The story of the fig and its wasp

Inside the rounded fruit of a fig tree is a maze of flowers. That is, a fig is not actually a fruit; it is an inflorescence—a cluster of many flowers and seeds contained inside a bulbous stem. Because of this unusual arrangement, the seeds—technically the ovaries of the fig—require a specialized pollinator that is adapted to navigate within these confined quarters. Here begins the story of the relationship between figs and fig wasps. The queen of the fig wasp is almost the perfect size for the job—except, despite her tiny body, she often times will lose her wings and antennae as she enters through a tight opening in the fig. “The only link the fig cavity has to the outside world is through a tiny bract-lined opening at the apex of the fig, called the ostiole, and it is by means of this passage that the pollinating fig wasp gains access to the florets,” as described in Figweb, a site by Iziko Museums of Cape Town. Once inside, the queen travels within the chamber, depositing her eggs and simultaneously shedding the pollen she carried with her from another fig. This last task, while not the queen’s primary goal, is an important one: She is fertilizing the fig’s ovaries. After the queen has laid her eggs, she dies and is digested by the fig, providing nourishment. Once the queen’s eggs hatch, male and female wasps assume very different roles. They first mate with each other (yes, brothers and sisters), and then the females collect pollen—in some species, actively gathering it in a specialized pouch and in others, accumulating it inadvertently—while the wingless males begin carving a path to the fig’s exterior. This activity is not for their own escape but rather to create an opening for the females to exit. The females will pollinate another fig as queens. The males will spend their entire lifecycle within a single fruit. While this tree-wasp relationship may not be common knowledge to all fig-eaters, it is well-known to biologists as one of the most solid examples of coevolution. “One of the best activities to do with an introductory biology class is to pass around Fig Newtons, let them take a bite and then tell them the story of the fig wasp life cycle,” said tropical plant ecologist Greg Goldsmith as we recently hiked through a cloud forest in Monteverde, Costa Rica. “It’s a fascinating story.” After learning the story of the fig and its wasp, the most common question is, “Do we eat wasps when we eat figs?” The short answer is that it depends—that is, some figs are parthenocarpic, meaning they are...

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Tracking seed-dispersing piranha in the Amazon

Fish are probably not the first animals that leap to mind when thinking of seed dispersers. Squirrels are well-known examples, but researchers have recently tracked a species of frugivorous—that is, fruit-eating—piranha in the Amazon that distribute seeds over more than five kilometers of flood plains. As Daniel Cressey described in a Nature News article, “Although fish have long been suspected of having an important role in seed distribution, proof of their ability to carry fertile seeds such distances has been lacking.” Ecologist Jill Anderson from Duke University and colleagues tracked the fish Colossoma macropomum—also called a tambaqui or pacu—during three flood seasons in Peru’s Pacaya-Samiria National Reserve. As they reported in a paper published today in Proceedings of the Royal Society Biological Sciences, these fish are dispersing seeds at some of the greatest distances ever reported by frugivores. And because the seeds are dispersed in flood plains, they have a good chance of germination once the waters recede. Ed Yong reported in Discover’s blog Not Exactly Rocket Science that “seeds find it slightly easier to germinate after a voyage through the tambaqui’s innards.” By tracking these fish, Anderson also found evidence that the populations are depleted due to overfishing. That is, she was unable to find any fish close to maximum size within the three seasons she was tracking them. As Yong concluded his post, “Other species of fruit-eating fish are facing similar problems. So fishermen are not only depriving the Amazon of some of its most effective seed dispersers, they are also taking the best carriers out of the game. In doing so, they are disrupting alliances between fish and plants that have been going on for millions years. And they risk the future of the same flooded forests that provide them with their livelihoods.” Photo Credit:...

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From the Community: whispering bats, terror birds and x-rays of flowers

Western barbastelle bats in Europe learn to use quieter echolocation when hunting moths, ecologists analyze the importance of and methods for communicating science during times of environmental controversy, researchers map the skull of an extinct terror bird, unraveling this prehistoric carnivore’s hunting behaviors and a photographer produces x-ray images of flowers to showcase their inner beauty.

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