Fungal partners accompany wider grass niches without faster diversification
A peer-reviewed comparison of Poa grasses linked fungal symbiosis with broader modelled habitat ranges. Evolutionary diversification did not rise in parallel: lower rates appeared in some young lineages, while older lineages showed no comparable association. The study compared species and their histories rather than experimentally adding fungi, leaving causation and actual occupied territory unresolved.
Science··Midday
Grasses with fungal partners have wider modelled ranges
Poa grasses associated with Epichloë fungi had broader modelled habitat ranges in a peer-reviewed comparative study. The fungi live inside plant tissues, forming a symbiosis in which the partners can benefit one another. The researchers combined literature information and microscopic seed screening to establish symbiosis status for 116 species: 50 with the fungi and 66 without them. Comparisons accounted for evolutionary relationships between the grasses, rather than treating every species as an entirely independent evolutionary history.[1]
Niche measures capture different parts of the association
Distribution models combined geographic observations with climate and soil information. For grasses carrying the fungi, estimated potential range size was larger by a factor of around 2.4–2.5. Their principal niche axis, a summary of environmental conditions, was about 1.38 times broader. A multivariate measure combining several niche dimensions did not show the same significant association. Symbiotic species were also associated with drier climates on average. The modelled ranges estimate environmental suitability rather than directly measuring the territory occupied by each species.[1]
Diversification differs between lineage states
Lower diversification accompanied symbiosis in young, rapidly diversifying lineage states, while older and slower states showed no comparable association. Additional unobserved lineage characteristics mattered in those models. The study did not experimentally add or remove fungi, and cannot show that fungi alone slow speciation. Incomplete sampling of Poa species and uncertainty in the evolutionary tree further constrain interpretation. Classifying partnerships as present or absent also compresses differences between fungal strains and plant populations.[1]
