Ectomycorrhizal fungi drive positive phylogenetic plant-soil feedbacks in a regionally dominant tropical plant family
Segnitz, R. M., S. E. Russo, S. T. J. Davies and K. G. Peay. 2020.
Abstract
While work in temperate forests suggests that there are consistent differences in
plant%u2013soil feedback (PSF) between plants with arbuscular and ectomycorrhizal associations, it
is unclear whether these differences exist in tropical rainforests. We tested the effects of mycorrhizal type, phylogenetic relationships to overstory species, and soil fertility on the growth of
tree seedlings in a tropical Bornean rainforest with a high diversity of both ectomycorrhizal
and arbuscular mycorrhizal trees. We found that ectomycorrhizal tree seedlings had higher
growth in soils conditioned by close relatives and that this was associated with higher mycorrhizal colonization. By contrast, arbuscular mycorrhizal tree seedlings generally grew more
poorly in soils conditioned by close relatives. For ectomycorrhizal species, the phylogenetic
trend was insensitive to soil fertility. For arbuscular mycorrhizal seedlings, however, the effect
of growing in soils conditioned by close relatives became increasingly negative as soil fertility
increased. Our results demonstrate consistent effects of mycorrhizal type on plant%u2013soil feedbacks across forest biomes. The positive effects of ectomycorrhizal symbiosis may help explain
biogeographic variation across tropical forests, such as familial dominance of the Dipterocarpaceae in southeast Asia. However, positive feedbacks also raise questions about the role of
PSFs in maintaining tropical diversity.
Key Words
biodiversity; conspecific negative density dependence; Dipterocarpaceae; Janzen-Connell; mycorrhizal fungi; natural enemies; soil fertility
