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Seedlings
and tropical
biodiversity

Whose shadow is safer?

September 27, 2017

Barro Colorado Island

A novel research project takes aim at the ageless question of what influences tropical seedling survival.

Tropical forest ecologists have long known that the farther a seed lands from its parent tree, the greater its chances are of growing into an adult. This is generally ascribed to the species-specific soil pathogens that live around the roots of the parent. Withstood by robust adults, these pathogens are often fatal to tiny seedlings. What happens if a seed disperses a long distance only to find itself in the shadow of another adult of the same species? Is it similarly doomed?

STRI fellow Jenalle Eck grows almost 300 seedlings in the Barro Colorado Island greenhouses as part of her experiment on pathogens and seedling survival.

Jenalle Eck, a Ph.D. student at Ohio State University, thinks that might not be the case. This hinges on a novel hypothesis that tropical pathogens are not so much species-specific as they are gene-specific. "Really, what pathogens are interacting with are the resistance genes of these tropical trees," said Eck. "If a seedling attempts to recruit near an adult of its own species, maybe it has a better chance of surviving under a non-parent, something that is less related to it at a genetic level."

To test this hypothesis, Eck is growing 275 potted seedlings of Virola surinamensis, or wild nutmeg, in soil collected from the base of their parent trees and of eight other adult trees of the same species. By March, she plans to measure their biomass and compare. If the differences are substantial, Eck may shed new light on how pathogens help shape biodiversity in tropical forests. "Ecologists have to move beyond a species-centric view of how diversity-promoting mechanisms operate," she said. "No one has really done that yet."
 

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