The diversity of plant communities mediates mycorrhizal fungal diversity Or, How graduate school is going to be way harder than I thought Marlene Tyner, University of Michigan R. Michael Miller, Argonne National Laboratory Alison Bennett, University of Wisconsin
Richness number of species in an area What is diversity? Evenness how those species are distributed in an area Evenness Most diverse Richness
Why is diversity important? Many studies have found diversity and ecosystem productivity to be intrinsically connected (Naeem et al. 1994, etc.) Contested by many ecologists! Some studies show that it maintains stability (Tilman and Downing 1994, etc.)
Diversity and climate change If diversity maintains stability, then highlydiverse communities should be more resilient against climate change less species migration into and out of communities AMF are critical in maintaining plant diversity (van der Heijden et al. 1998, Klironomos et al. 2000)
If AMF maintains plant diversity, then keeping soil AMF communities constant and with high species richness should help to maintain high plant community diversity and stability But does it go the other way? Does plant diversity maintain soil fungal diversity or shape fungal communities?
What are mycorrhizal fungi? Penetrate the roots of plants with growth called hyphae Exchange nutrients and water for carbohydrates from the plant Diagram of AM fungal structures UMN Great Lakes Worm Watch, 2007 Fungal hyphae act as root extensions, and allow plants to grow in nutrientstressed soils
AMF impacts on diversity and productivity Many studies have shown a strong correlation between AMF diversity and plant diversity Tall-grass prairies (Hartnett and Wilson 1999; Smith et al. 1999; Vogelsang, et al. 2006, etc.) Tropical forests (Kiers, Lovelock et al. 2000) Old-fields (van der Heijden et al. 1998) Hawaiian subtropical mesic habitats (Stampe and Daehler 2003) Many have also shown a meaningful relationship between AMF diversity and plant community productivity Old-fields (van der Heijden et al. 1998; Klironomos et al. 2000; Vogelsang et al. 2006)
Such good intentions: the experimental design Monocultures Polycultures A B C D AB AC AD BC BD CD ABC ABD ACD BCD ABCD Control AMF community: constant for all treatments contains inoculum from four fungal species in equal parts } X 10 per community
50 ml sterile soil 200 ml soil mixed with fungal inoculum 50 ml sterile soil
1 2 Start with flats filled with sterilized potting soil plant four plant species, allow for two weeks growth following seed germination Fill 4 pots with sterilized 1:1 field soil:sand mixed with fungal inoculum from four different species 3 Transplant two-week old seedlings to pots 4 Allow five months to grow, then collect soil cores to extract, count and identify spores
Scutellospora dipurpurescens Glomus claroideum Spore production analysis Examining spore abundances and species identity can tell us something about: Fungal fitness Fungal community structure Glomus mosseae Scutellospora fulgida Photographs INVAM website
1 Start with flats filled with sterilized potting soil plant four plant species, allow for two weeks growth following seed germination
Lessons learned Avoid House of Cards experimental designs
Possible results Difference in species composition under different individual plant species (monocultures) (Eom et al. 2000) A positive relationship between increased spore production and plant diversity (Burrows and Pfleger 2002, Eom et al. 2000) Increased plant diversity yielding higher spore richness in soils (Burrows and Pfleger 2002) Positive correlation between plant diversity and amount of total root colonization (Eriksson 2001) Difference in plant community structure based on the mycorrhizal dependency of the subordinate plants (Urcelay and Diaz 2003) Significant species-specific responses (van der Heijden et al. 1998)
Thank you! U.S. Department of Energy Office of Science GCEP SURE Program Dr. Mark Hunter, Susan Kabat, Susan Kirt, Jeffrey Walters, Dr. Jim Bever, Jeff Gaffney, Nancy Marley, Milton Constantin, Mikey Tackett, Rachel Vannette
Q-PCR or Real-Time PCR **Amplifies specific large ribosomal subunits (LSUs) using species-specific primers Able to quantify the amount of a specific species present relative to another species Measure fluorescence of probed and amplified DNA segments at each PCR cycle to quantify**