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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Zebra finches practice singing for the ladies

The male zebra finch (Taeniopygia guttata) learns to sing in private before performing for a female audience, according to Satoshi Kojima and Allison J. Doupe from the University of California, San Francisco. In addition, juvenile male finches seem to step up the quality of their singing, despite their immaturity, when in the presence of potential mates. As described in the blog Talking Science, part of National Public Radio’s Science Friday Initiative, “Male finches, by the time they are sexually mature, typically know two different forms of song: undirected, which is performed in isolation, and directed, which is performed for a female audience. Young males learn undirected song first, which characteristically sounds immature and is of variable quality. As adults, they become experts in directed song, a talent they refine specifically for the purpose of courting females.” As the researchers reported in the Proceedings of the National Academy of Sciences study, the juveniles, when performing for females, seemed to focus on the best parts of the songs that they practiced in private. Kara Rogers wrote in Talking Science, “The discovery reveals that the undirected song of young male finches disguises the actual extent of the birds’ song-learning capabilities…” In other words, despite their inexperience, immature male finches were able to sing at the level of mature finches in the appropriate social conditions: When there was a chance to  mate. Read about the zebra finch genome in Nature or take the songbird call challenge at enature.com. Photo Credit: Patricia van...

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Wet or dry: Butterflies reverse sex roles in extreme seasons

In the case of the African butterfly Bicyclus anynana, females develop ornate wings and court males if they spend the larval stage in a dry, cool environment. The reverse occurs, according to Kathleen Prudic from Yale University and colleagues, when the butterflies are exposed to wetter, warmer environments. “As expected, female Bicyclus anynana in warmer moister conditions that mimic the wet season in the native African range were more likely to mate with males with ornamented wings,” explained a Yale University press release. “However, the roles were reversed in cooler drier climates. Females played the role of suitors and flashed their eye spots to choosy males. When scientists studied the wing spots, which reflect light in the UV range, invisible to humans, they found they were brighter in the courting females relative to the males of that same season, or relative to females raised in the hotter season.” In a study published today in Science magazine, Prudic and colleagues suggested that the reversal is brought about by the environmental conditions. When transferring sperm, the male butterflies also administer nutrients, increasing the females’ chances of surviving the harsh conditions of a warm, dry season. Therefore, it is in the best interest of the female butterflies to attract males for their supply of nutrients, whereas males will be more selective in choosing females since they are limiting their own chances of survival by mating. As a result, the females that flash their showy spots are more likely to be chosen. Photo Credit: South African...

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Female jumping spiders fight to the death

Male jumping spiders (Phidippus clarus) size one another up before engaging in a fight—whether the aggression is based on rights to mating or territory—and in many cases, the pre-fight displays are sufficient to deter physical contact. The males do not nest but instead wander between female nests looking for opportunities to mate. The females, on the other hand, are not nomads—they build nests from silk and leaves in which they wait while they draw closer to sexual maturity.

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From the Community: Birds, bees, bats, beer and biofuels

A process of producing biofuels that yields brewer’s yeast, researchers’ evidence that human neurodegenerative disorders in Guam in the 1960s were linked to cyanobacteria, President Obama shows support for synthetic biology research and scientists track migratory birds at their farthest recorded distance. Here are highlights in ecology for the last week in May.

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From the Community: Pika population sees a boost, birds not spreading West Nile and five women honored for their role as environmentalists

Pika found to be flourishing in the Sierra Nevada region, bird migration patterns suggest mosquitoes are to blame for spreading West Nile and mice courtship rituals could shed light on autism. Here are news stories and studies on ecological science from the first week in March.

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