Conspecific leaf litter induces negative feedbacks in Asteraceae seedlings

Authors: ZARET, MAX - University Of Minnesota; BAUER, JONATHAN - Miami University - Ohio; CLAY, KEITH - Tulane University; Whitaker, Briana

Submitted to: Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/23/2021
Publication Date: 10/8/2021
Citation: Zaret, M.M., Bauer, J.T., Clay, K., Whitaker, B.K. 2021. Conspecific leaf litter induces negative feedbacks in Asteraceae seedlings. Ecology. 102(12). Article e03557. https://doi.org/10.1002/ecy.3557.
DOI: https://doi.org/10.1002/ecy.3557

Interpretive Summary: The plant microbiome, including pathogens and beneficial microbes, can have direct impacts on plant health and productivity, such as growth and yield, but can also have indirect impacts on plant-plant competition. The indirect effects of soil pathogens and mutualists has been well studied in wild plant systems, but less work has been done on aboveground pathogens and mutualists colonizing leaves, leaf litter, and stems. Researchers discovered that microbes in leaf litter can indirectly impact plant-plant competition for 6 out of 10 species tested. These results indicate that the indirect effects of pathogens and mutualists in the aboveground parts of plants are pervasive and important determinants of plant interactions in the wild, similar to the importance of soil microbes.

Technical Abstract: The plant soil feedback (PSF) framework has been instrumental in understanding the impacts of soil microbes on plant fitness and species coexistence. PSFs develop when soil microbial communities are altered due to the identity and density of a particular plant species, which can then enhance or inhibit the local survival and growth of that plant species as well as different plant species. The recent extension of the PSF framework to aboveground microbiota, termed here as plant phyllosphere feedbacks (PPFs), can also help to determine the impact of aboveground microbes on plant fitness and species interactions. However, experimental tests of PPFs during early plant growth are nascent and the prevalence of PPFs across diverse plant species remains unknown. Additionally, it is unclear whether plant host characteristics, such as functional traits or phylogenetic distance, may help to predict the strength and direction of PPFs. To test for the prevalence of litter-mediated PPFs, recently senesced plant litter from 10 native Asteraceae species spanning a range of life history strategies was used to inoculate seedlings of both conspecific and heterospecific species. We found that exposure to conspecific litter significantly reduced the growth of four species relative to exposure to heterospecific litter (i.e., significant negative PPFs), three species experienced marginally significant negative PPFs, and the PPF estimates for all 10 species were negative. However, neither plant functional traits, nor phylogenetic distance were predictive of litter feedbacks across plant species pairs, suggesting that other mechanisms or traits not measured may be driving conspecific negative PPFs. Our results indicate that negative, litter-mediated PPFs are common among native Asteraceae species and that they may have substantial impacts on plant growth and plant species interactions, particularly during early plant growth.