Selected quotes from Richard Corlett's sell-out talk at NUS on 10 Jan 2007:
10. What, if any, are the functional consequences of the observed differences between the biotas of the different rainforest regions?
"One of the questions that we looked at... is whether the big differences in tropical forests in distant parts of the world translate into difference in function, so if you are in a South American rainforest where there are no species shared with Southeast Asian rainforests, does this mean that the forest functions in different ways?"
"Just to give some examples of the real differences you get: if you go to rainforests in South or Central America, every rainforest has leaf-cutting ants. They cut off bits of leaves, pile them up, grow fungus on them and they eat the fungus – this doesn’t happen anywhere else in the world. Go to a tropical forest in Asia, Africa or Madagascar, and there are termites which use dead stuff, not live leaves, pile them up and grow a different fungus on it and live on the fungus. There’s no obvious reason why these two shouldn’t live together, since they live very different lifestyles, but they don’t – they have non overlapping distributions."
"One other example: bulbuls are birds you are familiar with. They swallow fruits whole, including the seed. The equivalent family of birds, the tanagers in the Neotropics, occupy pretty much the same range of niches. But tanagers squash out the seed before they swallow the fruit. There’s a big functional difference; superficially similar but functionally different."
"And the obvious question to ask is: do any of these differences between lineages of organisms present translate into differences in how the forests work? Does it affect nutrient cycling, that you have or haven’t got fungus-growing termites or you have or haven’t got leaf-cutting ants. Does it affect plant reproduction? Are gene flow distances different in tropical forests where the genes are carried by different pollinators? Is the impact of forest fragmentation different?"
9. Ecology of Fagaceae
"The Fagaceae – this is the oak and chestnut family. Most of you, even those who have spent most of your life in the tropics, think of the oaks as being temperate zone trees. In fact, Singapore has got more species in this family than the whole of Europe! Borneo’s got more species than the whole of North America. They are basically a tropical family with outliers in the temperate zone"
"And in many ways, the Fagaceae are a very odd rainforest family .. they are not like the majority of other rainforest plant families.. they are apparently ectomycorrhizal.. and they have non-fleshy, large, poorly dispersed fruits which are probably dispersed by rodents. Many species appear to mast fruit at long intervals and those of you who are forest ecologists will know that these characteristics in many ways are shared with the family Dipterocarpaceae."
"Yet you can open any issue of any tropical ecology journal and you find one or two papers on the ecology of the Dipterocarpaceae... for the tropical Fagaceae there’s probably one paper every 3 or 4 years. It’s a neglected group despite the fact that it’s almost as diverse, has a similar distribution and in some ways similar ecology."
8: Ecology of Babblers
"My favourite group of birds, apart from the bulbuls, are the babblers... Birdwatchers are well aware that there’s lots of babblers in Asian tropical forests. As a proportion of the bird fauna, they get richer and richer as you move north, so in the sub-tropical regions of Asia, babblers can make up 30-40% of the birds fauna and you can have 25-30 species co-existing in the forest"
"But they receive very little attention. They are the most diverse groups of birds. In sub-tropical and tropical Asia, you get many similar co-existing species... But very few species have been studied in any detail... there’s lots of suggestions that they have peculiar breeding systems, peculiar social systems etc... Also, although the literature tends to imply they are mainly insectivores... at least 20-30% have a diet of fruit. So they are probably very important seed dispersal agents in the rainforest understorey."
"In addition, many species are completely dependent on forests...generally, if you clear your forests, most of your babblers stay in the little fragments and they don’t occupy urban or agricultural habitats with a few exceptions."
7. Ecological consequences of Megafaunal extinctions
"In Southeast Asia 200,000 years ago, the forests had a very diverse, and judging from the fossils, very abundant megafauna.... you had stegodons and elephants at the same site.... giant tapirs... giant pangolins up to 2.5 m long… and Gigantopithecus, the largest ape that ever lived."
"This megafauna has either disappeared or the ranges of different species has shrunk… a lot of the species that are still here have had their ranges vastly reduced….. elephants, only 5,000 years ago ,went north to Beijing... there are many protected areas in the region where the only megafauna left are deer and pigs."
"We know that some of these species are important seed dispersal agents... some of these species are important as browsers… and they are also major natural disturbance agents… so tropical forests today must function in a very different way from the tropical forests which had all these megafauna – how we are going to study it I am not exactly sure.."
6. Are continental tropical forests resistant to invasive species?
"Continental tropical rainforests do seem to be resistant to invasion by plants… but it does appear that tropical forests may not be as resistant to animal invasions as they are to plant invasions."
5. What can we learn from the comparative phylogeography of tropical forest taxa?
"There’s been an explosion in this sort of phylogeographic information over the last 5 years; I reckon the literature doubles every 6 months... but really nothing interesting has been done with this... all that people do is basically storytell... I think we need to take a more systematic approach to this… in theory we ought to be able to work out the history of Southeast Asia based on the historical phylogeography of the region."
4. How far do genes flow in continuous and fragmented forests?
"A key problem with tropical forests is that they are becoming fragmented... with no gene flow, you are going to get eventually inbreeding, genetic drift, loss of fitness.... because both pollen and seed movements in plants generally depend on animals, it's very likely that gene flow is going to be disrupted in tropical forests."
3. What are the mechanisms of species loss from fragmented forests/landscapes?
"How are species lost in fragmented landscapes?... the reason we do not know this in my opinion is that everyone’s worked on too small a spatial scale... we do really need to look at the whole landscape to get an idea of the relative importance… and it turns out that Singapore is an ideal place to do this, because you have got reasonably complete lists of what species were present in Singapore more than 100 years ago. So we can look at species loss in the landscape and try and work out which mechanisms were most important."
2. How will tropical forests respond to climate change over the next 50-200 years?
"It’s an obvious question to ask. I think pretty much everyone has accepted that the global climate is changing and most people are accepting that there is a huge human contribution to that climate change...."
"... the region around Singapore... a plausible prediction is that Singapore in 70-100 years will basically have a permanent El Nino climate… we expect similar or somewhat higher temperature than today, perhaps 1 or 2 degrees higher... and lower and more variable rainfall... the current dry periods will be drier than they are now… also higher sea levels..."
1. How can we restore tropical forests on sites where they have been extirpated?
"More than half of all tropical rainforests are already gone. More than half of the forests that’s left are already massively degraded, and I think the number one thing that we need to know about Asian tropical forests is how to put them back together again – how do you reestablish rainforests from a site from which it has been extirpated?"
"Yes, we can plant trees… but really, this is just gardening with nature’s plants... When we are trying to restore a rainforest, we don’t just want one generation of trees to grow up... we want them to flower, the flowers to pollinate, we want the fruits to develop and be dispersed by dispersal agents, and probably most crucially of all, we want the conditions in which the seeds can germinate and grow up into the next generation. So, it's not just planting trees!"
"We then have to work out how we can establish plant populations… We really know almost none of this, and the fact that we can grow nature’s trees and they will apparently grow up has given us a false sense of security."