The early growth stage of plants is vital to community diversity and
community regeneration. Understandably, it is critical to explore the
mechanisms underpinning the spatial and temporal dynamic patterns of
seedling survival and growth. The Janzen--Connell hypothesis predicts
that conspecific density dependence lowers the survival of conspecific
seedlings by attracting specialist natural enemies, promoting the
recruitment and performance of heterospecific neighbors. Recent work has
underscored how this conspecific negative density dependence may be
mediated by mutualists -- such as how arbuscular mycorrhizal fungi may
mediate the accrual of host-specific pathogens beneath the crown of
conspecific. Aboveground mutualist and enemy interactions exist as well,
however, and may provide useful insight into density dependence that are
as of yet unexplored. Using a long-term seedling demographic dataset in
a subtropical forest plot in central China, we found that a mutualist
association with ants had significant positive effects on seedling
survival, but a negative effect on seedling growth. We also confirmed
that conspecific neighborhoods had a significant negative effect on
seedling survival, confirming that the Janzen-Connell hypothesis may
influence community composition in the subtropical forest. Overall, our
findings suggested that ants and conspecific neighborhoods played
important but inverse roles on seedling survival and growth, which
indicated that ants may mediate conspecific negative density dependence
at community level to some extent.