Influence of phylogenetic conservatism and trait convergence on the interactions between fungal root endophytes and plants

Abstract

Plants associate through their roots with fungal assemblages that impact their abundance and productivity. Non-mycorrhizal endophytes constitute an important component of such fungal diversity, but their implication in ecosystem processes is little known. Using a selection of 128 root-endophytic strains, we defined functional groups based on their traits and plant interactions with potential to predict community assembly and symbiotic association processes. In vitro tests of the strains' interactions with Arabidopsis thaliana, Microthlaspi erraticum and Hordeum vulgare showed a net negative effect of fungal colonization on plant growth. The effects partly depended on the phylogenetic affiliation of strains, but also varied considerably depending on the plant-strain combination. The variation was partly explained by fungal traits shared by different lineages, like growth rates or melanization. The origin of strains also affected their symbioses, with endophytes isolated from Microthlaspi spp. populations being more detrimental to M. erraticum than strains from other sources. Our findings suggest that plant-endophyte associations are subject to local processes of selection, in which particular combinations of symbionts are favored across landscapes. We also show that different common endophytic taxa have differential sets of traits found to affect interactions, hinting to a functional complementarity that can explain their frequent co-existence in natural communities.

Facultative root‐colonizing fungi dominate endophytic assemblages in roots of nonmycorrhizal Microthlaspi species

“…Hence, these groups seem to be important components of natural root‐endophytic communities, in which they may play relevant functions. Members of these lineages have distinctive sets of life history and functional traits suggestive of complementary niche occupancies, which may favor their frequent co‐occurrence in roots (Kia et al ., ).…”

“…This observation is reinforced by the variable morphological, physiological and functional traits of phylogenetically distant endophytic fungi that commonly co‐exist in Microthlaspi spp. roots (Kia et al ., ). Interspecies complementarity reduces competition, thereby promoting co‐occurrence in communities (Maherali & Klironomos, ).…”

Spatial patterns of pathogenic and mutualistic fungi across the elevational range of a host plant

“…We carefully classified fungi into pathogens and mutualists, and by their host specificity, given the ambiguous life histories in fungi (e.g. switching from asymptomatic occurrence on many plant species to pathogenic behaviour on a very few; Aguilar‐Trigueros, Powell, Anderson, Antonovics, & Rillig, ; Kia et al., ; Kiers et al., ; Klironomos, ). Since the focus of our study was on fungi relevant for P. cembra , we retained exclusively fungal OTUs known to be associated with Pinus .…”

Resilience to fire of phylogenetic diversity across biological domains

“…However, fungi may produce thick‐walled spores in hypogeous fruiting bodies or highly compacted mycelia that provide them with fire resistance (Horton, Cázares & Bruns, ; Tedersoo, Hansen, Perry & Kjøller, ). As evidence suggests that microbial functional traits tend to be phylogenetically conserved (Goberna & Verdú, ; Kia et al., ; Martiny, Treseder & Pusch, ), it could be expected that, similar to plants, the overrepresentation of heat‐resistant microbes would reduce soil microbial phylogenetic diversity immediately after fire. However, existing evidence for bacteria and fungi points the opposite way, as fire increases the phylogenetic diversity of soil microbial communities (Pérez‐Valera et al., ; Rincón, Santamaría‐Pérez, Ocaña & Verdú, ).…”