Seed source regions drive fitness differences in invasive macrophytes

Authors: GILLARD, MORGANE - University Of California, Davis; DRENOVSKY, REBECCA - John Carroll University; THIEBAUT, GABRIELLE - University Of Rennes, France; TARAYRE, MICHELE - University Of Rennes, France; Futrell, Caryn; Grewell, Brenda

Submitted to: American Journal of Botany
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/27/2020
Publication Date: 5/26/2020
Citation: Gillard, M., Drenovsky, R.E., Thiebaut, G., Tarayre, M., Futrell, C.J., Grewell, B.J. 2020. Seed source regions drive fitness differences in invasive macrophytes. American Journal of Botany. 107(5):749-760. https://doi.org/10.1002/ajb2.1475.
DOI: https://doi.org/10.1002/ajb2.1475

Interpretive Summary: Worldwide, ecosystems are threatened by biological invasions and global environmental changes. Invasive species arriving in novel environments experience new climatic conditions, and the extent to which they are pre-adapted to climate variation can affect their successful establishment. Examining functional plant traits can reveal physiological mechanisms expressed by invasive populations from contrasting environments. These trait responses provide a useful framework to assess species responses to climate change and the variability of these responses among source populations. Much research has focused on establishment of aquatic macrophytes from asexual fragments; however, colonization from seeds produced through sexual reproduction has rarely been studied. Our objective was to compare functional trait responses of plants generated from plant seeds sourced from three climatic regions but grown under common environmental conditions, using L. peploides subsp. montevidensis as a model taxon. We grew seedlings to reproductive stage in experimental mesocosms under a Mediterranean California (MCA) climate from seeds collected in oceanic France (OFR), Mediterranean France (MFR) and MCA. Seed source region was a major factor influencing differences among invasive plants recruiting from sexual propagules of L. p. subsp. montevidensis. Trait responses of young individual recruits from MCA and OFR, which were sourced from geographically distant and climatically distinct source regions, had the most different trait responses. MCA individuals accumulated more biomass, flowered earlier, and had higher leaf N concentrations than OFR plants. Those from MFR had intermediate profiles. This study provides new insights to the understanding of colonization and establishment of an invasive plant species, and informs its management under novel and changing environmental conditions.

Technical Abstract: Worldwide, ecosystems are threatened by biological invasions and global environmental changes. Invasive species arriving in novel environments experience new climatic conditions, and the extent to which they are pre-adapted to climate variation can affect their successful establishment. Examining functional traits of invasive populations from contrasting environments provides a useful framework to assess species responses to climate change and the variability of these responses among source populations. Much research has focused on establishment of aquatic macrophytes from asexual fragments; however, colonization from sexual propagules has rarely been studied. Our objective was to compare functional trait responses of plants generated from sexual propagules sourced from three climatic regions but grown under common environmental conditions, using L. peploides subsp. montevidensis as a model taxon. We grew seedlings to reproductive stage in experimental mesocosms under a Mediterranean California (MCA) climate from seeds collected in oceanic France (OFR), Mediterranean France (MFR) and MCA. Seed source region was a major factor influencing differences among invasive plants recruiting from sexual propagules of L. p. subsp. montevidensis. Trait responses of young individual recruits from MCA and OFR, which were sourced from geographically distant and climatically distinct source regions, had the most different trait responses. MCA individuals accumulated more biomass, flowered earlier, and had higher leaf N concentrations than OFR plants. Those from MFR had intermediate profiles. This study provides new insights to the understanding of colonization and establishment of an invasive plant species, and informs its management under novel and changing environmental conditions.