Format: ORAL

Blanca Gallego-Tvar1, Brenda J. Grewell2, John F.Gaskin???????3 and Jess M. Castillo???????1

1 Departamento de Biología Vegetal y Ecología, Universidad de Sevilla, Ap 1095, 41080 Sevilla, Spain 2 USDA-ARS Invasive Species and Pollinator Health Research Unit, Department of Plant Sciences MS-4, University of California, Davis, CA, 95616, USA, 3 USDA ARS Pest Management Research Unit, Northern Plains Area, 1500 North Central Avenue, Sidney, MT, 59270 USA

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.  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.