Gradient of genetic diversity of Erigeron annuus in the part of invasive European range

Erigeron annuus (L.) Pers. (Asteraceae) is native species to eastern North America, but has been introduced to Europe and many other temperate regions of the world. In order to assess the impact of spreading history and settlement time on the genetic diversity of invasive populations of E. annuus, individual plants were sampled from 16 populations located in Switzerland, Poland, Lithuania and Latvia along the south-northern expansion direction of this species in Europe. One population was collected in native range (New Brunswick, Canada). The analysis of ISSR polymorphism in 253 plants revealed 161 polymorphic bands. The highest genotype variation and genetic diversity parameters were revealed in the populations from Switzerland and Poland, the least – in Latvian populations. All 37 plants from Latvia were clones of the same genotype. The comparison of genetic diversity parameters of populations from different countries showed the decrease of genetic diversity on the south-north direction.