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

Abstract

Urbanization is associated with numerous environmental changes that may affect the timing of plant reproduction and foliar damage by pathogens, herbivores, and human activities. Yet such effects have not previously been quantified simultaneously in plant populations across levels of urbanization. Thus, it remains unclear how urbanization impacts multiple fitness components of a single plant species. Moreover, it is unclear which effects are consistent between species. We studied 22 populations of two co-occuring Plantago species in parks and nature areas spanning rural, suburban, and urban sections of the Greater St. Louis metropolitan area in the central United States. In monthly surveys of Plantago lanceolata and P. rugelii during summer–fall in two consecutive years, we quantified plant reproductive development and prevalence of powdery mildew infection. In the second year, we additionally quantified prevalence of insect herbivory and mowing damage and placed potted sentinel plants into the field populations to directly measure rates of infection and herbivory. 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 infection prevalence in more urban sites. Correspondingly, sentinels only became infected in suburban and urban sites. By contrast, there was less mildew infection on P. lanceolata, including on sentinels, suggesting low availability of pathogen genotypes able to infect this species. Urbanization accelerated early-summer herbivory on both plant species, but did not affect herbivory of wild or sentinel plants later in summer. Finally, prevalence of mowing damage on leaves was generally greater in urban and suburban than rural sites. Synthesis: We show that urbanization affects the timing of key reproductive events and multiple types of aboveground damage for wild herbaceous plants. The two plant species responded differently to urbanization in terms of their reproductive phenology. However, in months when significant effects of urbanization were detected, they were typically in the direction of greater rates of pathogen infection, herbivory, and mowing damage. Overall, these findings suggest multiple mechanisms by which urbanization may impact plant population growth.

Host developmental stages shape the evolution of a plant RNA virus

“…It has been reported that abiotic conditions associated with climate change can either induce or delay developmental processes and flowering in a genotype-dependent manner [43][44][45][46]. Flowering has been also described to be altered by the result of human activities such as urbanization [47,48] or biodiversity loss [49]. These changes in plant development will result in viruses facing host populations with altered levels of susceptibility.…”

Effects of microclimate on disease prevalence across an urbanization gradient

“…Data (Fox et al, 2024a) are available in Dryad at https:// doi.org/10.5061/dryad.wpzgmsbrn. Code (Fox et al, 2024b) is available at Zenodo at https://doi.org/10.5281/ zenodo.7458687.…”