Figs and the wasps that pollinate them present one of biologists' favorite examples of a beneficial relationship between two different species. In exchange for the pollination service provided by the wasp, the fig fruit provides room and board for the wasp's developing young. However, wasps do not always pollinate the fig. Fig trees "punish" these "cheaters" by dropping unpollinated fruit, killing the wasp's offspring inside, report researchers working at the Smithsonian Tropical Research Institute.
Their results, published in the Proceedings of the Royal Society, show that sanctions against cheaters may be critical to maintain the relationship.
"Relationships require give and take. We want to know what forces maintain this 80-million-year-old arrangement between figs and their wasp pollinators." said lead author, Charlotte Jandr, graduate student in Cornell University's Department of Neurobiology and Behavior, who conducted the study as a Smithsonian pre-doctoral fellow. "What prevents the wasps from reaping the benefits of the relationship without paying the costs?"
Some wasp species passively carry pollen that sticks to their bodies. Others actively collect pollen in special pouches. Jandr evaluated the ability of six different fig tree-fig wasp species pairs to regulate cheating. She introduced either a single pollen-free wasp, or a wasp carrying pollen, into a mesh bag containing an unpollinated fig. The wasps entered the figs to lay their eggs. Jandr found that trees often dropped unpollinated figs before young wasps could mature.
"This is really about the all-too-human theme of crime and punishment. We found that in actively pollinated fig specieswhen wasps expend time and energy to collect and deposit pollen-- wasps that did not provide the basic service of pollination were sanctioned. However, in passively pollinated specieswhen the wasps do not need to make an effort to pollinate--sanctions were absent," said All
|Contact: Beth King|
Smithsonian Tropical Research Institute