Johan van Valkenburg1, Edu Boer1 and Nicola Schoenenberger2
1National Plant Protection Organization, National Reference Centre, Geertjesweg 15, 6706EA, Wageningen, the Netherlands
2INNOVABRIDGE Foundation, Contrada al Lago 19, 6987 Caslano, Switzerland
In a nature reserve, in Ticino canton in Switzerland, amidst a mixed population of non-native Impatiens parviflora and I. glandulifera aberrant plants of I. parviflora were observed. An herbarium voucher and seeds were collected and seedlings subsequently raised in a greenhouse. Molecular analysis for ITS region and chloroplast markers revealed the plants to be a hybrid between I. parviflora and I. balfourii, another non-native Impatiens species occurring in the Ticino canton. I. parviflora is the mother plant of the hybrid. No out crossing nor reduced fertility was observed in F2 and F3 generations, raised in a greenhouse. Nuclear genome size, as measured by flow cytometry with propidium iodide, did not indicate polyploidy and the ITS region remained 100% uniform. Therefore a homoploid hybrid speciation event is assumed
We have proven, by raising an F2 generation twice and even an F5 generation, that the hybrid is fertile. Our molecular study revealed that outcrossing in F2 and F3 generation did not occur. However, the sizeable populations in Arbedo and Gudo in the absence of I. balfourii and the fact that at Carasso both parental species co-occur but no hybrids were found hints to a rare hybridization event resulting in a fertile lineage. Some of the reported findings are only based on observations and an experimental set-up would greatly improve our knowledge of the Impatiens hybrid. The assumed breeding system clearly needs further laboratory and greenhouse experiments. Habitat preferences and competitive ability of the Impatiens hybrid needs to be studied both in the field and in controlled garden experiments.
van Valkenburg J. L. C. H., Schoenenberger N., van de Vossenberg B. T. L. H., Man in ’t Veld W. A., 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. Bot. Lett., doi: 10.1080/23818107.2019.1584863.