Using molecular techniques to understand community structure
from the bottom up: interactions of environmental stress,
pinyon pine, mycorrhizae, soil microbes and insect herbivores
at Sunset Crater
INVITED SYMPOSIUM ORGANIZED BY MONIQUE GARDES
Whitham, Thomas. G.1, Catherine A.
Gehring1, Tad Theimer1, Steve Travis1,
Neil Cobb1, Cheryl R. Kuske2 and Paul Keim1
1Department of Biological Sciences,
Northern Arizona Univiversity, Flagstaff, AZ 86011, USA
2Environmental Molecular Biology, Los
Alamos National Laboratory, Los Alamos, NM 87545 USA
Abstract
Since the eruption of Sunset Crater in 1064AD, colonizing
pinyon pines have encountered a new stressful environment for
which they are not yet adapted. These stressful conditions
have resulted in an altered mycorrhizal and microbial
community, and increased susceptibility to a keystone insect
herbivore. RFLP analyses of the mycorrhizal community show a
pronounced shift in taxa, and greenhouse experiments suggest
that the ability of pinyons to survive in this new
environment is in part due to the acquisition of mycorrhiza
better suited to cinder soils. Genetic analyses of pinyons
show that trees resistant to insect attack are differentiated
from susceptible trees, and both tree types differ
quantitatively in their mycorrhizal community. Furthermore,
the interactions of environmental stress with the plant-
herbivore-mycorrhiza complex has ripple effects throughout
the community that affects seed dispersing birds and
mammalian seed predators. We believe that the application of
molecular techniques to the trees, their mycorrhiza, soil
microbes and insect herbivores represents a key aspect of
integrating the ecology and evolution of this system, and is
likely to show how a diverse community maps onto the
underlying genetic structure of the pinyon population. Also,
the responses of the 350+ species of this community to this
recently altered environment suggest how global climate
change could affect biodiversity.