Chapter 1 Figs: The wasp and the forbidden fruit We start our survey of symbiosis in a rainforest in Brazil - not the Amazon, but the Atlantic forest. I''ve come at the invitation of Alexandre Antonelli, head of science at the Royal Botanic Gardens at Kew in London, and founder of a 120-hectare reserve set in untouched Atlantic rainforest. A few months before this trip I had been sitting in Kew Gardens talking to Alex about his work on the importance of preserving and promoting biodiversity, and about my research for this book. He mentioned a project he is running in the rainforest, a complete biocensus of a giant old fig tree. Scientists, he told me, will sample and analyse DNA of all the life forms living on the tree, and from that try to build a picture of the symbiotic relationships between them. ''You should come and visit,'' he said. So I have. It''s my first time in Brazil, and later I realise it''s the first place that Charles Darwin visited after crossing the Atlantic on HMS Beagle .
Only twenty-three years old, eager as a spaniel, delighted to be on land after the long ocean crossing, he headed straight to the jungle. This is his journal entry for 29 February 1832: ''The day has passed delightfully. Delight itself, however, is a weak term to express the feelings of a naturalist who, for the first time, has wandered by himself in a Brazilian forest.'' I feel the same. And as much as I am struck by the exhilarating bloom of life, of different species packed to bursting all around, croaks and chirps and snatches of song I can''t identify, I am struck by the proliferation of decay. There is leaf litter and fungi and dead wood rotting and recycling everywhere I look. Thomas Berg, a Swedish-Brazilian biologist who runs the reserve, takes me to the fig tree. It is thought to be around one hundred years old, and is about thirty metres tall.
Like many big trees in the rainforest, its roots don''t penetrate deep into the soil, but spread in broad, tall buttresses. I''ve been looking forward to meeting this tree for months, and I lay my hands on the trunk in greeting. Scaffolding has been erected around the tree to help scientists access all parts of it. I don a hard hat, clip into a safety harness, and climb. As I pass the first branches I notice that they carry thick swatches of soil covered in mosses, lichens, orchids and bromeliads. It''s the same in any long-lived tree in the rainforest. Soils build up on the branches, rich in nutrients, thanks to symbiotic bacteria that draw nitrogen from the air and turn it into fertiliser. Branch soils, as they are known, store large amounts of water and carbon, and harbour diverse ecosystems; in fact are their own miniature forest-in-a-forest.
Every half-metre I climb takes me past cities and worlds full of life and drama. I settle down on the highest platform of the scaffold, with a view over the canopy and the surrounding forest. To my eyes, it''s a huge expanse of rolling shades of green. Yet the Atlantic forest now covers only 8 per cent of its original area. In Portuguese the word for forest is mata , or mato , so the Atlantic forest is the Mata Atl'ntica. But, Thomas tells me, mato has a negative meaning, of garbage, of something worthless; something which can be unthinkingly cleared to build houses, to raise cattle or crops, or as I saw on the drive up here, to replant with eucalyptus, from Australia. During colonial times, vast amounts of land were cleared and settled, first around São Paulo, and then on into the interior of Brazil. Indigenous people were pushed out, enslaved and killed.
The land grab was orchestrated by the bandeirantes , the ''flag carriers'' - who, as the journalist Eliane Brum points out, are honoured with statues all over the country. Colonisation, back then, had a positive meaning, like ''exploration'' did in frontier America. In Portuguese the forest is linguistically undervalued. We noted that René Descartes had set the stage for this exploitative view of nature in the seventeenth century, by declaring animals to be machines. Contrast the Portuguese word with the Yanomami word for forest, urihi . The Yanomami are hunter-gatherers who live up north, in the Amazon forest, and urihi is a term, like our word ecosystem, that encompasses the forest and the networks of relationships that exist in it. Urihi a Pree , ''the great land-forest'' is the Yanomami name for the world. Living on Urihi a Pree implicitly affirms that people have relationships with trees and monkeys and mushrooms and toucans - and spirits.
The Yanomami are effortlessly, automatically, linguistically part of nature. Ursula Le Guin develops this idea in her novella The Word for World Is Forest . The story is set on a planet called Athshe, which in the language of the native people living there means both forest, and the world. For the people of Athshe, the forest is their world. The meanings we assign to words matter. And we should bear in mind that words are placeholders; they are our attempt to label some aspect of the world, and as such they come laden with our values. Words are necessarily approximate, a feint at what is really happening. Words such as ''cooperation'' and ''competition'', for example.
Like ''symbiosis''. Young figs are developing on some of the branches. A wasp appears. Her scientific name is Pegoscapus assuetus - we''ll call her Peggy as we trace her journey. She has been flying in the forest for a while, resting on leaves when she can see they are free of ants or spiders. Now she catches the scent of something she didn''t know she wanted but since she''s sensed it, she''s mad for it. She flies up the concentration gradient of the smell, and lands on a small fig, hard and green. She folds her wings, never to use them again.
She fusses about the fruit until she finds a tiny opening at one end, then she fusses about some more. She touches the pollen pockets on her thorax above her waist: check. Then Peggy, with a goodbye salute to the outside world, enters the fruit. The journey to the centre of the fig is brutal. The passage is lined with scales, so tight that first her antennae and then her wings are torn off. Sometimes the females have to bite off a leg or two to get through. Stripped off too is most of the dirt she had with her, the bacteria and fungal spores on her body, but the golden pollen in her pockets survives the journey. And now she''s in the vault.
The interior of a fig is an inside-out flower, packed with hundreds of blooms, all fully developed. The flowers are the source of the scent that has called her. It''s a homecoming of sorts, since she was born in a flower chamber just like this. Now she gets to work, moving from floret to floret, pollinating each one and probing inside and laying an egg next to the tiny young seed in the base of the flower. Without this wasp - this particular species, mind - the fig won''t be pollinated, and without this fig, the wasp has nowhere to lay her eggs. Tree and insect are completely dependent on each other. There is a commotion at the portal as another wasp tries to get in, but the way now is too tight, and she is trapped. Peggy leaves her rival to die, she will join her soon enough.
Once she has carefully laid all her eggs, about 200, her work and her life are done. Our story moves to her children. These offspring, the wasp embryos, are developing inside the fig flowers: the fig converts some seeds into maternity units for larvae. Male wasps grow faster than females and the first male to emerge from his cocoon crawls among the tightly packed flowers inside the fig, looking for females still finishing off their transformation from grub to grown-up. When he finds one he cuts through the flower containing her and copulates with her drowsy, barely adult form. He does this again and again with any female he finds, and if he encounters another male in the darkness of the fruit he kills it. It''s dark stuff. Once he''s mated with as many females as he can find, our male wasp helps drag them (his sisters) out of their beds and they load up on pollen.
The male, close to the end now, bites a hole in the side of the fig, an escape tunnel for his fertilised sisters. He leaves first. He moves a little distance off the fruit, stamping his feet to attract ants, and gives his body to distract them so his mates can escape . The females leave the fig and take to the air, in search of the scent of a fig, and we''re back to the beginning again. The fig ripens fast, and if it''s not eaten on the branch, falls to the ground. Everyone in the forest loves a fig. Bats, coatis, deer, monkeys, any number of birds and rodents. Humans have always relied on them.
Because they ripen throughout the year, figs provide a crucial food resource for thousands of species when other fruits are not available. It is a keystone species in the forest: like the central stone in a Roman bridge, a keystone species holds the rest of the ecosystem together. Many animals are reliant on figs to a greater or lesser extent, but fig wasps really need figs. Every species of fig, and there are some 800 of them, has its own dedicated species of pollinating wasp. Only the right wasp can detect the scent of a fig flower, and only that wasp can get inside to pollinate it, and only in those figs will its young develop. If figs are not pollinated, they turn brown and fall. Symbiosis exists along a spectrum. ''Living together'' can mean different things at different times, so we need to tighten up the definition.
We don''t, for example, mean parasitism, when two species live together but one thrives at the expense of the other, such as a malaria parasite living.