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Arnold Arboretum

Biodiversity

April 22, 2011 by Cam Webb

In addition to documenting and analyzing forest composition, we will also be doing general plant collecting at all our sites to record the amazing biodiversity of this under-studied part of the world. We made our first collection during the hike into the forest: as I gingerly walked down the trunk of a fallen tree from a high bank into a riverbed, I saw that it had sent up living branches that were flowering and easy to collect. I knew at once that it was a Durio, the genus that includes the fabled durian fruit, but had never encountered this species myself.

We made a collection (‘XM-1’), and placed a small piece of leaf in blue silica gel for subsequent DNA analysis. As I write this now, during a quick trip back out to our home in nearby Sukadana, I’ve had a chance to consult a book (Peter Ashton’s Manual of the Non-Dipterocarp Trees of Sarawak) and Ferry Slik’s helpful website, and am pretty sure that XM-1 is Durio acutifolius (Mast.) Kosterm., a relatively small  member of the genus with bird-dispersed fruits. It appears not to be too rare, but the delight of the diversity of the rain forest is that one’s first encounter with even common species can sometimes take years.

Collection number 1: Durio acutifolius

Collection number 1: Durio acutifolius

One fun twist about this species is that the type specimen (the physical collection that anchors the taxonomic name) was collected by Odoardo Beccari in 1865, and the Arnold Arboretum has a copy (‘isotype’) of this collection as does Kew (with image). Beccari (1843-1920) was a probably the most famous nineteenth century botanist collecting in Borneo and wrote an engrossing book about his travels (Wanderings in the great forests of Borneo; travels and researches of a naturalist in Sarawak) which can be downloaded from the internet archive.

Luminescent mushrooms

Luminescent mushrooms

Many other types of organisms in the rain forest are just as diverse as plants, and I have been particularly struck by the large numbers of mushrooms fruiting at the moment. There are even fewer mycologists than botanists working in Borneo, and probably the majority of Bornean fungi have yet to be collected and described. For many taxa like fungi, it’s not a question of “can we find a new species,” it’s “how many new species do you have time to describe!”

Cordyceps on an ant

Cordyceps on an ant

One of the most wonderfully sinister fungi is Cordyceps, an endoparasite of insects. Let’s say Cordyceps spores enter the body of an ant: the resulting mycelium will release chemicals that alter the ant’s behavior, such as climbing up a sapling and biting the edge or midrib of a leaf. After the ant’s death by internal consumption, a fungal fruiting body will burst out of the ant’s body and release spores, repeating the macabre cycle. It is not uncommon to find dried, dead ants on the underside of leaves, with the brown or white branches of a fruiting body emerging from their heads. I showed one to the team and no one had ever noticed these before, but they loved the story. Great laughter followed. Edy, our tree climber, had been saying just that morning that he felt all itchy when he hadn’t been climbing for a while. “Edy,” someone said, “If we find you in the top of a tree, biting a leaf, we’ll know what has happened to you!”


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