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Dragon fruit. (Photo by R. Butler)
SEEDS and FRUITS
Many of the seeds and fruits produced by canopy trees fall to the ground where they provide food for seed gatherers (rodents, birds, fish, etc) and create a natural seed bank in the leaf litter. There are two growth strategies once seeds reach the ground. One strategy is to produce large seeds with food reserves enabling the seedling to survive in the low-light conditions of the understory. The second method characteristic of many pioneer species is to produce huge numbers of small seeds which only germinate under certain conditions (usually light gaps). When a light gap opens, these seeds sprout and the seedlings rapidly grow to once again plug the hole in the canopy.
Since seeds are the agents for future growth, many have defenses against predators to ensure some will be left untouched to germinate. Plants reduce herbivory and seed eating with structural defenses like thorns, stinging hairs, or spines and the production of toxic compounds which interfere with digestion or are unpalatable. Often the seed is surrounded by an edible fleshy material to make it palatable to birds and mammals who can disperse it, but the seed is toxic or indigestible so it will be passed out or discarded. For example, the cashew has a sweet and juicy stem but a toxic seed, so monkeys eat the fleshy stem and discard the seed.
Many rainforest trees, especially those of the forest interior, produce large cauliflorous fruits that grow directly out of the surface of the tree. This mechanism enables the tree to grow large, conspicuous fruits that attract larger animals. One of the largest cauliflorous fruits is the jackfruit of Southeast Asia which may be three feet long (1 m) and 110 pounds (50 kg). The jackfruit produces a strong odor that attracts nocturnal mammals like the flying fox. A famous cauliflorous fruit of Southeast Asia is the durian, a thorn covered fruit that is said to "taste like heaven but smell like hell." The odor of the durian is so offensive that its presence has been banned in some public places. Nevertheless, the durian is an important export for Malaysia, Indonesia, and Thailand, which exported nearly 1 million metric tons in 1992. Both cocoa and coffee beans grow as cauliflorous fruit.
Seeds and fruits provide an important food resource for forest-floor animals. To survive, a seed must elude these predators and many do so by being dispersed by specialized birds, mammals, and fish. These dispersers eat the fruit flesh without destroying the seed. Other seeds escape by being poisonous. Some of these toxins are useful to insects, which sequester them for their own purposes, and to humans. For example, many seed toxins have been chemically isolated and used to formulate drugs for humans, while umpteen insects naturally incorporate these compounds to render themselves toxic or use these toxins to produce scents to attract mates. For example, the male butterflies of the Danaiidae family convert alkaloids in the crotalaria plant into a scent to attract females.
Many large seeds have structured defenses against seed predators. In some cases seeds designed for gut passage by large mammals will have a sturdy seed coat, while bird-dispersed large-seeded fruit will often have seeds that are chemically defended. For example, the fruit of the nutmeg splits open to reveal a large seed covered with an orange-colored aril. The seed is highly aromatic, and the odor acts as a warning and toxic deterrent.
Review questions:
How do animals help the reproductive cycle of plants?
Important safeguards to protect rainforests lacking in REDD negotiating text
(11/06/2009) Important safeguards to protect natural forests are still lacking in negotiating text on REDD, a proposed mechanism for mitigating climate change by paying developing countries to keep trees standing, reports an alliance of activist groups.
World's first video of the elusive and endangered bay cat
(11/05/2009) Rare, elusive, and endangered by habitat loss, the bay cat is one of the world's least studied wild cats. Several specimens of the cat were collected in the 19th and 20th Century, but a living cat wasn't even photographed until 1998. Now, researchers in Sabah, Malaysian Borneo, have managed to capture the first film of the bay cat (Catopuma badia). Lasting seven seconds, the video shows the distinctly reddish-brown cat in its habitat.
Photos: Palm oil threatens Borneo's rarest cats
(11/04/2009) Oil palm expansion is threatening Borneo's rarest wild cats, reports a new study based on three years of fieldwork and more than 17,000 camera trap nights. Studying cats in five locations—each with different environments—in Sabah, Malaysian Borneo, researchers found that four of five cat species are threatened by habitat loss due to palm oil plantations. "No other place has a higher percentage of threatened wild cats!" Jim Sanderson, an expert on the world's small cats, told Mongabay.com. Pointing out that 80 percent of Borneo's cats face extinction, Sanderson said that "not one of these wild cats poses a direct threat to humans."
Conservation and Carbon in Borneo’s Heart and Ours
(11/04/2009) My friend Rezal Kusumaatmadja contacted me in July to ask if I could join him and some of his associates for a couple of days in the village Mendawai, located along the Katingan River in south central Kalimantan. The purpose of the gathering was to bring everyone in the group up to date on progress and challenges related to the Katingan Peat Conservation Project, as well as to give the group an opportunity to meet one another. The Katingan Project aims to create a forest-based carbon containment facility defined and guided by REDD (Reduced Emissions from Deforestation and forest Destruction in the developing world) principles and methodology. Currently, nearly 25% of human-generated greenhouse gas emissions are caused by felling, burning and converting the world’s remaining primary forests. While areas surrounding the Katingan peat forest vividly express this statistic, Katingan is part of a growing strategy to reverse the trend. The Katingan project endeavors to transform conservation into a product that might offer strong competition against illegal logging and expansion of industrial agricultural plantations - whose practices cause enormous emissions of greenhouse gasses, as well as destroying biodiversity, depleting and polluting watersheds and corroding native cultures.
Non-Malaysian and Indonesian palm oil producers pledge not to develop peatlands for plantations
(11/04/2009) Palm oil producers outside of Malaysia and Indonesia pledged to stop developing new plantations on peatlands, circumventing an impasse that developed between palm oil producers and environmental groups meeting this week at the Roundtable on Sustainable Palm Oil in Kuala Lumpur. The factions deadlocked over plans to account for emissions from plantation development, delaying the criteria for a year.
