Résumé
1. Among plant traits, plant secondary metabolites such as tannins mediate
plant herbivore interactions but also have after-life effects on litter
decomposition and nutrient cycling. We propose that niche construction
mechanisms based on positive plant-soil feedbacks (PSF) could influence
the evolution of tannin production. 2. By modeling the flow of nitrogen
(N) and carbon (C) through plants and soil in a spatially explicit
context, we explored the relative contribution of herbivory and positive
PSF as drivers of tannin evolution. We assumed soil N to be contained in
labile and recalcitrant compartments, the latter made of tannin-protein
complexes from which plants can absorb nutrients via associations with
mycorrhizal fungi. 3. In infertile environments and for plants with low
biomass turnover rates, we show that when tannins modify soil properties
locally, positive PSF alone can drive their evolution. We further predict
the existence of positive coevolutionary feedbacks between associations
with mycorrhizal fungi with a decaying ability and tannins, possibly
triggered by the evolution of the latter as protection against herbivores.
In line with our theoretical results, empirical evidence suggest that
tannins are mostly present in plants with low tissue turnover, associated
with mycorrhizal fungi able to decay organic matter and inhabiting
infertile environments. 4. Synthesis. Our model proposes that the
evolution of tannin production can be triggered by positive PSF, provided
that tannins promote the local N retention and that mycorrhizal fungi
associated with plants are able to absorb N from tannin-protein complexes.
In our model, tannin production evolves only in infertile ecosystems, in
agreement with field observations. Our findings highlight that the
strength of niche construction depends on the ecological context, hence
that global ecological properties constrain local eco-evolutionary
dynamics.