Climate warming stimulates germination and inital biomass production by seedlings of two invasive Ludwigia congeners

Authors: GILLARD, MORGANE - University Of Rennes, France; Grewell, Brenda; Futrell, Caryn; DELEU, CAROLE - University Of Rennes, France; THIEBAUT, GABRIELLE - University Of Rennes, France

Submitted to: Botanical Society of America Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 4/18/2018
Publication Date: 7/23/2018
Citation: Gillard, M., Grewell, B.J., Futrell, C.J., Deleu, C., Thiebaut, G. 2018. Climate warming stimulates germination and inital biomass production by seedlings of two invasive Ludwigia congeners. Botanical Society of America Abstracts. [Abstract].

Interpretive Summary: Invasive plants represent a serious threat to the native biodiversity of inland aquatic ecosystems throughout the world. Projected global climate changes, including temperature increase, are expected to strongly impact these ecosystems, and to magnify the negative impacts of invasive species. Understanding the colonization dynamics of aquatic invasive plant species is of high importance for preservation of native biodiversity, yet they are poorly understood in the context of global climate change. 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 work was to evaluate the germination capacity and the seedling growth of two water primrose species, Ludwigia hexapetala and Ludwigia peploides subsp. montevidensis (Onagraceae), both invasive in Europe and the US. For each taxa, seeds of two populations were collected in northwestern France as well as in California, two invasive ranges characterized by Oceanic and Mediterranean-type climates respectively. We performed a reciprocal transplant of the seeds into outdoor experimental gardens in each location. The experiments took place at the same time from May through June for 6 weeks during which seeds and seedlings experienced an average air temperature warming of 5.6°C. Our results showed that higher air temperatures increased or maintained germination percentages and velocity, decreased survivorship of germinants, but increased their production of biomass in the seedling life stage by 6.7 times. The provenance of the seeds had low impact on L. hexapetala responses to temperature, but greatly influenced those of L. peploides. Our results suggest that the invasiveness of water primroses in habitat with Oceanic climates might increase with temperature rise. The recruitment from seed banks by these taxa should be considered by managers to improve the conservation of native aquatic and wetland plant species.

Technical Abstract: Invasive plants represent a serious threat to the native biodiversity of inland aquatic ecosystems throughout the world. Projected global climate changes, including temperature increase, are expected to strongly impact these ecosystems, and to magnify the negative impacts of invasive species. Understanding the colonization dynamics of aquatic invasive plant species is of high importance for preservation of native biodiversity, yet they are poorly understood in the context of global climate change. 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 work was to evaluate the germination capacity and the seedling growth of two water primrose species, Ludwigia hexapetala and Ludwigia peploides subsp. montevidensis (Onagraceae), both invasive in Europe and the US. For each taxa, seeds of two populations were collected in northwestern France as well as in California, two invasive ranges characterized by Oceanic and Mediterranean-type climates respectively. We performed a reciprocal transplant of the seeds into outdoor experimental gardens in each location. The experiments took place at the same time from May through June for 6 weeks during which seeds and seedlings experienced an average air temperature warming of 5.6°C. Our results showed that higher air temperatures increased or maintained germination percentages and velocity, decreased survivorship of germinants, but increased their production of biomass in the seedling life stage by 6.7 times. The provenance of the seeds had low impact on L. hexapetala responses to temperature, but greatly influenced those of L. peploides. Our results suggest that the invasiveness of water primroses in habitat with Oceanic climates might increase with temperature rise. The recruitment from seed banks by these taxa should be considered by managers to improve the conservation of native aquatic and wetland plant species.