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Figs and fig wasps have evolved to help each other out:
Fig wasps lay their eggs inside the fruit where the wasp larvae can
safely develop, and in return, the wasps pollinate the figs.
But what happens when a wasp lays its eggs but fails to pollinate the
fig?
The trees get even by dropping those figs to the ground, killing the
baby wasps inside, reports a Cornell and Smithsonian Tropical Research
Institute study published in the Proceedings of the Royal
Society B: Biological Sciences.
The
findings suggest that when one species in a
mutually beneficial relationship fails to hold up its end of the
bargain, sanctions may be a
necessary part of maintaining the relationship.
"We want to know what
forces maintain this 80 million-year-old mutualism between figs and
their wasp pollinators," said lead author Charlotte
Jandér. |
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"What prevents the wasps from cheating and reaping the benefits of the
relationship without paying the costs?"
More than 700 species each of fig trees and wasps have co-evolved in
the tropics worldwide, with each fig tree species having its own
species of pollinating wasp. Jandér worked on six fig
tree-fig wasp pairs for the study. Some wasp species passively carry
pollen that sticks to their bodies, while others actively collect
pollen in special pouches.
The researchers found that in passively pollinated pairings, the tree
almost never aborted its fruit, and the wasp always carried pollen.
However, the researchers found that in actively pollinated pairings,
where the wasp needs to expend energy to collect pollen, the tree
dumped the fruit and killed the offspring when the wasps did not carry
pollen.
The researchers also found that among the actively pollinated fig
species, pollen-free wasps were much more common when the trees had
weak sanctions.
"Sanctions
seem to be a necessary force in keeping this and other mutually
beneficial relationships on track when being part of a
mutualism is costly," said Jandér.
"In our study, we saw less cheating when sanctions were stronger.
Similar results have been found among human societies and social
insects. It is very appealing to think that the same general principles
could help maintain cooperation both within and among species."
written by Krishna Ramanujan, ksr32@cornell.edu
source: Charlotte Jandér, Cornell University
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