genetic variation between most populations, that invasive populations were generally distinct from both native populations and from each other and that genetic variation away from founding populations can occur relatively quickly and within a small geographic area. Changes in the pattern of genetic variation observed in invasive populations strongly indicated that founder effects and genetic drift played a significant role in shaping their genetic structure. It was further concluded that gene flow had a homogenizing effect on the structure of invasive populations occurring in close proximity, increasing their allele content and potentially contributing to their successful establishment.