Phenology of plant reproduction, foliar infection, and herbivory change along an urbanization gradient

Abstract

AbstractUrbanization involves numerous environmental changes that may affect the timing of plant reproduction and foliar damage by pathogens, herbivores, and human activities. Yet such relationships have not been examined simultaneously in plant populations across levels of urbanization.We conducted monthly surveys of 22 populations of Plantago lanceolata and P. rugelii in parks spanning an urbanization gradient. We quantified plant reproductive development and prevalence of powdery mildew infection, insect herbivory, and mowing damage. Additionally, we placed potted “sentinel” plants into field populations to directly measure infection and herbivory rates.Urbanization was associated with earlier flowering and more seed production for P. rugelii, but less seed maturation for P. lanceolata. Mildew epidemics on P. rugelii started earlier and achieved greater prevalence in more urban sites. Correspondingly, sentinels only became infected in suburban and urban sites. There was less infection on P. lanceolata, including sentinels, suggesting low availability of pathogen genotypes able to infect this species. Early-summer herbivory on both plant species was accelerated in urban sites.Urbanization has species-specific associations with reproductive phenology and is associated with increased early-summer herbivory, larger epidemics of a foliar pathogen, and more mowing damage on two weedy herbs