Chemical differentiation between leaves of seedlings and spatially close adult trees from the tropical rainforest species Nectandra ambigens (Lauraceae): an alternative test of the Janzen-Connell model
Me. Sanchez-hidalgo et al., Chemical differentiation between leaves of seedlings and spatially close adult trees from the tropical rainforest species Nectandra ambigens (Lauraceae): an alternative test of the Janzen-Connell model, FUNCT ECOL, 13(5), 1999, pp. 725-732
1. We tested the hypothesis of Langenheim and Stubblebine that differences
in chemical composition between maternal trees and the seedlings under them
arise from differential mortality; only seedlings different from the mothe
r survive. Such mortality could explain at least some of the cases where se
edlings accumulate under adult conspecifics, contrary to the extreme form o
f the Janzen-Connell hypothesis.
2, We investigated Nectandra ambigens (Lauraceae), an upper-canopy tree at
Los Tuxtlas tropical rain forest, Mexico, whose seedlings survive under the
canopy of conspecific trees. We analysed chromatographic profiles of leaf
terpenoids of 15 groups, each formed by an adult tree and its surrounding s
eedlings.
3. We predicted that seedlings chemically similar to the adult would be abs
ent under the tree canopy and that they would be present outside that canop
y. We also predicted that younger seedlings would be more similar to the ad
ult than the older ones.
4. Chemical similarity analyses showed that most seedlings were significant
ly different from their closest adult and thus supported the Langenheim and
Stubblebine hypothesis. However, we did not find chemical differentiation
among seedlings regarding their age or their position inside or outside the
tree canopy.