Disentangling the genetic origin of Heracleum persicum (Apiaceae) in Europe: multiple introductions from multiple source populations

Unraveling the origin and colonization history of invasive plants is a long-standing challenge in evolutionary and conservation biology. The knowledge of the origin of the invasive plants in Europe is often confounded by limited sampling in the source region. We determined the extent of genetic structuring in the native range and reconstructed the origin and the invasion history of Persian hogweed, Heracleum persicum, into Europe. We used allelic polymorphism of microsatellite markers obtained from 36 Iranian populations from Middle East combined with data from 38 European populations representing the major native and introduced ranges, respectively. Comprehensive sampling in the native range covered 97% of allelic diversity found in the introduced range, and showed that allelic variation, heterozygosity and population differentiation are significantly reduced in the introduced populations. Results from Bayesian structure, neighbor-net, and ordination analyses showed that populations in the native range consist of three distinct genetic clusters: Eastern, Central, and Western. Although we observed high genetic differentiation among these groups, the Western cluster was genetically closer to the Central cluster. Approximate Bayesian Computation (ABC) analysis supports at least three independent origins for European populations. No European population originated from the Eastern cluster within the native range. Danish populations originated from the Central cluster, whereas the UK and Finland populations originated independently from the Western cluster. Norwegian populations originated from UK, and subsequently established the FI-Kar population in Finland. Our results shed light on the complex origin and history of an aggressive invasive plant species in Europe, supporting contribution from multiple genetic lineages in recent ancestry of introduced populations, thus suggesting the potential for ecological diversification within the introduced range.