01949nas a2200181 4500008004100000245005400041210005400095300001500149490000800164520142600172653001801598100001801616700001701634700001701651700001701668700001501685856006701700 2015 eng d00aMycorrhizal phenotypes and the law of the minimum0 aMycorrhizal phenotypes and the law of the minimum a1473 -14840 v2053 a

Mycorrhizal phenotypes arise from interactions among plant and fungal genotypes and the environment. Differences in the stoichiometry and uptake capacity of fungi and plants make arbuscular mycorrhizal (AM) fungi inherently more nitrogen (N) limited and less phosphorus (P) limited than their host plants. Mutualistic phenotypes are most likely in P-limited systems and commensal or parasitic phenotypes in N-limited systems. Carbon (C) limitation is expected to cause phenotypes to shift from mutualism to commensalism and even parasitism. Two experiments compared the influence of fertilizer and shade on mycorrhizas in Andropogon gerardii across three naturally N-limited or P-limited grasslands. A third experiment examined the interactive effects of N and P enrichment and shade on A. gerardii mycorrhizas. Our experiments generated the full spectrum of mycorrhizal phenotypes. These findings support the hypothesis that mutualism is likely in P-limited systems and commensalism or parasitism is likely in N-limited systems. Furthermore, shade decreased C-assimilation and generated less mutualistic mycorrhizal phenotypes with reduced plant and fungal biomass. Soil fertility is a key controller of mycorrhizal costs and benefits and the Law of the Minimum is a useful predictor of mycorrhizal phenotype. In our experimental grasslands arbuscular mycorrhizas can ameliorate P-limitation but not N-limitation.

10astoichiometry1 aJohnson, N.C.1 aWilson, G.T.1 aWilson, J.A.1 aMiller, R.M.1 aBowker, M. uhttps://nph.onlinelibrary.wiley.com/doi/full/10.1111/nph.1317202272nas a2200181 4500008004100000245008800041210006900129300001500198490000700213520170300220100001101923700001801934700001701952700001701969700002401986700001802010856006202028 2013 eng d00aPatterns of diversity and adaptation in Glomeromycota from three prairie grasslands0 aPatterns of diversity and adaptation in Glomeromycota from three a2573 -25870 v223 a

Arbuscular mycorrhizal (AM) fungi are widespread root symbionts that often improve the fitness of their plant hosts. We tested whether local adaptation in mycorrhizal symbioses would shape the community structure of these root symbionts in a way that maximizes their symbiotic functioning. We grew a native prairie grass (Andropogon gerardii) with all possible combinations of soils and AM fungal inocula from three different prairies that varied in soil characteristics and disturbance history (two native prairie remnants and one recently restored). We identified the AM fungi colonizing A. gerardii roots using PCR amplification and cloning of the small subunit rRNA gene. We observed 13 operational taxonomic units (OTUs) belonging to six genera in three families. Taxonomic richness was higher in the restored than the native prairies with one member of the Gigaspora dominating the roots of plants grown with inocula from native prairies. Inoculum source and the soil environment influenced the composition of AM fungi that colonized plant roots. Correspondingly, host plants and AM fungi responded significantly to the soil–inoculum combinations such that home fungi often had the highest fitness and provided the greatest benefit to A. gerardii. Similar patterns were observed within the soil–inoculum combinations originating from two native prairies, where five sequence types of a single Gigaspora OTU were virtually the only root colonizers. Our results indicate that indigenous assemblages of AM fungi were adapted to the local soil environment and that this process occurred both at a community scale and at the scale of fungal sequence types within a dominant OTU.

1 aJi, B.1 aGehring, C.A.1 aWilson, G.T.1 aMiller, R.M.1 aFlores-Renteria, L.1 aJohnson, N.C. uhttps://onlinelibrary.wiley.com/doi/abs/10.1111/mec.1226800474nas a2200145 4500008004100000245005200041210005200093260003200145300001100177100001700188700001700205700001800222700001800240856007000258 2012 eng d00aArbuscular Mycorrhizae and Grassland Ecosystems0 aArbuscular Mycorrhizae and Grassland Ecosystems aOxford, UKbWiley-Blackwell a59 -851 aMiller, R.M.1 aWilson, G.T.1 aJohnson, N.C.1 aSouthwood, D. uhttps://onlinelibrary.wiley.com/doi/abs/10.1002/9781118314364.ch302196nas a2200217 4500008004100000245008100041210006900122300001500191490000800206520156800214653001601782653002301798653001401821653001501835100001801850700001701868700001501885700001701900700001701917856004401934 2010 eng d00aResource limitation is a driver of local adaptation in mycorrhizal symbioses0 aResource limitation is a driver of local adaptation in mycorrhiz a2093 -20980 v1073 a

Symbioses may be important mechanisms of plant adaptation to their environment. We conducted a reciprocal inoculation experiment to test the hypothesis that soil fertility is a key driver of local adaptation in arbuscular mycorrhizal (AM) symbioses. Ecotypes of Andropogon gerardii from phosphorus-limited and nitrogen-limited grasslands were grown with all possible “home and away” combinations of soils and AM fungal communities. Our results indicate that Andropogon ecotypes adapt to their local soil and indigenous AM fungal communities such that mycorrhizal exchange of the most limiting resource is maximized. Grasses grown in home soil and inoculated with home AM fungi produced more arbuscules (symbiotic exchange structures) in their roots than those grown in away combinations. Also, regardless of the host ecotype, AM fungi produced more extraradical hyphae in their home soil, and locally adapted AM fungi were, therefore, able to sequester more carbon compared with nonlocal fungi. Locally adapted mycorrhizal associations were more mutualistic in the two phosphorus-limited sites and less parasitic at the nitrogen-limited site compared with novel combinations of plants, fungi, and soils. To our knowledge, these findings provide the strongest evidence to date that resource availability generates evolved geographic structure in symbioses among plants and soil organisms. Thus, edaphic origin of AM fungi should be considered when managing for their benefits in agriculture, ecosystem restoration, and soil-carbon sequestration.

10acoevolution10ageographic mosaics10amutualism10aparasitism1 aJohnson, N.C.1 aWilson, G.T.1 aBowker, M.1 aWilson, J.A.1 aMiller, R.M. uhttps://www.pnas.org/content/107/5/209301911nas a2200169 4500008004100000245012800041210006900169300001500238490000700253520134600260100001801606700001701624700001801641700001801659700001601677856004801693 2001 eng d00aEvidence of a mycorrhizal mechanism for the adaptation of Andropogon gerardii (Poaceae ) to high- and low-nutrient prairies0 aEvidence of a mycorrhizal mechanism for the adaptation of Androp a1650 -16560 v883 aAndropogon gerardii seed obtained from Kansas and Illinois was grown in a controlled environment in their own and each other's soils, with and without arbuscular mycorrhizal fungi (AMF). Each ecotype grew comparatively better in its own soil indicating adaptation to its soil of origin. Overall, A. gerardii benefited more from AMF in low-nutrient Kansas soil than Illinois soil. The two ecotypes, however, did not benefit equally from mycorrhizal infection. The Kansas ecotype was three times more responsive to mycorrhizal infection in the Kansas soil than was the Illinois ecotype. Our results indicate that plant adaptation to the nutrient levels of their local soils is likely to be due, at least in part, to a shift in their dependence on mycorrhizal fungi. The Illinois ecotype of A. gerardii has evolved a reduced dependence upon these fungi and greater reliance on a more highly branched root system. In contrast, the Kansas ecotype had a significantly coarser root system and invested proportionately greater carbon in the symbiotic association with AMF as measured by spore production. This study provides the first demonstration that plants can adapt to changing soil nutrient levels by shifting their dependence on AMF. This result has broad implications for our understanding of the role of these fungi in agricultural systems.1 aSchultz, P.A.1 aMiller, R.M.1 aJastrow, J.D.1 aRivetta, C.V.1 aBever, J.D. uhttp://www.ncbi.nlm.nih.gov/pubmed/2166969902440nas a2200145 4500008004100000245005800041210005800099300001500157490000700172520197500179100001702154700002002171700001702191856008602208 1997 eng d00aMycorrhizal fungi affect root stele tissue in grasses0 aMycorrhizal fungi affect root stele tissue in grasses a1778 -17840 v753 aAlthough arbuscular mycorrhizal symbiosis was initially believed to have little or no impact on root morphology, we now recognize that subtle changes do occur and that these changes may be of considerable consequence to host growth and nutrition, as well as functional growth strategy. In examining the stele and root diameters of C3 and C4 grasses, C4 grasses were demonstrated to have a significantly larger proportion of their fibrous roots occupied by stele tissue than do C3 grasses. In fact, functional growth strategy (C3 versus C4) was observed to be a relatively good predictor of stele area. Mycorrhizal fungi also influenced the amount of stele tissue, but the effect was not the same for both C3 and C4 grasses. The stele area of all C4 grasses except for Sorghastrum nutans was greater in the presence of mycorrhizal colonization. Among the C3 grasses, only Bromus inermis showed a significant increase, although Elymus cinereus and Lolium perenne displayed significant decreases in response to arbuscular mycorrhizal colonization. Changes in the stele area of the plant species were closely related to their responsiveness to mycorrhizal symbiosis and might in part explain both beneficial and detrimental responses of plants to mycorrhizae. An increase in stele circumference induced by mycorrhizae would allow for greater uptake and passage of water and nutrients to the vascular cylinder, and growth depressions could be a direct outcome of reduced stele circumference. Thus, differences in stele circumference represent a possible mechanism for mycorrhizal impacts on host plants. These findings indicate that structural differences among grasses are related to different functional capabilities and further emphasize the need for better integration of comparative anatomy and morphology procedures in the study of mycorrhizal symbiosis. Key words: stele, root anatomy, mycorrhizal dependency, functional growth strategy, mycorrhiza, C3 and C4 grasses.1 aMiller, R.M.1 aHetrick, B.A.D.1 aWilson, G.T. uhttp://knz.lternet.edu/content/mycorrhizal-fungi-affect-root-stele-tissue-grasses