The role of plant mycorrhizal type and status in modulating the relationship between plant and arbuscular mycorrhizal fungal communities

Abstract

Interactions between communities of plants and arbuscular mycorrhizal (AM) fungi shape fundamental ecosystem properties. Experimental evidence suggests that compositional changes in plant and AM fungal communities should be correlated, but empirical data from natural ecosystems are scarce. We investigated the dynamics of covariation between plant and AM fungal communities during three stages of grassland succession, and the biotic and abiotic factors shaping these dynamics. Plant communities were characterised using vegetation surveys. AM fungal communities were characterised by 454-sequencing of the small subunit rRNA gene and identification against the AM fungal reference database MaarjAM. AM fungal abundance was estimated using neutral-lipid fatty acids (NLFAs). Multivariate correlation analysis (Procrustes) revealed a significant relationship between plant and AM fungal community composition. The strength of plant-AM fungal correlation weakened during succession following cessation of grassland management, reflecting changes in the proportion of plants exhibiting different AM status. Plant-AM fungal correlation was strong when the abundance of obligate AM plants was high, and declined as the proportion of facultative AM plants increased. We conclude that the extent to which plants rely on AM symbiosis can determine how tightly communities of plants and AM fungi are interlinked, regulating community assembly of both symbiotic partners.

Asymmetric patterns of global diversity among plants and mycorrhizal fungi

“…Our results show that this expected positive correlation between the diversity of ECM fungi and their plant hosts was not evident at the global scale in terms of ECM plant diversity but was in terms of ECM plant frequency (Figure ). Moreover, we found a non‐significant correlation between the diversity of AM fungi and the diversity of their plant hosts, although positive relationships between AM plant and fungal diversity have emerged in experiments (van der Heijden et al, ) and in local‐scale descriptive studies (García de León et al 2016; Hiiesalu et al, ; Neuenkamp et al, ). We showed, however, that high AM fungal diversity was associated with high AM plant frequency.…”

Passengers and drivers of arbuscular mycorrhizal fungal communities at different scales

“…Placing these two studies in the context of the driver–passenger hypothesis (plant communities drive AM fungal communities or vice versa) or of the habitat hypothesis (plant and AM fungal communities co‐vary along changes in their habitat, see Zobel & Öpik, ), Neuenkamp et al . clearly find support for the first, whereas Van Geel et al . rather find support for the habitat hypothesis, since both plant and AM fungal communities were shaped by abiotic conditions. Both studies are among the few that test the question ‘Who is the driver and who is the passenger?’ in a spatially explicit community context.…”

“…This disagreement can also be found in two studies included in this issue of New Phytologist : Van Geel et al . (pp. 1262–1272) and Neuenkamp et al . (pp. 1236–1247), since the former emphasizes the importance of abiotic, soil based parameters for AM fungal community assembly, while the latter reports a strong effect of host plants and their traits, that is, a biotic filtering process.…”

“…Conversely, the study sites of Neuenkamp et al . consisted of 25 sites within an area of 2 km², representing successional gradients, from grasslands to young pine forests including an intermediate stage of transitional grasslands, on each site. This strong shift in the plant community led to the hypothesized shift in AM fungal communities as well.…”

“…The question of the relative strength of abiotic filtering can only be studied when considering well‐replicated systems that differ considerably in their abiotic properties (Van Geel et al .). The question of co‐variation between plant and AM fungal communities can only be studied in the context of a substantial plant community turnover in close spatial proximity, such as successional gradients (Neuenkamp et al .). Nevertheless, it would be important to systematically study the effect of scale on the relative importance of assembly factors for AM fungal communities, to be able to possibly solve this apparent contradiction and to see under which conditions the predictions made in Vályi et al .…”