A hybrid of alien Impatiens in the natural environment in the EPPO region
In 2011, atypical Impatiens parviflora (Balsaminaceae) plants differing in flower colour and morphology were collected in the nature reserve Bolle di Magadino, Ticino canton, Switzerland. Initially, these individuals were thought to be a hybrid of I. parviflora and I. glandulifera (EPPO List of Invasive alien Plants) as both species were observed to be growing together in the understory of the alluvial forest. However, I. balfourii is also present in the national park and thus a study was conducted to evaluate the parents of the hybrid. In 2012, further voucher specimens and seeds were collected at three locations in Bolle de Magadino, Ziegelbrücke (St. Gallen canton) and in Winterthur (Zurich canton), and in 2014 specimens were collected from five locations in Ticino canton. All voucher specimens were deposited at the National Plant Protection Organization in the Netherlands (Wageningen). Gemination trials were conducted to evaluate the viability of the seeds and to evaluate if the hybrid could produce a self-sustaining population in the absence of the parent species. Molecular analysis was conducted on the hybrid and compared to other Impatiens species. The results showed that the individuals were a hybrid between I. parviflora and I. balfourii. In germination trials, only seed collected from Bolle di Magadino germinated, where 4 weeks of cold stratification and moist storage produced 95 % germination.F2 and F3 generation plants were grown, proving the hybrid is fertile. Sizable populations of the hybrid were observed in 2014 in the Ticino canton in the absence of the parental species. The hybrid I. parviflora x I. balfourii is an annual herb up to 60 cm tall.The stem is erect or ascending and the leaves are alternate.
Sources
Van Valkenburg JLCH, Schoenenberger N, van de Vossenberg BTLH, Man in’t Veld WA, Westenberg M, Boer E (2019) A natural hybrid of Impatiens, in the introduced range, demonstrated by sequence analysis of the nuclear ribosomal DNA-gene repeat. Botany Letters166, 144-152.