On November 11, 2016 Ms. Simona Paolacci successfully defended her PhD thesis entitled “A comparative study of the invasive species Lemna minuta and the co-generic native Lemna minor”.
Internal examiner was Dr. Pádraig Whelan, an expert on invasive plants based in UCC, Ireland.
External examiner was Prof. Klaus Appenroth from the University of Jena in Germany. Prof. Appenroth is a highly regarded expert on Lemnaceae and amongst others, a founding member and current head of the International Steering Committee on Duckweed Research and Applications (ISCDRA).
In her PhD thesis Simona explored the hypothesis that alien, invasive Lemna minuta is an opportunistic (competitor/ruderal) species, while native Lemna minor is more of a stress-tolerator. Some of the data in the thesis support this hypothesis. For example, Lemna minor can grow under comparatively low light intensities and nutrient concentrations. In comparison, Lemna minuta is better in taking advantage of high light intensities, and high nutrient concentrations. However, there is only limited support for the notion that Lemna minor is more stress tolerant than Lemna minuta. In fact, several stressors had less of an impact on Lemna minuta than Lemna minor.
A key difference between the two species is the relative tolerance of Lemna minor to low temperatures, which was associated with a relatively high growth rate of this species in the winter months. Thus, although Lemna minuta outgrows Lemna minor throughout the summer period, an early start after the winter assures a competitive advantage for the latter species, which can therefore co-exist with the alien invader.
Simona Paolacci was funded by the Irish Research Council (IRC) and jointly supervised by Dr. Simon Harrison and Prof. Marcel Jansen.