Abstract
The ectomycorrhizal (ECM) symbiosis connects mutualistic plants and fungal species into bipartite networks. While links between one focal ECM plant and its fungal symbionts have been widely documented, systemic views of ECM networks are lacking, in particular, concerning the ability of fungal species to mediate indirect ecological interactions between ECM plant species (projected-ECM networks). We assembled a large dataset of plant–fungi associations at the species level and at the scale of Corsica using molecular data and unambiguously host-assigned records to: (i) examine the correlation between the number of fungal symbionts of a plant species and the average specialization of these fungal species, (ii) explore the structure of the plant–plant projected network and (iii) compare plant association patterns in regard to their position along the ecological succession. Our analysis reveals no trade-off between specialization of plants and specialization of their partners and a saturation of the plant projected network. Moreover, there is a significantly lower-than-expected sharing of partners between early- and late-successional plant species, with fewer fungal partners for early-successional ones and similar average specialization of symbionts of early- and late-successional plants. Our work paves the way for ecological readings of Mediterranean landscapes that include the astonishing diversity of below-ground interactions.
Highlights
Evaluating the extent and functions of the ecological links that soil biota create among terrestrial plants is a fascinating challenge in ecology
Among the 16 plant species, association patterns varied from species-poor fungal communities associated with Betulaceae (Alnus, Betula, Corylus, whose number of associated ECM fungal species ranged from 14 to 46) and Cistaceae (Cistus and Halimium with kp = 26 and kp = 12, respectively) to rich ECM fungal assemblages associated with Quercus suber and Quercus ilex evergreen oaks
(A) Distribution of 16 ECM plant species according to their degree in the bipartite network, kp, i.e., the number of their fungal partner species (X axis), and the average number of host species of their symbionts, cp (Y axis)
Summary
Evaluating the extent and functions of the ecological links that soil biota create among terrestrial plants is a fascinating challenge in ecology. In temperate and boreal forests, ectomycorrhizal (ECM) symbiosis ecologically binds together 3% of terrestrial plant species and more than 6000 filamentous fungal species. ECM symbiosis contributes to indirect interactions among trees through shared fungus partners (Bingham and Simard, 2012), and these interactions facilitate seedling establishment (Richard et al, 2009) and species coexistence (Selosse et al, 2006) in plant communities. ECM symbiosis thereby contributes to plant community dynamics during both primary (Nara, 2006) and secondary ecological succession (Simard et al, 1997; Richard et al, 2009; van der Heijden and Horton, 2009; Bingham and Simard, 2012).
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