van Loo1, D. Lazic2 and M. H. J. Barfuss1
1Department of Botany and Biodiversity Research, University of Vienna, Rennweg 14, 1030 Vienna, Austria
2University of Natural Resources and Life Sciences, Peter-Jordan Strasse 82, A-1190, Vienna, Austria
Tree-of-heaven (Ailanthus altissima (Mill.) Swingle) is a dioecious pioneer tree species, which reproduces both sexually and asexually. Early sexual maturity, prolific fruiting, ready germination, adaptability to infertile sites and rapid growth rates make A. altissima an intensely spreading tree in many countries where it has been introduced. According to historical records, first seeds were sent from Peking (China) to Paris in the 1740s (Hu 1979). The tree-of-heaven soon became a popular planted species also in other European cities. Consequently cities became the place where the establishment and naturalization of this tree species principally started. At present, this tree grows throughout the majority of European countries.
In our study, we focus on the comparison of 289 A. altissima trees, collected mainly in large cities across 31 European countries and 389 trees from Vienna (Austria), in which we analysed patterns of genetic variation and structure in order to identify the geographic origin and dispersal patterns. In both comparisons (Europe vs Vienna), trees planted in botanical gardens and in urban parks, and naturalised along roads and rivers were genotyped using both nuclear DNA (Dallas et al. 2005, Kurochochi et al. 2015) and plastid DNA markers (Liao et al. 2014). We found three different plastid haplotypes present in European samples, whereas only one was present in Vienna, indicating a common geographic origin from north-eastern China. Within Vienna and across Europe, similar patterns of genetic structure (five identical genetic clusters) have been revealed allowing us to hypothesize that (i) the introduction area in China comprises several differentiated populations, and (ii) cities may harbor large genetic diversity and genetic pattern comparable to large areas and thus should not be underestimated in studies of invasion biology (based on results from Vienna, where sexual reproduction was more pronounced than asexual reproduction).
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Kurokochi H., Saito Y. & Ide Y. (2015) Genetic structure of the introduced heaven tree (Ailanthus altissima) in Japan: evidence for two distinct origins with limited admixture. Botany 93: 133–139.
Liao Y. Y., Guo Y. H., Chen J. M. & Wang Q. F. (2014) Phylogeography of the widespread plant Ailanthus altissima (Simaroubaceae) in China indicated by three chloroplast DNA regions. J. Syst. Evol. 52: 175–185.