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Invasive, exotic grasses are increasing in tallgrass prairie and their dominance may be contributing to the decline of grassland butterflies through alterations in forage quality. Tall fescue (Schedonorus arundinaceus (Schreb.) Dumort.), an exotic grass covering millions of acres in the United States, can host a fungal endophyte, Epichloë coenophiala (Morgan-Jones & Gams). Alkaloids produced by the endophyte are known to be toxic to some foliar-feeding pest insects. Endophyte-infected tall fescue is commonly planted in hayfields, pastures, lawns, and is invading natural areas, but effects of the endophyte on nonpest insects such as butterflies are relatively unknown. Our objective was to investigate the role that tall fescue and its endophyte might play in the decline of grass skippers (Hesperiidae). We examined growth and survival parameters of tawny-edged skippers (Polites themistocles (Latreille)) that were reared on endophyte-infected tall fescue (E+), endophyte-free tall fescue (E-), and Kentucky bluegrass (KBG). KBG was included as a comparison because it is a cool season grass known to be palatable to P. themistocles larvae. Interestingly, results showed that the endophyte did not affect growth and survival of larvae compared to uninfected tall fescue, even though significant amounts of loline alkaloids (average 740 ppm) were measured in endophyte-infected plant material. Larvae feeding on KBG grew faster with greater survival rates than larvae on both tall fescue treatments. These results confirm that tall fescue invasion and dominance may be deteriorating the quality of grassland habitats for native pollinators; however, this effect does not appear to be linked to endophyte infection. [ABSTRACT FROM AUTHOR]

The microbes contained within free‐living organisms can alter host growth, reproduction, and interactions with the environment. In turn, processes occurring at larger scales determine the local biotic and abiotic environment of each host that may affect the diversity and composition of the microbiome community. Here, we examine variation in the diversity and composition of the foliar fungal microbiome in the grass host, Andropogon gerardii, across four mesic prairies in the central United States. Composition of fungal endophyte communities differed among sites and among individuals within a site, but was not consistently affected by experimental manipulation of nutrient supply to hosts (A. gerardii) or herbivore reduction via fencing. In contrast, mean fungal diversity was similar among sites but was limited by total plant biomass at the plot scale. Our work demonstrates that distributed experiments motivated by ecological theory are a powerful tool to unravel the multiscale processes governing microbial community composition and diversity. [ABSTRACT FROM AUTHOR]

Abstract: Tall fescue (Schedonorus arundinaceous (Schreb.)) is often infected with a common toxic fungal endophyte (Neotyphodium coenophialum) capable of producing alkaloids that affect grazing animal health, insect herbivory, plant production, and litter decomposition. The strength of these endophyte-associated effects is thought to depend on the abiotic and biotic conditions of a specific site. Prior work from Georgia, USA, has demonstrated that fungal endophyte infection can increase soil carbon pools of tall fescue pastures; however, for endophyte infection to contribute substantially to regional carbon sequestration, this result would have to hold true across the broad range of environmental conditions that support tall fescue growth. In this study, we evaluated whether endophyte infection consistently alters various soil parameters, including carbon storage, of tall fescue stands located throughout the southeastern United States. Soil samples were collected from nine sites with established paired high- and low- endophyte-infected tall fescue stands. These samples were analyzed for basic soil parameters, soil organic carbon (SOC), soil total nitrogen (TN), particulate and non-particulate organic matter-C and -N (POM, n-POM), C and N mineralization rates, and microbial biomass and community composition. Averaged across all sites, endophyte-infected tall fescue stands had 6% greater SOC and 5% greater TN pools in surface soil than adjacent endophyte-free stands. The lack of a significant interaction between site and endophyte infection status indicated that this result was relatively consistent across sites, despite differences in stand age, climate, and other environmental conditions. While POM C and POM N tended to be higher in endophyte-infected than endophyte-free stands, this result was not significant. However, greater pools of n-POM C and N were observed in endophyte-infected vs. endophyte-free stands when averaged across all the sites, suggesting increased retention of recalcitrant substrates occurred in response to fungal endophyte infection. Total microbial biomass, measured via phospholipid fatty acid (PLFA) analysis, was greater in endophyte-infected than endophyte-free soils when averaged across sites, reflecting the trends observed with SOC and TN. Microbial community composition shifted somewhat in response to fungal endophyte infection: significantly higher fungal to bacterial ratios were observed in endophyte-free compared to endophyte-infected stands. However, ordinations of the PLFA data demonstrated only slight separation of endophyte-infected and endophyte-free microbial communities at some sites and no clear separation at others. Enhanced SOC, TN, recalcitrant n-POM C and N pools, and altered microbial biomass and communities suggest that this aboveground fungal endophyte symbiosis has widespread effects on soil biology and biochemistry, and that high prevalence of the aboveground endophyte increases C sequestration capacity of tall fescue stands throughout the southeastern USA. [Copyright &y& Elsevier]

Climate warming may stimulate microbial metabolism of soil carbon, causing a carbon-cycle-climate feedback whereby carbon is redistributed from the soil to atmospheric CO 2 . The magnitude of this feedback is uncertain, in part because warming-induced shifts in microbial physiology and/or community composition could retard or accelerate soil carbon losses. Here, we measure microbial respiration rates for soils collected from 22 sites in each of 3 years, at locations spanning boreal to tropical climates. Respiration was measured in the laboratory with standard temperatures, moisture and excess carbon substrate, to allow physiological and community effects to be detected independent of the influence of these abiotic controls. Patterns in respiration for soils collected across the climate gradient are consistent with evolutionary theory on physiological responses that compensate for positive effects of temperature on metabolism. Respiration rates per unit microbial biomass were as much as 2.6 times higher for soils sampled from sites with a mean annual temperature of -2.0 versus 21.7 °C. Subsequent 100-d incubations suggested differences in the plasticity of the thermal response among microbial communities, with communities sampled from sites with higher mean annual temperature having a more plastic response. Our findings are consistent with adaptive metabolic responses to contrasting thermal regimes that are also observed in plants and animals. These results may help build confidence in soil-carbon-climate feedback projections by improving understanding of microbial processes represented in biogeochemical models.