Genetic and phenotypic differentiation in functional traits of Iris pseudacorus L. in native and introduced Mediterranean climate ranges

Authors: GALLEGO-TEVAR, B - University Of Seville; Grewell, Brenda; Gaskin, John; CASTILLO, JESUS - University Of Seville

Submitted to: Biological Invasions
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/16/2024
Publication Date: 5/29/2024
Citation: Gallego-Tevar, B., Grewell, B.J., Gaskin, J.F., Castillo, J.M. 2024. Genetic and phenotypic differentiation in functional traits of Iris pseudacorus L. in native and introduced Mediterranean climate ranges. Biological Invasions. 26:2869-2882. https://doi.org/10.1007/s10530-024-03350-1.
DOI: https://doi.org/10.1007/s10530-024-03350-1

Interpretive Summary: Intraspecific variation in functional traits of a plant species in its alien vs. native habitat range may explain the resilience and invasiveness of alien weeds. We explored if observed phenotypic variation of yellow flag iris (Iris pseudacorus L.) between populations in the native vs. introduced ranges resulted from genetic differentiation and/or phenotypic plasticity (flexible changes in morphological or physiological traits in response to unique environmental conditions). Seeds were collected from populations along estuarine stress gradients within populations in both Guadalquivir Estuary (Andalusia, Spain) and San Francisco Bay-Delta Estuary (California, USA). Genetic analysis was performed on leaf tissue from plants in each seed donor population. Germinants were grown for 12 months in a greenhouse common garden experiment (CGE). We then evaluated 20 traits including growth, biomass allocation, morphological and biochemical responses. Geographic range explained relative intraspecific trait variation segregating native from alien phenotypes. Native plants had lower specific leaf area (-23%) and carbohydrate concentration in rhizomes (-63%) than introduced plants, providing evidence of genetic differentiation. Higher genetic diversity and 27% higher phenotypic variation (CGE) of native vs. alien plants indicated longer-term adaptive processes in the native range. Genetic distance of alien populations (field) increased along with their phenotypic distance (CGE), suggesting rapid genetic differentiation. Phenotypic plasticity also explained some observed inter-range differences under field conditions not expressed by plants in the CGE. Management of the alien yellow flag iris populations should be established urgently since they represent novel genotypes with key functional traits that can support invasiveness through increased competitive ability and physiological stress tolerances to sea level rise.

Technical Abstract: Intraspecific variation in functional traits between native and alien invasive plant species may underlie resilience and invasiveness of aliens facing new physiological limits in response to climate change. Using a common garden experiment, we explored if observed phenotypic variation of Iris pseudacorus L. between tidal wetland populations in the native vs. invaded range may be explained by genetic differentiation and/or phenotypic plasticity. Iris seeds were collected from populations under Mediterranean climate along estuarine salinity and inundation gradients within four native and invasive populations in both Guadalquivir Estuary (Andalusia, Spain) and San Francisco Bay-Delta Estuary (California, USA). Germinants were potted (6 plants x 4 populations x 2 ranges; n = 48 experimental plants) and grown for 12 months under uniform environmental conditions. We then evaluated 23 functional traits including growth, biomass allocation, morphological and biochemical responses. Genetic analysis was performed on leaf tissue collected from plants in each seed donor population. Geographic range explained relative intraspecific trait variation segregating native from alien phenotypes. Native plants had lower SLA (-23%) and rhizome TNC concentrations (-63%) than introduced plants, providing evidence of genetic differentiation. Higher genetic diversity in the field and 27% higher phenotypic variation in the CGE for native compared to alien plants indicate longer-term adaptive processes in the native range, while genetic distance of alien field populations increased along with their phenotypic distance in the CGE suggesting rapid genetic differentiation. Phenotypic plasticity also explained some observed inter-range phenotypic differences in response to environmental conditions, since these field differences were not expressed by plants in the CGE. In the view of our results, management of alien I. pseudacorus in the invaded estuary should be established urgently since they represent novel genotypes with key functional traits that can support invasiveness through high competitive ability and physiological stress tolerance responses to sea level rise.