Response of Seedlings and AMF Spores to Vertebrates 305seedlings respond to spores dispersed by terrestrial
vertebrates under varying conditions is critical to
understanding the importance of spore dispersal
by these animals.
Second, for AMF, it is important to gain a bet-
ter understanding of how important spores are
as propagules. Recent molecular techniques that
allow the determination of the presence, absence,
and abundance of AMF in root tissue allow esti-
mates of the diversity of mycorrhizal species
colonizing roots to be assessed (e.g., Husbandetal.
2002, Rosendahl and Stukenbrock 2004). This
technology allows direct comparison of the fun-
gal community that has established on plant roots
with the fungal community present in the soil or
in the feces of terrestrial vertebrates.
Third, given that in many systems seedlings
remain in the understory for years or decades, the
full suite of vertebrate effects may not be expressed
for very long periods of time, so long-term studies,
or studies comparing sites with intact faunas with
sites which have been defaunated for long peri-
ods, are required to understand the ultimate fate
of defaunated forests. For example, if vertebrates
maintain seedling densities below levels where
competitive interactions are important, then the
effect of defaunation may not be expressed until
seedling densities have recovered to the point
where these interactions come into play. Even
though seedling densities across all our exclo-
sure plots increased in the absence of vertebrates,
most had still not approached the initial density of
our most densely populated plot after 4 years of
exclosure. Likewise, vertebrate-induced changes
intheAMFcommunityavailabletocolonizeplants
may take relatively long periods to alter seedling
abundance and composition. Unfortunately, the
current rate of loss of many vertebrate species
from tropical rainforests worldwide means that
many forests will lose important vertebrate com-
ponents before we fully understand their potential
role in influencing diversity.
ACKNOWLEDGMENTS
We thank S. Schnitzer and W. Carson for the
opportunity to contribute a chapter to this vol-
ume, two anonymous reviewers for their helpful
comments, J. Connell and P. Green for stimulat-
ing discussions and invaluable assistance in the
field, the CSIRO Tropical Forest Research Centre
for generous access to facilities, and the National
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