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Abstract 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 onPlantagohost species in (1) “pandemic pivot” surveys in which undergraduate students recorded shade and infection status of thousands of plants along road verges in urban and suburban residential neighborhoods, (2) monthly surveys of plant populations in 22 parks along an urbanization gradient, and (3) a manipulative field experiment directly testing the effects of shade on the growth and transmission of powdery mildew. Together, our field survey results show strong positive effects of shade on mildew infection in wildPlantagopopulations across urban, suburban, and rural habitats. Our experiment suggests that this relationship is causal, where microclimate conditions associated with shade promote pathogen growth. Overall, infection prevalence increased with urbanization despite a negative association between urbanization and tree cover at the landscape scale. These findings highlight the importance of taking microclimate heterogeneity into account when establishing links between macroclimate or land use context and prevalence of disease.
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This content will become publicly available on May 28, 2027
Foliar pathogens and drought drive plant–soil feedback between two co-occurring herbaceous plant species
Abstract Plants alter soil biotic and abiotic properties with consequences for plant community dynamics at local and global scales, but how plant–soil interactions are affected by other environmental and biotic interactions remains poorly understood. We performed a fully reciprocal plant–soil feedback (PSF) experiment between two herbaceous plants, Monarda fistulosa and Plantago lanceolata, and tested how PSFs were influenced by drought and foliar powdery mildew pathogen infection. We observed significant negative feedbacks between the two plant species, but only when plants were grown with live soil biota and infected with powdery mildew. The strongest feedback was observed under both foliar infection and drought. High-throughput sequencing of soil fungi and bacteria from the treatment groups with foliar infection and drought revealed that both fungal and bacterial community composition were influenced by soil condition (live versus sterile) and soil training (Monarda versus Plantago). Together, our results indicate that the observed negative PSF was driven by foliar pathogens and plant species-specific soil microbial communities and intensified by drought. Our study suggests that PSF can be sensitive to both aboveground plant–pathogen interactions and climatic factors, improving our understanding of microbial impacts on plant community dynamics. This article is part of the theme issue ‘Wild plant pathosystems’.
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- PAR ID:
- 10685984
- Publisher / Repository:
- Royal Society Publishing
- Date Published:
- Journal Name:
- Philosophical Transactions B
- Volume:
- 381
- Issue:
- 1951
- ISSN:
- 0962-8436
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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