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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. [ABSTRACT FROM AUTHOR]

The altitudinal distribution of plants is restricted by various environmental factors, with climatic conditions being one of the primary constraints. Here, we investigate what limits the altitudinal range of the introduced species Erigeron annuus in the Swiss Alps. We planted offspring of E. annuus plants originating from different altitudes into two common gardens, one located at an altitude representing the main area of distribution (400 m) and the other close to the current altitudinal limit of E. annuus in Switzerland (1000 m). In both common gardens all established plants survived and grew vigorously during the growing season. However, there was high winter mortality of seedlings at 1000 m. Furthermore, plant phenology was delayed and reproductive output was reduced at 1000 m, although the seeds produced were larger. The general lack of adaptation to altitude and only moderate levels of plasticity suggest that there is little potential for E. annuus to persist beyond its current altitudinal limit in the Swiss Alps. However, climate warming might promote the upward range expansion of E. annuus by reducing winter mortality and by increasing the chance of producing seeds within the growing season. [ABSTRACT FROM AUTHOR]