Conspecific leaf litter induces negative feedbacks in Asteraceae seedlings

The plant soil feedback (PSF) framework has been instrumental in
quantifying soil microbial impacts on plant fitness and mechanisms for
species coexistence. The recent extension of the PSF framework to microbes
associated with aboveground tissues of plants, termed here as plant
phyllosphere feedbacks (PPFs), can also help determine the role of
aboveground microbes as drivers of plant-plant interactions. However,
experimental tests of PPFs in wild hosts is nascent and their prevalence
across diverse hosts remains largely unknown. Additionally, the
relationship between plant host characteristics, such as functional traits
and evolutionary history, with PPFs is unclear, in contrast to a
substantial body of PSF literature. To test for the prevalence and
mechanisms driving PPFs across diverse hosts, plant litter from ten
Asteraceae species spanning slow to fast life history strategies was used
to inoculate con- and heterospecific seedlings in a full factorial
experimental design. We found that four species experienced significant
negative PPFs and three experienced marginally significant negative
feedbacks, while the feedback estimates for all ten species were negative.
However, neither plant functional traits, nor phylogenetic distance were
predictive of PPFs among species pairs, suggesting that other mechanisms
or traits not measured may be driving these negative PPFs. Our results
indicate that negative PPFs are common among native Asteraceae species and
that they may have substantial impacts on plant growth and plant-plant
interactions, particularly during early plant development.