Organization of genetic variation in individuals of arbuscular mycorrhizal fungi

the microbial communities from each site by growing either C. maculosa from the same region used in experiment 1, or a Festuca bunchgrass native to the region of soil origin, in pure soil. The two Festuca species (idahoensis and ovina) were chosen because they are similar in size and appearance and co-occur naturally with C. maculosa in their respective native lands. The use of a single Festuca species might have biased the relationship between the plant and microbes of a different continent in ways that might differ from a plant and microbes from the same region. Five plants were grown for 110 days in each of 40 4-litre pots: n ¼ 10 for Montana soil with C. maculosa; Montana soil with F. idahoensis; French soil with C. maculosa; and French soil with F. ovina. After the 110-day pre-culturing period, half of the soil in each pot was triple-autoclaved on three successive days to kill the microbial community, and then the non-sterilized and sterilized soil from each 4-litre pot was used to inoculate two sterile 15:85 soil:sand mixtures and two non-sterile 15:85 soil:sand mixtures in 525 cm 3 pots. We used the soil in the 525 cm 3 pots for two experiments: one in which C. maculosa was grown alone in sterile and non-sterile soil, and one in which C. maculosa was grown with F. idahoensis as a competitor. In the no-competition experiment, Centaurea seeds were planted in all pots and grown for 91 days during which they were fertilized and watered as in experiment 1. In the competition experiment, F. idahoensis, which grows more slowly than C. maculosa, was planted first, and after 14 days C. maculosa seeds were planted in half of the pots and grown for 91 days. At the end of the experiments all plants were harvested, dried at 60 8C and weighed. We compared the post-removal effects of C. maculosa on the growth of conspecifics to those of the native grass Pseudoroegneria spicata. Ten C. maculosa and ten P. spicata were planted in random locations outdoors in the Deittart Experimental Gardens in April 2001. The site historically supported native grasslands. These plants were grown until 10 August 2003, when they were harvested aboveground. One C. maculosa was grown at each of the 20 sites from 10 August to 14 September 2003 when they were harvested aboveground, dried at 60 8C and weighed. indirectly enhance competitive effects …