Seed-bank dynamics of native and invasive Impatiens species during a five-year field experiment under various environmental conditions

Hana Skálová,Lenka Moravcová,Petr Pyšek,Jan Čuda

doi:10.3897/neobiota.50.34827

Abstract

Despite recent evidence on the important role of seed banks associated with plant invasions, and a large body of literature on invasive annual Impatiens species, little is known about the seed bank characteristics of Impatiens species. To bridge this gap, we conducted a five-year field experiment where we buried seeds of two invasive species (I. glandulifera and I. parviflora) and one native species (I. noli-tangere) across four localities in the Czech Republic, harbouring all three Impatiens species and differing in the environmental conditions. We found that the three Impatiens species differed in the characteristics of their seed banks. Both invasive species had a high seed germination rate of almost 100% in the first year after seed burial, while &lt;50% of seeds of the native I. noli-tangere germinated during this year. In I. parviflora all seeds germinated in the first year after seed burial and later decomposed, i.e. the species had a transient seed bank. For I. glandulifera, the most invasive species, the survival of seeds differed among localities. At the first and second localities, the seeds decomposed in the first year after seed burial; in the third locality the seeds germinated in the second year; and in the fourth one, the seeds still germinated in the fourth year. The native I. noli-tangere formed a short-term persistent seed bank across all localities. Germinating or dormant seeds were found in the third year after burial in all localities, and in one locality the seeds persisted until the fifth year. The germination and dormancy in I. noli-tangere were constrained by low minimum temperatures during winter. In addition, germination was highest at intermediate soil moisture, and the most dormant seeds were recorded in soils with intermediate nitrogen concentration. The germination of I. glandulifera was slightly limited by low soil nitrogen. However, no such effect was found in I. parviflora. We suggest that in the invasive Impatiens species seed resistance to environmental factors and high germination at least partly explain their wide distribution.

Highlights

Factors driving invasion success of alien plant species are a significant research topic in ecology and invasion biology, and this research has considerable applied relevance (Vilà et al 2011, Pyšek et al 2012a, Simberloff et al 2013)
As we found differentiation among species with I. glandulifera occurring in less shaded sites than I. noli-tangere and I. parviflora (Čuda et al 2014), the bags were buried within the respective populations
Germination was much higher for the invasive I. glandulifera and I. parviflora, with almost all seeds germinating (95%), compared to the native I. noli-tangere, where less than half of the seeds germinated (42%)

Summary

Introduction

Factors driving invasion success of alien plant species are a significant research topic in ecology and invasion biology, and this research has considerable applied relevance (Vilà et al 2011, Pyšek et al 2012a, Simberloff et al 2013). Of these factors, species traits have been a research focus, and many studies have predicted a set of key traits associated with successful invaders, including traits related to reproduction (for a review see Pyšek and Richardson 2007, van Kleunen et al 2010). The role of seed banks in population persistence has to be taken into account during eradication, because a few viable seeds in the soil may allow re-invasions (Fletcher et al 2015, Leary et al 2018, Moravcová et al 2018)

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Conclusion