Effects of microclimate on disease prevalence across an urbanization gradient

Increased temperatures associated with urbanization (the “urban heat island” effect) have been shown to impact a wide range of traits across diverse taxa. At the same time, climatic conditions vary at fine spatial scales within habitats due to factors including shade from shrubs, trees, and built structures. Patches of shade may function as microclimate refugia that allow species to occur in habitats where high temperatures and/or exposure to ultraviolet radiation would otherwise be prohibitive. However, the importance of shaded microhabitats for interactions between species across urbanized landscapes remains poorly understood. Weedy plants and their foliar pathogens are a tractable system for studying how multiple scales of climatic variation influence infection prevalence. Powdery mildew pathogens are particularly well suited to this work, as these fungi can be visibly diagnosed on leaf surfaces. We studied the effects of shaded microclimates on rates of powdery mildew infection on P..., Surveys (park/field and road verge): In each survey, we first identified a patch of Plantago lanceolata or P. rugelii. Within this patch, we arbitrarily chose the first focal plant of either species and marked the survey starting location using a smartphone. For each focal plant, we recorded binary (presence/absence) data on powdery mildew infection, herbivore chewing damage, leaf mines, and lawnmower damage (leaves cut cleanly across by mower blade). In addition, we recorded whether the plant was in the sun or shade at the time of the survey. We also estimated the total number of conspecifics and number of infected conspecifics within a 1.5 m radius of the focal plant (ordered categorical variable in bins of 0, 1-10, 11-50, or 51-100 plants). We then walked a few paces in a predetermined direction (e.g., continuing unidirectionally along a roadside or within a park lawn for the entire survey) and arbitrarily selected the next focal plant. Focal plants were always at least 1 m from the ..., , # Effects of microclimate on disease prevalence across an urbanization gradient

Data (Fox et al. 2024) are available in Dryad at [https://doi:10.5061/dryad.wpzgmsbrn](https://doi:10.5061/dryad.wpzgmsbrn) and code (Fox et al. 2024) is available at Zenodo at [https://doi.org/10.5281/zenodo.7458687](https://doi.org/10.5281/zenodo.7458687).

## General Information:

Included here are data and code from Fox et al. (2024). This study investigated how within-population microclimate variation due to shade influences rates of powdery mildew infection on *Plantago rugelii* and *P. lanceolata* host species. This study had three major components: 1) *Road verge surveys:* observational surveys along road verges in St. Louis, Missouri in 2020 focusing on the powdery mildew infection status of *Plantago* plants and shade availability, 2) *Urbanization surveys:* observational surveys from 22 urban, suburban, and rural parks in the St. Louis, Missouri metro area in 2020, also focused on mildew infectio...