Plants Make the Most of Visiting Ants
Many picnickers have had to relocate after ants invaded
and began to carry off their sumer supper. But certain epiphytes,
those wily plants that live on trees, derive much of their nutrients
from visiting ants, a new study shows.
In exchange for shelter, ants provide the plants with
significant amounts of carbon dioxide and nitrogen, Kathleen K.
Treseder of Stanford University and her colleagues report in
the May 11 Nature.
_Dischidia major_, an epiphyte from Sarawak, Malaysia, gets
39 percent of its carbon from carbon dioxide exhaled by ants living
in its sacklike leaves, the team reports. The carbon diffuses through
small openings in the leaves.
Almost 30 percent of _D. major's_ nitrogen comes from ant
debris, including feces, dead ants, and scavenged insect parts. Plants
send their roots to areas where this nutritious debris accumulates.
Treseder and her colleagues calculated how much of the plants'
carbon and nitrogen comes from the ants by analyzing isotopes
of these elements, she says. Ants respire carbon dioxide that lacks
carbon-13 isotopes, and ant debris is rich in nitrogen-15 isotopes,
they report.
The researchers knew how much carbon-13 the plants would
contain if they derived their carbon from the atmosphere only. They
had also determined the nitrogen concentration of the leaves of a
different _Dischidia_ species that grows on the same trees but does
not harbor ants.