Potential local adaptation in populations of invasive reed canary grass (Phalaris arundinacea) across an urbanization gradient

• Published in: Ecology and evolution 2021-08, Vol.11 (16), p.11457-11476
• Main Authors: Weston, Leah M., Mattingly, Kali Z., Day, Charles T. C., Hovick, Stephen M.
• Format: Article
• Language: English
• Subjects: Adaptation; adaptive plasticity; Anthropogenic factors; Divergence; Dry matter; Evolution; Experiments; Gene expression; Genetic diversity; Grasses; Human influences; Introduced species; Invasive species; Metals; Natural selection; Nonnative species; Original Research; Phalaris arundinacea; Phenotypic plasticity; Plastic properties; Plasticity; Population; Populations; root mass ratio; root traits; Seeds; Site selection; stress tolerance; Urban areas; urban evolution; Urban populations; Urbanization; wetland invader; Wetlands
• ISSN: 2045-7758; 2045-7758
• DOI: 10.1002/ece3.7938

Urban stressors represent strong selective gradients that can elicit evolutionary change, especially in non‐native species that may harbor substantial within‐population variability. To test whether urban stressors drive phenotypic differentiation and influence local adaptation, we compared stress responses of populations of a ubiquitous invader, reed canary grass (Phalaris arundinacea). Specifically, we quantified responses to salt, copper, and zinc additions by reed canary grass collected from four populations spanning an urbanization gradient (natural, rural, moderate urban, and intense urban). We measured ten phenotypic traits and trait plasticities, because reed canary grass is known to be highly plastic and because plasticity may enhance invasion success. We tested the following hypotheses: (a) Source populations vary systematically in their stress response, with the intense urban population least sensitive and the natural population most sensitive, and (b) plastic responses are adaptive under stressful conditions. We found clear trait variation among populations, with the greatest divergence in traits and trait plasticities between the natural and intense urban populations. The intense urban population showed stress tolerator characteristics for resource acquisition traits including leaf dry matter content and specific root length. Trait plasticity varied among populations for over half the traits measured, highlighting that plasticity differences were as common as trait differences. Plasticity in root mass ratio and specific root length were adaptive in some contexts, suggesting that natural selection by anthropogenic stressors may have contributed to root trait differences. Reed canary grass populations in highly urbanized wetlands may therefore be evolving enhanced tolerance to urban stressors, suggesting a mechanism by which invasive species may proliferate across urban wetland systems generally. We tested whether populations of a ubiquitous wetland invader, reed canary grass (Phalaris arundinacea), differed phenotypically across an urbanization gradient, suggesting evolutionary responses to common urban stressors. We found clear trait and trait plasticity variation among populations, suggesting reed canary grass may be evolving enhanced tolerance to anthropogenic stressors.