Germination and Seedling Growth of Water Primroses: A Cross Experiment between Two Invaded Ranges with Contrasting Climates.

Morgane Gillard,Gabrielle Thiébaut,Caryn J Futrell,Carole Deleu,Brenda J Grewell

doi:10.3389/fpls.2017.01677

Abstract

Aquatic ecosystems are vulnerable to biological invasions, and will also be strongly impacted by climate change, including temperature increase. Understanding the colonization dynamics of aquatic invasive plant species is of high importance for preservation of native biodiversity. Many aquatic invasive plants rely on clonal reproduction to spread, but mixed reproductive modes are common. Under future climate changes, these species may favor a sexual reproductive mode. The aim of this study was to test the germination capacity and the seedling growth of two water primrose species, Ludwigia hexapetala and Ludwigia peploides, both invasive in Europe and in the United States. We performed a reciprocal transplant of seeds of L. hexapetala and L. peploides from two invasive ranges into experimental gardens characterized by Oceanic and Mediterranean-type climates. Our results showed that higher temperatures increased or maintained germination percentages and velocity, decreased survivorship of germinants, but increased their production of biomass. The origin of the seeds had low impact on L. hexapetala responses to temperature, but greatly influenced those of L. peploides. The invasiveness of water primroses in ranges with Oceanic climates might increase with temperature. The recruitment from seed banks by these species should be considered by managers to improve the conservation of native aquatic and wetland plant species.

Highlights

Invasive plants represent a serious threat to the native biodiversity of inland aquatic ecosystems throughout the world
There was a significant interaction between seed provenance and species for mean time to germination (MTG) (Table 3); seed provenance had only a significant effect on MTG for L. hexapetala (Figure 2A)
We showed that the effect of climate conditions on germination percentage and on seed viability depended on species and on seed origin

Summary

Introduction

Invasive plants represent a serious threat to the native biodiversity of inland aquatic ecosystems throughout the world. The damages caused by these non-native species are mostly linked to their high biomass, and their presence modifies water quality, hydrology (Strayer, 2010), or the composition and structure of native communities (Michelan et al, 2010; Stiers et al, 2011). Exotic aquatic species have been shown to have proportionally larger ecological and economic impacts than exotic species in terrestrial ecosystems (Vilà et al, 2010). This suggests that there are fundamental differences in the colonization dynamics of aquatic ecosystems, and further demonstrates the vulnerability of these systems to invasion. Recent studies suggest that warmer thermal conditions will result in a shift from native to exotic aquatic plant dominance (Hussner, 2014), and dominance of exotic macrophytes can modify the species composition of the standing vegetation and the persistent soil-stored seed bank by depleting the seed bank of native species (Vojtkó et al, 2017)

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